C-C Cross Couplings with 3d Base Metal Catalysts 3031328663, 9783031328664

Citation preview

Topics in Organometallic Chemistry  93

Xiao-Feng Wu   Editor

C-C Cross Couplings with 3d Base Metal Catalysts

93

Topics in Organometallic Chemistry Series Editors Matthias Beller, Leibniz-Institut für Katalyse e.V., Rostock, Germany Pierre H. Dixneuf, Université de Rennes 1, Rennes CX, France Jairton Dupont, UFRGS, Porto Alegre, Brazil Alois Fürstner, Max-Planck-Institut fur Kohlenforschung, Mülheim, Germany Frank Glorius, WWU Münster, Münster, Germany Lukas J. Gooßen, Ruhr-Universität Bochum, Bochum, Germany Steven P. Nolan, Ghent University, Ghent, Belgium Jun Okuda, RWTH Aachen University, Aachen, Germany Luis A. Oro, University of Zaragoza-CSIC, Zaragoza, Spain Michael Willis, University of Oxford, Oxford, UK Qi-Lin Zhou, Nankai University, Tianjin, China

Aims and Scope The series Topics in Organometallic Chemistry presents critical overviews of research results in organometallic chemistry. As our understanding of organometallic structure, properties and mechanisms increases, new ways are opened for the design of organometallic compounds and reactions tailored to the needs of such diverse areas as organic synthesis, medical research, biology and materials science. Thus the scope of coverage includes a broad range of topics of pure and applied organometallic chemistry, where new breakthroughs are being achieved that are of significance to a larger scientific audience. The individual volumes of Topics in Organometallic Chemistry are thematic. Review articles are generally invited by the volume editors. All chapters from Topics in Organometallic Chemistry are published Online First with an individual DOI. In references, Topics in Organometallic Chemistry is abbreviated as Top Organomet Chem and cited as a journal.

Xiao-Feng Wu Editor

C-C Cross Couplings with 3d Base Metal Catalysts With contributions by C. M. A. Afsina
T. Aneeja
G. Anilkumar
B. M. Bhanage
Z. Chen
M. Gao
C. Gosmini
Y. Hou
P. A. Jagtap
Y. A. Kolekar
J. Li
Y. Li
M. S. Lokolkar
J. Long
N. P. Mankad
P. Tung
C. Wang
X.-F. Wu
W. Xu
Y. Yang
G. Yin
X. Zeng
Q. Zhang
S.-F. Zhu

Editor Xiao-Feng Wu Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian, China

ISSN 1436-6002 ISSN 1616-8534 (electronic) Topics in Organometallic Chemistry ISBN 978-3-031-32866-4 ISBN 978-3-031-32867-1 (eBook) https://doi.org/10.1007/978-3-031-32867-1 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

The construction of new carbon–carbon bonds is one of the most important missions in synthetic chemistry. Since the middle of the twentieth century, many name reactions have been developed for C–C cross-coupling reactions, including Suzuki-Miyaura coupling, Negishi coupling, Stille coupling, Hiyama coupling, Kumada coupling, Sonogashira coupling, Heck reaction, etc. In these well-known transformations, palladium catalysts are usually needed together with even more expensive phosphine ligands. From a large-scale applications point of view, cheaper catalytic systems are always attractive; from an academic research point of view, alternative catalysts might also lead to distinct reactivities. Here is where 3d base metal catalysts come into the view of scientists. According to the periodic table of elements, 3d base metals are among the group 4 elements containing from potassium to germanium. However, among them the ones that show catalytic activity in C–C bond formation are Cr, Mn, Fe, Co, Ni, Cu, and Zn. Their unique configuration of electrons leads to exceptional activities for inert bond activation leading to C–C bond formations. In this volume, the recent achievements on 3d base metal-catalyzed C–C bond cross coupling reactions were summarized and discussed. Scientists from America, Asia, and Europe contribute to the success of this volume. The contents of this volume will be useful for researchers, graduate students, and synthetic chemists at all levels in academia and industry. I would like to thank all the authors for their excellent contributions and forgive my “kind reminder” e-mails during the preparation process. I’m also grateful to Ms. Désirée Claus, Dr. Charlotte Hollingworth, and Ms. Alamelu Damodharan (Springer Nature) for their continuous assistance to complete this volume. Finally, I wish to take this chance to thank the understanding from my family (Qingyuan, Nuoyu, Nuolin, Nuodi-our dog) and the organization and strong support from my bosses (Prof. Pierre H. Dixneuf, Prof. Matthias Beller)! Thank you! Dalian, China March 2023

Xiao-Feng Wu

v

Contents

C–C Cross Couplings with Chromium Catalysis . . . . . . . . . . . . . . . . . . Yunqian Hou, Wen Xu, and Xiaoming Zeng

1

Mn-Catalyzed C–C Coupling Reactions . . . . . . . . . . . . . . . . . . . . . . . . . Yunhui Yang and Congyang Wang

17

Iron-Catalyzed Carbon–Carbon Coupling Reaction . . . . . . . . . . . . . . . . Qiao Zhang and Shou-Fei Zhu

53

Cobalt-Catalyzed C–C Coupling Reactions with Csp3 Electrophiles . . . . 113 Jie Li Co-catalyzed C–C Coupling Reactions with Csp2 Electrophiles . . . . . . . 145 Corinne Gosmini and Mengyu Gao Recent Advances in Nickel-Catalyzed C-C Cross-Coupling . . . . . . . . . . 181 Yangyang Li, Jiao Long, and Guoyin Yin Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Zhengkai Chen and Xiao-Feng Wu Cu-Catalyzed C–C Bond Formation with CO . . . . . . . . . . . . . . . . . . . . . 255 Pinku Tung and Neal P. Mankad Cu-Catalyzed C-C Coupling Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Manjunath S. Lokolkar, Yuvraj A. Kolekar, Prafull A. Jagtap, and Bhalchandra M. Bhanage Zinc-Catalyzed C-C Coupling Reactions . . . . . . . . . . . . . . . . . . . . . . . . . 385 C. M. A. Afsina, Thaipparambil Aneeja, and Gopinathan Anilkumar

vii

Top Organomet Chem (2023) 93: 1–16 https://doi.org/10.1007/3418_2023_91 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 5 May 2023

C–C Cross Couplings with Chromium Catalysis Yunqian Hou, Wen Xu, and Xiaoming Zeng

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Cr-Catalyzed Cross Couplings of C–O Bonds to Form C–C Bonds . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Cr-Catalyzed Kumada Coupling of C–O Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Cr-Catalyzed Cross-Electrophile-Coupling of C–O Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Cr-Catalyzed Cross Couplings of C–N Bonds to Form C–C Bonds . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Cr-Catalyzed Kumada Coupling of C–N Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Cr-Catalyzed Cross-Electrophile-Coupling of C–N Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Cr-Catalyzed Cross Couplings of C–Halide, C–S and C–P Bonds to Form C–C Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 3 3 6 9 9 10 12 14 14

Abstract Chromium is one of the earth-abundant transition metals. The use of chromium as low-cost alternative to precious metals for catalysis is of great synthetic and mechanistic interest. Progress in the development of cross-coupling reactions by chromium catalysis has been recently made, offering valuable strategies to forge C– C bonds under mild conditions. This chapter aims to highlight recent achievements in the development of strategies for constructing ubiquitous C–C bonds through chromium catalysis in recent years. It is organized by cross couplings with chemically inert C–heteroatom and C–H bonds in forming C–C bonds, mainly focusing on the discussion of plausible mechanisms for insight into design of robust catalysts, as well as the development of new coupling models and catalytic strategies. Keywords C–C bond formation · Chromium · Cross-coupling · Homogeneous catalysis

Y. Hou, W. Xu, and X. Zeng (✉) Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, China e-mail: [email protected]; [email protected]; [email protected]

2

Y. Hou et al.

1 Introduction Chromium is frequently found in the form of high-valent chromite in earth crust. It is one of the most abundant transition metals on earth. Despite that Cr serves as a low-cost alternative to precious metals, synthetic chemistry that was catalyzed by group 6 metal Cr remains underdeveloped. The catalytic activities of Cr in cross couplings are largely unexplored [1–7], although industrially important Phillips catalyst, composed by Cr as the reactive metal species, has been dominated in supply of almost 40% of the total world demand for high-density polyethylene [8]. Cross couplings have appeared as one of the most powerful tools in modern chemistry. Achievements in the field typically include the use of precious metal catalysts such as palladium [9], ruthenium [10], and rhodium [11] in the development of strategies to construct C–C bonds. Recently, the use of earth-abundant metals of nickel [12], cobalt [13], iron [14], even manganese [15] as catalysts has attracted broad interests of chemists, and remarkable advances have been achieved. However, probably because of low reactivity of many structurally defined Cr complexes, there still has limited success with respect to developing coupling strategies that are promoted by Cr catalysis. Cr in the high-valent state (≥ + 2) is usually employed as catalyst, which has been typified by Nozaki–Hiyama–Kishi (NHK) [16] and Takai–Utimoto reactions [17] by mechanistically involving process of one-electron oxidative addition (OA). Given that metal in a low-valent state favors the process of two-electron OA, studying the reactivity of Cr in a low-valent state provides an opportunity in the development of new cross coupling strategies. In pass years, synthetic chemistry which is enabled by low-valent Cr catalysis has been developed, and numerous cross couplings with chemically inert C–O, C–N, and C–X bonds have been disclosed in the formation of C–C bonds [7]. This chapter focuses on summarizing recent developments in cross couplings of C–C bonds by Cr catalysis and will discuss detailed mechanisms that are involved in these transformations. Fürstner and co-workers have reported the NHK reactions by using catalytic amounts of CrCl2 as precatalyst combined with manganese as reductant [18]. Although it showed a pioneering example of using Cr catalysis for coupling reaction, challenges in the catalytic cleavage of σ-bonds by Cr through process of two-electron OA are remained. Therefore, the major task in the development of cross couplings by Cr catalysis is to enhance the reactivity of Cr in the cleavage of σ-bonds by two-electron OA process and promote reductive elimination (RE) in the formation of new σ-bonds (Scheme 1). The auxiliary groups of substrates or external ligands by chelation with Cr may render the metal more electron richness, facilitating the catalytic cleavage of σ-bonds via process of two-electron OA, which may also stabilize reactive chromate intermediates for transmetalation and RE in affording C– C bonds.

C–C Cross Couplings with Chromium Catalysis

3

Scheme 1 General mechanism involved in the Cr-catalyzed cross couplings of electrophiles with nucleophiles

2 Cr-Catalyzed Cross Couplings of C–O Bonds to Form C–C Bonds 2.1

Cr-Catalyzed Kumada Coupling of C–O Bonds

Cross-coupling using arenol derivatives as partners has emerged as an ecological and atom-efficient strategy in forging C–C bonds, by the cleavage of unactivated C–O bonds. Because of their naturally abundant and nontoxic nature, the use of phenol derivatives as partners in the development of coupling methods has attracted broad interest of synthetic community compared with their halide counterparts. Although elegant catalytic strategies have been reported, the direct functionalization of arenol derivatives by the cleavage of unactivated aryl C–O bonds still remains a challenge [19]. Historically, the transformations of unactivated C–O bonds have been mainly dominated by catalysis of ruthenium [20–22] and nickel [23]. The oxophilicity of Cr may provide the opportunity for the development of cross couplings with arenol derivatives as partners by Cr catalysis. Unsolved issue is how to form reactive Cr species in responsibility for the catalytic coupling of arenol derivatives. Recent report by Zeng and co-workers suggested that commercially available and low-cost CrCl2 salts combined with organomagnesium could promote the Kumada coupling of unactivated C(aryl)–O bonds of arylmethyl ethers at room temperature (Scheme 2a) [24]. The imino group serving as auxiliary plays an important role in promoting the conversion, giving ortho-functionalized benzaldehyde derivatives after a hydrolysis. Commonly used directing groups such as carboxamides, amides, carbonyl, and pyridinyl showed no efficiency in promoting the Cr-catalyzed Kumada coupling of aryl C–O bonds. Inferior performance was observed when the use of Cr(acac)3 as precatalyst (Scheme 2b). Other first-row metal salts such as FeCl2, CoCl2, and Ni(COD)2 are inefficient in the coupling. The reactive Cr species might be formed in situ by the reduction of Cr precatalyst with Grignard reagent, which may be responsible for the Kumada coupling by the cleavage of unactivated C–O bonds [25].

4

Y. Hou et al.

Scheme 2 Cr-catalyzed Kumada coupling of unactivated aryl C–O bonds [24]

Because of the use of imino auxiliary, high regioselectivity is achieved in the coupling. Only the ortho-C–O bonds are functionalized in the formation of C–C bonds, allowing for keeping the aryl C–O bonds at other positions intact. Numerous functional groups, such as fluoride, chloride, trifluoromethyl, alkoxy, amino, and olefin, are tolerated by the reaction system [24]. Different from the reaction with acyclic C–O bonds, the cross-coupling by the cleavage of cyclo-C–O bond is able to keep synthetically useful hydroxyl group on the scaffold, offering a value-addition strategy to hydroxyl-tethered coupling products. The dual ring-opening/cross-coupling reactions by the use of bis(2,3-dihydrobenzofuran) and bis(chroman) occur smoothly, forming complex dihydroxyl-tethered dicarbaldehydes 7 via the cleavage of two ortho-cyclo-C–O bonds (Scheme 2c). Given that the bifunctionalization of aryl ortho-C–O bond and ortho’-C–H bonds of benzaldimines could rapidly increase the complexity of the molecules by introducing two substituents, the reactivity of Cr in the catalytic promoting the bifunctionalization of ortho-imino-containing aryl methyl ethers was studied. By exploring the effect of auxiliary on the Cr-catalyzed difunctionalization, good results are obtained by using N-benzyl-substituted imino as auxiliary combined with 2,3-dichlorobutane (DCB) as oxidant (Scheme 3a) [26]. Functionalities of methoxy, chloride, fluoride, and methylthio are compatibility with the reaction system. The

C–C Cross Couplings with Chromium Catalysis

5

Scheme 3 Cr-catalyzed sequential functionalization of ortho-C–O and ortho’-C–H bonds [26]

Scheme 4 Cross couplings by using organic halides as precursors and pyridyl as auxiliary [27, 28]

reactions with PhMgBr under Cr catalysis followed by the addition of another arylmagnesium bromide with 1,2-dichloropropane oxidant enable sequential incorporation of two aryls into the ortho position of benzaldehydes, by the functionalization of aryl ortho-C–O and ortho’-C–H bonds. The extension of this protocol in the sequential functionalization of cyclo-C–O and C–H bonds was successful, providing access to ring-opening and hydroxyl-tethered diarylated benzaldehydes (Scheme 3b). The sequential difunctionalization of ortho-C–O and ortho’-C–H bonds by Cr catalysis can be carried out on gram scale without loss of efficiency. In addition to the reaction with Grignard reagents, organic bromides can be used in the cross-coupling with aryl C–O bonds [27]. In the presence of 2.2 equivalents of magnesium, the cross-coupling with C–O bonds by 10 mol% of CrCl2 occurs smoothly, the formation of ortho-arylated benzaldehydes in good yields (Scheme

6

Y. Hou et al.

Scheme 5 Cr-catalyzed cross-coupling of alkenyl C–O bonds with alkyl Grignard reagents [29]

4a). The related aryl Grignard reagents may be formed in situ by reaction of organic bromides with Mg, which couple with C–O bond in forming C–C bonds by Cr catalysis. Variation of auxiliary groups in the Kumada coupling of C–O bonds by Cr catalysis was studied. It is suggested that pyridinyl serving as auxiliary could enhance the reactivity of Cr in the catalytic cleavage of C–O bonds, achieving the Kumada coupling with aryl Grignard reagents under mild conditions (Scheme 4b) [28]. Analogously, only the C(aryl)–OPy bonds are cleaved and coupled with Grignard reagent, providing access to materially interesting biaryl motifs. The corresponding 2-pyridinol was obtained after quenching the reaction by hydrolysis. Knochel and Li recently reported the Kumada coupling of alkenyl C–O bonds with Cr catalysis [29]. Alkenyl acetates are used as precursors in coupling with primary, secondary, and tertiary alkyl Grignard reagents, resulting in the formation of C(sp2)–C(sp3) bonds at ambient temperature (Scheme 5). This ligand-free Cr catalysis can be extended to the electrophilic alkenylation between alkylmagnesium halides and alkenyl acetates. The coupling by using stereodefined alkenyl acetates occurs in a stereoretentive fashion to afford C–C bonds. The use of the strategy in modifying pharmaceutically relevant estrone derivatives demonstrates its potential for molecular construction. Preliminary mechanistic studies indicated that the in situ formed low-valent Cr(I) might serve as catalytically active species involving in the catalysis. Which breaks the alkenyl C–O bond via the OA process, and forms C(sp2)C(sp3) bond through transmetalation and RE process.

2.2

Cr-Catalyzed Cross-Electrophile-Coupling of C–O Bonds

Since reactive nucleophilic reagents are usually prepared from the related electrophiles, cross couplings by the direct use of two electrophiles as partners feature the advantage of step-efficiency over reaction between electrophiles and nucleophiles. Breakthroughs have been achieved in the field in last 10 years. Illustrative examples

C–C Cross Couplings with Chromium Catalysis

7

H + Ar

OMe

Ar

PivO 24

1

3

O Naph N

N TS1

Cr O

N

Ar

Ar

Mg (3.5 equiv) THF, 40 oC, 48 h Then HCl (aq), rt, 0.5 h

t-Bu

N

CHO

CrCl2/dtbpy (10 mol%)

Nt-Bu

5.8

Me IN1

NtBu

N Cr

O 1/2 Mg

N

t-Bu

OMe

N t-Bu IN2

N Cr

N t-Bu IN3

1/2 Mg(OMe)2

DFT-identified pathway

O

Naph O t-Bu

21.2

TS2

N

N

OMe 1/2 Mg

NtBu 1/2 Mg(OPiv)2

N N Naph Cr OPiv N t-Bu IN5

N

TS3 23.7 t-Bu

t-Bu

IN4

Naph N

Cr Naph OPiv N t-Bu

N

N

Scheme 6 Cr-catalyzed chemoselective cross-electrophile-coupling between two unactivated and different aryl C–O bonds [31]

include the cross-electrophile-coupling of two organohalide partners by nickel catalysis or nickel/palladium co-catalysis [30]. However, probably because of the issue associated with the suppression of side homo-couplings when obtaining high chemoselectivity and the challenge in the cleavage of two unactivated bonds for their cross couplings, the use of two chemically inert electrophiles as partners in reductive cross-coupling has been less developed. The combination of low-cost CrCl2 salt, 4,4′-di-tert-butyl-2,2′-dipyridyl (dtbpy) as ligand, and magnesium reductant shows high reactivity in promoting the reductive cross-coupling of aryl methyl ether derivatives with aryl esters, by the cleavage of two unactivated and different aryl C–O bonds in achieving cross-electrophile coupling under mild conditions (Scheme 6) [31]. The reaction provides a value-addition strategy in accessing biaryl motifs by the formation of C–C bonds. The deuterium experiments suggest that the C–O bond of phenyl methyl ether could be deuterated after quenching the reaction with the in situ formed reactive Cr by D2O. In contrast, the aryl C–O bond of pivalate is not deuterated by similar operation. These results indicate that Cr might prefer to the breakage of C–O bonds of phenyl methyl ether in the chelation help of dtbpy ligand and imino auxiliary. Theoretical studies by density functional theory (DFT) calculations suggest that the cleavage of ether C–O bond by Cr overcomes a low activation barrier (5.8 kcal mol-1), affording cyclochromate intermediate IN5. Which is reduced by Mg and ligation with naphthyl pivalate by the breakage of ester C–O bond in the second OA. Relatively high energy barrier (23.7 kcal mol-1) for the formation of C–C bond by RE is suggested by DFT calculations. It may serve as the rate-determining step involving in the

8

Y. Hou et al.

O2Ct-Bu

CrCl2/dnbpy (10 mol%)

t-BuN

+

F

25

27 (87%)

26

Mechanistic studies:

26

CHO

Mg (1.5 equiv) THF, 40 oC, 24 h then HCl (aq)

t-Bu

H dnbpy (20 mol%)

CrCl2 (20 mol%) Mg (1.5 equiv) THF, 40 oC, 24 h

N Cr

Non

THF N

oC,

THF, 40 1h Filtration Washing with hexane

N Non Detected by HRMS analysis

CHO CHO D

+

25 (20 mol%) THF, 40 oC, 12 h then D2O

28 (47%) D

27 (35%)

29 (nd)

Scheme 7 Cr-catalyzed cross-coupling of unactivated aryl C–O and C–F bonds [32]

cross-electrophile-coupling. In addition to coupling with acyclic ether C–O bonds, the cyclo-C(aryl)-O bonds of 2,3-dihydrobenzofuran and 1,3-benzodioxole derivatives couple with ester C–O bond smoothly, providing a strategy in the construction of hydroxyl-tethered and carbaldehyde-containing biaryl motifs. Using Cr catalysis, the cross-electrophile coupling of fluoroarenes with aryl pivalates is achieved under mild conditions (Scheme 7) [32]. It demonstrates a pioneering example of reductive cross-coupling between unactivated C–F and C– O bonds, allowing for forming C–C bonds in obtaining high chemoselectivity. The ligand of 4,4′-dinonyl-2,2′-bipyridyl (dnbpy) plays an important role in enhancing the reactivity of Cr in the orthogonal coupling. Mechanistic experiments suggested that the reactive Cr initially breaks unactivated C–F bonds to form cyclochromate species, and followed by reducing with Mg in affording chromate(I) which can be detected by the analysis of the residue with high-resolution mass spectroscopy (HRMS). Further reaction with aryl pivalate furnishes the desired biaryl products. Quenching the reaction with D2O, the deuterated benzaldehyde compound was formed without detection of related deuterated naphthalene. Compared with the process of RE, a sluggishly OA for the cleavage of ester C(aryl)–O bond by Cr may be considered in the catalytic cycle.

C–C Cross Couplings with Chromium Catalysis

9

3 Cr-Catalyzed Cross Couplings of C–N Bonds to Form C–C Bonds 3.1

Cr-Catalyzed Kumada Coupling of C–N Bonds

Aromatic C–N bonds are centrally important and common motifs in organic molecules. The cleavage of unactivated aryl C–N bonds is of significant synthetic and mechanistic interest [33]. By using 10 mol% of CrCl2 as precatalyst and tert-butylsubstituted imino as auxiliary, the directing group, the ortho-C(aryl)–N bond is cleaved and efficiently couples with aryl Grignard reagents, leading to the formation of C–C bonds at room temperature (Scheme 8) [34]. The Kumada coupling features

H

H

O

Nt-Bu NMe2

Ar

+

CrCl2 (10 mol%)

ArMgBr 9

29

Ar 3

CrCl2 + 2ArMgX

CHO

two-electron reduction

Ar

LnCr0

donation

29

(quintet state)

THF

t-Bu

t-Bu

Cr Ph

Cr

Cr

NMe2

THF

N

N

THF

N H

Ar

THF, rt, 15 h then HCl (aq)

THF

N

IN6

Cr

IN10 THF

t-Bu

THF

t-Bu

Mechanism identified by DFT calculations

THF

N

H

Cr Ph

N

NMe2

t-Bu

t-Bu

THF

N

H

THF

N

THF THF Cr

Cr

NMe2

Ph IN9

ligation

THF Cr

TS4

TS5

H

H

t-Bu

H

THF

N

IN7

THF Cr NMe2

Me2NMgX(THF)

Ph Mg Br IN8

ArMgX

THF

Scheme 8 Cr-catalyzed Kumada coupling with unactivated C(aryl)–N bonds [34]

10

Y. Hou et al.

high regioselectivity, and only the ortho-C(aryl)–N bonds are arylated in keeping the C(aryl)–N bonds at other positions intact. The kinetic studies suggested an inverse half-order in ortho-imino-substituted aniline concentrations, first-order in phenyl Grignard reagent concentrations, and half-order in CrCl2 concentrations. The existence of an off-cycle equilibrium between active Cr complex and inactive species, mostly including a reversible coordination of ortho-imino-bearing aniline with the complex of [Cr(aniline)(THF)2] by serving as bidentate ligand to give inactive and off-cycle complex such as [Cr(aniline)2(THF)2], might be considered in the catalysis. DFT calculations suggested that the active Cr(0) complex IN6, ligation by imino and amino scaffolds and two THF molecules, adopts a tetragonal pyramid model with placing the amino at the axial position (Scheme 8) [34]. Note that the imino in IN6 serves as a π-acceptor rather than a σ-donor to coordinate with the quintet Cr (0) because the empty π*(C=N) orbital can accept and stabilize the paired d electrons of high-spin chromium. The cleavage of C(aryl)–N bond by Cr has a relatively low activation barrier of 13.6 kcal mol-1 via the three-membered ring transition state TS4. Wherein two orbital interactions may dominate the breakage of C(aryl)–N bond with Cr, including the donation of two paired electrons in the dxy(Cr) orbital of Cr to the σ-antibonding orbital of C(aryl)-N bond, and the dative interaction of the lone pair of nitrogen to the Cr(0). After the cleavage of C(aryl)–N bond, the cyclochromate complex IN7 undergoes transmetalation with aryl Grignard in dissociation of amido scaffold, and followed by RE through the transition state TS5 in the formation of C(aryl)–C(aryl) bond. The catalytic functionalization of amides by the cleavage of unactivated C–N bonds provides a valuable strategy in forging C–C bonds. Recent development suggested that CrCl3 is an effective precatalyst combined with chlorotrimethylsilane (TMSCl) in promoting the coupling of N-tert-butyl-substituted amides with arylmagnesium bromide (Scheme 9) [35]. Mechanistic studies indicate that TMSCl plays important roles in the transformation, which reacts with the in situ formed reactive Cr and aryl Grignard in giving Cr(aryl)(TMS) species. Using Grignard reagent as base, the secondary amide can be deprotonated and reacts with TMSCl in affording related benzimidate intermediate. Subsequent addition of Cr–Si bond to C=N bond may occur in the regioselective fashion, and followed by the process of RE to form C–C bond and regenerate reactive Cr. The final ketone compound is given upon a hydrolysis.

3.2

Cr-Catalyzed Cross-Electrophile-Coupling of C–N Bonds

Similar to the reductive cross-coupling of two different C(aryl)–O bonds by Cr catalysis, the ortho-C(aryl)–N bonds of benzaldimines smoothly couple with unactivated C(aryl)–O bonds of aryl esters, leading to forming C–C bonds at ambient temperature (Scheme 10) [36]. It was disclosed that the ligand of bipyridine derivative is particularly important in enhancement of the reactivity of Cr in the

C–C Cross Couplings with Chromium Catalysis

11

O

O NH

Ar

CrCl3 (10 mol%)

ArMgBr

+

9

30

TMS

O Ar

Ar 31

CrCl3

O Ph Ph N Ph TMS

hydrolysis

Ar

TMSCl, THF, rt, 12 h then NH4Cl/H2O

t-Bu

PhMgBr/THF LnCr

PhMgBr TMSCl

Ar TMS Ph Ph

O N Cr Ln TMS

IN13

MgBrCl

Proposed mechanism

Ph

LnCr(Ph)(TMS) IN11 TMS

O

Ph N Cr Ln Ph TMS IN12

O

Ph

Ph

TMS N

Ph

Scheme 9 Cr-catalyzed Kumada coupling of amides in forming C–C bonds [35]

Scheme 10 Cr-catalyzed cross-electrophile-coupling between unactivated C(aryl)–O and C(aryl)– N bonds [36]

coupling reaction. Good result was obtained when electron-rich dtbpy ligand was used. Other earth-abundant metal catalysts such as FeCl2, CoCl2, and NiCl2(PPh3)2 showed no efficiency in promoting the transformation. The deuterium experiments indicate a preferential cleavage of ortho-C(aryl)–N bond by Cr, giving cyclochromate that is subsequently reduced by Mg to afford reactive Cr species in responsibility to break C(aryl)–O bond. Given that the ortho-C(aryl)-N and C(aryl)-H bonds are adjacent to the imino auxiliary, the sequential functionalizations of these two bonds have been achieved

12

Y. Hou et al.

with Cr catalysis. The reductive coupling of C(aryl)–N and C(aryl)–O bonds can be carried out initially in giving biaryl aldehyde under standard conditions. After undergoing a condensation in incorporating benzyl-substituted benzaldimine, it is followed with an oxidative coupling of ortho-C(aryl)–H bond with Grignard reagent to form C–C bond. This protocol provides a valuable strategy in the buildup of 2,6-disubstituted benzaldehyde derivative.

4 Cr-Catalyzed Cross Couplings of C–Halide, C–S and C–P Bonds to Form C–C Bonds Group of Knochel performed the program studying the ability of catalytical amount of simple Cr salts promoting the Kumada coupling of carbon–halide bonds [37]. Chloropyridines and analogs are chosen to react with aryl Grignard reagents (Scheme 11a). Using 3 mol% of CrCl2 at room temperature for 15 min or 2 h, the C2-arylated pyridine derivatives 33 are obtained in good yields. In addition, 2-chlorobenzophenone is a suitable partner in the Kumada coupling with aryl Grignard, tolerancing reactive carbonyl in affording the related polyfunctionalized ketones (35). The authors suggested that only the chloro substituents at the C2 position of pyridine or quinoline derivatives are regioselective functionalized by Cr catalysis. As a consequence, it provides a value-addition strategy in the construction of chloride-containing arylated N-heteroarene motifs [38]. Variation by the use of aliphatic Grignard reagents in the Kumada coupling was studied [39]. The cross couplings with 2-halo-substituted quinolines occur smoothly at room temperature, furnishing the alkylated derivatives 37 in high yields within 15 min (Scheme 11b). (a) Cr-catalyzed Kumada coupling with aryl Grignard reagents (2013) ArMgX·LiCl CrCl2 (3 mol%)

FG N

X

(d) Proposed mechanism 2 CrCl2

FG

THF, rt, 15 min–2 h

Ar

N

32

Ar–MgX

33 O Ph

Ar

Alkyl

Ar

CrIIX

(b) Cr-catalyzed Kumada coupling with alkyl Grignard reagents (2016) Alkyl–MgX CrCl3·3THF (3 mol%) N

X

Ar

R

THF, rt, 15 min

N 37

36

Alkyl

Alkyl

One-electron OA

Two-electron RE

35

R

2 CrIX

Ph

THF, rt, 15 min–2 h

Cl 34

Ar–Ar O

ArMgX·LiCl CrCl2 (3 mol%)

X

CrII

IN14

IN15

(c) Cr-catalyzed Kumada coupling with iodoalkanes (2019) I R

ArMgX CrCl2 (10 mol%) THF, 0–23 °C, 16 h

38

Ar

Transmetalation MgX2

R

CrII Alkyl

Alkyl

Ar–MgX

39

Scheme 11 Cr-catalyzed Kumada coupling using organic halides as partners [29, 37–39]

I

C–C Cross Couplings with Chromium Catalysis

13

Scheme 12 Cr-catalyzed Kumada couplings of C(aryl)–S and C(aryl)–P bonds [40, 41]

The diastereoselective cross-coupling of aryl Grignard reagents with cyclohexyl iodides has been reported by Knochel and Li with metal-free Cr catalysis (Scheme 11c) [29]. It was noteworthy that the coupling reaction takes place in the diastereoselective fashion, giving arylated cyclohexanes in usually surpassing 90: 10 of d.r. value. Functionalities of fluoride, alkoxy, hydroxyl, amino, and cyano are compatibility with the reaction system. Because cyclized product of cyclopentane derivative is formed by reaction with 6-iodo-1-hexene, reaction pathway involving process of single electron transfer (SET) may be considered. The reaction initiates with the in situ formed Cr(I) species, which reacts with iodoalkane by SET process to afford alkylated chromate species IN14 (Scheme 11d). Subsequently a transmetalation and RE is carried out in the formation of C(sp2)–C(sp3) bond, along with the regeneration of reactive Cr(I) catalyst. In addition to common C–halide, C–O and C–N bonds, recent studies suggested that unactivated C(aryl)–S bonds could be cleaved by reactive Cr in coupling with aryl Grignard reagents (Scheme 12a) [40]. The reaction forms C(sp2)–C(sp2) bonds in the chelation with the help of ortho-imino auxiliary. The related cyclochromate intermediate that is formed by the cleavage of C(aryl)–S bond can be detected by HRMS analysis. The catalytic cleavage of unactivated C(aryl)–P bonds of aryl phosphine derivatives by metals remains a challenge in organic chemistry. In chelation assistance by ortho-imino auxiliary, the in situ formed low-valent Cr shows interesting reactivity in breaking C(aryl)–P bonds, achieving the coupling with aryl Grignard reagents and alkyl bromides under mild conditions (Scheme 12b) [41]. In the presence of 1,2-dichloropropane (DCP) as oxidant, the ortho-C(aryl)–P and ortho’-C(aryl)–H bonds can be synchronously arylated, providing access to difunctionalized terphenyl

14

Y. Hou et al.

carbaldehyde product 10a in good yield. Note that the leaving diphenylphosphino functionality couples with alkyl bromide in the formation of alkylated diphenylphosphine motif.

5 Conclusions As demonstrated in this chapter, great progress in the development of Cr-catalyzed C–C cross coupling has been made in pass years. Simple and low-cost Cr salts such as CrCl2 and CrCl3 are usually used as effective precatalysts in promoting the couplings, therefore offering operationally simple and cost-effective strategies in the construction of appealing structural motifs by forming C–C bonds. Although here are remarkable achievements in the arena, there still have several key challenges that are required for addressing for future development. For instance, the isolation and characterization of catalytically active Cr species are urgent tasks for understanding detailed mechanism involving in the coupling. In mostly couplings, reductants such as Grignard reagents or metallic magnesium are used to reduce Cr salts in giving reactive low-valent Cr species in situ. The development of robust structurally defined low-valent Cr complexes with ancillary ligands is of direction for future endeavors. Compared with commonly used palladium and nickel catalysis in cross couplings of C–C bonds, the sorts of couplings by Cr catalysis are still limited. Expanding the scopes of Cr-catalyzed cross couplings in the construction of other σ-bonds such as centrally important C–N and C–O bonds is necessary for diversification of Cr catalysis. Finally, the development of strategies in Cr-catalyzed cross couplings of C–C bonds that have potential for industrial applications is important. We hope that this chapter could attract more attentions from the synthetic community in contributing to the field. Acknowledgments We thank the National Natural Science Foundation of China (Nos. 22125107, 21971168 and 21572175) for financial support. We also thank the authors whose names are listed in the references for their contributions in the field. Notes The author declares no competing financial interest.

References 1. Fürstner A, Shi N (1996) J Am Chem Soc 118:2533 2. Agapie T (2011) Coord Chem Rev 255:861 3. Zeng X, Cong X (2015) Org Chem Front 2:69 4. Zeng X (2020) Synlett 31:205 5. Fürstner A (1999) Chem Rev 99:991 6. Li J, Knochel P (2019) Synthesis 51:2100 7. Cong X, Zeng X (2021) Acc Chem Res 54:2014

C–C Cross Couplings with Chromium Catalysis

15

8. Barzan C, Piovano A, Braglia L, Martino GA, Lamberti C, Bordiga S, Groppo E (2017) J Am Chem Soc 139:17064 9. Seechurn CCCJ, Kitching MO, Colacot TJ, Snieckus V (2012) Angew Chem Int Ed 51:5062 10. Trost BM, Toste FD, Pinkerton AB (2001) Chem Rev 101:2067 11. Song G, Li X (2015) Acc Chem Res 48:1007 12. Diccianni J, Lin Q, Diao T (2020) Acc Chem Res 53:906 13. Sun C-L, Li B-J, Shi Z-J (2011) Chem Rev 111:1293 14. Gao K, Yoshikai N (2014) Acc Chem Res 47:1208 15. Hu Y, Zhou B, Wang C (2018) Acc Chem Res 51:816 16. Okude Y, Hirano S, Hiyama T, Nozaki H (1977) J Am Chem Soc 99:3179 17. Takai K, Kataoka Y, Okazoe T, Utimoto K (1987) Tetrahedron Lett 28:1443 18. Fürstner A, Shi N (1996) J Am Chem Soc 118:12349 19. Tobisu M, Chatani N (2015) Acc Chem Res 48:1717 20. Kakiuchi F, Usui M, Ueno S, Chatani N, Murai S (2004) J Am Chem Soc 126:2706 21. Ueno S, Mizushima E, Chatani N, Kakiuchi F (2006) J Am Chem Soc 128:16516 22. Zhao Y, Snieckus V (2014) J Am Chem Soc 136:11224 23. Cornella J, Zarate C, Martin R (2014) Chem Soc Rev 43:8081 24. Cong X, Tang H, Zeng X (2015) J Am Chem Soc 137:14367 25. Albahily K, Shaikh Y, Sebastiao E, Gambarotta S, Korobkov I, Gorelsky SI (2011) J Am Chem Soc 133:6388 26. Rong Z, Luo M, Zeng X (2019) Org Lett 21:6869 27. Tang J, Luo M, Zeng X (2017) Synlett 28:2577 28. Fan F, Tang J, Luo M, Zeng X (2018) J Org Chem 83:13549 29. Li J, Ren Q, Cheng X, Karaghiosoff K, Knochel P (2019) J Am Chem Soc 141:18127 30. Weix DJ (2015) Acc Chem Res 48:1767 31. Tang J, Liu LL, Yang S, Cong X, Luo M, Zeng X (2020) J Am Chem Soc 142:7715 32. Fan F, Zhao L, Luo M, Zeng X (2022) Organometallics 41:561 33. Ouyang K, Hao W, Zhang W-X, Xi Z (2015) Chem Rev 115:12045 34. Cong X, Fan F, Ma P, Luo M, Chen H, Zeng X (2017) J Am Chem Soc 139:15182 35. Chen C, Liu P, Luo M, Zeng X (2018) ACS Catal 8:5864 36. Tang J, Fan F, Cong X, Zhao L, Luo M, Zeng X (2020) J Am Chem Soc 142:12834 37. Steib AK, Kuzmina OM, Fernandez S, Flubacher D, Knochel P (2013) J Am Chem Soc 135: 15346 38. Steib AK, Kuzmina OM, Fernandez S, Malhotra S, Knochel P (2015) Chem A Eur J 21:1961 39. Bellan AB, Kuzmina OM, Vetsova VA, Knochel P (2016) Synthesis 49:188 40. Zeng H, Yang S, Li C, Fan F, Ling L, Luo M, Zeng X (2022) Chem Commun 58:7094 41. Tang J, Ling L, Yuan S, Luo M, Zeng X (2022) Org Lett 24:1581

Top Organomet Chem (2023) 93: 17–52 https://doi.org/10.1007/3418_2023_92 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 5 May 2023

Mn-Catalyzed C–C Coupling Reactions Yunhui Yang and Congyang Wang

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 C-H Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Addition to Polar Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Addition to Nonpolar Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Addition to Mn=C Bond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Substitutive C-H Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Hydrocarbofunctionalization of Unsaturated C–C Bond Without C-H Activation . . . . . . . . . 4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18 18 18 24 41 42 46 50 50

Abstract Manganese-catalyzed C–C bond coupling reactions are such an attractive alternative tool for the synthesis of organic functional molecules that they are gained considerable attention in the last decade. This chapter highlights selected examples of the recent advances in the catalytic functionalization of inert Csp2–H bonds through organometallic C–H activation. Reactions involving the hydrocarbofunctionalization of unsaturated C–C bonds leading to C–C bonds formation are also briefly addressed herein. Keywords C–C bond formation · C–H activation · C–Mn bond · Catalysis · Hydrocarbofunctionalization · Manganese

Y. Yang and C. Wang (✉) Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China e-mail: [email protected]; [email protected]

18

Y. Yang and C. Wang

1 Introduction Transition metal catalyzed C–C bond coupling reactions, especially that utilize inert C–H bonds as latent functional groups, have been considered as a powerful tool for the synthesis of organic molecules with notable applications toward pharmaceutical industries, material science, and biochemistry areas, among others. Thus far, the noble transition metal catalysts, such as Pd, Ir, Rh, Ru, dominate the stage of C-H functionalization, yet their cost-intensive and toxic characteristics are averse to the sustainable development. Given the cost-effective and non-toxic nature of earthabundant manganese, the development of catalysts based on manganese for the construction of C–C bonds has gained considerable attention as an environmentally benign and economically attractive alternative. In this regard, the past decade has witnessed significant achievements of organic synthesis based on manganese catalysis, such as C-H activation, hydroarylation, hydroalkenylation, cross-coupling, hydrogen-borrowing, and dehydrogenative coupling reactions, and so on. The manganese-catalyzed Kumada/Stille-type cross-couplings, manganese-mediated radical processes, and manganese-catalyzed hydrogen-borrowing/dehydrogenative coupling reactions usually do not involve an organometallic C-H activation step and will not be considered in this chapter. Numbers of excellent reviews have focused on reporting relevant transformations [1–5]. This chapter aims to cover the progress of manganese-catalyzed C-C coupling reactions via C-H activation, as well as the new occurrence of hydrocarbofunctionalization of unsaturated C–C bond, over the last 10 years with the literature leading up to the June 2022.

2 C-H Activation 2.1

Addition to Polar Bonds

In this field, pioneering work was disclosed by Takai, Kuninobu, and coworkers, who performed a directed addition of C–H bond of 1-methyl-2-phenyl-1H imidazole into C=O bond of aldehydes with the assistance of 2.0 equivalents of triethylsilane under manganese catalysis regime [6]. Afterwards, Wang group developed a dual activation strategy to perform such a Grignard-type nucleophilic C-H addition reaction with a wide substrate scope in an excellent regio- and stereoselective manner (Scheme 1) [7]. Therein, the C-H activation is triggered by manganese catalyst and the aldehyde or nitrile is activated by a Lewis acid, i.e. zinc salt. Mechanistically, the catalytic precursor 1-Mn-1, which generates from the reaction between pentacarbonyl manganese bromide and dimethylzinc, reacts with arene substrate yielding five-membered manganacycle 1-Mn-2 and releasing methane simultaneously. The activated polar unsaturated bonds of aldehydes or nitriles undergo a sequential coordination and migratory insertion into Mn–C bond of 1-Mn-2 to form seven-membered manganacycle 1-Mn-3, which further transforms into 1-Mn-4 via ligand metathesis. Ligand exchange of 1-Mn-4 species with another

Mn-Catalyzed C–C Coupling Reactions

19

Scheme 1 Nucleophilic C-H addition to aldehydes and nitriles

molecule of arene generates 1-Mn-5 and 1-Zn-1. Intramolecular C-H activation of 1-Mn-5 regenerates 1-Mn-2, on the one hand; on the other hand, 1-Zn-1 is converted into the alcohols 1–3 or ketones 1–5 upon hydrolysis. Similar research on generating benzylic alcohols through addition of C2–H bond of indoles into aldehydes and ketones was reported by Ackermann and coworkers [8]. This protocol proceeds with additive-free manganese catalysis and the carbonyl compounds are limited to electron-deficient ones. In addition, aldimines have been proven to be a suitable substrate under this catalysis regime to give addition products with moderate to good yields. Mechanistic studies show a similar catalytic cycle involving a sequence of cyclomanganation of 1–6, coordination/insertion of C=O bond of 1–7, and protonative demetalation of a seven-membered manganacycle species (Scheme 2a). A manganese-catalyzed and borane-mediated access to isobenzofuranones via C–H bond activation has been documented by the group of Kuninobu [9]. As proposed, the oxirane 1–9 is isomerized to an aldehyde with the assistance of triphenylborane before participating into the catalytic cycle (Scheme

20

Y. Yang and C. Wang (a) Ackermann, 2016 R1

X

+

N 2-py(m) 1-6

R1

Mn2(CO)10 (5-10 mol%)

R2

R3

N

Dioxane or Toluene or Et2O o 100 C, 16-24 h

2-py(m) 1-8 X = O, 34 examples 61%-95% yield X = NTs, 5 examples 55%-93% yield

1-7

(R2, R3 = CO2Et, CF3, ...)

(b) Kuninobu, 2016 O OMe +

R1

XH R2 R3

O O R2 R3 1-9 BPh3

Mn2(CO)10 (5 mol%) BPh3 (1.0 equiv.) DCE/Hexane o 150 C, 24 h

R1 O

R2

R1

O

R3 R2 1-10 29 examples 23%-84% yield

H (c) Glorius, 2018

MnBr(CO)5 (10 mol%) NaOAc (10 mol%) o

Dioxane, 80 C, 5.5 h DG Ar

+ (CH2O)n 1-11

DG Ar

OH

1-12 18 examples 15%-99% yield

1) MnBr(CO)5 (10 mol%) NaOAc (10 mol%) Dioxane, 80 oC, 5.5 h . 2) Fe(NO3)3 9H2O/TEMPO/NaCl (15 mol%), open air, 6 h

DG Ar CHO 1-13 12 examples NR to 84% yield

Scheme 2 C-H addition to C=O bond of various carbonyl sources

2b). Glorius group reported a C-H hydroxymethylation using paraformaldehyde as the C1 source [10]. The C=O bond of 1–11 inserts into the Mn–C bond of manganacycle analog of 1-Mn-2 to form alcohol 1–12, which also can be further oxidized to the C-H formylation products 1–13 in the air with iron catalysis in one pot (Scheme 2c). Isocyanate group, which contains two unsaturated bonds, is a highly reactive moiety and has been used in manganese-catalyzed C2-H aminocarbonylation of indoles/pyrroles by Ackermann group in 2015 [11]. As proposed, the unsaturated C=N bond inserts into Mn–C bond of the five-membered manganacycle species to form amide derivatives. This reaction proceeds well with either aryl or alkyl isocyanates with excellent regioselectivity. What’s more, the authors demonstrated the synthetic utility by providing examples of traceless removal of the pyridyl directing group (Scheme 3a). A related reaction reported by Wang group was [3 + 2] cyclization of aromatic ketones and aryl or alkyl isocyanates, which generates 3-alkylidene phthalimidines by employing a trio of Me2Zn/AlCl3/AgOTf as essential additives [12]. Mechanistically, the seven-membered manganacycle 1-Mn-6 undergoes intramolecular N-nucleophilic attack on the directing group, carbonyl

Mn-Catalyzed C–C Coupling Reactions

21

Scheme 3 C-H addition to C=N bond of isocyanates

group of ketones, to deliver 1-Mn-7, which releases the final product 1–14 via elimination process (Scheme 3b). Ketenimines, which contain similar cumulative unsaturated bond, have been employed in the manganese-catalyzed C-H enaminylation reaction [13, 14]. Analogous seven-membered manganacycle is formed through migratory insertion of the C=N bond of ketenimines. Interestingly, an intramolecular nucleophilic aromatic substitution (SNAr) occurs with aryl-substituted ketenimines to deliver 1-(pyrimidin2-yl)-1H-indoles 1–15 [13]. While triaryl-substituted ketenimines 1–16 are formed without the migration of directing group (DG) in the cases of ester-substituted ketenimines (Scheme 4) [13, 14]. Another kind of compound containing C=N bond is imine, which has been used for the C-H aminomethylation under manganese catalysis (Scheme 5) [8, 15, 16]. Synthetically useful heteroarenes [8, 15] and aromatic ketones [16] react with

22

Y. Yang and C. Wang

 Scheme 4 C-H addition to C=N bond of ketenimines

Scheme 5 C-H addition to C=N bond of imines

Mn-Catalyzed C–C Coupling Reactions

23

Scheme 6 C-H cyanation reactions of indole derivatives

various N-sulfonyl aldimines efficiently to give the corresponding aromatic C-H addition products 1–17 and 1–18. Noting that the acetophenone derivatives, bearing α-H, are successfully converted into the desired product and the classic Mannich reaction is circumvented completely in the presence of catalytic MnBr(CO)5 [16]. In addition, cyclization and three-component reaction take place smoothly under different reaction conditions to give exo-olefinic isoindolines 1–19 and methylated isoindolines 1–20, respectively. A study by the Ackermann group probed into the C-H cyanation of electron-rich heteroarenes with N-cyano-N-phenyl-p-toluenesulfonamide (NCTS) under a synergistic heterobimetallic catalysis (Scheme 6a) [17]. The mechanism based on experimental and computational insights is proposed to proceed through a facile C-H activation and a rate-determining C–C bond formation step. Notably, the key C-C formation is facilitated by the synergistic effect of the heterobimetallic catalysis, which decreases the energies of the cyclomanganated transition state and sevenmembered intermediate. Similar protocol has been demonstrated by the Bao group, using N-cyano-N-(4-methoxy)phenyl-p-toluenesulfonamide for the C-H cyanation of arenes under a synergy of manganese/base catalysis regime (Scheme 6b) [18].

24

2.2

Y. Yang and C. Wang

Addition to Nonpolar Bonds

For the addition of inert C–H bond to unpolarized C–C multiple bonds, a number of significant reactions of (hetero)arenes with various reaction partners bearing C  C and C=C bonds, such as alkynes, alkenes, and allenes, have been disclosed to date. In 2013, Wang and coworkers pioneered the manganese/base co-catalyzed aromatic C–H bond alkenylation reaction with alkynes [19]. Anti-Markovnikov addition of Csp2-H to various terminal alkynes produces E-alkenylated products in the presence of catalytic amounts of bromopentacarbonylmanganese and dicyclohexylamine. The presence of dicyclohexylamine facilitates the C–H bond cleavage, whose barrier is 12.5 kcal/mol, to yield the manganacycle 1-Mn-8 via base-assisted deprotonation process. Subsequent coordination and migratory insertion of alkyne deliver the seven-membered manganacycle 1-Mn-9, which has been confirmed experimentally by Fairlamb, Lynam, and coworkers through a similar transformation [20]. A second alkyne coordinates with 1-Mn-9 to further deliver 1-Mn-10 via ligand-to-ligand H-transfer (LLHT), followed by ligand exchange and σ-bond metathesis to close the catalytic cycle (Scheme 7). Afterwards, extensions of the manganese/base synergetic catalysis were achieved by the same group for the access to alkenylated aromatic nitriles [21] and amidines [22] (Scheme 8a, b). These C-H addition reactions proceed well with both terminal and internal alkynes, yielding the desired products with excellent monoselectivity and E-stereoselectivity. In addition, many other research groups have developed related manganese-catalyzed C-H alkenylation reactions of (hetero)arenes with assistance of catalytic or subcatalytic amounts of bases. In 2018, Rueping et al. described a regioselective C-H alkenylation of indoles with internal as well as terminal alkynes in the presence of 50 mol% of sodium acetate (Scheme 8c) [23]. Cao and Xu et al. reported the direct C6-H alkenylation of 2-pyridones with various alkynes [24]. Of note, methyl tert-butyl ether (MTBE) and dichloromethane (DCM) are proved to be optimal reaction medium for the terminal and internal alkynes, respectively (Scheme 8d). Glorius et al. further extended the scope of the alkenylation reagents to 1,3-diynes to deliver 1,3-enynes derivatives (Scheme 8e) [25]. Application of this strategy was reported by Ackermann at el. toward late-stage diversification of the structurally complex peptides (Scheme 8f) [26]. This methodology features excellent functional group tolerance and chemo-position-selectivity and provides access to cyclic peptides conveniently. An analogous methodology was set out by Li and coworkers in 2015, who utilized catalytic amount of acid as selectivity controller of C-H alkenylation and [2 + 2 + 2] cyclization (Scheme 9) [27]. Mechanistically, the cyclomanganation and migration insertion processes are similar to that of previous report [19]. However, H-transfer process occurs in the presence of benzoic acid to further deliver C2-alkenylated indoles (1–26). In the absence of acid, the manganese species 1-Mn-11 is generated through coordination-insertion of a second alkyne followed by oxidative addition of C3–H bond of substrate 1–24. Then 1-Mn-11 converts to carbazole derivatives (1–27) and releases manganese hydride species [HMn

Mn-Catalyzed C–C Coupling Reactions

25

Scheme 7 C-H addition to C  C bond of terminal alkynes

(CO)4]. Moreover, hydrogen and hydrogenation product of alkyne, which originate from the reaction of HMn(CO)4 with substrate 1–24 and 1–25, respectively, have been detected. Incidentally, this transformation proceeds efficiently with a quite similar catalysis regime in mechanochemical manner [28]. In 2017, Ackermann and coworkers developed a analogous chemoselective C-H alkenylation protocol employing a synergistic Brønsted acid/manganese catalysis regime [29]. Propargylic alkynes are converted into hydroarylated alkenes (1–28 and 1–29) exclusively in the presence of 20 mol% of HOAc, and the key

26

Y. Yang and C. Wang

Scheme 8 C-H addition to C  C bond with the assistance of bases

protodemetalation of intermediate 1-Mn-12 proceeds through an intramolecular proton transfer process (Scheme 10a). In contrast, allene (1–30) is obtained in 63% yield through β-oxygen-elimination in the absence of carboxylic acids. The synergistic catalysis regime plays an essential role for the unique chemoselectivity. Noting that this reaction is able to proceed in continuous flow more efficiently under an atmosphere of ambient air. Further synthetic application for the access to fluorogenic probes has been documented by the same group, and the addition of (1-Ad)CO2H is proposed to facilitate the protodemetalation via carboxylate-assisted C-H activation (Scheme 10b) [30]. The reactivity of alkynes in manganese catalysis regime is not restricted to simple addition reactions, but the annulation as well as domino reactions are also feasible. Thus, Wang et al. reported the first dehydrogenative [4 + 2] annulation of N-H imines and alkynes catalyzed by manganese (Scheme 11) [31]. Biologically meaningful isoquinolines are easily prepared obviating the necessary for any oxidants, external ligands or additives. The proposed mechanism proceeds through C-H manganation, alkyne coordination and insertion to furnish the intermediate 1-Mn13. Then, intramolecular cyclization occurs to form a fused manganacycle 1-Mn-14, which undergoes β-H elimination to deliver coordination-unsaturated Mn-H species

Mn-Catalyzed C–C Coupling Reactions

Scheme 9 Dichotomy of manganese catalysis controlled by acid

Scheme 10 C-H addition to C  C bond under synergistic manganese/acid catalysis

27

28

Y. Yang and C. Wang

Scheme 11 [4 + 2] Annulation of N-H imines and alkynes

(1-Mn-15). Coordination of the substrate 1–31 to Mn-H species followed by C-H activation regenerating the five-membered manganacycle and releasing H2, as the sole byproduct, via a concerted dehydrogenation process. What’s more, the density functional theory (DFT) calculations, which has been investigated systematically by Fu and Shi’s group [32], depicted further understanding of the mechanism and provided more theoretical basis for this transformation. A strategy reported by Glorius nicely provided isoquinoline and related analogs from N-H ketimines and propargyl carbonates under manganese/base catalysis regime (Scheme 12) [33]. This protocol features high selectivity with unsymmetrical alkynes to give the desired product as a single regioisomer. Mechanistically, the catalytic cycle is triggered with base-assisted cyclomanganation of imine. Thereafter, successive coordination of oxygen atom of carbonyl, regioselective insertion of alkynes, β-oxygen elimination produce an allenylated intermediate, which then converted to the final product through a fast intramolecular cyclization process. The cyclization mechanism of imine with propargyl carbonates is significantly different from that with simple alkynes [31]. Density functional theory calculations indicate that the excellent regioselectivity is origin from the steric repulsion between

Mn-Catalyzed C–C Coupling Reactions

29

Scheme 12 [4 + 2] Annulation of N-H imines and propargyl carbonates

the aryl moiety of 1–34 and the quaternary carbon group of 1–35 in the alkyne insertion step [34]. In contrast, only 2-allenylindoles rather than cyclization products are formed when pyridyl-directed indole derivatives are treated with propargylic carbonates under the similar reaction conditions [35]. Analogously, Glorius et al. have developed an approach to diheteroarylmethanes with heteroarenes and ethynyl benzoxazinanones, adopting the previous manganese/ base strategy (Scheme 13) [36]. The corresponding allene intermediate, originating from decarboxylative β-oxygen elimination, undergoes successive regioselective allene insertion, protonation, and intramolecular cyclization to furnish the final product. In 2019, Li [37] and Ackermann [38] independently presented a domino annulation with heteroarenes and propargyl carbonates to afford fused carbo/heterocycle derivatives (Scheme 14a, b). It was proposed that the mechanism operated through C-H manganation, migratory insertion, and β-oxygen elimination to produce allene intermediate, showing the same reactivity as previous reports. The difference is that the allene species further undergoes intramolecular [4 + 2] Diels–Alder and retroDiels–Alder reaction along with the cyanide extrusion. Further development of propargyl carbonates by Li led to the access to fused eight- or four-membered carbocycles through redox-neutral coupling with 3-alkenyl- or 3-allylindoles [39]. Therein, the key allenylation intermediate undergoes pericyclic reactions to produce the desired products with good functional group compatibility and high selectivity (Scheme 14c, d). Using 4-hydroxy-2-alkynoates as the coupling partners,

30

Y. Yang and C. Wang

Scheme 13 C-H (2-indolyl)methylation of heteroarenes via allene intermediate

Scheme 14 Domino annulation reactions with propargyl alcohol derivatives

Mn-Catalyzed C–C Coupling Reactions

31

lactonization products are achieved via alkenylated indole intermediates (Scheme 14e) [40]. A tandem reaction of indoles with 1,6-enynes, which involves alkenyl-Mn(I) intermediates (1-Mn-16), is used to controllable access the divergent annulative C-C coupling products under optimal reaction conditions (Scheme 15a) [41]. Specifically, 1-Mn-16 undergoes intramolecular Michael addition promoted by BPh3 to produce the exocyclic olefin attached to a tetrahydrofuran ring 1–37, while fused phenols 1–38 are obtained from 1-Mn-16 through successive protonolysis, intramolecular Diels-Alder (IMDA) reaction, and intramolecular elimination (IME) of an alcohol in the presence of Zn(OAc)2/PivOH. Later, Lin and coworkers independently reported a similar methodology for the synthesis of 1–37 from 2-arylpyridines and 1,6-enynes under manganese catalysis with the assistance of catalytic amount of Cy2NH [42]. Exploitation of alkyne-functionalized 1,3-cyclopentadiones or 1,3-cyclohexadiones as synthetic precursors to indoles was introduced by Li et al., which furnishes seven- or eight-membered carbocycles (Scheme 15b) [43]. A manganese-catalyzed C-H activation and regioselective insertion of alkyne permit formation of Mn–C(alkenyl) species, which is followed by a cascade of carbonyl addition/retro-Aldol reactions for ring expansion. A related sequential annulation reaction between indoles and 1,6-diynes was disclosed by Chen and coworkers, leading to the fused carbazole derivatives (Scheme 15c) [44]. The corresponding alkenyl manganese species furnishes the seven-membered manganacycle through successive alkyne insertion and β-C-H oxidative addition, then transforms into the desired product via reductive elimination. In 2017, Ackermann et al. described the substitutive C-H alkynylation of heteroarenes with haloalkynes (Scheme 16) [45]. The scope of the reaction includes varied silyl-substituted alkynyl halides, as well as alkyl- or aryl-substituted bromoalkynes. It was proposed that the mechanism operated through sevenmembered manganacycle 1-Mn-17, which was generated through C-H cyclomanganation and subsequent migratory insertion of alkynes; then, the crucial β-Br elimination of 1-Mn-17 was accelerated by catalytic amount of BPh3, resulting in the corresponding products 1–41 via manganese species 1-Mn-18. Further application of this methodology for the late-stage of amino acids and peptides towards the design of BODIPY fluorogenic probes has been reported by the same group [30]. In 2014, Wang et al. reported the direct aromatic C-H conjugate addition to α,β-unsaturated carbonyls utilizing manganese-base synergetic catalysis regime (Scheme 17a) [46]. The C-H alkylated product is generated with excellent monoselectivity and good functional group tolerance. The mechanism proceeds in a similar fashion to the previously reported C-H alkenylation [19] [cf. Scheme 7]. This methodology was later extended to the synthesis of fused β-lactams, using stoichiometric dimethylzinc as the indispensable additive (Scheme 17b) [47]. Both ketimines and aldimines reacted with α,β-unsaturated esters to produce the cis-β-lactams directly through bicyclic annulation pathway in an excellent chemoand diastereoselective manner. A related example reported by Ackermann et al. provided an access to cis-β-amino acid esters from ketimines and α,β-unsaturated esters through an additive-free manganese-catalyzed C-H annulation reaction

32

Y. Yang and C. Wang

Scheme 15 Domino annulation reactions with multifunctional molecules

(Scheme 17c) [48]. Song, Gong [49], and Patel [50] independently extended the C-H addition reaction to electron-deficient maleimides, devising routes to the corresponding 3-substituted succinimide derivatives directly (Scheme 17d–f). Related research using α-diazoketone as the precursor for the β-(hetero)aryl/alkenyl

Mn-Catalyzed C–C Coupling Reactions

33

Scheme 16 Substitutive C-H alkynylation of heteroarenes with haloalkynes

ketones through manganese/silver relay catalysis was reported by Glorius et al. (Scheme 17g) [51]. The silver-catalyzed denitrogenation/carbene rearrangement of the precursor leads to the α,β-unsaturated ketones, which further undergoes previously described C-H alkylation under manganese catalysis to furnish the final products with unusual regioselectivity. In2016, Ackermann and coworkers continued their efforts in the discovery of methodologies involving C-H addition to unsaturated molecules containing C=C double bonds. The group focused on the use of allylic carbonates and imines as precursors for the synthesis of allylated ketones (Scheme 18) [52]. Mechanically, the catalytic cycle might commence with cyclomanganation through base-assisted internal electrophilic-type substitution (BIES) process, then coordination, migratory insertion, and β-oxygen elimination occurred successively to give the final C-H allylation product upon acidic workup. The combination of C-H activation and β-elimination process, under manganese catalysis, has been widely adopted for the versatile C-H allylation reactions. Ackermann [53], Glorius [54], and Hajra [55] groups independently reported C-H allylation of (hetero)arenes by using dioxolanone as allylating reagents via sequential C-H activation and β-oxygen elimination process, leading to the corresponding allylic alcohols products in accessible E/Z ratios (Scheme 19a–c). In 2019, Ackermann and coworkers successfully expanded the C-H allylation strategy for the late-stage functionalization of C-H fused peptide hybrids and C-H glycosylations, which provided modular access to diversification of structurally complex peptides [56] and glycopeptides [57] (Scheme 19d, e). The reaction of (hetero)arenes with perfluoroalkyl alkenes generated the fluoro-allylated indoles, ketones, and peptides (Scheme 19f) [58]. It was envisaged that β-fluoro elimination took place after the sequence of C-H cyclomanganation and migratory insertion of C=C double bond of alkenes. Incidentally, fluoro-alkenylation of indoles with gem-difluoro alkenes/perfluoroalkenes via β-defluorination has also been documented independently by Ackermann [58] and Feng & Loh groups [59] (Scheme 19g, h). Zhang

34

Y. Yang and C. Wang

Scheme 17 C-H addition to α,β-unsaturated molecules

et al. developed a strategy for 3,3-difluoroallylation of pyridones and indoles by exploiting 3-bromo-3,3-difluoropropene as model substrate, via β-bromo elimination (Scheme 19i) [60]. The contribution was published by Wu et al. in 2018, documenting the use of 2-(bromomethyl) acrylates as allylation partner in C2-H allylation of indoles through β-bromine elimination in likewise (Scheme 19j) [61]. Later in 2019, the Wang group reported the aromatic C-H allylation of ketones by employing allyl halides or allyl trifluoroacetates as the allylation reagents,

Mn-Catalyzed C–C Coupling Reactions

35

Scheme 18 C-H allylation of imines with allylic carbonates

yielding the mono-allylated ketones with good regio- and chemo-selectivity (Scheme 19k) [62]. A study by the Glorius group looked into the C-H allylation of heteroarenes with activated vinylcyclopropanes [54]. The reaction proceeded through a more challenging successive C-H/C-C activation, affording the corresponding allylated indole, benzene, and thiophene derivatives in moderate yields (Scheme 20a). Another notable work from Ackermann detailed a similar protocol with synergetic manganese/base catalysis regime (Scheme 20a) [63]. Experimental and computational mechanistic studies unveiled a successive process involving facile C-H activation, migratory insertion, and key C–C bond cleavage steps. It was noted that the considerable contribution from London dispersion interactions tended to stabilize the key E-transition state structure, leading to a higher diastereoselectivity. Additional studies performed by Glorius on the C-H allylation reaction utilized diazabicycle as precursor for the synthesis of aryl- and aminoalkyl cyclopentenes through C-H activation and β-nitrogen elimination successively (Scheme 20b) [54]. In 2018, Wang et al. developed a protocol for the generation of olefinated benzylic alcohols from aromatic ketones and unactivated alkenes (Scheme 21) [64]. The reaction proceeded through C–H bond cleavage via an unprecedented Mn-Zn-enabled concerted bis-metalation deprotonation (CBMD) pathway. Then, alkene insertion into the Mn–C bond of intermediate 1-Mn-19, followed by direct intramolecular H-transfer and transmetalation to form the final product upon hydrolysis. Notably, the carbonyl moiety of ketones functioned both as directing group and as intramolecular hydrogen acceptor; and dimethylzinc worked not only as a transmetalation reagent, but also as a promotor for C-H activation through a Mn-Zn synergetic mode.

36

Y. Yang and C. Wang

Scheme 19 C-H allylation reactions involving C-H activation and β-elimination

Mn-Catalyzed C–C Coupling Reactions

37

Scheme 20 C-H allylation reactions involving C-H activation and C-X cleavage

Scheme 21 Redox-neutral C-H olefination of ketones with unactivated alkenes

In 2017, Ackermann and coworkers presented a procedure for the C-H annulation using ketimines with methylenecyclopropanes (MCPs), which afforded tetra- and pentacyclic aniline derivatives (Scheme 22) [65]. This reaction proceeded through a C-H activation/Povarov cycloaddition cascade, beginning with the generation of manganacycle species 1-Mn-20. Migratory insertion of MCPs resulted in the manganacycle species 1-Mn-21, followed by C–C bond cleavage to furnish the

38

Y. Yang and C. Wang

Scheme 22 Annulations of imines with MCPs via C–H/C–C bond cleavage

intermediate 1-Mn-22. Intramolecular nucleophilic attack onto the imine moiety formed the alkene intermediate 1–51 after proto-demetallation step. The final product was achieved through Povarov cycloaddition of 1–51 which was promoted by stoichiometric zinc chloride. Allenes are intriguing coupling partners in C-H activation due to their multi-fold chemical reactivities. Early contribution made by Wang et al. in 2017 introduced 1,1-disubstitiuted allenes as substrates for polycyclization with ketimines through a C-H allylation/Povarov reaction under manganese/silver cascade catalysis manifold (Scheme 23a) [66]. Specifically, the C-H allylation products were formed firstly through a successive C-H activation, allene coordination, migratory insertion and protonation under manganese catalysis. Subsequent in situ Povarov cyclization catalyzed by silver furnished the final polycyclic products 1–54. Correspondingly, a report from Ding group described a [3 + 2] cyclization reaction by exploiting esteractivated allenes with ketimines via the analogous intermediate 1-Mn-23, which underwent an intramolecular nucleophilic addition to furnish 1-aminoindane derivatives 1–56 (Scheme 23a) [67]. Additional studies on the use of 1,1-disubstitiuted allenes as substrate for the generation of allylated (hetero)arenes were performed by Wang and coworkers (Scheme 23b) [68]. Further studies on the use of allenes as substrates to heteroaromatic rings were performed by the same group [69]. The publication presented a cascade C-H activation/Smiles rearrangement of heteroarenes with tri- and tetra-substituted allenes, resulting in the formation of bicyclic or tricyclic compounds bearing an

Mn-Catalyzed C–C Coupling Reactions

39

Scheme 23 Cyclization reactions of imines with multisubstituted allenes

exocyclic C=C double bond (Scheme 24). Notably, the directing group not only functioned to ensure the reactivity and regioselectivity, but also participated in the reaction as a migrating group. It was envisaged that the N-to-C 1,4-migration of the directing group, namely Smiles rearrangement, might result from the strong nucleophilicity of the polarized Mn–C bond of the intermediate 1-Mn-24. Concurrently, a similar protocol reported by Rueping et al. generated the 1–57 analogs from trisubstituted allenes through cascade cyclization in the presence of stoichiometric amount of NaOAc at lower temperature (Scheme 25) [70]. Additional investigation of 1,3-disubstituted allenes leads to the formation of C2-H alkenylated indoles/pyrroloindolones with excellent regio- and stereoselectivity. Systematic DFT calculations on these C-H functionalization reactions (cyclization vs hydroarylation) revealed that the substrate-controlled chemoselectivity is origin from the ligand–substrate interactions [71]. Specifically, trisubstituted allene system, the steric repulsions between the carboxide ligand and the substituent group in the allene substrate resulted in a high energy barrier, which arrested the protonation of seven-membered cyclometalated intermediate (1-Mn-23 analogs, cf. Scheme 23).

40

Y. Yang and C. Wang

Scheme 24 Mn(I)-catalyzed C-H activation and Smiles rearrangement cascade



Scheme 25 Substrate-controlled chemoselectivity C-H cyclization vs hydroarylation

“Ketone to enol” isomerization, a 1,4-heteroaryl shift, and β-methoxyl elimination process occurred in succession furnishing the pyrroloindolone derivatives. On the contrary, the alkenylated products were formed from seven-membered cyclometalated intermediate more favorably due to the lack of ligand–substrate steric interactions for disubstituted allene system. Further research using bromoallenes to C-H propargylation of heterocycles was reported by Glorius et al. (Scheme 26) [72]. Both internal and terminal alkynes were obtained in moderate to good yields with excellent chemoselectivity, which was also seen in the late-stage diversification of complex steroid derivative. Derivatization of the substituents on C1 gave products containing secondary, tertiary, and even quaternary carbon centers at the propargylic position. The mechanism proceeded in similar fashion to the one shown in Scheme 23, except that the final products were generated from the seven-membered manganacycle via a β-bromo elimination process.

Mn-Catalyzed C–C Coupling Reactions

41

Scheme 26 C-H propargylation of heterocycles with bromoallenes

2.3

Addition to Mn=C Bond

Diazo compounds, due to their diverse and rich reactivity, have been widely used in organic transformations. Pioneering work by Pérez et al. in 2016 reported the use of ethyl diazoacetate as carbene precursor in the manganese-catalyzed C-H alkylation of simple benzene derivatives [73]. Although this reaction does not involve C-H activation step, it provides the first example of C–C bond formation via C(sp2)-H functionalization with diazo compound catalyzed by manganese-based complexes. After anion exchange of the Mn(II) precatalyst, the diazo ester coordinates to the manganese center of 1-Mn-25, which further furnish the metallocarbene species 1-Mn-27 via intermediate 1-Mn-26, along with N2 releasing. An outer sphere interaction between the carbene moiety of 1-Mn-27 with the arene gives rise to the Wheland-type intermediate 1-Mn-28, and subsequent 1,2-hydrogen shift of the 1-Mn-28 yields the desired product and regenerates the active catalytic species 1-Mn-25 (Scheme 27). In 2018, Rueping et al. reported the use of diazo esters in the C-H alkylation of Npyrimidinyl indoles via C-H activation process, catalyzed by manganese (Scheme 28) [74]. Experimental and computational investigation support the formation of (CO)3Mn(κ2-OAc) complex (1-Mn-30) as the catalytic active species in the presence of NaOAc. Based on the mechanistic findings, coordination of the indole substrate and reversible C-H cleavage furnish the five-membered manganacycle 1-Mn-31. Subsequent proposed formation of manganese carbenoid intermediate 1-Mn-32 sets stage for the following intramolecular carbene insertion into the Mn–C bond to form the intermediate 1-Mn-33, and protonation to release the final product 1–62 along with regeneration of 1-Mn-30. A related protocol has been demonstrated by the Sen

42

Y. Yang and C. Wang

Scheme 27 C-H alkylation of arenes with diazo compound via outer sphere manner

group, using acetyl as the directing group for the cyclopropanation of N-acetyl indoles with diazo esters (Scheme 28) [75]. In contrast, the proposed mechanism suggested the formation of the manganese carbenoid intermediate 1-Mn-34 initially, which then coordinates with the acetyl moiety of the indole substrate 1–63. Subsequent cyclization of 1-Mn-35 provides the manganese species 1-Mn-36, followed by the release of final product 1–64 as well as the regeneration of catalytic active manganese species 1-Mn-29. Additional studies on the use of N-benzyl and N-Boc pyrroles as substrates were performed under blue LED, also providing corresponding cyclopropanated compounds [76]. However, C2-H alkylated pyrrole derivatives were accessed through a carbene insertion pathway with the neutral or electron-rich NH-pyrroles, under the same conditions, as main products.

2.4

Substitutive C-H Activation

Manganese-catalyzed C–C bond formation via organometallic C-H activation does not restrict to addition reactions that call for coupling partners containing multiple bonds under manganese(I/0) complexes. The direct coupling of alkyl bromides with an inert C–H bond by manganese(II) catalysis was first demonstrated by Ackermann and coworkers [77]. This triazolyldimethylmethyl (TAM) amide directed alkylation procedure utilized MnCl2 as the catalytic precursor, in the presence of excessive isopropylmagnesium bromide and tetramethylethylenediamine (TMEDA), to provide versatile C-H alkylated (hetero)arenes (Scheme 29a). Notably, the alkyl bromides containing β-hydrogen were solely transformed into the desired product with

Mn-Catalyzed C–C Coupling Reactions

43

Scheme 28 C-H alkylation and cyclopropanation of indoles with diazo compound

excellent chemoselectivity. Thereafter, Ackermann et al. extended the scope of alkyl halides to primary and secondary alkyl chlorides/bromides which displayed wide functional group tolerance (Scheme 29b) [78]. A number of alkylated picolinamides were synthesized on a chemoselective manner. In addition, Punji and coworkers expanded the scope of alkyl halides to iodides to achieve the regio-/chemo-selective C-H alkylation of indoles and benzo[h]quinoline derivatives (Scheme 29c) [79]. The proposed mechanism proceeds via a reversible C-H manganation to produce manganacycle 1-Mn-37. Subsequent single-electron oxidation and radical rebound form intermediate 1-Mn-38, which occurs reductive elimination to release the final product along with the regeneration of the active manganese catalyst (Scheme 29c).

44

Y. Yang and C. Wang

Scheme 29 C-H alkylation of (hetero)arenes with alkyl halides

Extension of the aforementioned protocol, described by Ackermann et al., led to the development of C-H oxidative coupling reaction with MeMgBr in the presence of 2,3-dichlorobutane (DCB) (Scheme 30a) [77]. After experimental and computational DFT studies, the C-H activation was suggested to proceed through σ-bond metathesis to form the manganacycle 1-Mn-40, which is oxidized by DCB via a single-electron transfer pathway leading to manganese intermediate 1-Mn-41. Subsequent transmetalation of 1-Mn-41 with alkylation reagent releases an alkylated manganese species 1-Mn-42. Reductive elimination and a second one-electron oxidation step afford the final product and the active catalyst 1-Mn-39. In the same year, Ilies and Nakamura et al. described a related analogs for C-H methylation of (hetero)aryl and alkenyl carboxamides by using MnCl2.2LiCl as catalytic precursor, 1-bromo-2-chloroethane (BCE) as the terminal oxidant, affording the desired product in moderate to excellent yields (Scheme 30b) [80].

Mn-Catalyzed C–C Coupling Reactions

45

Scheme 30 C-H methylation with magnesium methyl bromide

Further research using continuous-flow system to C-H arylation of azines with magnesium aryl bromides was reported by Ackermann and coworkers [81]. This methodology requires the use of neocuproine as a ligand, 1,2-dichloro2methylpropane (DCIB) as an oxidant, and TMEDA for the deaggregation of the Grignard reagents (Scheme 31). It was proposed that the mechanism operated through a MnII-MnIII-MnI reaction pathway, in a similar fashion to the previously reported C-H alkylation reaction. What’s more, the continuous-flow system had significant advantages in efficiency over batch-scale processes, which delivered the desired product in a short period of time and maintain a good yield. Extension of this work has led to the development of a heterogeneous manganese-catalyzed [82] and manganaelectro-catalyzed [83] C-H arylations/alkylations of azines.

46

Y. Yang and C. Wang a) continuous-flow system O N H

Het

MnCl2 (10 mol%) L (20 mol%)

R

Ar

N H

Het

+

Me

O

L=

R

TMEDA, THF

ArMgBr

DCIB

o

29 examples 50%-80% yield

80 C, 100 min

N N Me neocuproine

b) heterogeneous manganese catalysis N O N H

Het

R

+ Ar/Alk MgBr

Mn (9 mol%) TMEDA (2.0 equiv.) 2,3-DCB (3.0 equiv.) o

THF, 70 C, 16 h

Ar/Alk Het

[Mn]

Mn =

O N H

N

R

34 examples 0 to 95% yield c) manganaelectro catalysis O Het

N H

R

+ Ar/Alk MgBr

MnCl2 (10 mol%) Ar/Alk O Neocuproine (20 mol%) R TMEDA (2.0 equiv.) N o Het H THF, 60 C, 18 h CCE = 3.0 mA 28 examples NR to 78% yield

Me

L=

N N Me neocuproine

Scheme 31 C-H arylation/alkylation of azines with Grignard reagents

3 Hydrocarbofunctionalization of Unsaturated C–C Bond Without C-H Activation The manganese-catalyzed addition reaction of unsaturated C–C bond with organoboronic acids has been mainly reported by Xie and Wang groups in recent 5 years. Therein, arylboronic acids and alkenyl boronic acids have proven to be suitable substrates. Mechanistically, these processes proceed through transmetalation to form an arylmanganese(I) or alkenylmanganese(I) species 2-Mn-1. Subsequent migratory insertion of unsaturated C–C bond into Mn–C bond in 2-Mn-1 gives carbomanganization intermediate 2-Mn-2. The following protodemetalation releases the desired products along with an active manganese catalytic species to close the catalytic cycle (Scheme 32). In 2018, Xie and coworkers presented a selective hydroarylation of unsymmetrical 1,3-diyne alcohols with a wide range of commercially available arylboronic acids by using Mn2(CO)8Br2 as the catalyst precursor (Scheme 33) [84]. Hydroarylation proceeds in regio-, stereo-, and chemoselective manner to afford various multisubstituted Z-configurated conjugated enynes. Initiation generates the reactive manganese species 2-Mn-3 from the dimeric precursor in the presence of NaOAc. Arylboronic acids undergo transmetalation with 2-Mn-3 forming the nonchelated Ar-Mn intermediate 2-Mn-4, which further converts into the intermediate 2-Mn-5 through sequential coordination and migratory insertion. Final product is generated via protodemetalation by protons existing in the reaction

Mn-Catalyzed C–C Coupling Reactions

47

Scheme 32 Proposed mechanism for the manganese-catalyzed addition reaction with organoboronic acids

Scheme 33 Hydroarylation of 1,3-diyne alcohols

media. Worth noting that the regioselectivity of β-carbon center of 1,3-diyne might be due to the weak OH–π interaction between the OH group in 1,3-diyne alcohol and the aryl group in 2-Mn-4, and Z-configuration of the product is kinetically controlled according to the DFT calculation results. In 2020, Wang et al. reported a regioselective hydroarylation of unactivated alkenes to access a range of δ- and γ-arylated amides, ketones, pyridines, and amines with the assistance of remote coordinating functional groups (Scheme 34a) [85]. The scope of aryl boronic acid can be expanded to alkenylboronic one, which proceeds to form a hydroalkenylation product in 97% yield with excellent regio- and E/Z selectivity. The proposed mechanism suggested the transmetalation between MnBr (CO)5 and arylboronic acid, leading to the formation of ArMn(CO)5 with assistance of base. Coordination of alkene delivers the manganacycle 2-Mn-7, which further undergoes intramolecular migratory insertion to form manganacycle 2-Mn-8. Subsequent protonation, transmetalation, and ligand exchange release the final product and regenerate the manganese species 2-Mn-6. A related publication from Xie group detailed the use of analogous strategy of amide directing auxiliary to undergo hydrocarbofunctionalization of internal alkenes to the corresponding γ-functionalized amide derivatives in moderate to good yields (Scheme 34b) [86]. In 2020, the Xie group adapted their previous methodology [84], using unsaturated amides and commercially available aryl- and alkenyl-boronic acids for the construction of β-arylated/alkenylated amides (Scheme 35a, b) [87]. This reaction

48

Y. Yang and C. Wang

Scheme 34 Hydrocarbofunctionalization of unactivated alkenes

Scheme 35 Hydrocarbofunctionalization of alkenes reported by Xie’s group

Mn-Catalyzed C–C Coupling Reactions

49

proceeded with good regio- and chemoselectivity and showed compatibility with a number of functional groups under air atmosphere. The mechanism proceeds in a similar fashion to the one shown in Scheme 33; the alkene moiety of amide coordinates to the Ar-Mn intermediate rapidly, which is followed by migratory insertion and protodemetalation sequence, furnishing the final products and regenerating the coordination-unsaturated manganese species. Further variations of the substrates to enamides gave β-arylated/alkenylated amine derivatives through manganese-catalyzed anti-Markovnikov hydroarylation/hydroalkenylation reactions (Scheme 35c) [88]. Additional investigation was made by Xie et al. into the hydroarylation of the triple bond of tertiary propargyl alcohols with aromatic boronic acids (Scheme 36a) [89]. This procedure featured high efficiency under air atmosphere in the presence of water, and provided the desired product in regio-, chemo-, and stereoselective manner. Notably, complex bioactive molecules were compatible with the selective nature of this protocol, highlighting application in future drug discovery. Subsequent density functional theory (DFT) calculations and experimental studies provided insights into the origin of regiodivergent selectivities in this reaction (Scheme 36b) [90]. The mechanism proceeds via activation of the bimetallic precatalyst to an active a monometallic catalyst, which runs the alkyne migratory insertion, protonation, and self-regeneration in succession, and alkyne insertion step determines the regioselectivity of this reaction. The noncovalent interaction and steric hindrance between the substrate and the Mn catalyst in the 1,2- or 2,1-insertion transition state (TS-1 and TS-2) is responsible for the regioselectivity during formation of the corresponding γ- or β-arylated product as well as the mixture of both.

Scheme 36 Hydroarylation of propargyl alcohols with aromatic boronic acids

50

Y. Yang and C. Wang

4 Conclusion Manganese-catalyzed C-C coupling reactions have been extensively developed over the past 10 years. A variety of methodologies, including C-H alkylation, alkenylation, arylation, and cyclization, as well as hydroarylation/hydroalkenylation of akenes or alkynes, have been achieved through elegant design and implementation. Mechanically, most transformations catalyzed by manganese(I/0) are proposed to proceed migratory insertion of Mn–C bond into the unsaturated C-X (X = C, O, N) double or triple bonds to form the new C–C bonds in a redox-neutral pathway. In contrast, variable oxidation states are observed within the catalytic cycles involving single-electron transfer processes based on manganese(II) catalysts. The catalysis based on manganese possesses unique reactivity and provides a valuable alternative for organic synthesis.

References 1. Cahiez G, Duplais C, Buendia J (2009) Chem Rev 109:1434–1476 2. Valyaev DA, Lavigne G, Lugan N (2016) Coord Chem Rev 308:191–235 3. Shinokubo H, Oshima K (2004) Eur J Org Chem 2004:2081–2091 4. Irrgang T, Kempe R (2019) Chem Rev 119:2524–2549 5. Snider BB (1996) Chem Rev 96:339–364 6. Kuninobu Y, Nishina Y, Takeuchi T, Takai K (2007) Angew Chem Int Ed 46:6518–6520 7. Zhou B, Hu Y, Wang C (2015) Angew Chem Int Ed 54:13659–13663 8. Liang YF, Massignan L, Liu W, Ackermann L (2016) Chem A Eur J 22:14856–14859 9. Sueki S, Wang Z, Kuninobu Y (2016) Org Lett 18:304–307 10. Zhu C, Pinkert T, Greßies S, Glorius F (2018) ACS Catal 8:10036–10042 11. Liu W, Bang J, Zhang Y, Ackermann L (2015) Angew Chem Int Ed 54:14137–14140 12. Huo J, Yang Y, Wang C (2021) Org Lett 23:3384–3388 13. Zhou X, Li Z, Zhang Z, Lu P, Wang Y (2018) Org Lett 20:1426–1429 14. Xu Z, Wang Y, Zheng Y, Huang Z, Ackermann L, Ruan Z (2020) Org Chem Front 7:3709– 3714 15. Liang Y-F, Massignan L, Ackermann L (2018) ChemCatChem 10:2768–2772 16. Zhou B, Hu Y, Liu T, Wang C (2017) Nat Commun 8:1169–1177 17. Liu W, Richter SC, Mei R, Feldt M, Ackermann L (2016) Chem A Eur J 22:17958–17961 18. Yu X, Tang J, Jin X, Yamamoto Y, Bao M (2018) Asian J Org Chem 7:550–553 19. Zhou B, Chen H, Wang C (2013) J Am Chem Soc 135:1264–1267 20. Yahaya NP, Appleby KM, Teh M, Wagner C, Troschke E, Bray JT, Duckett SB, Hammarback LA, Ward JS, Milani J, Pridmore NE, Whitwood AC, Lynam JM, Fairlamb IJ (2016) Angew Chem Int Ed 55:12455–12459 21. Yang X, Jin X, Wang C (2016) Adv Synth Catal 358:2436–2442 22. Jia T, Wang C (2019) ChemCatChem 11:5292–5295 23. Wang C, Rueping M (2018) ChemCatChem 10:2681–2685 24. Wan S, Luo Z, Xu X, Yu H, Li J, Pan Y, Zhang X, Xu L, Cao R (2021) Adv Synth Catal 363: 2586–2593 25. Cembellín S, Dalton T, Pinkert T, Schäfers F, Glorius F (2020) ACS Catal 10:197–202 26. Kaplaneris N, Kaltenhuser F, Sirvinskaite G, Fan S, De Oliveira T, Conradi LC, Ackermann L (2021) Sci Adv 7:eabe6202

Mn-Catalyzed C–C Coupling Reactions

51

27. Shi L, Zhong X, She H, Lei Z, Li F (2015) Chem Commun 51:7136–7139 28. Das D, Bhosle AA, Panjikar PC, Chatterjee A, Banerjee M (2020) ACS Sustain Chem Eng 8: 19105–19116 29. Wang H, Pesciaioli F, Oliveira JCA, Warratz S, Ackermann L (2017) Angew Chem Int Ed 56: 15063–15067 30. Kaplaneris N, Son J, Mendive-Tapia L, Kopp A, Barth ND, Maksso I, Vendrell M, Ackermann L (2021) Nat Commun 12:3389 31. He R, Huang ZT, Zheng QY, Wang C (2014) Angew Chem Int Ed 53:4950–4953 32. Yang Y, Zhang Q, Shi J, Fu Y (2016) Acta Chim Sin 74:422–428 33. Lu Q, Gressies S, Cembellin S, Klauck FJR, Daniliuc CG, Glorius F (2017) Angew Chem Int Ed 56:12778–12782 34. Wang Z, Zhu L, Zhong K, Qu LB, Bai R, Lan Y (2018) ChemCatChem 10:5280–5286 35. Lu Q, Gressies S, Klauck FJR, Glorius F (2017) Angew Chem Int Ed 56:6660–6664 36. Lu Q, Cembellin S, Gressies S, Singha S, Daniliuc CG, Glorius F (2018) Angew Chem Int Ed 57:1399–1403 37. Zheng G, Sun J, Xu Y, Zhai S, Li X (2019) Angew Chem Int Ed 58:5090–5094 38. Zhu C, Kuniyil R, Ackermann L (2019) Angew Chem Int Ed 58:5338–5342 39. Xu Y, Zheng G, Kong L, Li X (2019) Org Lett 21:3402–3406 40. Kumar A, Muniraj N, Prabhu KR (2019) Adv Synth Catal 361:4933–4940 41. Liu B, Li J, Hu P, Zhou X, Bai D, Li X (2018) ACS Catal 8:9463–9470 42. Tan YX, Liu XY, Zhao YS, Tian P, Lin GQ (2019) Org Lett 21:5–9 43. Liu B, Yuan Y, Hu P, Zheng G, Bai D, Chang J, Li X (2019) Chem Commun (Camb) 55: 10764–10767 44. Yi X, Chen K, Chen W (2018) Adv Synth Catal 360:4497–4501 45. Ruan Z, Sauermann N, Manoni E, Ackermann L (2017) Angew Chem Int Ed 56:3172–3176 46. Zhou B, Ma P, Chen H, Wang C (2014) Chem Commun 50:14558–14561 47. Hu Y, Wang C (2016) Sci China Chem 59:1301–1305 48. Liu W, Zell D, John M, Ackermann L (2015) Angew Chem Int Ed 54:4092–4096 49. Liu SL, Li Y, Guo JR, Yang GC, Li XH, Gong JF, Song MP (2017) Org Lett 19:4042–4045 50. Ghosh S, Khandelia T, Patel BK (2021) Org Lett 23:7370–7375 51. Lu Q, Mondal S, Cembellin S, Glorius F (2018) Angew Chem Int Ed Engl 57:10732–10736 52. Liu W, Richter SC, Zhang Y, Ackermann L (2016) Angew Chem Int Ed 55:7747–7750 53. Wang H, Lorion MM, Ackermann L (2017) Angew Chem Int Ed 56:6339–6342 54. Lu Q, Klauck FJR, Glorius F (2017) Chem Sci 8:3379–3383 55. Kumar Ghosh A, Kanta Das K, Hajra A (2021) Adv Synth Catalogue 363:4974–4981 56. Kaplaneris N, Rogge T, Yin R, Wang H, Sirvinskaite G, Ackermann L (2019) Angew Chem Int Ed Engl 58:3476–3480 57. Wang W, Subramanian P, Martinazzoli O, Wu J, Ackermann L (2019) Chem A Eur J 25: 10585–10589 58. Zell D, Dhawa U, Müller V, Bursch M, Grimme S, Ackermann L (2017) ACS Catal 7:4209– 4213 59. Cai SH, Ye L, Wang DX, Wang YQ, Lai LJ, Zhu C, Feng C, Loh TP (2017) Chem Commun 53: 8731–8734 60. Ni J, Zhao H, Zhang A (2017) Org Lett 19:3159–3162 61. Wu S, Yang Q, Hu Q, Wang Y, Chen L, Zhang H, Wu L, Li J (2018) Org Chem Front 5:2852– 2855 62. Ali S, Huo J, Wang C (2019) Org Lett 21:6961–6965 63. Meyer TH, Liu W, Feldt M, Wuttke A, Mata RA, Ackermann L (2017) Chem A Eur J 23:5443– 5447 64. Hu Y, Zhou B, Chen H, Wang C (2018) Angew Chem Int Ed 57:12071–12075 65. Liang YF, Muller V, Liu W, Munch A, Stalke D, Ackermann L (2017) Angew Chem Int Ed 56: 9415–9419 66. Chen SY, Li Q, Liu XG, Wu JQ, Zhang SS, Wang H (2017) ChemSusChem 10:2360–2364

52

Y. Yang and C. Wang

67. Lei C, Peng L, Ding K (2018) Adv Synth Catal 360:2952–2958 68. Chen SY, Li Q, Wang H (2017) J Org Chem 82:11173–11181 69. Chen SY, Han XL, Wu JQ, Li Q, Chen Y, Wang H (2017) Angew Chem Int Ed 56:9939–9943 70. Wang C, Wang A, Rueping M (2017) Angew Chem Int Ed 56:9935–9938 71. Ma X, Dang Y (2019) J Org Chem 84:1916–1924 72. Zhu C, Schwarz JL, Cembellin S, Gressies S, Glorius F (2018) Angew Chem Int Ed 57:437–441 73. Conde A, Sabenya G, Rodriguez M, Postils V, Luis JM, Diaz-Requejo MM, Costas M, Perez PJ (2016) Angew Chem Int Ed 55:6530–6534 74. Wang C, Maity B, Cavallo L, Rueping M (2018) Org Lett 20:3105–3108 75. Dutta PK, Chauhan J, Ravva MK, Sen S (2019) Org Lett 21:2025–2028 76. Sar S, Das R, Sen S (2021) Adv Synth Catal 363:3521–3531 77. Liu W, Cera G, Oliveira JCA, Shen Z, Ackermann L (2017) Chem A Eur J 23:11524–11528 78. Shen Z, Huang H, Zhu C, Warratz S, Ackermann L (2019) Org Lett 21:571–574 79. Jagtap RA, Verma SK, Punji B (2020) Org Lett 22:4643–4647 80. Sato T, Yoshida T, Al Mamari HH, Ilies L, Nakamura E (2017) Org Lett 19:5458–5461 81. Zhu C, Oliveira JCA, Shen Z, Huang H, Ackermann L (2018) ACS Catal 8:4402–4407 82. Choi I, Shen Z, Ronge E, Karius V, Jooss C, Ackermann L (2021) Chemistry 27:12737–12741 83. Massignan L, Zhu C, Hou X, Oliveira JCA, Salamé A, Ackermann L (2021) ACS Catal 11: 11639–11649 84. Yan Z, Yuan XA, Zhao Y, Zhu C, Xie J (2018) Angew Chem Int Ed Engl 57:12906–12910 85. Liu T, Yang Y, Wang C (2020) Angew Chem Int Ed Engl:14256–14260 86. Wang D, He Y, Dai H, Huang C, Yuan XA, Xie J (2020) Chin J Chem 38:1497–1502 87. Wang D, Dong J, Fan W, Yuan XA, Han J, Xie J (2020) Angew Chem Int Ed Engl 59:8430– 8434 88. He YJ, Du CY, Han J, Han J, Zhu CJ, Xie J (2022) Chin J Chem 40:1546–1552 89. Pang Y, Liu G, Huang C, Yuan XA, Li W, Xie J (2020) Angew Chem Int Ed Engl 59:12789– 12794 90. Huang C, Pang Y, Yuan XA, Jiang YY, Wang X, Liu P, Bi S, Xie J (2022) J Org Chem 87: 4215–4225

Top Organomet Chem (2023) 93: 53–112 https://doi.org/10.1007/3418_2023_90 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 28 April 2023

Iron-Catalyzed Carbon–Carbon Coupling Reaction Qiao Zhang and Shou-Fei Zhu

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2 Fe-Catalyzed Coupling Reaction of Electrophilic Reagents and Nucleophilic Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 2.1 Fe-Catalyzed C(sp2)─C(sp3) Coupling Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 2.2 Fe-Catalyzed C(sp2)–C(sp2) Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2.3 Fe-Catalyzed C(sp3)–C(sp3) Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 2.4 Fe-Catalyzed C(sp3)–C(sp) Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 3 Fe-Catalyzed C–H Direct Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.1 Fe-Catalyzed C–H Direct Coupling–C(sp3)–C(sp2) Coupling . . . . . . . . . . . . . . . . . . . . . . . 84 3.2 Fe-Catalyzed C–H Direct Coupling–C(sp2)–C(sp2) Coupling . . . . . . . . . . . . . . . . . . . . . . . 89 3.3 Fe-Catalyzed C–H Direct Coupling–C(sp2)–C(sp) Coupling . . . . . . . . . . . . . . . . . . . . . . . . 97 4 Fe-Catalyzed Oxidative/Reductive Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 4.1 Fe-Catalyzed Oxidative Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 4.2 Fe-Catalyzed Reductive Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Abstract Transition metal-catalyzed coupling reaction is one of the most effective strategies to construct carbon–carbon bonds. Because iron is Earth abundant and environmental benign, the Fe-catalyzed carbon–carbon coupling reactions have attracted extensive attention in the past two decades. A variety of iron catalysts have been developed to realize cross-coupling of electrophilic and nucleophilic reagents, oxidative coupling, reductive coupling, and C–H bond direct coupling reactions. The asymmetric carbon–carbon coupling reactions have also been successfully achieved using chiral iron catalysts. This chapter reviews the recent research progress of Fe-catalyzed carbon–carbon coupling reaction, mainly from

Q. Zhang and S.-F. Zhu (✉) Frontiers Science Center for Organic Matter, State Key Laboratory and Institute of ElementoOrganic Chemistry, College of Chemistry, Nankai University, Tianjin, China e-mail: [email protected]

54

Q. Zhang and S.-F. Zhu

the perspective of the type of newly formed carbon–carbon bonds, reaction conditions, substrate types, and reaction mechanisms. Keywords Transition-metal catalysis · Iron catalyst · Carbon–carbon coupling

1 Introduction In the past few decades, transition metal-catalyzed carbon–carbon coupling reaction has been one of the hottest topics in the field of organic chemistry [1–4]. Through this kind of reaction, a variety of complex and high-value pharmaceuticals and natural products could be prepared with high efficiency [5–7]. In such reactions, palladium and nickel complexes generally exhibit high conversion and selectivity [8–13]. Nevertheless, the coupling reaction catalyzed by palladium or nickel complex also has certain limitations: the expensive metal palladium complex restricts its application in practical production, and the biological toxicity of palladium and nickel ion might have adverse effects on productive and environmental safety. In addition, palladium or nickel complexes fail to give good results for some specific coupling reagents, such as Grignard reagents and lithium reagents. Therefore, it is urgent to explore cheap and low-toxic metal complexes to solve this long-standing problem. Iron widely exists in the Earth’s crust. Its rich reserves, low price, and good biological compatibility make it a “perfect catalyst.” As early as the 1940s, it has been reported that iron complexes could catalyze carbon–carbon coupling reactions. However, in the following decades, the coupling reaction catalyzed by palladium and nickel was developing vigorously, and the coupling reaction catalyzed by iron did not attract the attention of chemists. This field was re-focused until the 1970s when Kochi’s research group reported the Fe-catalyzed carbon–carbon coupling reaction. Many researchers developed a variety of iron catalytic systems to achieve different types of carbon–carbon coupling reactions, even those which could not be achieved by palladium or nickel catalysts [14–17]. In this chapter, the Fe-catalyzed carbon–carbon coupling reactions developed in the past two decades were reviewed based on the newly formed carbon–carbon bond types, different substrate types, and reaction mechanisms.

Iron-Catalyzed Carbon–Carbon Coupling Reaction

55

2 Fe-Catalyzed Coupling Reaction of Electrophilic Reagents and Nucleophilic Reagents 2.1

Fe-Catalyzed C(sp2)─C(sp3) Coupling Reaction

According to the type of substrates, Fe-catalyzed C(sp2)–C(sp3) coupling reactions could be divided into two types: one is the coupling reactions of aryl/alkenyl halides with alkyl metal reagents; the other is the coupling reactions of aryl/alkenyl metal reagents with alkyl halides. The literatures were reviewed mainly based on these two types of reactions.

2.1.1

Fe-Catalyzed C(sp2)X–C(sp3)M Coupling

As early as 1941, Fields [18] discovered that iron salts could promote the coupling reaction between aryl Grignard reagents and aryl bromides to prepare biaryl compounds. But until the 1970s when Kochi et al. [19] systematically studied FeCl3catalyzed coupling reaction of alkenyl halides and alkyl Grignard reagents, the Fe-catalyzed carbon–carbon coupling reactions drew increasing attention from synthetic chemists (Scheme 1). In the subsequent mechanism studies [20, 21], the researchers proposed that the reaction went through three elementary steps: oxidative addition, transmetalation, and reductive elimination (Scheme 2). Using Fe (DBM)3 as the catalyst, Walborsky et al. [22] realized the similar coupling reaction of alkenyl bromides and alkyl organometallic reagents in 1981 (Scheme 3). However, the poor stereoselectivity and narrow substrate scope were the main problems in these reactions. Aiming at the mechanism of the coupling system developed by Kochi [23, 24], Neidig et al. carried out a detailed study in 2016, in which [MgCl (THF)5][Fe8Me12] was separated as the effective active catalyst. It was proved that the active catalyst was consistent with the iron catalyst found by Kochi through single crystal diffraction, EPR experiment, and magnetic circular dichroism (MCD) test methods. In 2002, Fürstner et al. [25] reported the Fe-catalyzed coupling reaction of aryl halides with organic Mg, Zn, Mn, and other alkyl metal reagents (Scheme 4). Lots of simple iron salts such as FeCln (n = 2, 3), Fe(acac)n (n = 2, 3), or the Fe(salen)Cl could catalyze the reaction. Many substituents, such as ester group, cyano group,

Scheme 1 The early example of Fe-catalyzed C–C coupling reaction

56

Q. Zhang and S.-F. Zhu

Scheme 2 The original proposed reaction mechanism of Fe-catalyzed C–C coupling

Scheme 3 Fe(DBM)3-catalyzed methylation of alkenyl bromides

Scheme 4 Fe-catalyzed alkylation of aryl/heteroaryl chlorides, triflates, and tosylates

trifluoromethyl group, sulfonic esters, and sulfonamides, could be tolerated. They believed that the iron salt (FeCl2) generates “inorganic Grignard reagent” ([Fe (MgX)2]) under the action of excessive Grignard reagent, which catalyzes the whole reaction. In 2013, Ren et al. [26] conducted the DFT calculation, proposed a detailed reaction process, and pointed out that the reductive elimination step of the intermediate [Ar-(nhexyl)-Fe(MgBr)2] to [Fe(MgBr)2] is the rate-determining step (Scheme 5). Subsequently, the Fürstner group [27] synthesized [Me4Fe]Li2 species in 2004. When the species was used as the catalyst, similar efficiency was obtained as using Fe(acac)3 catalyst, which further verified the high catalytic activity of the above “inorganic Grignard reagent” (Scheme 6).

Iron-Catalyzed Carbon–Carbon Coupling Reaction

57

Scheme 5 Fe-catalyzed mechanism of C–C coupling involved “inorganic Grignard”

Scheme 6 Fe-catalyzed methylation of triflates with [Me4Fe]Li2

In the following years, other research groups have developed different catalytic systems for similar carbon–carbon coupling reactions. Introducing cosolvent into the system is a very effective strategy. In 2013, using Fe(acac)3 as catalyst, Malhotra et al. [28] realized the continuous coupling reaction of dihaloaromatics with alkyl Grignard reagents under the assistance of NMP, and obtained the dialkyl-substituted heterocyclic compounds (Scheme 7). The sequence of the reaction sites of the dialkyl halides is affected by the position of the halogen, the solvent, and the properties of the nucleophilic reagents. In 2015, the Quan/Wang group [29] reported the FeCl2-catalyzed coupling reaction of heteroaromatic tosylates with alkyl Grignard reagents to synthesize polysubstituted pyridine derivatives with the assistance of NMP (Scheme 8). In 2017, Szostak et al. [30] also realized the coupling reaction

58

Q. Zhang and S.-F. Zhu

Scheme 7 Fe-catalyzed alkylation of dihaloaromatics with NMP

Scheme 8 Fe-catalyzed alkylation of heteroaromatic tosylates in the presence of NMP

Scheme 9 Fe-catalyzed alkylation of polyaromatic tosylates in the presence of NMP

of polyaromatic tosylates and alkyl Grignard reagents under similar conditions and obtained a variety of alkyl-substituted polycyclic compounds (Scheme 9). According to the results of the competition experiments between polyaromatic tosylates and polyaromatic chlorides, they proposed that the reaction might generate low-valence iron intermediate via two-electron-transfer mechanism. In 2017, Szostak et al. [31] reported the Fe(acac)3-catalyzed coupling reaction of aryl chlorides and tosylates with alkyl Grignard reagents (Scheme 10). The low-toxic DMI and DMPU promoted the reaction efficiently. The activity of aryl tosylates is lower than aryl chlorides according to substrates’ evaluation. In addition, a dual NK1/serotonin receptor antagonist could be synthesized in multiple steps using this

Iron-Catalyzed Carbon–Carbon Coupling Reaction Fe(acac)3 (5 mol%) L (2.0 or 6.0 equiv)

Ar(Het) X + C14H29 MgCl X = Cl, OTs Me

N

N

Me

90% (DMPU) 96% (DMI) 94% (N-Me-CPL) 94% (NBP)

N Me

Me N

DMI

C14H29 F3C

THF, 0 oC

O

O DMPU

59

C14H29

Ar(Het) C14H29

O N Me N-Me-CPL

N

Me NBP

C14H29

C14H29

NC 92% (DMPU) 89% (DMI) 91% (N-Me-CPL) 91% (NBP)

O N

N 93% (DMPU) 88% (DMI) 81% (N-Me-CPL) 81% (NBP)

96% (DMPU) 98% (DMI) 92% (N-Me-CPL) 92% (NBP)

Scheme 10 Fe-catalyzed alkylation of aryl chlorides/tosylates in the presence of low-toxic DMI, DMPU, N-Me-CPL, and NBP

Scheme 11 The synthesis of dual NK1/serotonin receptor antagonist

reaction. Subsequently, Bisz/Szostak’s group [32] realized the Fe(acac)3-catalyzed coupling reaction of aryl chlorides/aromatic tosylates with alkyl Grignard reagents (Scheme 10). Compared to the highly toxic cosolvent NMP, the low-toxic cosolvent N-methylcaprolactam (N-Me-CPL) exhibited higher activity. Varieties of substrates containing sensitive groups (ester group, cyano group, or sulfonamide group) or heterocycles (pyridine or quinoline groups) could react smoothly, expanding substrate scope of the reaction. In 2021, the same research group realized the coupling of aryl chlorides and alkyl Grignard reagents using N-butylpyrrolidone (NBP) as the cosolvent (Scheme 10) [33]. In this reaction, alkenyl bromides could also react smoothly with good selectivity, further expanding the substrate scope. The researcher synthesized high-value bioactive molecular fibrinolysis inhibitors efficiently using this reaction as key step (Schemes 11 and 12). In 2018, using the environmentally friendly 2-MeTHF as the solvent [34], the coupling reaction of aryl chlorides/aryl sulfonates and alkyl Grignard reagents was realized by the same group

60

Q. Zhang and S.-F. Zhu

Scheme 12 The synthesis of fibrinolysis inhibitor AZD6564

Scheme 13 Fe-catalyzed alkylation of aryl chlorides/tosylates in 2-MeTHF

Scheme 14 Fe-catalyzed alkylation of alkenyl halides with tetradentate bipyridine diimide

(Scheme 13), which solved the defect that the polyaromatic substrates in the NMP system could not be extended to the aryl substrate. The introduction of nitrogen, NHC, and phosphine ligands into the system could further improve the reaction activity and the reaction could be achieved only with a catalytic amount of ligands, which greatly improves the reaction efficiency. For example, in 2012, Thomas et al. [35] realized the FeCl2-catalyzed coupling reaction of alkenyl iodides, bromides, and chlorides with alkyl Grignard reagents with catalytic amount of tetradentate bipyridine diimide as ligand (Scheme 14). The obtained alkene compounds could be further reduced to give alkane compounds. NHC ligands have also been applied in these reactions. In 2009, Shi et al. [36] reported that the coupling of alkenyl/aryl carboxylates with alkyl Grignard reagent could be catalyzed by FeCl2 (Scheme 15). The NHC ligand inhibited β-H elimination and prevents the rearrangement side reactions of the products. In 2012, Garg et al. [37] realized the coupling of aryl sulfamates and carbamates with alkyl Grignard reagents using the catalyst of FeCl2/NHC (Scheme 16). The use of aryl

Iron-Catalyzed Carbon–Carbon Coupling Reaction

61

Scheme 15 Fe-catalyzed alkylation of alkenyl/aryl carboxylates with SIMes

Ar OR + Alkyl MgCl R = SO2NMe2 or CONEt2

FeCl2 (5 mol%) SIMes HCl (15 mol%)

Ar

o

Alkyl

CH2Cl2, THF, 65 C

Me Me Hex R = SO2NMe2, 84% R = CONEt2, 78% Me N

R = SO2NMe2, 93% R = CONEt2, 99%

Hex

Hex

Hex N

R = SO2NMe2, 98:2 E/Z

O

Me Me 78%,D >98:2 E/Z O

O

O

O H O

O Me Me 61%,D

Si(iPr)3

BnO

Ar

OBn BnO Ar = 4-ClC6H4 41%,E >98:2 E/Z

Scheme 105 Fe-catalyzed cross-coupling of glycosyl chlorides and aryl/alkenyl halides with Mn as reductant

Scheme 106 The proposed mechanism of Fe-catalyzed cross-coupling of glycosyl chlorides and aryl/alkenyl halides

addition, the target products were obtained when the pre-prepared Fe(I) complex was used for reaction, indicating that Fe(I) active species might be existing in the transformation. X-ray photoelectron spectroscopy shows that Fe(I) and Fe(III)

106

Q. Zhang and S.-F. Zhu

R

X

R2 R1

+

R3

O OMe

O

o

CH3CN, 25 C

O

R = Aryl, Alkenyl X = F, Cl, Br, I

Fe(acac)3 (8 mol%) MgCl2 (2.0 equiv) PBI (1.0 equiv) R Zn (2.5 equiv)

O

Br

standard conditions Br

O recovered ~50%

R5

R4

O R4 = H, R5 = H: 49% R4 = Me, R5 = Me: 38%

OMe +

O

Me Me

Ph

O

Me Me O BzO

N

N

PBI

standard conditions

OMe + Ph

O

R5

H N

10-95%

Me Me O R4

R

R1 R2 3

Me Me BzO 98:2) (Scheme 22). Alkyl carboxylic acids are ubiquitous in chemistry, ranging from natural products to medicine to materials. Therefore, if alkyl carboxylic acids can be used as alternative coupling partners, it would greatly expand the synthetic scope. In 2016, the Baran group [73] reported a decarboxylative C(sp3)-C(sp3) cross-coupling of alkyl carboxylic acid activated by tetrachloro N-hydroxyphthalimide with dialkylzinc reagents by nickel-catalysis (Scheme 23). This protocol shows extremely broad substrate scope (> 70 examples), including primary, secondary, and even tertiary alkyl carboxylic acids. The fly in the ointment is that relative high catalyst loading is required to ensure the high efficiency. Apart from alkyl carboxylic acids, alkyl amines are also prevalent in a myriad of biologically active molecules and preclinical candidates. The seminal work on deaminative cross-coupling is from M. P. Watson and coworkers (Scheme 24) [74]. Similarly, the transformation of alkyl amine into Katritzky pyridinium salts serves as the real hero in this reaction. This success provides an efficient route to convert ubiquitous NH2 groups into C(sp3) frameworks. This method also features wide substrate scope and excellent functional group tolerance.

2.3

Suzuki-Miyaura Cross-Coupling

Metal-catalyzed Suzuki-Miyaura cross-coupling reaction is the most popular protocol to construct carbon–carbon bonds using available, stable, and non-toxic aryl organoboron reagents as nucleophiles couple with aryl halides or surrogates as electrophiles. Since the first example on nickel-catalyzed Suzuki-Miyaura coupling reactions was reported by Miyaura in 1996 [75], great interest has been aroused in the synthetic community.

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

195

Scheme 24 M. P. Watson’s nickel-catalyzed cross-coupling of alkyl pyridinium salts and alkylzinc reagents

Scheme 25 Hartwig’s heteroaryl–heteroaryl Suzuki-Miyaura cross-coupling

2.3.1

C(sp2)-C(sp2) Bond Formation

Due to their prevalence in drug molecules, the construction of biheteroaryl building blocks is extremely important. An elegant protocol toward biheteroaryls by Ni-catalyzed Suzuki-Miyaura reaction was reported by the Hartwig group in 2012 (Scheme 25) [76]. The key to this success was the use of a nickel precatalyst prepared from cinnamyl chloride and [(dppf)Ni(COD)], K2CO3•1
5H2O as the activator of boronic acids, and acetonitrile as solvent. The practicability of this protocol has been demonstrated by the conduction under air and with a low catalyst loading (0.3 mol%). This reaction is also merited by its mild reaction conditions, wide substrate scope, and good functional group compatibility.

196

Y. Li et al.

Scheme 26 Garg’s heteroaryl–heteroaryl Suzuki-Miyaura cross-coupling

Scheme 27 Kirchner’s heteroaryl–heteroaryl Suzuki-Miyaura cross-coupling

Soon after, in 2013, a new protocol for the heteroaryl–heteroaryl Suzuki crosscoupling was disclosed by Garg and coworkers [77], which is characterized by the application of PCy3-ligated nickel catalyst and green solvent (2-MeTHF or t-amyl alcohol) (Scheme 26). This protocol tolerates a wider scope of heteroaryl electrophiles, such as esters, ethers, carbamates, sulfamates, and halides, albeit higher reaction temperature is required for those with an inert C–O bond. Moreover, a protocol featuring an air-stable triazine-based Ni(II)/PNP pincer complexes as precatalyst was demonstrated by the Kirchner group in 2016 (Scheme 27) [78]. Generally, excess exogenous bases are required to facilitate the transmetalation of boron reagents in Suzuki-Miyaura cross-coupling reactions. However, this would cause many side reactions, limit substrate scope as well as functional group compatibility. Therefore, seeking a base-free Suzuki-Miyaura cross-coupling reaction is highly demanding. An important contribution comes from the Sanford group, and in 2018 they [79] disclosed a base-free, nickel-catalyzed decarbonylative SuzukiMiyaura coupling of acid fluorides (Scheme 28a). Experimental evidences were provided for transmetalation with active Ni(II)-F intermediates, probably the

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

197

Scheme 28 Base-free Suzuki-Miyaura cross-coupling reactions

generation of fluoride serves as the activator of boronic acids. Soon later, in 2019, Rueping and coworkers [80] developed a Ni-catalyzed cross-coupling of aryl aldehydes with aromatic boronic acids under base-free conditions (Scheme 28b). The key to the success was the addition of an inexpensive ketone as hydride acceptor to generate a base in situ. Recently, the Chatani group described an amide-directed, nickel-catalyzed Suzuki-Miyaura cross-coupling of electrophiles with strong chemical bonds, such as C–O [81] and C–F bonds [82] (Scheme 29).

198

Y. Li et al.

Scheme 29 Chatani’s amide-directed Suzuki-Miyaura cross-coupling of electrophiles with strong chemical bonds

Scheme 30 Doyle’s nickel-catalyzed Suzuki-Miyaura cross-coupling of chromene acetals

2.3.2

C(sp2)-C(sp3) Bond Formation

In 2012, Doyle et al. described a nickel-catalyzed Suzuki-Miyaura cross-coupling of chromene acetals (Scheme 30) [83]. In the presence of Ni(COD)2/PPh3, readily accessible 2-ethoxy-2H-chromenes undergo C(sp3)-O cleavage and C(sp2)-C(sp3) bond formation to transform to 2-aryl-2H-chromenes. This method can be applied in late-stage incorporation of complex molecules, such as loratadine and indomethacin methyl ester. Notably, this reaction is also a base-free protocol. Stereospecific cross-coupling represents an important manifold to construct chiral molecules. In 2013, Jarvo et al. developed a nickel-catalyzed stereospecific coupling of chiral benzylic carbamates and pivalates with aryl boronic esters (Scheme 31) [84]. The reaction outcome depends on the choice of the ligand: tricyclohexylphosphine (PCy3) affording the products with stereocenter retention, while an N-heterocyclic carbene providing the product with stereocenter inversion.

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

199

Scheme 31 Jarvo’s nickel-catalyzed stereospecific Suzuki-Miyaura cross-coupling of chiral alkyl electrophiles

Scheme 32 Shi’s nickel-catalyzed Suzuki-Miyaura cross-coupling of allylic alkyl ethers

Recently, the Shi group developed a highly efficient protocol for direct crosscoupling of allylic alkyl ethers and organoboron compounds through the cleavage of inert C(sp3)-O(alkyl) bonds (Scheme 32) [85]. By using nickel/triphenylphosphine (PPh3) as catalyst, several types of allylic alkyl ethers can couple with various boronic acids or their derivatives to give the corresponding allylarenes in good to excellent yields with wide functional group tolerance and excellent regioselectivity. Alkyl carboxylic acids are a class of widely available feedstock chemicals. Concomitant with the development of Negishi cross-coupling, the Baran group reported the Suzuki-Miyaura cross-coupling of redox-active esters (TCNHPI) in 2016 (Scheme 33) [86]. Numerous examples have been presented to demonstrate the broad scope and functional group tolerance of this transformation. This study provides a beautiful union of the two most popular building blocks. Similarly, the M. P. Waston group developed a nickel-catalyzed Suzuki-Miyaura cross-coupling of Katritzky pyridinium salts in 2017 (Scheme 34) [87]. This reaction also shares the merits of practicability, broad scope, and functional group tolerance. A Ni(I)/Ni(III) catalytic cycle is proposed to rationale this transformation. The pyridinium salt undergoes single-electron transfer (SET) with a Ni(I) intermediate, which triggers fragmentation to give alkyl radical B. Then the alkyl radical recombines with an arylnickel(II) intermediate to give Ni(III) species C. Reductive elimination eventually provides cross-coupling products. Later, they achieved the cross-coupling of benzylic pyridinium salts with arylboronic acids [88], providing a one-pot procedure to diarylmethanes from benzyl amines.

200

Y. Li et al.

Scheme 33 Baran’s nickel-catalyzed cross-coupling of TCNHPI redox-active esters with boronic acids

Scheme 34 M. P. Watson’s nickel-catalyzed Suzuki-Miyaura cross-coupling of alkylpyridinium salts with aryl boronic acids

Chain-walking provides an opportunity to construct chemical bonds at sites that are different from the original one. In 2020, the Yin group developed a nickelcatalyzed migratory Suzuki-Miyaura cross-coupling featuring high benzylic or allylic selectivity (Scheme 35) [89]. Through this method, a wide range of unactivated alkyl electrophiles and aryl or vinyl boronic acids can be transferred to

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

201

Scheme 35 Yin’s nickel-catalyzed migratory Suzuki-Miyaura cross-coupling of alkyl electrophiles

diarylalkane or allylbenzene derivatives under mild reaction conditions in a highly efficient and selective fashion. In addition, the original-site cross-coupling products can be obtained by alternating the ligand, wherein the formation of the selective products has been rationalized by a radical chain process.

2.3.3

C(sp3)-C(sp3) Bond Formation

Since the seminal nickel-catalyzed, aryl-directed asymmetric Suzuki-Miyaura coupling of alkyl-(9-BBN) reagents with secondary alkyl halides reported by the Fu group in 2008 [90], significant progress was made by the same group [91–93]. In 2012, Fu and coworkers [94] disclosed a nickel-catalyzed asymmetric SuzukiMiyaura reaction with secondary alkyl halides bearing carbonates, sulfonamides, or sulfones as directing groups (Scheme 36). Notably, for those directing groups, oxygen is more likely coordinating with nickel to control the enantioselectivity. Besides, the distance between the directing group and the electrophilic site also effects the ee of this reaction. Moreover, the addition of alcohol plays the role to facilitate the boron reagent transmetalation.

2.4

Stille Cross-Coupling

The cross-coupling reaction of organohalides with organostannanes is called Stille cross-coupling. The first nickel-catalyzed Stille cross-coupling reaction was developed by the group of Percec in 1995 [95]. But this reaction exhibited low reactivity and with a large amount of homocoupling side products due to low efficiency of transmetalation from the tin reagent to nickel. In 2019, Neufeldt and coworkers [96]

202

Y. Li et al.

 

Scheme 36 Fu’s nickel-catalyzed asymmetric cross-coupling of secondary alkyl halides and alkylboron reagents

Scheme 37 Neufeldt’s nickel-catalyzed Stille cross-coupling of phenol derivatives

reported a Ni-catalyzed Stille cross-coupling of phenol derivatives (Scheme 37). The key to this success was the use of KF additive to facilitate the transmetalation step. This protocol can construct both aryl-heteroaryl and aryl-alkenyl bonds, as well as tolerates diverse functional groups.

2.5

Mizoroki-Heck Cross-Coupling

Mizoroki-Heck cross-coupling reactions, as an important strategy to synthesize substituted alkenes, have been attracted wide interest over the past decade (Scheme 38). In 2012, the Lei group disclosed a nickel-catalyzed Heck cross-coupling of secondary and tertiary α-carbonyl alkyl bromides, providing alkenyl carbonyl

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

203

Scheme 38 Lei’s nickel-catalyzed Heck cross-coupling of α-carbonyl alkyl bromides and α-cyano alkyl bromides

Scheme 39 Lei’s nickel-catalyzed oxidative Heck cross-coupling of aryl boronic acids

products with high E/Z selectivity (Scheme 38a) [97]. Soon after, they extended the substrates to α-cyano alkyl bromides, opening an avenue to β, γ-unsaturated nitriles (Scheme 38b) [98]. Notably, high temperature is required for non-electron-rich olefins, probably due to the difficulty in radical oxidation. In 2014, the Lei group also disclosed an oxidative Heck cross-coupling reaction of arylboronic acids with TEMPO as oxidant (Scheme 39) [99]. The combination of Ni(acac)2 and PPh3 is proved as the effective promoter to this reaction. This protocol could yield a series of 1,2-diarylalkenes with high efficiency and excellent thermodynamic E-selectivity.

204

Y. Li et al.

3 Reductive Cross-Coupling Compared with classical cross-couplings, reductive cross-couplings are utilization of two electrophiles as coupling partners with external reductants to maintain the catalytic cycle [100]. Reductive cross-coupling reactions have the advantage of avoiding the use of air- and moisture-sensitive organometallic reagents. Among this arena, the application of earth-abundant nickel-catalysts is particularly attractive.

3.1

C(sp2)-C(sp2) Bond Formation

An important contribution to nickel-catalyzed reductive coupling reaction was from Jutand and Mosleh in 1997 [101], albeit this reaction was limited to homocoupling of aryl halides. Two decades later, in 2013, the Gong group [102] achieved the first cross-coupling of two different aryl halides for the synthesis of unsymmetrical biaryls (Scheme 40). It is worth noting that the addition of pyridine and Bu4NI is crucial for the success of this reaction. Moreover, this protocol is sensitive to the electrical properties of the substrates, and a big gap of electrical properties of the substrates, such as one is electron-rich and another is electron-deficient, is required to ensure the high chemoselectivity. Soon after, in 2014, the Duan group [103] disclosed a method for the synthesis of unsymmetrical bipyridines by nickelcatalysis without external ligand (Scheme 41). Notably, this protocol can directly synthesize Caerulomycin F from commercially available materials by one step. Later, Gong, Zhang, and Ren [104] expanded the substrate scope from the aryl halides to vinyl halides (Scheme 42). This reaction displays a broad substrate scope with high chemoselectivity and excellent Z-selectivity (E/Z > 99:1). Of note is that both low temperature (≤20°C) and the addition of MgBr2 are important factors to this success. Unluckily, this reaction cannot tolerate Z-selective vinyl bromides, as

Scheme 40 Gong’s nickel-catalyzed reductive cross-coupling of aryl halides

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

205

Scheme 41 Duan’s nickel-catalyzed reductive cross-coupling of 2-halopyridines

Scheme 42 Gong’s reductive cross-coupling of aryl halides with vinyl bromides

well as limits to activated vinyl bromides. A related work was from the collaboration of Lian, Cheng, and Cramer [105], and they described a reductive cross-coupling of aryl bromides with 2,2-difluorovinyl tosylate in 2020 (Scheme 43). This method allows the synthesis of gem-difluorovinyl arenes, an important skeleton widely spread in compounds of medicinal interest, in a highly efficient manner. Mechanistic investigations suggest that Zn(II) salts play an important role in modulating the transmetalation step by forming a 1,1-difluorovinyl zinc reagent, and a catalytic cycle involving two nickel(II) species transmetalation is probably operated in this reaction. Aryl chlorides are widespread in biologically-relevant targets and generally cheaper than their analogues (Br, I). However, due to their relative lower reactivity, aryl chlorides are less employed in reductive cross-couplings. An important advance came from Lautens and coworkers in 2021 [106], who achieved nickel-catalyzed reductive cross-coupling of two aryl chlorides with broad substrate scope and high efficiency (31 examples, up to 94% yield) (Scheme 44). The catalytic system is comprised with NiI2 and 2,2′-bipyridine as catalyst, Zn as reductant, and MgCl2 as additive. The employment of MgCl2 is thought to facilitate the reduction of Ni(II) in the catalytic cycle. Similar to the reaction with aryl bromides, this reaction is also sensitive to the electrical properties of substituents on aryl chlorides, for example,

206

Y. Li et al.

Scheme 43 Lian, Cheng, and Cramer’s reductive cross-coupling of aryl bromides with 2,2-difluorovinyl tosylate

Scheme 44 Lautens’s reductive cross-coupling of aryl chlorides

substrate bearing an electron-rich methoxyl substituent giving low reactivity (8% yield). In the same year, the group of Chatani developed an amide-directed, reductive cross-coupling of aryl fluorides with other aryl partners, such as Aryl-Cl, -OTf, and -OTs (Scheme 45) [107]. Compared with aryl–aryl or aryl–vinyl combinations, the vinyl–vinyl coupling is more challenging by using single metal catalyst. Very recently, in 2022, Shu and coworkers [108] disclosed a Ni-catalyzed reductive cross-coupling of vinyl triflates with boron-substituted vinyl bromides, providing an elegant protocol for the synthesis of structurally-diverse dienylboronates (Scheme 46). Notably, the obtained excellent stereoselectivity (Z/E > 20:1) is probably due to the coordination of boron with nickel catalyst.

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

207

Scheme 45 Chatani’s amide-directed reductive cross-coupling reactions of aryl fluorides

Scheme 46 Shu’s reductive cross-coupling reactions of vinyl triflates with boron-substituted vinyl bromides

Nickel-catalyzed reductive cross-coupling reactions always employ stoichiometric amounts of metals, such as Zn and Mn, as reductant reagents, resulting in the formation of metal salts as by-products which may have a detrimental effect on the environment. Recently, an important advance was achieved by Li and coworkers [109], who reported a nickel-catalyzed cross-coupling of aryl triflates and aryl bromides by using N2H2 as an alternative reductant, with the releasing of N2 and H2 (Scheme 47). Nickel-catalyzed asymmetric reductive homo-coupling reactions for the synthesis of biaryl atropisomers were developed by the group of Mei [110] (Scheme 48) and Watson [111] (Scheme 49), respectively. Carbon dioxide (CO2), as a greenhouse gas, has negative impact on the environment, and the conversion of CO2 into value-added chemicals is an important and attractive topic. With respect to the synthetic chemistry, CO2 is recognized as a C1

208

Y. Li et al.

Scheme 47 Nickel-catalyzed reductive cross-coupling reactions of aryl triflates with aryl bromides

Scheme 48 Mei’s enantioselective nickel-catalyzed electrochemical reductive homocoupling of aryl bromides

Scheme 49 Watson’s enantioselective nickel-catalyzed reductive homocoupling of ortho-(iodo)arylphosphine oxides

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

209

Scheme 50 Nickel-catalyzed reductive cross-coupling of aryl electrophiles with CO2

synthon and electrophiles [112, 113]. However, owing to its thermodynamically and kinetically stable, it is rather difficult to activate. Transition metal catalysis offers an opportunity to address this obstacle, especially with nickel-based catalysts. An important work on nickel-catalyzed reductive cross-coupling of sp2-carbon electrophiles and CO2 was disclosed by Tsuji and coworkers in 2012 (Scheme 50a) [114]. Soon after, this transformation with abundant phenol derivatives, particularly to those with a relative inert C–O bond, was achieved by the Martin group (Scheme 50b) [115], and the scope was continued to be extended to aryl fluorosulfates by the Mei group (Scheme 50c) [116]. Recently, Martin and coworkers [117] found aryl sulfonium salts could also be used as alternative electrophiles via C–S bond cleavage (Scheme 50d). It should be noted that Zn metal not only serves the role of terminal reductant, but also facilitates the activation of C–S bond by in situ generation of arylzinc species in this reaction.

210

3.2

Y. Li et al.

C(sp2)-C(sp3) Bond Formation

In 2015, Doyle et al. reported benzylic acetals, a new class of substrates, participated nickel-catalyzed reductive cross-coupling reaction [118] (Scheme 51). A catalytic cycle involving α-oxy radicals that generated from benzylic acetals, TMSCl and Zn, was proposed for this transformation. C-aryl nucleosides have great utility in medicinal chemistry, chemical biology, and synthetic biology. Recently, Li et al. described a cross-electrophile coupling protocol to prepare C-aryl nucleoside analogues from readily available furanosyl acetates and aryl iodides (Scheme 52) [119]. The catalytic system features the application of tridentate pyridine-based ligand. This approach is characterized by its mild reaction conditions, broad substrate scope, excellent β-selectivity, and wide functional group compatibility. The introduction of fluorine atom into organic molecules always has a positive effect on their biological properties. In 2017, Y. Fu and coworkers [120] achieved a nickel-catalyzed defluorinative reductive cross-coupling of gem-difluoroalkenes with alkyl halides using B2pin2/K3PO4 as terminal reductant (Scheme 53). All primary, secondary, and tertiary alkyl halides underwent this reaction to transfer the corresponding mono-fluoroalkenes with excellent (Z )-selectivity. This success

Scheme 51 Doyle’s nickel-catalyzed reductive cross-coupling of acetals and aryl iodides

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

211

Scheme 52 Li’s nickel-catalyzed reductive cross-coupling of furanosyl acetates with aryl iodides

Scheme 53 Y. Fu’s nickel-catalyzed reductive cross-coupling of gem-difluoroalkenes with alkyl halides

suggests that the cleavage of C–F bond by β-F elimination is much easier than by oxidative addition. In 2018, Zhang et al. described a method for preparation of difluoromethyl arenes through nickel-catalyzed reductive cross-coupling of ClCF2H with (hetero)aryl chlorides (Scheme 54) [121]. The method is characterized by its high efficiency, mild reaction conditions, and broad scope. Moreover, the reliable practicability and scalability of this protocol have also been demonstrated by several 10 g scale reactions without loss of reactivity. Preliminary mechanistic studies reveal that the reaction starts from the oxidative addition of aryl chlorides to Ni(0) and with a difluoromethyl radical addition as a key step.

212

Y. Li et al.

Scheme 54 Zhang’s nickel-catalyzed reductive cross-coupling of ClCF2H with aryl chlorides

All-carbon quaternary centers are ubiquitous in bioactive molecules and nature products. However, the construction is highly challenging due to the steric hindrance. The Gong group made great contribution to address this strategy by reductive cross-electrophile couplings. For example, in 2015, they developed a method that allows the construction of all-carbon quaternary centers through using tertiary alkyl bromides and aryl bromides as coupling partners (Scheme 55a) [122]. This protocol exhibits good functional group tolerance and high regioselectivity. However, this method is limited to electron-deficient aryl bromides. Later, they addressed this limitation by using 3-fluoropyrindine as the ligand (Scheme 55b) [123]. At the same time, (+)-asperazine and (+)-pestalazine A were facilely synthesized by this protocol. In 2019, they extended this strategy to the coupling of electron-deficient aryl chlorides with tertiary alkyl oxalates (Scheme 55c) [124]. The Reisman group has made important contributions to the enantioselective cross-electrophile couplings [125]. Over the past 10 years, they have succeeded in a variety of cross-coupling partner combinations for the asymmetric construction of C (sp2)-C(sp3) bonds (Scheme 56). For instance, the cross-coupling of vinyl bromides with secondary benzyl chlorides in 2014 (Scheme 56a) [126], heteroaryl iodides with α-chloronitriles in 2015 (Scheme 56b) [127], (hetero)aryl iodides with benzylic chlorides and N-hydroxyphthalimide esters with vinyl bromides in 2017 (Scheme 56c, d) [128, 129], vinyl bromides with (chlorobenzyl)silanes in 2018 (Scheme 56e) [130], as well as alkenyl bromides with benzyl chlorides in 2019 [131]. In 2018, the Yin group reported a ligand-controlled, nickel-catalyzed reductive migratory cross-coupling of alkyl bromides with aryl bromides, which afforded

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

213

Scheme 55 Gong’s nickel-catalyzed reductive cross-coupling of tertiary alkyl (pseudo)halides with aryl halides

1,1-diarylalkanes with good to excellent yields and regioselectivity (Scheme 57) [132]. The key to the success of this reaction is the application of sterically hindered bathocuproine ligand. Under the context of C(sp2)-C(sp3) bonds formation, another important reaction is nickel-catalyzed carboxylation of alkyl halides with CO2. In 2017, the Martin group discovered the first nickel-catalyzed regio- and chemoselective remote carboxylation of alkyl halides under 1 bar pressure of CO2 (Scheme 58a) [133]. Notably, the halogenated compounds can be prepared from according hydrocarbons without isolation or purification, showing the robustness of this methodology. Interestingly, a kinetic or thermodynamic switch in chemoselectivity was made by a small change in reaction temperature; that is, lower temperatures resulted in the formation of linear carboxylic acids, while higher temperatures promoted the formation of branched carboxylic acids (Scheme 58b). The same group also extended the substrates to unactivated primary, secondary, and tertiary alkyl chlorides [134]. Importantly, these protocols provide a platform to valuable fatty acids from petroleum processing unrefined raw materials, such as alkanes or unrefined mixtures of alkenes without purification of the intermediates. Later, Martin in collaboration with Hopmann explained the reactivity of [(phenanthroline)Ni] species with CO2 in Ni-catalyzed carboxylation reactions [135]. They demonstrated that the insertion of CO2 into a

214

Y. Li et al.

Scheme 56 Reisman’s nickel-catalyzed asymmetric reductive cross-coupling reactions

(phen)-Ni(I)-alkyl complex was the critical elementary step, consistent with the discovery from the Diao group [136]. Transition metal-catalyzed cross-coupling of C-O electrophiles has recently garnered tremendous attention, due to the ready accessibility of alcohols. In this regard, an interesting nickel-catalyzed switchable site-selective reductive carboxylation of allylic alcohols with CO2 was documented by the Martin group recently, wherein regiodivergency was solely determined by the ligand backbone geometry (Scheme 59) [137]. Mechanistic studies indicated the formation of η1-Ni(I) intermediates with

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

215

Scheme 57 Yin’s nickel-catalyzed reductive relay cross-coupling of alkyl bromides with aryl bromides

Scheme 58 Martin’s nickel-catalyzed remote carboxylation of halogenated aliphatic hydrocarbons with CO2

rigid bidentate ligands, while tridentate ligands facilitate the formation of η1-Ni (II) intermediates.

216

Y. Li et al.

Scheme 59 Martin’s nickel-catalyzed switchable site-selective carboxylation of allylic alcohols with CO2

3.3

C(sp3)-C(sp3) Bond Formation

The first catalytic reductive cross-coupling reaction using two different alkyl electrophiles enabled by nickel catalyst with zinc as reductant was disclosed by the Gong group in 2011 (Scheme 60) [138]. This method could efficiently construct alkyl– alkyl bonds with good functional group compatibility. However, one of the alkyl halides was used threefold amounts in this reaction. Later, they improved the efficiency by using bis(pinacolato)diboron instead of zinc as terminal reductant [139]. High efficiency was generally obtained from 1° to 2° cross-couplings, but not from 2° to 2° couplings. Control experiments ruled out the pathway of borylation/Suzuki-Miyaura cross-coupling. The reductive coupling of tertiary alkyl electrophiles with another alky partners for the construction of all-C(sp3) quaternary centers can be challenging as the side reactions of dehalogenation and homocoupling may be involved. In 2018, Gong and coworkers [140] succeeded in the reductive cross-coupling of tertiary alkyl electrophiles with primary alkyl electrophile (Scheme 61). In this reaction, activated primary allylic carbonates are selected to couple with tertiary alkyl halides, and

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

217

Scheme 60 Gong’s Ni-catalyzed reductive alkyl–alkyl cross-coupling of unactivated alkyl halides

Scheme 61 Gong’s Ni-catalyzed reductive cross-coupling of unactivated tertiary alkyl halides with primary allylic carbonates

the nitrogen-based ligands play an important role in modulating the reactivity and selectivity. Soon after, the Shu group [141] disclosed the reductive cross-coupling of benzyl oxalates with alkyl bromides (Scheme 62). The rational choice of oxalate as leaving group is highlighted by the fact that other leaving groups lead to either lower or no reactivity. Additionally, the choice of DMSO as cosolvent can eliminate the formation of ArCH2OH. Recently, Watson and coworkers [142] achieved a nickelcatalyzed reductive cross-coupling of alkyl pyridinium salts with methyl iodide.

218

Y. Li et al.

Scheme 62 Shu’s Ni-catalyzed reductive cross-coupling of benzyl oxalates with alkyl bromides

Scheme 63 Yin’s Ni-catalyzed reductive migratory alkyl–alkyl cross-coupling

In 2020, Yin and coworkers [143] took advantage of chain-walking to achieve a reductive migratory alkyl–alkyl cross-coupling (Scheme 63), which could forge 2°-2° C(sp3)-C(sp3) bonds from 1° and 2° carbon electrophiles. This protocol exhibited good regioselectivity, even for the substrates containing a 7-carbon chain. Of note, deuterium-labeled experiment indicates that nickel chain-walking occurs in both coupling partners. The key to the success of this reaction was the identification of bidentate PyrOx ligand.

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

219

4 Oxidative Cross-Coupling The cross-coupling of two different nucleophiles under oxidative conditions is called oxidative cross-coupling. As shown in Scheme 64, this strategy also has a wide substrate scope and broad applications, as there are several binding modes, including two different R-Nu integration, R1-H integrated with R2-Nu as well as two different R-H combination [144–147]. Especially for the last pattern, which is the most ideal route as only producing H2 as by-products. Additionally, many oxidants could be employed, such as molecular oxygen, TEMPO, or metal salts, etc. The Lei group has made great contributions to the construction of C(sp2)-C(sp3) bonds. For example, they [148] disclosed a nickel-catalyzed site-selective crosscoupling of cyclic ethers with aryl boronic acids by using DTBP as terminal oxidant in 2013 (Scheme 65a). Of note, this protocol could also achieve the arylation of C (sp3)-H adjacent to nitrogens. Soon after, Lei and Lan [149] achieved the arylation of more challengeable cyclohexane (Scheme 65b). Simultaneously, Cai and coworkers

Scheme 64 Nickel-catalyzed oxidative cross-coupling reactions

Scheme 65 Lei’s nickel-catalyzed oxidative arylation of C(sp3)-H bonds

220

Y. Li et al.

Scheme 66 Cai’s nickel-catalyzed switchable site-regioselective oxidative cross-coupling of 1.4dioxane with indole derivatives

[150] disclosed a nickel-catalyzed oxidative alkylation of indoles with 1,4-dioxane via dual C-H activation (Scheme 66). Intriguingly, the site-selectivity was controlled by the choice of the catalyst: the catalytic system of Ni(acac)2/Zn(OTf)2 is responsible for the C-3 selectivity, while the system of NiF2/PPh3 leads to the C-2 alkylation.

5 Cross-Coupling of C–H Bonds Direct cross-coupling of C–H bonds provides straightforward and greener approach toward the targets by eliminating the utilization of prefunctionalized reagents, such as aryl halides or metal reagents. Therefore, it is an ideal synthetic route [18].

5.1

C(sp2)-C(sp2) Bond Formation

From the aspect of step and atom economy, direct C-H activation is a desirable and straightforward strategy to forge C(sp2)-C(sp2) bonds. In 2012, the Itami group described a direct cross-coupling of azoles with phenol derivatives in the presence of Ni(COD)2/dcype (Scheme 67a) [151]. In this same year, the authors extended the success to aryl esters (Scheme 67b) [152]. This strategy can be applied to rapidly synthesize muscoride A, an important drug of antibacterial activity. Soon after, they extended the strategy to alkenyl [153] and aryl [154] carboamides (Scheme 67c, d). Notably, a Ni(0/II) catalytic cycle, evidenced by the isolation and characterization of an arylnickel(II) pivalate intermediate, was proposed by the cooperation of Itami, Lei, and Yamaguchi [155]. This type of substrates have also attracted wide attention in cross-coupling of inert chemical bonds, for instance, in 2017, the Kalyani group

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

221

Scheme 67 Nickel-catalyzed C-H arylation and alkenylation of (hetero)arenes

[156] reported the cross-coupling with aromatic nitriles (Scheme 67e) and Ong and Zhao [157] disclosed the cross-coupling of aryl methoxylethers (Scheme 67f). Heteroaromatic rings that contain activated hydrogen are used in the abovementioned studies. In contrast, direct activation of common arenes is much difficult. A directing group installed on the aryl ring is always necessary. In 2014, the Chatani group reported a chelation-assisted direct C-H arylation of common arenes by using

222

Y. Li et al.

Scheme 68 Nickel-catalyzed C-H activation via directing group assistant

8-aminoquinoline as a directing group (Scheme 68a) [158]. Based on experimental mechanistic studies, the Ni(0)/Ni(II) catalytic cycle was ruled out and a Ni(II)/Ni (IV) catalytic cycle was proposed. Soon after, the You and coworkers achieved a Ni-catalyzed direct oxidative cross-coupling of two heteroarenes by using 8-aminoquinoline as directing group and Ag2CO3 as oxidant (Scheme 68b) [159]. The mechanistic studies indicate that the C–H bond activation serves as a rate-determining step in this reaction. In the same year, the Shi group using a unique PIP as directing group achieved a nickel-catalyzed oxidative coupling of heteroaryls

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

223

Scheme 69 Punji’s nickel-catalyzed C-H arylation of arenes and indoles

with arylsilanes (Scheme 68c) [160]. In 2017, the group of Hoover extended the strategy to coupling with aryl acids (Scheme 68d) [161]. Very recently, Punniyamurthy and coworkers demonstrated that oxazoline-aniline could also be used as the directing group in oxidative cross-coupling of bi(hetero)aryls (Scheme 68e) [162]. In 2017, Punji and coworkers [163] achieved a solvent-free, pyridine-directed of C–H bond arylation reaction by using tridentate nitrogen ligated nickel catalyst (Scheme 69). This reaction features excellent chemoselectivity, short reaction time (30–120 min) as well as high functional group compatibility. Soon later, in 2019, the same group [164] extended the substrates from aryl bromides and iodides to aryl chlorides by using dppf as an alternative ligand.

5.2

C(sp2)-C(sp3) Bond Formation

In 2014, You et al. disclosed a nickel-catalyzed unactivated β-C(sp3)–H bond arylation of aliphatic acid derivatives with both aryl iodides and bromides via bidentate chelation-assistance of an 8-aminoquinoline moiety (Scheme 70) [165]. In 2016, the Walsh group developed a nickel-catalyzed cross-coupling of heteroaryl-containing diarylmethanes with both aryl halides, which provides a direct route to triarylmethanes from heteroaryl-containing diarylmethanes (Scheme 71)

224

Y. Li et al.

Scheme 70 You’s nickel-catalyzed unactivated β-C(sp3)–H bond arylation of aliphatic acid derivatives

Scheme 71 Walsh’s nickel-catalyzed arylation of heteroaryl-containing diarylmethanes

[166]. The success of this reaction relies on the introduction of a unique Ni(0)/ NiXantphos-based catalyst, which exhibits enhanced reactivity over Xantphos derivatives and other Ni(phosphine)-based catalysts examined in the reaction. Subsequently, in 2019, they achieved the arylation of toluene derivatives with a similar nickel(II)/NiXantphos-based catalyst(Scheme 72) [167]. The key factor to success is the activation of toluene by a cation-π complex, enabling methyl arenes (pKa ≈ 43) to be deprotonated with the relatively mild base NaN(SiMe3)2. This method allows the rapid access to a variety of sterically and electronically diverse aryl and heteroaryl-containing diarylmethanes. Recently, Punji et al. contributed an excellent and detailed account [18], which summarized the developments in nickel-catalyzed regioselective functionalization of azoles and indoles with a considerable focus on the reaction mechanism, thus the relevant contents will not be repeated.

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

225

Scheme 72 Walsh’s nickel-catalyzed arylation of toluene derivatives

Scheme 73 Hu’s nickel-catalyzed alkylation of unactivated C(sp3)-H bonds

5.3

C(sp3)-C(sp3) Bond Formation

Compared with C(sp2)-C(sp2) bond formation via C–H bond activation, the development of C(sp3)-C(sp3) bond formation by C(sp3)-H bond activation is quite slow. A prominent work is from the Hu group [168], and they describe a Ni-catalyzed alkylation of C(sp3)-H bonds of aliphatic amides bearing bidentate directing group (Scheme 73). Of note, due to the steric effects, the methyl groups prior to be

226

Y. Li et al.

Scheme 74 Watson’s nickel-catalyzed C-alkylation of nitroalkanes

activated over the methylene groups. Besides, the C(sp3)-H bonds of methyl groups also prefer to be activated over the C(sp2)-H bonds of arenes. Based on experimental studies, the authors proposed a possible catalytic cycle with Ni(II)-mediated C-H activation and alkyl radical addition as key steps to rationale this transformation. Nitroalkanes, as versatile building blocks, have been widely used in organic synthesis. C-Alkylation of nitroalkanes provides an opportunity for transformation of simple nitroalkanes into complex ones. However, its development is highly lagged due to the competition of O-alkylation. To the Watson group address this challenge by changing the classical two-electron chemistry to single-electron pathway. In 2017, they disclosed a Ni-catalyzed protocol for C-alkylation of nitroalkanes with alkyl iodides (Scheme 74) [169]. This protocol is distinguished by its simple catalyst, mild reaction conditions, and wide substrate scope. Particularly noteworthy is that anti-viral drug adapromine can be prepared in only two steps by this method. Later, in 2019, they also achieved an enantioselective C-alkylation of nitroalkanes by nickel-catalysis, providing an approach for the synthesis of enantioenriched β-nitroamides (Scheme 75) [170].

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

227

Scheme 75 Watson’s nickel-catalyzed asymmetric C-alkylation of nitroalkanes

6 Conclusion Transition metal-catalyzed carbon–carbon bonds formation reactions have been developed to be a fundamental tool in synthetic chemistry. Nickel-catalysis, as a member of d10 metals, features many unique properties, for instance facile oxidative addition, disfavored β-hydride elimination as well as multiple oxidation states, that allow the bonding formation in multiple binding modes and the development of various innovative strategies. Tremendous advances have been made over the past decade, and corresponding mechanisms have been discussed in this chapter. However, some detailed reaction intermediates are still unclear due to their unstable and the rapid assembly of complex compounds remains challenging. Along with in-depth study and profound insights into this nickel-catalyzed C–C bonds formation, other different catalytic modes have emerged, like dual-metal system, photoand electrochemistry synergistic catalysis with nickel, as well as C–C π-bonds could be involved and followed by cross-couplings. These emerged catalytic strategies that greatly extend the synthetic scope and establish novel reaction mechanism will become a more applicable and welcome direction in the future.

References 1. Miyaura N (ed) (2001) Cross-coupling reactions: a practical guide. Wiley, Chichester 2. Corbet J-P, Mignani G (2006) Chem Rev 106:2651 3. Magano J, Dunetz JR (2011) Chem Rev 111:2177

228

Y. Li et al.

4. Astruc D (2011) Anal Bioanal Chem 399:1811 5. Fu GC (2017) ACS Cent Sci 3:692 6. Tasker SZ, Standley EA, Jamison TF (2014) Nature 509:299 7. Zheng B, Tang F, Luo J, Schultz JW, Rath NP, Mirica LM (2014) J Am Chem Soc 136:6499 8. Camasso NM, Sanford MS (2015) Science 347:1218 9. Lin C-Y, Power PP (2017) Chem Soc Rev 46:5347 10. Diccianni JB, Joseph Katigbak HC, Diao T (2019) J Am Chem Soc 141:1788 11. Leatherman MD, Svejda SA, Johnson LK, Brookhart M (2003) J Am Chem Soc 125:3068 12. Xu H, White PB, Hu C, Diao T (2017) Angew Chem Int Ed 56:1535 13. Xu H, Hu CT, Wang X, Diao T (2017) Organometallics 36:4099 14. Rosen BM, Quasdorf KW, Wilson DA, Zhang N, Resmerita AM, Garg NK, Percec V (2011) Chem Rev 111:1346 15. Yamaguchi J, Muto K, Itami K (2013) Eur J Org Chem 2013:19 16. Cheng L, Zhou Q (2020) Acta Chim Sin:78 17. Khake SM, Chatani N (2019) Trends Chem 1:524 18. Jagtap RA, Punji B (2021) Chem Rec 21:3573 19. Subaramanian M, Sivakumar G, Balaraman E (2021) Org Biomol Chem 19:4213 20. Xue W, Jia X, Wang X, Tao X, Yin Z, Gong H (2021) Chem Soc Rev 50:4162 21. Iwasaki T, Kambe N (2016) Top Curr Chem (Z) 374:66 22. Li Z, Liu L (2015) Chin J Catal 36:3 23. Diccianni JB, Diao T (2019) Trends Chem 1:830 24. Ackerman LK, Lovell MM, Weix DJ (2015) Nature 524:454 25. Huang L, Ackerman LKG, Kang K, Parsons AM, Weix DJ (2019) J Am Chem Soc 141:10978 26. Yi L, Ji T, Chen K-Q, Chen X-Y, Rueping M (2022) CCS Chem 4:9 27. Milligan JA, Phelan JP, Badir SO, Molander GA (2019) Angew Chem Int Ed 58:6152 28. Qi X, Diao T (2020) ACS Catal 10:8542 29. Wang X-X, Lu X, Li Y, Wang J-W, Fu Y (2020) Sci China Chem 63:1586 30. Zhang Z, Bera S, Fan C, Hu X (2022) J Am Chem Soc 144:7015 31. Ye Y, Lin Y, Mao ND, Yang H, Ye XY, Xie T (2022) Org Biomol Chem. https://doi.org/10. 1039/D2OB01855A 32. Tamao K, Sumitani K, Kumada M (1972) J Am Chem Soc 94:4374 33. King AO, Okukado N, Negishi E-i (1977) J Chem Soc Chem Commun 19:683 34. Negishi E, King AO, Okukado N (2002) J Org Chem 42:1821 35. Negishi E (2002) Acc Chem Res 15:340 36. Miyaura N, Yanagi T, Suzuki A (1981) Synth Commun 11:513 37. Watanabe T, Miyaura N, Suzuki A (1992) Synlett 1992:207 38. Miyaura N, Suzuki A (1995) Chem Rev 95:2457 39. Stille J (1986) Angew Chem Int Ed 25:508 40. Stille JK (1985) Pure Appl Chem 57:1771 41. Corriu RJP, Masse JP (1972) J Chem Soc Chem Commun 42. Zhang ZB, Ji CL, Yang C, Chen J, Hong X, Xia JB (2019) Org Lett 21:1226 43. Taylor BL, Harris MR, Jarvo ER (2012) Angew Chem Int Ed 51:7790 44. Tobisu M, Chatani N (2015) Acc Chem Res 48:1717 45. Tobisu M, Takahira T, Chatani N (2015) Org Lett 17:4352 46. Tobisu M, Takahira T, Morioka T, Chatani N (2016) J Am Chem Soc 138:6711 47. Hostier T, Neouchy Z, Ferey V, Gomez Pardo D, Cossy J (2018) Org Lett 20:1815 48. Ho YA, Leiendecker M, Liu X, Wang C, Alandini N, Rueping M (2018) Org Lett 20:5644 49. Klaus M, Christoph F, Francois D (2007) Science 317:1881 50. Hagmann WK (2008) J Med Chem 51:4359 51. Meanwell NA (2011) J Med Chem 54:2529 52. Motohashi H, Mikami K (2018) Org Lett 20:5340 53. Mills LR, Edjoc RK, Rousseaux SAL (2021) J Am Chem Soc 143:10422 54. Cossy J, Polak P (2022) Synlett 33:1629

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

229

55. Polak P, Cossy J (2022) Eur J Chem 28:e202104311 56. Terao J, Watanabe H, Ikumi A, Kuniyasu H, Kambe N (2002) J Am Chem Soc 124:4222 57. Vechorkin O, Hu X (2009) Angew Chem Int Ed 48:2937 58. Perez Garcia PM, Di Franco T, Orsino A, Ren P, Hu X (2012) Org Lett 14:4286 59. Breitenfeld J, Ruiz J, Wodrich MD, Hu X (2013) J Am Chem Soc 135:12004 60. Baba S, Negishi E (1976) J Am Chem Soc 98:6729 61. Zhou JS, Fu GC (2003) J Am Chem Soc 125:14726 62. Fischer C, Fu GC (2005) J Am Chem Soc 127:4594 63. Smith SW, Fu GC (2008) Angew Chem Int Ed 47:9334 64. Do HQ, Chandrashekar ER, Fu GC (2013) J Am Chem Soc 135:16288 65. Devasagayaraj A, Stüdemann T, Knochel P (1996) Angew Chem Int Ed 34:2723 66. Giovannini R, Knochel P (1998) J Am Chem Soc 120:11186 67. Giovannini R, Studemann T, Devasagayaraj A, Dussin G, Knochel P (1999) J Org Chem 64: 3544 68. Piber M, Jensen AE, Rottländer M, Knochel P (1999) Org Lett 1:1323 69. Schmidt J, Choi J, Liu AT, Slusarczyk M, Fu GC (2016) Science 354:1265 70. Schwarzwalder GM, Matier CD, Fu GC (2019) Angew Chem Int Ed 58:3571 71. Yang ZP, Freas DJ, Fu GC (2021) J Am Chem Soc 143:8614 72. Huo H, Gorsline BJ, Fu GC (2020) Science 367:559 73. Qin T, Cornella J, Li C, Malins LR, Edwards JT, Kawamura S, Maxwell BD, Eastgate MD, Baran PS (2016) Science 352:801 74. Plunkett S, Basch CH, Santana SO, Watson MP (2019) J Am Chem Soc 141:2257 75. Saito S, Sakai M, Miyaura N (1996) Tetrahedron Lett 37:2993 76. Ge S, Hartwig JF (2012) Angew Chem Int Ed 51:12837 77. Ramgren SD, Hie L, Ye Y, Garg NK (2013) Org Lett 15:3950 78. Mastalir M, Stoger B, Pittenauer E, Allmaier G, Kirchner K (2016) Org Lett 18:3186 79. Malapit CA, Bour JR, Brigham CE, Sanford MS (2018) Nature 563:100 80. Guo L, Srimontree W, Zhu C, Maity B, Liu X, Cavallo L, Rueping M (2019) Nat Commun 10: 1957 81. Morishige A, Iyori Y, Chatani N (2021) Helv Chim Acta 104:e2100089 82. Zhang T, Nohira I, Chatani N (2021) Org Chem Front 8:3783 83. Graham TJA, Doyle AG (2012) Org Lett 14:1616 84. Harris MR, Hanna LE, Greene MA, Moore CE, Jarvo ER (2013) J Am Chem Soc 135:3303 85. Li X, Li Y, Zhang Z, Shi X, Liu R, Wang Z, Li X, Shi D (2021) Org Lett 23:6612 86. Wang J, Qin T, Chen T-G, Wimmer L, Edwards JT, Cornella J, Vokits B, Shaw SA, Baran PS (2016) Angew Chem Int Ed 55:9676 87. Basch CH, Liao J, Xu J, Piane JJ, Watson MP (2017) J Am Chem Soc 139:5313 88. Liao J, Guan W, Boscoe BP, Tucker JW, Tomlin JW, Garnsey MR, Watson MP (2018) Org Lett 20:3030 89. Li Y, Luo Y, Peng L, Li Y, Zhao B, Wang W, Pang H, Deng Y, Bai R, Lan Y, Yin G (2020) Nat Commun 11:417 90. Saito B, Fu GC (2008) J Am Chem Soc 130:6694 91. Lundin PM, Fu GC (2010) J Am Chem Soc 132:11027 92. Lu Z, Wilsily A, Fu GC (2011) J Am Chem Soc 133:8154 93. Zultanski SL, Fu GC (2011) J Am Chem Soc 133:15362 94. Wilsily A, Tramutola F, Owston NA, Fu GC (2012) J Am Chem Soc 134:5794 95. Percec V, Bae J-Y, Hill DH (1995) J Org Chem 60:6895 96. Russell JEA, Entz ED, Joyce IM, Neufeldt SR (2019) ACS Catal 9:3304 97. Liu C, Tang S, Liu D, Yuan J, Zheng L, Meng L, Lei A (2012) Angew Chem Int Ed 51:3638 98. Tang S, Liu C, Lei A (2013) Chem Commun 49:2442 99. Liu D, Liu C, Lei A (2014) Pure Appl Chem 86:321 100. Wang X, Dai Y, Gong H (2016) Top Curr Chem 374:43 101. Jutand A, Mosleh A (1997) J Org Chem 62:261

230

Y. Li et al.

102. Lin K, Qian Q, Zang Z, Wang S, Chen Y, Gong H (2013) Synlett 24:619 103. Liao LY, Kong XR, Duan XF (2014) J Org Chem 79:777 104. Liu J, Ren Q, Zhang X, Gong H (2016) Angew Chem Int Ed 55:15544 105. Xiong B, Wang T, Sun H, Li Y, Kramer S, Cheng G-J, Lian Z (2020) ACS Catal 10:13616 106. Mirabi B, Marchese AD, Lautens M (2021) ACS Catal 11:12785 107. Nohira I, Chatani N (2021) ACS Catal 11:4644 108. Xu G-L, Liu C-Y, Pang X, Liu X-Y, Shu X-Z (2022) CCS Chem 4:864 109. Lv L, Qiu Z, Li J, Liu M, Li CJ (2018) Nat Commun 9:4739 110. Qiu H, Shuai B, Wang YZ, Liu D, Chen YG, Gao PS, Ma HX, Chen S, Mei TS (2020) J Am Chem Soc 142:9872 111. Zuo Z, Kim RS, Watson DA (2021) J Am Chem Soc 143:1328 112. Tortajada A, Julia-Hernandez F, Borjesson M, Moragas T, Martin R (2018) Angew Chem Int Ed 57:15948 113. Davies J, Lyonnet JR, Zimin DP, Martin R (2021) Chem 7:2927 114. Fujihara T, Nogi K, Xu T, Terao J, Tsuji Y (2012) J Am Chem Soc 134:9106 115. Correa A, Leon T, Martin R (2014) J Am Chem Soc 136:1062 116. Ma C, Zhao CQ, Xu XT, Li ZM, Wang XY, Zhang K, Mei TS (2019) Org Lett 21:2464 117. Yanagi T, Somerville RJ, Nogi K, Martin R, Yorimitsu H (2020) ACS Catal 10:2117 118. Arendt KM, Doyle AG (2015) Angew Chem Int Ed 54:9876 119. Li Y, Wang Z, Li L, Tian X, Shao F, Li C (2022) Angew Chem Int Ed 61:e202110391 120. Lu X, Wang Y, Zhang B, Pi JJ, Wang XX, Gong TJ, Xiao B, Fu Y (2017) J Am Chem Soc 139:12632 121. Xu C, Guo WH, He X, Guo YL, Zhang XY, Zhang X (2018) Nat Commun 9:1170 122. Wang X, Wang S, Xue W, Gong H (2015) J Am Chem Soc 137:11562 123. Wang X, Ma G, Peng Y, Pitsch CE, Moll BJ, Ly TD, Wang X, Gong H (2018) J Am Chem Soc 140:14490 124. Ye Y, Chen H, Sessler JL, Gong H (2019) J Am Chem Soc 141:820 125. Poremba KE, Dibrell SE, Reisman SE (2020) ACS Catal 10:8237 126. Cherney AH, Reisman SE (2014) J Am Chem Soc 136:14365 127. Kadunce NT, Reisman SE (2015) J Am Chem Soc 137:10480 128. Poremba KE, Kadunce NT, Suzuki N, Cherney AH, Reisman SE (2017) J Am Chem Soc 139: 5684 129. Suzuki N, Hofstra JL, Poremba KE, Reisman SE (2017) Org Lett 19:2150 130. Hofstra JL, Cherney AH, Ordner CM, Reisman SE (2018) J Am Chem Soc 140:139 131. DeLano TJ, Reisman SE (2019) ACS Catal 9:6751 132. Peng L, Li Y, Li Y, Wang W, Pang H, Yin G (2018) ACS Catal 8:310 133. Julia-Hernandez F, Moragas T, Cornella J, Martin R (2017) Nature 545:84 134. Borjesson M, Moragas T, Martin R (2016) J Am Chem Soc 138:7504 135. Somerville RJ, Odena C, Obst MF, Hazari N, Hopmann KH, Martin R (2020) J Am Chem Soc 142:10936 136. Diccianni JB, Hu CT, Diao T (2019) Angew Chem Int Ed 58:13865 137. van Gemmeren M, Borjesson M, Tortajada A, Sun SZ, Okura K, Martin R (2017) Angew Chem Int Ed 56:6558 138. Yu X, Yang T, Wang S, Xu H, Gong H (2011) Org Lett 13:2138 139. Xu H, Zhao C, Qian Q, Deng W, Gong H (2013) Chem Sci 4:4022 140. Yu Y, Chen H, Qian Q, Yao K, Gong H (2018) Tetrahedron 74:5651 141. Yan XB, Li CL, Jin WJ, Guo P, Shu XZ (2018) Chem Sci 9:4529 142. Bercher OP, Plunkett S, Mortimer TE, Watson MP (2021) Org Lett 23:7059 143. Li Y, Li Y, Peng L, Wu D, Zhu L, Yin G (2020) Chem Sci 11:10461 144. Huang Z, Tang S, Lei A (2015) Sci Bull 60:1391 145. Tang S, Zeng L, Lei A (2018) J Am Chem Soc 140:13128 146. Yuan Y, Lei A (2019) Acc Chem Res 52:3309 147. Wang H, Gao X, Lv Z, Abdelilah T, Lei A (2019) Chem Rev 119:6769

Recent Advances in Nickel-Catalyzed C-C Cross-Coupling

231

148. Liu D, Liu C, Li H, Lei A (2013) Angew Chem Int Ed 52:4453 149. Liu D, Li Y, Qi X, Liu C, Lan Y, Lei A (2015) Org Lett 17:998 150. Jin LK, Wan L, Feng J, Cai C (2015) Org Lett 17:4726 151. Muto K, Yamaguchi J, Itami K (2012) J Am Chem Soc 134:169 152. Amaike K, Muto K, Yamaguchi J, Itami K (2012) J Am Chem Soc 134:13573 153. Meng L, Kamada Y, Muto K, Yamaguchi J, Itami K (2013) Angew Chem Int Ed 52:10048 154. Nakamura K, Tobisu M, Chatani N (2015) Org Lett 17:6142 155. Muto K, Yamaguchi J, Lei A, Itami K (2013) J Am Chem Soc 135:16384 156. Hanson MG, Olson NM, Yi Z, Wilson G, Kalyani D (2017) Org Lett 19:4271 157. Wang T-H, Ambre R, Wang Q, Lee W-C, Wang P-C, Liu Y, Zhao L, Ong T-G (2018) ACS Catal 8:11368 158. Yokota A, Aihara Y, Chatani N (2014) J Org Chem 79:11922 159. Cheng Y, Wu Y, Tan G, You J (2016) Angew Chem Int Ed 55:12275 160. Zhao S, Liu B, Zhan BB, Zhang WD, Shi BF (2016) Org Lett 18:4586 161. Honeycutt AP, Hoover JM (2017) ACS Catal 7:4597 162. Sarkar T, Maharana PK, Roy S, Punniyamurthy T (2022) Chem Commun 58:5980 163. Jagtap RA, Soni V, Punji B (2017) Chem Sus Chem 10:2242 164. Pandey DK, Vijaykumar M, Punji B (2019) J Org Chem 84:12800 165. Li M, Dong J, Huang X, Li K, Wu Q, Song F, You J (2014) Chem Commun 50:3944 166. Cao X, Sha SC, Li M, Kim BS, Morgan C, Huang R, Yang X, Walsh PJ (2016) Chem Sci 7: 611 167. Jiang H, Sha SC, Jeong SA, Manor BC, Walsh PJ (2019) Org Lett 21:1735 168. Wu X, Zhao Y, Ge H (2014) J Am Chem Soc 136:1789 169. Rezazadeh S, Devannah V, Watson DA (2017) J Am Chem Soc 139:8110 170. Devannah V, Sharma R, Watson DA (2019) J Am Chem Soc 141:8436

Top Organomet Chem (2023) 93: 233–254 https://doi.org/10.1007/3418_2023_82 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 18 February 2023

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2 Zhengkai Chen and Xiao-Feng Wu

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Copper-Catalyzed Carboxylation of Organometallic Reagents to Form C–C Bonds . . . . . 2.1 Copper-Catalyzed Carboxylation of Organoboron Reagents . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Copper-Catalyzed Carboxylation of Organosilane Reagents . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Copper-Catalyzed Carboxylation of Organoaluminum Reagents . . . . . . . . . . . . . . . . . . . . 2.4 Copper-Catalyzed Carboxylation of Organotin Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Copper-Catalyzed Carboxylation of Organic Halides to Form C–C Bonds . . . . . . . . . . . . . . . 4 Copper-Catalyzed Carboxylation of C–H Bonds to Form C–C Bonds . . . . . . . . . . . . . . . . . . . . 5 Copper-Catalyzed Carboxylation of C–C Double Bonds to Form C–C Bonds . . . . . . . . . . . 5.1 Carboxylation of Alkenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Carboxylation of Allenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Carboxylation of Dienes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Copper-Catalyzed Carboxylation of C–C Triple Bonds to Form C–C Bonds . . . . . . . . . . . . . 6.1 Carboxylation of Terminal Alkynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Carboxylation of Internal Alkynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Carboxylation of Benzynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

234 235 235 237 238 239 239 241 243 243 244 245 246 246 248 250 251 251

Abstract C–C bonds are ubiquitous in the skeleton of natural products, drugs, materials, ligands, and various bioactive molecules. Transition metal-catalyzed carboxylation reactions with abundant CO2 provide a direct and efficient method Z. Chen (✉) Key Laboratory of Surface and Interface Science of Polymer Materials of Zhejiang Province, Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou, P. R. China e-mail: [email protected] X.-F. Wu (✉) Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, P. R. China Leibniz-Institut für Katalyse e. V., Rostock, Germany e-mail: [email protected]; [email protected]

234

Z. Chen and X.-F. Wu

to forge C–C bonds, thereby producing various valuable carboxylic acids and their derivatives. Compared with other transition metal catalysts, copper catalysts have the merits of easy availability, low toxicity, and unique catalytic activity. This chapter systematically overviews the development of copper-catalyzed carboxylation reactions with CO2 to realize the formation of C–C bonds based on the type of the reactive substrates. Keywords Carboxylation · Carboxylic acids · C-C bond formation · CO2 · Coppercatalyzed

1 Introduction Carboxylic acids and their derivatives are regarded as one of the most important types of chemical compounds, which have been widely applied in the fields of organic synthesis, chemical industry, agrochemicals, pharmaceuticals, and functional materials [1–3]. The past few decades have witnessed the flourishing developments of efficient strategies for the construction of carboxylic acids, among which transition metal-catalyzed carboxylation reactions using CO2 to enable the formation of C–C bonds constitute a practical and straightforward route to build carboxylic acids and their derivatives [4–8]. Due to its abundance, nontoxicity, and recyclability, CO2 is considered as an ideal and renewable C1 feedstock in modern synthetic chemistry. The carbon dioxide capture and utilization (CCU) has emerged as a hot topic among chemists in recent years [6, 7, 9–14], although the difficulties caused by the thermodynamic stability and kinetic inertness of CO2 always exist. The significant advance about CCU has been obtained, in which CO2 could be incorporated into various high value-added chemicals under different catalytic systems [13, 15–17]. Noteworthy is that the conventional catalytic systems involving CO2 fixation mainly focus on C–O or C– N bond-forming reactions to synthesize polycarbonates, cyclic carbonates, or urea. The development of facile methods for CO2 utilization to forge the ubiquitous C–C bonds in organic molecules will be more valuable and desirable. Among diverse transition metal catalysts, copper catalysts attract enormous attention because of its excellent properties, such as easy availability, environmental friendliness, and inexpensiveness. According to the previously reported coppermediated carboxylation reactions employing CO2 [18–21], the generation of key nucleophilic C-Cu species could be readily trapped by CO2 to form the copper carboxylate, followed by the release of carboxylate and copper catalyst [22]. The lower CO2 insertion barrier of C–Cu bond largely facilitates the CO2 insertion step [23]. This chapter will summarize recent advance in copper-catalyzed carboxylation reactions with CO2 to render the C–C bond formation (Scheme 1).

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

235

Scheme 1 Coppercatalyzed formation of C–C bonds via carboxylation of different kinds of substrates with CO2

Scheme 2 Coppercatalyzed carboxylation of aryl- and alkenyl-boronic esters

2 Copper-Catalyzed Carboxylation of Organometallic Reagents to Form C–C Bonds 2.1

Copper-Catalyzed Carboxylation of Organoboron Reagents

Traditional methods involving direct carboxylation of organolithium and Grignard reagents with CO2 provide a rapid pathway for the assembly of carboxylic acids, which usually are limited by harsh reaction conditions and poor functional groups compatibility. Organoboron reagents are a kind of mild organometallic reagents and have been frequently utilized as reactive partners to couple with CO2. As early as 2008, Iwasawa and co-workers reported the copper-catalyzed carboxylation reaction of aryl- and alkenyl-boronic esters with CO2 to lead to the corresponding aryl and alkenyl acids (Scheme 2a) [24]. A unique bisoxazoline ligand was used to promote the reaction. At the same time, Hou and co-workers achieved the similar transformation in the presence of (IPr)CuCl catalyst under the mild conditions (Scheme 2b) [25]. Both the above two reactions exhibit the good functional group tolerance. In Hou’s work, the in-situ generated (IPr)CuOt-Bu reacts with the aryl- or alkenylboronic ester could deliver the active RCu(IPr) intermediate, followed by the CO2 insertion to afford copper carboxylate, which acts as a rate-determining step based on DFT calculation [26].

236

Z. Chen and X.-F. Wu

Scheme 3 Coppercatalyzed carboxylation of alkylborons

Scheme 4 Copper-catalyzed carboxylation of various alkenyl boron reagents

In 2011, Sawamura and co-workers described the copper-catalyzed carboxylation reaction of alkylboron compounds (alkyl-9-BBN) with CO2 under the catalysis of CuOAc/1,10-phenanthroline (Scheme 3a) [27]. The alkylboranes could be easily prepared by the alkene hydroboration, thereby realizing a reductive carboxylation of alkenes with CO2. The developed protocol features broad functional group compatibility and a variety of alkyl carboxylic acids are furnished from readily available alkenes. At the same year, Hou’s group accomplished the same reaction using (IPr)CuCl as a catalyst (Scheme 3b) [28]. The detailed mechanistic studies had been performed to elucidate the carboxylation reaction process, as demonstrated that several key active intermediates, including (IPr)CuOMe, RCu(IPr), and RCO2Cu(IPr), were successfully isolated and characterized. The carboxylation reactions of allylboronic pinacol esters with CO2 in the presence of a Cu(I)/NHC catalyst were developed by Duong and co-workers, producing the more substituted β,γ-unsaturated carboxylic acids with high regioselectivity [29]. On the basis of the precedent pioneered works, Mo and co-workers realized a copper/N-heterocyclic carbene (NHC) catalyzed carboxylation of arylboronic acids under one atmospheric pressure of CO2 (Scheme 4a) [30]. The protocol shows excellent functional group compatibility and a library of sensitive functional groups could be tolerated. The base used in the reaction had a vital role in generating the copper alkoxide complex [(IPr)Cu(OMe)] and promoting the transmetalation step.

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

237

Subsequently, the same authors applied alkenyl boric acids, alkenyl-boronic acid pinacol esters, and potassium (E)-trifluoro(styryl)borate as suitable substrate to react with CO2 with the simple CuCl as a catalyst, in which various α, β-unsaturated carboxylic acids were produced in moderate to high yield (Scheme 4b) [31].

2.2

Copper-Catalyzed Carboxylation of Organosilane Reagents

Arylsilanes prepared by catalytic C-H silylation are a kind of bench-stable organometallic reagents and can be used in carboxylation reaction with CO2 to build carboxylic acids. Kobayashi and co-workers developed a series of copper-catalyzed carboxylation of organosilane compounds in recent years. They initially completed CuI-catalyzed direct carboxylation of benzoxasiloles with carbon dioxide to provide a number of phthalides after an acid work-up [32] (Scheme 5a). Noteworthy is that the oxygen atom in benzoxasiloles could coordinate with copper center in an intramolecular fashion to facilitate either the transmetalation or carboxylation steps. Afterwards, the same authors extend the above strategy as a general method to explore a Cu-catalyzed direct carboxylation of aryl- and alkenyltrialkoxysilanes with CsF as an activator, affording carboxylic acids in good to high yields under atmospheric pressure of CO2 [33] (Scheme 5b). They also described a coppercatalyzed a carboxylation reaction of HOMSi (dimethyl(o-hydroxymethylphenyl) silane) reagents under a milder reaction temperature, in which the structural modifications of the silane could tune the reactivity and selectivity of the organometallic nucleophile [34] (Scheme 5c). Scheme 5 Coppercatalyzed carboxylation of organosilane reagents

238

2.3

Z. Chen and X.-F. Wu

Copper-Catalyzed Carboxylation of Organoaluminum Reagents

Hou and co-workers prepared diverse alkenylaluminum species through hydroalumination or methylalumination of alkynes catalyzed by Sc, Zr, and Ni complexes, which could be adopted to proceed carboxylation with CO2 in the presence of N-heterocyclic carbene (NHC)–copper catalyst (Scheme 6a) [35]. By this methodology, a wide range of α, β-unsaturated carboxyl acids were synthesized with well-controlled regio- and stereoselectivity in a simple one-pot reaction operation. During the Cu-catalyzed carboxylation, the stereoconfiguration of the resulting alkenylaluminum species was well maintained. Then, Hou’s group applied the developed carboxylation strategy to arylaluminum species, which were easily prepared by the deprotonative alumination of various aromatic compounds with a mixed alkyl amido lithium aluminate compound i-Bu3Al(TMP)Li (Scheme 6b) [36]. Except for aryl rings, several heteroarenes were also viable substates as well as good functional group tolerance. The copper aryl and isobutyl complexes were regarded as key intermediates and were successfully isolated and structurally characterized. The NHC-copper-catalyzed carboxylation of the aryloxy allylaluminum species with CO2 for the synthesis of 2-aryloxy butenoates was achieved by Hou and co-workers (Scheme 7) [37]. The allylaluminum compound was generated by the deprotonative C–H alumination of allyl aryl ethers with an aluminum ate compound i-Bu3Al(TMP)Li. Notably, by the addition of a catalytic amount of DBU, the 2-aryloxy-3-butenoate products could be transformed into (Z)-2-aryloxy-2-butenate

Scheme 6 Copper-catalyzed carboxylation of organoaluminum reagents Scheme 7 Coppercatalyzed carboxylation of organoaluminum reagents

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

239

isomers with high regio- and stereoselectivity. The present protocol was also amenable to the benzylic carboxylation of common allylbenzenes or a toluene derivative.

2.4

Copper-Catalyzed Carboxylation of Organotin Reagents

Vasdev, Dahl, and co-workers reported a copper-mediated carboxylation reaction of aryl- and heteroaryl-stannanes and the radiochemical yield for [11C]benzoic acid formation was also evaluated (Scheme 8) [38]. In the reaction, the arylstannanes could be transformed into organocuprates via the transmetalation step, which underwent CO2-insertion to form the carboxylate species. TMEDA serves as the ligand for the active Cu(I) species. The method was successfully utilized for the radiosynthesis of [11C]bexarotene and for the reaction of 13CO2 and 14CO2.

3 Copper-Catalyzed Carboxylation of Organic Halides to Form C–C Bonds Organic halides can be inserted by copper catalyst to form nucleophilic C–Cu (I) bonds, followed by the coupling with CO2 to furnish carboxylate complex. In 2013, Daugulis and co-workers presented the first copper-catalyzed carboxylation of aryl iodides with carbon dioxide, which employed the catalytic combination of CuI/TEMDA or DEMDA and Et2Zn in DMSO or DMA (Scheme 9) [39]. A variety of aryl acids were afforded in 40–88% yields with the tolerance of many sensitive functional groups. The addition of mercury additive resulted in the rapid decrease of the reaction yield, verifying the generation of copper clusters in the reaction. The oxidative addition of Cu(0) species into ArI gave ArCu(I) complex, which underwent CO2 insertion to lead to a copper carboxylate. Then, the reaction of

Scheme 8 Coppermediated 11C-carboxylation of arylstannanes

Scheme 9 CuI-catalyzed carboxylation of aryl iodides

240

Z. Chen and X.-F. Wu

Scheme 10 Coppercatalyzed electrocatalytic carboxylation of allylic halides

Scheme 11 Coppercatalyzed carboxylation of C–F bonds

copper carboxylate with Et2Zn could produce zinc carboxylate and the following protonation step delivered the acid products. Lu, Wang, and co-workers prepared the silver encapsulated copper salen complex and used it as a cathode for electrocarboxylation of cinnamyl chloride with CO2 (Scheme 10) [40]. The corresponding β,γ-Unsaturated carboxylic acids were synthesized with good yield and moderate selectivity. The protocol was also amenable to several allylic halides and aryl halides. The key Cu(III)salen-cinnamyl complex was generated by the reaction of nucleophilic Cu(I)salen anion and cinnamyl chloride. Then the reduction of Cu(III) complex by one-electron transfer formed cinnamyl anion, which coupled with CO2 to give carboxylates. Compared with the reactive C–X (X = Cl, Br or I) bonds, the activation of exceptionally inert C–F bonds is more difficult due to its high bond dissociation energy. The direct C–F bond carboxylation of organofluorines with CO2 remains a challenging task. In 2019, a selective defluorinative carboxylation of gemdifluoroalkenes under photoredox/palladium dual catalysis was realized by Feng and co-workers, which involved a fluorovinyl radical generated by single electron reduction [41]. Yu and co-workers developed a Cu-catalyzed selective formal carboxylation of C–F bonds. By the employment of gem-difluoroalkenes, gem-difluorodienes, and α-trifluoro-methyl alkenes as starting materials, a wide range of important α-fluoroacrylic acids and α,α-difluorocarboxylates were constructed in good to high yields (Scheme 11) [42]. Mechanistic studies indicated that the in-situ generated fluorinated pinacol alkenylboronate served as the vital intermediate. Then, two possible pathways exist. For path A, a subsequent Cu(I)-catalyzed transmetalation/ carboxylation process of vinylboronate ester gave the desired α-fluoroacrylic acids.

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

241

Scheme 12 Coppercatalyzed carboxylation of gem-difluoroalkenes

For path B, the direct carboxylation of vinylboronate ester with CO2 might also happen, albeit in a less efficient manner. The methodology exhibits high mono-, chemo-, and stereoselectivities; scalability and good utility for accessing various bioactive molecules. Zhou, Wu, and co-workers also achieved the similar copper-catalyzed defluorinative carboxylation of gem-difluoroalkenes with CO2 (Scheme 12) [43]. With available CuI as the catalyst and bis(pinacolatodiboron) as the stoichiometric reductant, a myriad of fluoroalkenyl carboxylic acids were obtained with high stereoselectivity in good to excellent yields. The transformation possibly underwent sequential borylation and carboxylation process, which was analogous to the Yu’s work [42]. Later, the theoretical calculations of copper-catalyzed carboxylation of the C–F bonds were implemented by Shi, Yu, and co-workers, [44] which demonstrated that the sequential migratory insertion of difluoroalkene on the boryl–Cu (I) species, syn β-F elimination, transmetalation, and carboxylation steps were involved in the reaction. In line with Yu’s work, [42] the regioselectivity of the reaction was determined by the migration insertion step.

4 Copper-Catalyzed Carboxylation of C–H Bonds to Form C–C Bonds Direct carboxylation of C–H bonds with CO2 constitutes a straightforward and atomeconomical route to carboxylic acids. Over the past decades, various types of C–H bonds could be carboxylated under the catalysis of different transition metals and tremendous advance has been gained. For the copper catalysts, the carboxylation of activated heterocyclic and allylic C–H bonds has been well explored. Hou and co-workers reported the first example of copper-catalyzed carboxylation of C–H bonds of heterocyclic compounds with CO2 for producing carboxylic esters (Scheme 13) [45]. With NHC-copper(I) complex [Cu(IPr)Cl] and KOt-Bu as catalytic system, the potassium benzoxazole-2-carboxylate salt could be formed and characterized by NMR spectroscopic analysis. Notably, acidification of carboxylate salt did not give rise to the corresponding carboxylic acid along with the rapid decarboxylation, whereas the treatment with an alkyl iodide could smoothly deliver the carboxylic ester product. The reaction was initiated by the coupling of the copper alkoxide complex [Cu(IPr)(Ot-Bu)] with heterocyclic compound to afford organocopper species A through C-H activation. Then, insertion of CO2 into the Cu–C bond of A delivered the carboxylate B, which reacted with KOt-Bu to give the potassium carboxylate C and regenerated the copper alkoxide [Cu(IPr)(Ot-Bu)].

242

Z. Chen and X.-F. Wu

Scheme 13 Copper-catalyzed carboxylation of heteroarenes Scheme 14 Coppercatalyzed carboxylation of aromatic substrates

Scheme 15 Coppercatalyzed carboxylation of allylic C–H bonds

Finally, the reaction of C with alkyl iodide afforded the ester products. The protocol was not suitable for the benzothiazole, 4-phenyloxazole, and benzofuran due to the weak acidity of these substrates. After 2 years, Hou’s group applied 1,2,3-triazol-5-ylidene copper(I) complexes (tzNHC-Cu) as an efficient catalyst to enable the direct C–H carboxylation of benzoxazole and benzothiazole derivatives with CO2 [46]. A series of eaters could be obtained in excellent yields after treatment with alkyl iodides. Nolan and co-workers also described a copper-catalyzed direct carboxylation of heteroaromatic compounds and polyfluorinated arenes (Scheme 14) [47]. Under the developed catalytic system using NHC-copper(I) hydroxide complexes, the pKa values of the substrates below 27.7 were capable of undergoing carboxylation. Except for C–H bonds, many N–H bonds could also be carboxylated with high regioselectivity. Murakami and co-workers developed a UV light-induced carboxylation reaction of allylic C–H bonds of simple alkenes with CO2 in the presence of a ketone and a copper complex (Scheme 15) [48]. The transformation was regarded to be divided into two sequences, that is, the photoreaction of the ketone and the copper-catalyzed carboxylation. The endergonic photoreaction of ketones with alkenes could give

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

243

homoallyl alcohol intermediates, which proceeded a thermal copper-catalyzed allyl transfer reaction to CO2. The key factor for the success of this reaction lies in the copper complex barely absorbing the light of wavelength of UV light, thereby avoiding decomposition of the complex and suppression of photoreactions of ketones.

5 Copper-Catalyzed Carboxylation of C–C Double Bonds to Form C–C Bonds 5.1

Carboxylation of Alkenes

As aforementioned, Hou [28] and Sawamura [27] independently reported a coppercatalyzed hydroboration-carboxylation sequence of terminal olefins in the presence of 9-BBN dimer to forge linear aliphatic carboxylic acids. Both protocols utilized strong alkoxides as additives and are limited to construction of primary acids. Skrydstrup and co-workers expanded the strategy to disubstituted alkenes using a mild additive, cesium fluoride (Scheme 16) [49]. The corresponding secondary carboxylic acids could be synthesized starting from cyclohexenes, stilbenes, and styrenes. The similar mechanism of Hou and Sawamura’s work was proposed, which involved the σ-bond metathesis reaction of active IPr-ligated copper-fluoride species with the preformed alkylborane species and the subsequent CO2 insertion. Under the current reaction system, a double carboxylation of terminal alkynes occurred to produce many synthetically useful malonic acid derivatives in acceptable yields. Popp and co-workers disclosed a copper-catalyzed regioselective boracarboxylation of vinyl arenes with B2pin2 and CO2 to produce various boronfunctionalized α-aryl carboxylic acids (Scheme 17) [50]. The reaction might proceed through olefin borylcupration by a Cu-boryl species and CO2 insertion into a Cu-alkyl species. The challenge of this transformation is the competition between carboxylation of Cu-alkyl species and β-hydride elimination/protodecupration. The use of strongly σ-donating N-heterocyclic carbene ligands could increase the nucleophilicity of Cu-alkyl intermediate, thereby facilitating the carboxylation reaction. Scheme 16 Coppercatalyzed carboxylation of hydroborated disubstituted alkenes

Scheme 17 Coppercatalyzed boracarboxylation of vinyl arenes

244

Z. Chen and X.-F. Wu

The further derivatization of the carbon–boron bond gave rise to the hydroxy- and fluorocarboxylation products, which demonstrated the synthetic utility of the method. The detailed mechanistic studies toward the carboxylation step in copper(I)catalyzed boracarboxylation of vinyl arenes have been accomplished by the same authors, which include the isolation of the key intermediates and density functional theory (DFT) calculation analysis [51]. Noteworthy is that Lu and co-workers also performed the computational exploration of ligand effects in copper-catalyzed boracarboxylation of styrene [52]. The results of DFT indicate that the bulk of the NHC ligands exerts significant steric effects on the reactivity, as verified that the ineffectiveness of bidentate phosphine ligands comes from the large distortion of the copper catalyst and CO2.

5.2

Carboxylation of Allenes

The carboxylation of allenes using CO2 under the catalysis of Ni and Pd catalyst was achieved previously with good selectivity, but only one regioisomer was obtained [53, 54]. Tsuji and co-workers developed a copper-catalyzed regiodivergent silacarboxylation of single allenes under 1 atm of CO2 with PhMe2Si–B(pin) as a silicon source (Scheme 18) [55]. The regioselectivity of the reaction could be highly controlled by the proper choice of ligand, in which carboxylated vinylsilanes were afforded with rac-Me-DuPhos as the ligand and carboxylated allylsilanes were synthesized by using PCy3 as the ligand. The regioselectivity reversal in the reaction might be resulted from the difference in relative steric bulk between the Cu-ligand species and SiMe2Ph moieties. Subsequently, Miao, Liu, and co-workers conducted the mechanistic study on ligand-controlled copper-catalyzed regiodivergent silacarboxylation of allenes [56]. The DFT calculations indicated that the observed regioselectivity was controlled by the feasibility of alkene migratory insertion. Tsuji, Fujihara, and co-workers achieved a selective C–C bond-forming transformation of CO2 to the alcohol oxidation level under a copper/hydrosilanes catalyst system (Scheme 19) [57]. In this transformation, CO2 was chemoselectively reduced to the alcohol oxidation level with other reducible functionalities being intact. By Scheme 18 Coppercatalyzed regiodivergent silacarboxylation of allenes

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

245

Scheme 19 Coppercatalyzed hydrocarboxylation of allenes

Scheme 20 Copper-catalyzed alkylative carboxylation of allenamides Scheme 21 Coppercatalyzed 1,2-hydrocarboxylation of 1,3-dienes

increasing the amount of the base from 5 mol% to 1.0 equiv., the product could be completely switched from homoallylic alcohols to β,γ-unsaturated carboxylic acids in moderate yields. Hydrosilane acted as a mild and easy-to-handle reducing agent. Hou, Takimoto, and co-workers explored a copper-catalyzed regioselective alkylative carboxylation of allenamides with CO2 and dialkylzinc reagents, preparing a wide range of (Z)-α,β-dehydro-β-amino acid esters in good yields (Scheme 20) [58]. High regioselectivity of the reaction was observed, where the alkyl group was introduced onto the less hindered γ-carbon and the carboxyl group could be introduced onto the β-carbon atom of the allenamides. An alkenylzinc intermediate was initially formed by alkylative zincation of the allenamides, which possibly underwent nucleophilic addition to CO2. Noteworthy is that the transmetalation between the copper species and zinc species could be a reversible process and the carboxylation would preferentially take place at the alkenyl-copper species.

5.3

Carboxylation of Dienes

Zhang and co-workers developed a copper-catalyzed highly regioselective 1,2-hydrocarboxylation of terminal 1,3-diene with CO2 for the assembly of bioactive and synthetically useful 2-benzyl-β,γ-unsaturated acid derivatives (Scheme 21). The allylic pinacol boronate formed by Cu–B complex with 1,3-diene was regarded as the key intermediate, as verified by the results of the control experiments. Yu and co-workers disclosed the highly selective copper-catalyzed functionalization of 1,3-dienes with CO2 for accessing valuable hydroxyl compounds with chiral all-carbon acyclic quaternary stereocenters [59, 60]. Various 1,3-diene derivatives

246

Z. Chen and X.-F. Wu

underwent reductive hydroxymethylation to forge C–C bond formation with high chemo-, regio-, E/Z-, and enantioselectivities.

6 Copper-Catalyzed Carboxylation of C–C Triple Bonds to Form C–C Bonds 6.1

Carboxylation of Terminal Alkynes

The catalytic carboxylation of terminal alkynes with CO2 provides a rapid and powerful route to propiolic acid derivatives. Inoue and co-workers pioneered the copper-catalyzed carboxylation of terminal alkynes in the presence of excess amount of base at high temperature [61]. The past decades have witnessed tremendous achievements about carboxylation of terminal alkynes with CO2 under the catalysis of various copper catalysts. Lu and co-workers presented an N-heterocyclic carbene copper(I) complex (IPr)CuCl catalyzed carboxylative coupling of terminal alkynes, allylic chlorides, and CO2 for the selective synthesis of a variety of functionalized allylic 2-alkynoates (Scheme 22a) [62]. The benzyl and similarly reactive organic chlorides could also be adopted as the alkylating agents. The limitation of this reaction is the use of 1.5 MPa of CO2. In 2012, Kondo and co-workers reported a carboxylation of terminal alkynes using a copper/phosphine catalyst system at ambient CO2 pressure under mild conditions (Scheme 22b) [63]. A variety of functionalized alkyl 2-alkynoates were obtained in moderate to excellent yields. Gooßen and co-workers employed a phenanthroline/copper complex as a highly active catalyst to render the insertion of CO2 into C–H bonds of terminal alkynes (Scheme 23a) [64]. Various terminal alkynes were viable substrates under the optimal conditions to give rise to the propiolic acids by crystallization in high yields. The developed catalytic system also allowed the carboxylation of heterocycles that had a similar pKa to alkynes. Meanwhile, Zhang and co-workers reported a coppercatalyzed and copper–N-heterocyclic carbene-cocatalyzed carboxylation of terminal alkynes for the transformation of CO2 to carboxylic acids (Scheme 23b) [65]. Under

Scheme 22 Copper-catalyzed carboxylation of terminal alkynes

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

247

Scheme 23 Copper complex-catalyzed carboxylation of terminal alkynes

Scheme 24 Carboxylation of terminal alkynes with CO2 catalyzed by supported copper catalyst

ambient conditions, P(NHC)0.5(NHC-CuCl)0.5 catalyst showed a synergistic effect of an organometallic catalyst and an organocatalyst and a broad range of carboxylic acids could be afforded in good to excellent yields. Beletskaya and co-workers firstly prepared the copper particles supported on Al2O3 and used it as a heterogeneous, highly active, and recyclable catalyst to promote direct carboxylation of terminal alkynes with 2 atm of CO2 (Scheme 24a) [66]. High selectivity and efficiency of this catalyst were observed, as illustrated by the large-scale CuNPs covered by oxide layer and less prone to erosion. The developed copper catalyst could be recycled for five runs without the obvious activity decrease. Kim and co-workers synthesized a novel CuCl2@Poly-GLY (1-Vim)3(OMs)3 catalyst and applied it to carboxylation of terminal alkynes with 4 MPa of CO2, which furnished the numerous carboxylic esters in high yields (Scheme 24b) [67]. The catalytic activity behavior of this heterogeneous copper catalyst was explained by predicted mechanism. Due to the easy availability, high catalytic activity, and recyclability, the utilization of heterogeneous copper catalyst in carboxylation of terminal alkynes has attracted considerable attention in recent years. A series of heterogeneous catalytic systems have been established for the carboxylation of terminal alkynes under 1 atm of CO2 to build the corresponding propiolic acids (Scheme 25) [68–70]. Different characterization methods were used to characterize the synthesized heterogeneous copper catalyst, which could further elucidate the catalytic mechanism. Good recycling efficiency was observed in these reactions, as verified by the no significant loss of catalytic activity after five reaction cycles. Singh, Trivedi, and co-workers exploited a cis-1,2-bis(diphenylphosphino)ethylene copper(I)-catalyzed carboxylation of terminal alkynes (Scheme 26a)

248

Z. Chen and X.-F. Wu

Scheme 25 Heterogeneous copper-catalyzed carboxylation of terminal alkynes with CO2

Scheme 26 Copper-catalyzed carboxylation of terminal alkynes for the synthesis of propiolic acids Scheme 27 Coppercatalyzed hydrocarboxylation of alkynes

[71]. The reaction proceeded smoothly at atmospheric pressure and ambient temperature to afford the propiolic acid products in excellent yields. Copper acetylide is the key intermediate to be inserted by CO2 for the formation of carboxylic acids. The terminal alkyne carboxylation with CO2 could be achieved using the combination of simple copper salts and quaternary ammonium salts, which was reported by Bao and co-workers (Scheme 26b) [72]. Mechanistic studies revealed that n-Bu4NOAc in the reaction served as a phase transfer catalyst to increase the solubility of carbonate anion and an activator for CO2. In 2021, Bongarzone and co-workers developed a copper-catalyzed coupling of terminal alkynes and cyclotron-produced carbon-11 carbon dioxide ([11C]CO2) for the radiosynthesis of carbon-11 radiolabelled carboxylic acids [73].

6.2

Carboxylation of Internal Alkynes

The copper-catalyzed hydrocarboxylation of alkynes using CO2 was disclosed by Tsuji and co-workers, which utilized easy-to-handle hydrosilane as a reducing agent (Scheme 27) [74]. The method was amenable to both symmetrical and unsymmetrical aromatic alkynes, producing the α, β-unsaturated carboxylic acids in moderate

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

249

Scheme 28 Coppercatalyzed boracarboxylation of alkynes

Scheme 29 Coppercatalyzed silacarboxylation of internal alkynes

to good yields with E stereochemistry. The copper complex [IMesCuF] was synthesized from [IMesCuCl] and its structure was confirmed by X-ray crystallography. Stoichiometric reactions relevant to the catalytic process were conducted and the result supported the generation of active [Cl2IPrCuH] species, which underwent syn-addition to an alkyne to lead to a copper alkenyl intermediate. The subsequent CO2 insertion and metathesis with a hydrosilane delivered the corresponding silyl ester, followed by protonation to give the final α, β-unsaturated carboxylic acid products. Catalytic heterocarboxylation reaction could simultaneously incorporate heteroatom functionality and CO2 into unsaturated substrates. Hou and co-workers applied an N-heterocyclic carbene copper(I) complex as a catalyst to enable the boracarboxylation of various alkynes in the presence of a diborane compound (Scheme 28) [75]. The reaction proceeded a borylcupration/carboxylation cascade for affording α,β-unsaturated β-boralactone derivatives regio- and stereoselectively in high yields. The authors had been previously demonstrated the [(IPr)Cu(Ot-Bu)] could act as an efficient catalyst for the carboxylation of various nucleophiles. The [(IPr)Cu(Ot-Bu)] reacted with B2Pin2 gave the borylcopper complex [(IPr)CuB (pin)], which coupled with diphenylacetylene furnished β-boryl alkenyl-copper complex to undergo the CO2 insertion. The obtained boracarboxylation products could take place the Suzuki-Miyaura cross-coupling reaction with iodobenzene to give rise to the tetrasubstituted alkenes. The first copper-catalyzed silacarboxylation of internal alkynes employing CO2 and silylborane was realized by Tsuji and co-workers, which provided a direct route to silalactone products in high yields (Scheme 29) [76]. The transformation occurred through two sequential reactions of silaboration of an alkyne followed by the carboxylation of the resulting vinylboronic ester. Intramolecular cyclization of copper carboxylate species delivered the synthetically useful silalactone products. The reaction was applicable to diverse alkynes containing different functional groups. The copper-catalyzed alkylative carboxylation of ynamides and allenamides with CO2 and alkylzinc halides was reported by Hou and co-workers, which a variety of α,β-unsaturated carboxylic acids bearing α,β-dehydroamino acid skeleton were synthesized in good yields (Scheme 30) [77]. The alkylative carboxylation contains

250

Z. Chen and X.-F. Wu

Scheme 30 Copper-catalyzed alkylative carboxylation of ynamides Scheme 31 Coppercatalyzed double carboxylation of o-alkynyl acetophenone

Scheme 32 Coppercatalyzed couplings of arynes, terminal alkynes, and CO2

Cu-catalyzed carbozincation of ynamides and the subsequent LiCl-promoted nucleophilic carboxylation of the alkenylzinc species with CO2. The carbonyl group on the ynamide moiety could act as the directing group to facilitate the carbocupration process for the formation of the alkenylcopper species. Several sensitive functional groups such as ester, silyl ether, and nitrile groups were tolerated in the reaction. A similar transformation involving NHC–Cu-catalyzed regioselective alkylative carboxylation of ynamides with CO2 and alkylzinc halides had been developed by the same authors [78]. Zhang and co-workers described a copper-catalyzed double carboxylation of oalkynyl acetophenone with CO2 to build 1(3H)-isobenzofuranylidene dicarboxylic esters in good yields (Scheme 31) [79]. The cascade reaction was triggered by α-carboxylation of the carbonyl group and then proceeded through a carboxylation/intramolecular cyclization/s carboxylation sequence. The steric factor of alkyne moiety had a significant effect on the reaction due to the hindrance of the insertion of the second carbon dioxide. Alkyl-substituted substrates showed higher selectivity than aryl-substituted substrates.

6.3

Carboxylation of Benzynes

Arynes are highly unstable species and serve as reactive intermediates in multicomponent reactions. The three-component coupling reaction of in-situ generated arynes, terminal alkynes, and CO2 with an N-heterocyclic carbene (NHC) copper complex as a catalyst was achieved by Kobayashi and co-workers (Scheme 32) [80]. By this methodology, various isocoumarins could be assembled in

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

251

moderate to good yields. Arynes had been utilized in CO2 incorporation reactions with imines and amines as nucleophilic partners to prepare benzoxazinones and anthranilic acids [81, 82]. The reaction of in-situ generated arynes and copper acetylide generated ortho-alkynyl copper complex, followed by the CO2 insertion and a 6-endo-dig cyclization to form endocyclic copper heterocycle. The key to this reaction lies in the use of a versatile N-heterocyclic carbene/copper complex being capable of catalyzing multiple transformations.

7 Conclusion Carboxylation reactions of diverse kinds of substrates with CO2 under the catalysis of transition metals provide a facile and straightforward route to synthetically valuable carboxylic acids and their derivatives. Among various transition metal catalysts, copper catalysts have many obvious advantages, including abundance, easy availability, low toxicity, and high catalytic activity. The C–Cu bond in copper species serves as a reactive nucleophile and is liable to undergo CO2 insertion to generate the key copper carboxylates. The C–C bond formation via direct carboxylation reactions has constituted an attractive and fascinating topic in chemical community. Although remarkable advance has been gained regarding copper-catalyzed carboxylation reactions with CO2, the limitations and challenges remain. For some existing transformations, the high reactive activators or additives, such as Et2Zn, HSi (OEt)3, HSi(OMe)2Me, B2(pin)2, and PhMe2Si-B(pin) reagents, are inevitably employed. Furthermore, the application of the reaction for the large-scale production of carboxylic acids has not yet reached. Much effort should be devoted to exploring more efficient and practical methodologies under mild conditions to achieve the efficient utilization of CO2.

References 1. Chand P, Babu YS, Bantia S et al (1997) J Med Chem 40:4030–4052 2. Ballatore C, Huryn DM, Smith Iii AB (2013) ChemMedChem 8:385–395 3. Morgunov IG, Kamzolova SV, Dedyukhina EG et al (2017) Appl Microbiol Biotechnol 101: 921–932 4. Tortajada A, Julia-Hernandez F, Borjesson M et al (2018) Angew Chem Int Ed 57:15948– 15982 5. Chen Y-G, Xu X-T, Zhang K et al (2017) Synthesis 50:35–48 6. Yan S-S, Fu Q, Liao L-L et al (2018) Coord Chem Rev 374:439–463 7. Yeung CS (2019) Angew Chem Int Ed 58:5492–5502 8. Zhang W, Lv X (2012) Chin J Catal 33:745–756 9. Sakakura T, Choi J-C, Yasuda H (2007) Chem Rev 107:2365–2387 10. Huang K, Sun CL, Shi ZJ (2011) Chem Soc Rev 40:2435–2452 11. Wang W, Wang S, Ma X et al (2011) Chem Soc Rev 40:3703–3727

252

Z. Chen and X.-F. Wu

12. He M, Sun Y, Han B (2013) Angew Chem Int Ed 52:9620–9633 13. Liu Q, Wu L, Jackstell R et al (2015) Nat Commun 6:5933 14. Dabral S, Schaub T (2019) Adv Synth Catal 361:223–246 15. Tlili A, Blondiaux E, Frogneux X et al (2015) Green Chem 17:157–168 16. Wang S, Xi C (2019) Chem Soc Rev 48:382–404 17. Zhong J, Yang X, Wu Z et al (2020) Chem Soc Rev 49:1385–1413 18. Zhang L, Hou Z (2013) Chem Sci 4:3395–3403 19. Wang S, Du G, Xi C (2016) Org Biomol Chem 14:3666–3676 20. Zhang L, Li Z, Takimoto M et al (2020) Chem Rec 20:494–512 21. Song Y, Zhang Y, Chen Z et al (2022) Asian J Org Chem 11:e202200237 22. Ebert GW, Juda WL, Kosakowski RH et al (2005) J Org Chem 70:4314–4317 23. Vummaleti SVC, Talarico G, Nolan SP et al (2016) Org Chem Front 3:19–23 24. Takaya J, Tadami S, Ukai K et al (2008) Org Lett 10:2697–2700 25. Ohishi T, Nishiura M, Hou Z (2008) Angew Chem Int Ed 47:5792–5795 26. Dang L, Lin Z, Marder TB (2010) Organometallics 29:917–927 27. Ohmiya H, Tanabe M, Sawamura M (2011) Org Lett 13:1086–1088 28. Ohishi T, Zhang L, Nishiura M et al (2011) Angew Chem Int Ed 50:8114–8117 29. Duong HA, Huleatt PB, Tan Q-W et al (2013) Org Lett 15:4034–4037 30. Nayal OS, Hong J, Yang Y et al (2019) Org Chem Front 6:3673–3677 31. Hong J, Nayal OS, Mo F (2020) Eur J Org Chem 2020:2813–2818 32. Nguyen TVQ, Rodríguez-Santamaría JA, Yoo W-J et al (2017) Green Chem 19:2501–2505 33. Nguyen TVQ, Yoo W-J, Kobayashi S (2018) Asian J Org Chem 7:116–118 34. Yoo W-J, Kondo J, Kobayashi S (2019) Chem Lett 48:1248–1250 35. Takimoto M, Hou Z (2013) Chem Eur J 19:11439–11445 36. Ueno A, Takimoto M, Wylie WNO et al (2015) Chem Asian J 10:1010–1016 37. Ueno A, Takimoto M, Hou Z (2017) Org Biomol Chem 15:2370–2375 38. Duffy IR, Vasdev N, Dahl K (2020) ACS Omega 5:8242–8250 39. Tran-Vu H, Daugulis O (2013) ACS Catal 3:2417–2420 40. Wu L-X, Zhao Y-G, Guan Y-B et al (2019) RSC Adv 9:32628–32633 41. Zhu C, Zhang YF, Liu ZY et al (2019) Chem Sci 10:6721–6726 42. Yan S-S, Wu D-S, Ye J-H et al (2019) ACS Catal 9:6987–6992 43. Xie S-L, Cui X-Y, Gao X-T et al (2019) Org Chem Front 6:3678–3682 44. Liu J, Nie W, Yu H et al (2020) Org Biomol Chem 18:9065–9071 45. Zhang L, Cheng J, Ohishi T et al (2010) Angew Chem Int Ed 49:8670–8673 46. Inomata H, Ogata K, Fukuzawa S-I et al (2012) Org Lett 14:3986–3989 47. Boogaerts II, Fortman GC, Furst MR et al (2010) Angew Chem Int Ed 49:8674–8677 48. Ishida N, Masuda Y, Uemoto S et al (2016) Chem Eur J 22:6524–6527 49. Juhl M, Laursen SLR, Huang Y et al (2017) ACS Catal 7:1392–1396 50. Butcher TW, McClain EJ, Hamilton TG et al (2016) Org Lett 18:6428–6431 51. Baughman NN, Akhmedov NG, Petersen JL et al (2021) Organometallics 40:23–37 52. Lv X, Wu Y-B, Lu G (2017) Catal Sci Technol 7:5049–5054 53. Takimoto M, Kawamura M, Mori M et al (2005) Synlett 2005:2019–2022 54. Takaya J, Iwasawa N (2008) J Am Chem Soc 130:15254–15255 55. Tani Y, Fujihara T, Terao J et al (2014) J Am Chem Soc 136:17706–17709 56. Han S-M, Wang X, Miao S et al (2017) RSC Adv 7:29035–29041 57. Tani Y, Kuga K, Fujihara T et al (2015) Chem Commun 51:13020–13023 58. Gholap SS, Takimoto M, Hou Z (2016) Chem Eur J 22:8547–8552 59. Gui Y-Y, Hu N, Chen X-W et al (2017) J Am Chem Soc 139:17011–17014 60. Chen X-W, Zhu L, Gui Y-Y et al (2019) J Am Chem Soc 141:18825–18835 61. Fukue Y, Oi S, Inoue Y (1994) J Chem Soc Chem Commun:2091–2091 62. Zhang W-Z, Li W-J, Zhang X et al (2010) Org Lett 12:4748–4751 63. Inamoto K, Asano N, Kobayashi K et al (2012) Org Biomol Chem 10:1514–1516 64. Gooßen LJ, Rodríguez N, Manjolinho F et al (2010) Adv Synth Catal 352:2913–2917

Copper-Catalyzed C–C Bond Formation via Carboxylation Reactions with CO2

253

65. Yu D, Zhang Y (2010) Proc Natl Acad Sci U S A 107:20184–20189 66. Bondarenko GN, Dvurechenskaya EG, Magommedov ES et al (2017) Catal Lett 147:2570– 2580 67. Chaugule AA, Tamboli AH, Kim H (2017) Chem Eng J 326:1009–1019 68. Chowdhury AH, Kayal U, Chowdhury IH et al (2019) ChemistrySelect 4:1069–1077 69. Yang P, Zuo S, Zhang F et al (2020) Ind Eng Chem Res 59:7327–7335 70. Bu R, Zhang L, Gao L-L et al (2021) Mole Catal 499 71. Trivedi M, Smreker JR, Singh G et al (2017) New J Chem 41:14145–14151 72. Wang WH, Jia L, Feng X et al (2019) Asian J Org Chem 8:1501–1505 73. Goudou F, Gee AD, Bongarzone S (2021) J Label Compd Radiopharm 64:237–242 74. Fujihara T, Xu T, Semba K et al (2011) Angew Chem Int Ed 50:523–527 75. Zhang L, Cheng J, Carry B et al (2012) J Am Chem Soc 134:14314–14317 76. Fujihara T, Tani Y, Semba K et al (2012) Angew Chem Int Ed 51:11487–11490 77. Takimoto M, Gholap SS, Hou Z (2019) Chem Eur J 25:8363–8370 78. Takimoto M, Gholap SS, Hou Z (2015) Chem Eur J 21:15218–15223 79. Zhang W-Z, Yang M-W, Yang X-T et al (2016) Org Chem Front 3:217–221 80. Yoo W-J, Nguyen TVQ, Kobayashi S (2014) Angew Chem Int Ed 53:10213–10217 81. Yoshida H, Fukushima H, Ohshita J et al (2006) J Am Chem Soc 128:11040–11041 82. Yoshida H, Morishita T, Ohshita J (2008) Org Lett 10:3845–3847

Top Organomet Chem (2023) 93: 255–276 https://doi.org/10.1007/3418_2023_84 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 5 March 2023

Cu-Catalyzed C–C Bond Formation with CO Pinku Tung and Neal P. Mankad

Contents 1 2 3 4

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydride Nucleophile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Boron Nucleophile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon (Pro-)Nucleophiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Carbonylative Cross Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Insertion into CuH or CuBpin Intermediates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Radical Cascade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Nitrogen Nucleophiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Oxygen Nucleophiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Silicon Nucleophiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

256 257 258 259 260 263 267 270 270 270 273 273

Abstract Construction of C–C and C–X bonds via carbonylation provides an attractive strategy to synthesize carbonyl compounds such as ketones, amides, esters, and carboxylate derivatives at mild and atom-economical reaction conditions. To complement historic progress in noble metal-catalyzed carbonylation, more sustainable avenues involving earth-abundant metals are actively being investigated. Copper has recently emerged as one of the most suitable metals with unique catalytic carbonylation reactivity. Here, we provide a comprehensive review of carbonylative C–C coupling and cover selected examples of carbonylative C–X coupling catalyzed by copper. The contents have been divided based on the nucleophiles applied in carbonylative coupling with carbon-centered electrophiles. Discussions of substrate scope and mechanisms are included. Keywords Acyl radicals · Carbon monoxide · Carbonylation · Copper · Cross coupling P. Tung and N. P. Mankad (✉) Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA e-mail: [email protected]

256

P. Tung and N. P. Mankad

1 Introduction Carbonyl compounds including ketones, aldehydes, carboxylic acids, amides, esters, and other carboxylate derivatives are ubiquitous as chemical reagents and in important organic scaffolds. They are embedded in the cores of many natural products, bioactive molecules, and organic materials and often play critical roles in their functional properties. Among various methods to synthesize carbonyl compounds, carbonylation reactions are used widely in industry due to economical use of CO as a C1 feedstock to introduce the carbonyl functionality while extending the carbon chain [1]. The use of transition metal catalysis in carbonylation dates back to 1938 when Roelen developed the first carbonylation reaction, the oxo synthesis also known as hydroformylation [2]. Today, carbonylation reactions such as hydroformylation and methanol carbonylation represent the largest-scale examples of homogeneous catalysis in the entire chemical industry [3, 4]. Although many of these reactions were originally discovered using base metals such as cobalt [5–8], industrial processes typically employ precious metals such as rhodium [3] and palladium [9, 10] due to the availability of lower catalyst loadings, milder reaction conditions, and catalyst recyclability. However, as the scarcity of these metals continues to threaten sustainability, alternative approaches are much desired [11]. In this regard, first-row transition metals represent excellent alternatives due to their earth abundance. Additionally, because these 3d metals sometimes operate in different mechanistic manifolds than their 4d/5d counterparts, they provide venues for new reaction discovery. Accordingly, recently there has been renewed research activity toward developing non-precious metal-catalyzed carbonylation reactions [12, 13]. Although copper-catalyzed coupling reactions are well established [14], historically copper has not played an important role in carbonylation chemistry, possibly due to the poor ability of copper complexes to bind CO. However, since 2017 there has been a surge in reports of carbonylation reactions catalyzed by copper [15]. Typically, copper-catalyzed carbonylation reactions are three-component transformations coupling CO with an alkyl electrophile and a nucleophile. Thus, CO forms a C– C bond with the electrophile and a C–C or C–X bond with the nucleophile (Fig. 1a). These reactions tend to rely on the availability of single-electron Cu(I)/Cu(II)/Cu(III) redox cycling during catalysis (Fig. 1b). In a typical reaction pathway, an electronrich copper(I) catalyst engages the alkyl electrophile in single-electron transfer (SET) activation, generating a persistent copper(II) intermediate along with a transient alkyl radical. Under CO atmosphere, alkyl radicals are known to undergo facile carbonylation to generate acyl radicals [16]. Rebound of the acyl radical with copper (II) generates an acylcopper(III) intermediate, which readily undergoes reductive elimination to release the carbonylated product. (In some cases, e.g., involving tertiary alkyl electrophiles, the acyl radical can carry forward a radical chain process known as atom transfer carbonylation, or ATC [16], rather than recombining with copper. This will be described in some case studies below.) Under this dominant paradigm for Cu-catalyzed carbonylation, it is not required for the weakly π-basic

Cu-Catalyzed C–C Bond Formation with CO (a) Ralkyl

X

O

257

Nuc

O

Cu cat.

C

Ralkyl

Nu

(b) Nu = H, B, C, N, O, Si

LCu(I)-Nu R X

LCu(II)-Nu R

O

O

CO

R Nu Cu(III)L

R

X

R = alkyl

LCu(I)X O R

Nu

LCu(II)-Nu

Fig. 1 (a) General schematic for Cu-catalyzed carbonylation reactions, and (b) a dominant mechanistic paradigm involving radical intermediates

copper center to activate CO directly. An additional advantage is the lack of any alkylcopper intermediate that might perform β-hydride elimination to form unwanted side products. Overall, the diversity in carbonylative coupling reactions catalyzed by copper derives from the different nucleophiles capable of forming active copper catalysts capable of initiating SET processes. Thus, this chapter organizes Cu-catalyzed carbonylation reactions by nucleophile. For carbon nucleophiles, i.e., reactions in which two C–C bonds with CO are formed, a comprehensive review is presented for published reports through 2022. For hydride and heteroatom nucleophiles, i.e., reactions in which CO forms one C–C and one C–X bond, selected examples from the recent literature are given in lieu of comprehensive reviews to help highlight the variety of multicomponent coupling reactions available.

2 Hydride Nucleophile Alcohols are abundant in nature and ubiquitous in chemical transformations. Introducing an alcohol functionality in an organic scaffold is usually performed via reduction of pre-installed carbonyl functional groups. Recently, Zhao et al. developed a complementary approach by formulating a copper-catalyzed hydroxymethylation of alkyl halides in the presence of a hydrosilane reductant, with CO as the C1 source (Fig. 2) [17]. The important facets of this strategy are in-situ generation of aldehyde intermediate from the alkyl halide and its subsequent reduction to afford one carbon extended alcohols. Primary, secondary, and tertiary iodides as well as biologically relevant structures were successfully converted into one carbon extended alcohols in moderate to excellent yields. Mechanistic investigation indicated a metal-free ATC pathway to generate an acyl iodide intermediate, followed in tandem by two CuH-mediated hydrosilylation processes to afford the alcohols upon workup. However, a Cu-mediated pathway for alkyl iodide

258

P. Tung and N. P. Mankad MeIPrCuCl

RAlkyl

I

CO

(EtO)2MeSiH

(10 mol%) LiOMe (2.0 equiv) 1,4-Dioxane, 60 oC, 16 h

H RAlkyl

(TBAF workup)

H OH

via:

O

RAlkyl

H

OH OH

OH iPr

Me Me

iPr N

N

iPr

iPr

MeIPr

O Me Me

O

OH H Me

Me Me

H O 41%

Me

Me H

O

O

62%

89%

75%

OH

HO

H

OH

50%

Fig. 2 Hydroxymethylation of alkyl iodides using CO as the C1 source

carbonylation (as in Fig. 1b) was not ruled out and may be operative for primary alkyl derivatives.

3 Boron Nucleophile Organoboron compounds are very useful synthetic moieties owing to their widespread use in organic transformations including the Suzuki-Miyaura coupling reaction. Despite the established chemistry of organoboron compounds, acylborons are quite rare due to their reactive nature. Moreover, the synthesis of acylboron compounds requires multiple steps or uses stoichiometric organometallic reagents or oxidants [18]. To address these limitations, recently Cheng et al. have developed a one-step, copper-catalyzed, carbonylative borylation of alkyl halides that uses a commercially available boron source, cheap and earth-abundant copper catalyst, and CO as a C1 feedstock (Fig. 3) [19]. A subsequent workup with aqueous KHF2 delivered bench-stable potassium acyltrifluoroborates (KATs), which have applications in bioconjugation and peptide synthesis. Different alkyl halide substrates were well tolerated under the reaction conditions. The mechanistic study indicated an ATC pathway to deliver a key acyl iodide intermediate, which undergoes Cu-catalyzed borylation to form a tetra-coordinated boron species with sufficient stability at ambient conditions. Based on this mechanism, recently a Cu-catalyzed borylation reaction of activated anhydride substrates was reported, providing access to KATs even from protected amino acid derivatives [20].

Cu-Catalyzed C–C Bond Formation with CO

259

ClIPrCuCl

(1.0 mol%) LiOtBu (2.0 equiv.) KHF2 (aq), rt, 2 h THF, 60 oC, 15 h

RAlkyl

O

B2pin2

CO

X

Cl iPr

Cl

N

N

iPr

iPr

RAlkyl

BF3K

iPr

ClIPr

O Ph

O

O Ph

BF3K

N

O

BF3K

4

81%

74%

61%

O

O

O Me Me

BF3K

BF3K O

Me 65%

BF3K

4

BF3K Me 49%

64%

CO

RAlkyl

RAlkyl

O

O RAlkyl

O RAlkyl

X

RAlkyl

Bpin Cu(III)ClIPr X

O RAlkyl

X

B O

O

LiOtBu

ClIPrCu(I)Bpin ClIPrCu(I)X

O Li Bpin(OtBu) B2pin2

ClIPrCu(I)OtBu

O

LiX

LiOtBu

B B O

RAlkyl B tBuO O

LiX

O

O B2pin2 =

LiOtBu

O

ClIPrCu(I)X

Fig. 3 Carbonylative borylation of alkyl halides

4 Carbon (Pro-)Nucleophiles Ketones are prevalent in natural products, organic materials, bioactive molecules, and photosensitizers. They play pivotal roles in multistep organic syntheses, and thus are very attractive to synthetic chemists. Traditionally, they are synthesized via oxidation of secondary alcohols. However, transition metal-catalyzed carbonylation reactions have emerged as a complementary tool to access these compounds. Palladium-catalyzed carbonylative Kumada, Negishi, Stille, Suzuki, Heck, and Sonogashira reactions have been reported for the construction of the ketone C–C

260

P. Tung and N. P. Mankad

bonds [9, 21, 22]. However, use of copper as a catalyst for carbonylative ketone formation was less explored until recently.

4.1

Carbonylative Cross Coupling

Carbonylative cross coupling catalyzed by copper dates to 1996, when Kang and co-workers reported a copper-catalyzed carbonylative Stille coupling with organostannanes and hypervalent iodine species under mild reaction conditions, furnishing ketones with high yields (Fig. 4) [23]. Furthermore, a Suzuki-type variant was also carried out, thus avoiding the need for stoichiometric tin. Biaryl ketones, enones, and ynones were obtained under atmospheric CO pressure at room temperature. The use of catalytic CuI could deliver the ketones with good yields. In 2005, Yu and co-workers reported a carbonylative Suzuki coupling based on Kang’s previous report by modifying the hypervalent iodine reagent to provide more general access to ynones (Fig. 5) [24]. Copper-catalyzed carbonylative coupling of alkynyl iodonium salts and organoboronic acids was carried out in presence of potassium carbonate at ambient temperature. A diverse substrate scope was examined for this transformation and resulted in high yields. As a complementary approach to ynone synthesis, in 2008 Bhanage and co-workers developed a copper-catalyzed carbonylative Sonogashira coupling (Fig. 6) [25]. This was the first report of a Sonogashira-type coupling that did not require a palladium co-catalyst. Various alkyl and aryl substituted alkynes reacted with aryl iodides in presence of triethylamine base and Cu(TMHD)2 catalyst in

O Aryl

I Ph X

CO

R1 SnBu3

O

O

85%

94%

CuI (2.5 mol%) DME, rt, 10-120 min

I Ph BF4

CO

O

O

O

Ph

I

84%

R1 B(OR)2

O

O

78%

63%

83%

O

CuI (2 mol%) NaOH (3.0 equiv.)

R1

DME/H2O (4:1) 35 oC, 30 min O

OMe

Fig. 4 Carbonylative Stille and Suzuki reactions

R1

Aryl

68%

Cu-Catalyzed C–C Bond Formation with CO

RAlkyl/Aryl

CO

I Ph BF4

261 CuI (5 mol%) K2CO3

R B(OH)2

O

O

n-Bu

R

O

n-Bu 74%

O RAlkyl/Aryl

DME/H2O (4:1) 20 oC, 2-3 h

t-Bu 63%

O

77%

OMe O

O

t-Bu

O

Ph

Ph

Cl 72%

77%

S

61%

Cl

Fig. 5 Carbonylative Suzuki coupling to afford ynones

RAlkyl/Aryl

H

CO

RAryl

O

I

Cu(TMHD)2 (5 mol%) Et3N (3.0 equiv.) Toluene, 90

oC,

14 h

O

n-Bu

Me

n-Bu

RAryl

O n-Hex

63%

68%

O RAlkyl/Aryl

77% O

OMe O Ph

O

O

Ph

80%

t-Bu TMHD

Ph 78%

O

t-Bu

68% Me

NO2

Fig. 6 Carbonylative Sonogashira coupling

toluene solvent at 90°C. Substrates with different steric and electronic profiles sustained the reaction, providing excellent yields of the ynones. In 2014, Hans and co-workers reported a carbonylative Suzuki coupling catalyzed by ligand-free nanocopper in PEG-400 [poly(ethylene glycol)] (Fig. 7) [26]. Aryl iodides and aryl boronic acids were reacted together under ambient CO pressure to deliver biaryl ketones at 80–100°C. Nanocopper catalyst was found to be more effective than copper salts such as CuCl or CuBr. KF as an additive provided effective catalysis at the required elevated temperature. Exhaustive substrate screening suggested neither sterics nor electronics of either coupling partner had any influence on the reaction outcome, as the ketones were invariably obtained with excellent yields. It is noteworthy that the catalyst can be recycled up to 10 times with only slight decrease in yield. In 2017, Pye et al. reported a Cu/Mn co-catalyzed approach for accessing alkyl/ aryl ketones by carbonylative Suzuki coupling (Fig. 8) [27]. Alkyl halides and arylboronic esters were subjected to carbon monoxide atmosphere in presence of alkoxide base to obtain the desired products. Detailed control experiments suggested

262

P. Tung and N. P. Mankad I

Cu (20 mol%) K3PO4, KF

B(OH)2 CO

t-BuCOOH, PEG-400 80-100 oC

Aryl

Aryl

O Aryl

Aryl

O

O

O

O2N

Me 93%

F3C 90%

75%

O

O

O

Me

CN

82%

Cl

OMe

88%

71%

Fig. 7 Carbonylative Suzuki coupling to afford biaryl ketones L1:

O B Aryl

Me Me RAlkyl

CO

O

I

LCuCl (15 mol%) Na[Mn(CO)5] (7.5 mol%)

N

O

KOMe(1.5 equiv.) THF, 60 oC, 15 h

N

RAlkyl

Aryl

IPr L2: N

N

ItBu O

O

O

O

Me

Me

Me

Me

5

5

5

5

Me

MeO2C

MeO L1, 70%

NC

L1, 65%

L1, 68% O

O

MeO2C

Me L2, 77%

O

Me L2, 64%

Me L2, 72%

O Ar

L1, 86%

[Mn(CO)5] R X

R

MeO X LCu Ar O

LCuOMe

R Mn(CO)5 R

Ar B(OR')2

MeOB(OR')2

Mn(CO)5

CO

Fig. 8 Cu/Mn co-catalyzed carbonylative Suzuki coupling to afford alkyl/aryl ketones

Cu-Catalyzed C–C Bond Formation with CO

263

both the metals are required for catalytic turnover. Primary and secondary alkyl halides reacted with the boronic esters regardless of their electronic nature, providing high yields of the corresponding ketones. A smaller, more electron-donating ItBu ligand in place of IPr was found to be necessary to obtain high yields with secondary alkyl halides. Based on their mechanistic study, the authors proposed that the reaction is an extension of the alkoxycarbonylation and aminocarbonylation reactions catalyzed by cobalt and manganese carbonylates previously reported by Heck and Breslow [6], here with an arylcopper intermediate generated by transmetalation from the arylboronic ester acting as the nucleophile.

4.2

Insertion into CuH or CuBpin Intermediates

In 2017, Cheng et al. discovered a hydrocarbonylative coupling strategy to synthesize unsymmetrical dialkyl ketones using alkyl iodides and terminal alkynes in the presence of a hydrosilane reductant, polymethylhydrosiloxane (PMHS) [28]. A series of primary and secondary alkyl iodides along with diverse terminal alkynes were found to be compatible under the reaction conditions, providing high yields of the corresponding dialkyl ketones (Fig. 9). Based on mechanistic investigations, the authors proposed formation of a key CuH intermediate that subsequently performs hydrocupration of the alkyne, yielding a vinylcopper(I) intermediate capable of SET activation of the alkyl iodide. Upon carbonylation of the resulting alkyl radical, recombination to form an acylcopper(III) intermediate followed by reductive elimination generates an α,β-unsaturated ketone. This intermediate subsequently undergoes 1,4-hydrosilylation via another CuH catalytic cycle to deliver the observed dialkyl ketones upon workup in an overall tandem catalytic manifold. Under very similar reaction conditions, in 2018 Cheng et al. reported that combinations of sterically hindered alkyl halides and alkynes undergo hydrocarbonylative coupling to yield allylic alcohols selectively rather than dialkyl ketones upon workup (Fig. 10) [29]. Secondary and primary alkyl halides generated allylic alcohols when coupled with internal rather than terminal alkynes, while tertiary alkyl halides showed high selectivity for allylic alcohols even with terminal alkynes. The latter cases provided access to challenging, quaternary carbon centers. Based on mechanistic investigations, the authors proposed that the dialkyl ketoneforming and allylic alcohol-forming reactions proceed by a common α,β-unsaturated ketone intermediate that undergoes CuH-mediated hydrosilylation in tandem. Regioselectivity for 1,2-hydrosilylation to provide allylic alcohols vs. 1,4-hydrosilylation to provide dialkyl ketones is presumably controlled by sterics of the two coupling partners, with 1,2-hydrosilylation being favored in more hindered cases. A preliminary DFT study in the original report provided a transition state model for this regioselectivity, which received further support from

264

P. Tung and N. P. Mankad

R'Alkyl

RAlkyl

CO

IPrCuCl (10 mol%) KOMe (3.0 equiv.) PMHS (6.0 equiv.)

I

THF, 60 oC, 15 h

O Me

N

82%

Me

5

4

RAlkyl

Me

O 5

Me

O

Me

5

71%

Me

74% O

O Me

O R'Alkyl

Me

6

6

Me

O

82%

55%

[Si]-OMe + KI KOMe + [Si]-H

IPrCu(I)H

R'Alkyl

R'Alkyl

IPrCu(I)I

RAlkyl IPrCu(I)H

O R'Alkyl

RAlkyl

[Si]-H

Cu(I)IPr

R'Alkyl

O

I R'Alkyl

RAlkyl

RAlkyl Cu(III)IPr I

R'Alkyl

RAlkyl

RAlkyl O[Si]

OCu(I)IPr

R'Alkyl R'Alkyl

RAlkyl O

Cu(II)IPr I

O RAlkyl

CO

Fig. 9 Hydrocarbonylative coupling of alkynes and alkyl iodides to access dialkyl ketones

an independent theoretical investigation [30]. It should also be noted that, for the hydrocarbonylative coupling portion of the tandem process, mechanistic data indicated that tertiary alkyl halides react by an ATC pathway rather than a Cu-based carbonylation mechanism, thus proceeding by an acyl halide intermediate that is vinylated by the hydrocupration intermediate [29]. This is distinct from primary and secondary substrates, for which the ATC pathway is likely inaccessible due to unfavorable thermodynamics of atom transfer between alkyl radical and acyl halide intermediates. Instead, such substrates would follow the Cu-mediated carbonylation pathway previously uncovered for the dialkyl ketone-forming reaction. Later in 2018, Cheng et al. devised a boracarbonylative coupling reaction of internal alkynes and alkyl halides, providing access to β-borylated enones by fourcomponent coupling (Fig. 11) [31]. Readily available alkynes, alkyl halides, bis (pinacolato)diboron (B2pin2), and CO were treated with the copper catalyst and

Cu-Catalyzed C–C Bond Formation with CO

265 ClIPrCuCl

(10 mol%) KOMe (3.0 equiv.) PMHS (6.0 equiv.)

R

RAlkyl

CO

R'

X

H

OH

R

THF, rt, 15 h

R'

OH

OH Me 7

78% (12:1)

Ph Ph

66% (12:1)

4

Me Me

OH Me

O

Ph

Br

Me Me Me

68%

OH O

RAlkyl

OH

Me Me Me

Me Me Me

H

4

Br

77% (8:1)

70% (15:1)

CO R' O

RAlkyl

RAlkyl

R O

RAlkyl Cu(III)ClIPr X

R' R

RAlkyl

X

RAlkyl

ClIPrCu(I)H

RAlkyl

O

[Si]-H

O X R' R

ClIPrCu(I)X

KOMe + [Si]-H ClIPrCu(I)H

R

R'

R'

R' R

Cu(I)ClIPr

RAlkyl OCuClIPr

R

RAlkyl O[Si]

[Si]-OMe + KX

Fig. 10 Hydrocarbonylative coupling of alkynes and tertiary alkyl halides to access allylic alcohols. The mechanism shown does not include initiation of the radical chain process

alkoxide base at ambient temperature, resulting in tetrasubstituted enone derivatives. Since the β-borylated, tetrasubstituted enones were found to be slightly unstable during silica gel purification, a reductive workup was carried out to generate more stable oxaboroles. However, the enone intermediates were also found to undergo subsequent reactions such as Pd-catalyzed Suzuki coupling without purification. Alkynes with an electron-donating substituent provided moderate to good yields, while electron-deficient alkynes performed poorly under the reaction conditions. The synthetic utility of this method was demonstrated by conducting series of transformations with an oxaborole to construct C–C and C–X bonds. Mechanistically, the authors proposed a pathway like the hydrocarbonylative coupling reactions studied previously, but here involving borylcupration rather than hydrocupration of the alkyne. In 2020, Wu and co-workers extended the boracarbonylative coupling reactions from alkynes to alkenes (Fig. 12) [32]. This copper-catalyzed carbonylation method for synthesizing β-borylated ketones uses unactivated alkenes, alkyl iodides, and

266

P. Tung and N. P. Mankad

R

R'

Ph

X

B

Me HO

6

B

HO L1, 68%

O

B

Ph

Ph

Ph

nBu

B

OMe

O

HO

B

L2, 75%

O

N

N

L1, 68%

nBu

7

HO

L1:

O SIMes

L1, 43%

nBu

HO

O

6

Me

S

O

RAlkyl B

Ph

Me 6

R' R

2. NaBH4 (2.0 equiv.) MeOH, rt, 0.5 h

S

Ph HO

RAlkyl

B2pin2

CO

1. LCuCl (10 mol%) KOMe (3.0 equiv.) THF, rt, 15 h

O

HO

L2, 60%

B

L2:

Me Me Me

N

O

N

MeIMes

L2, 60%

KX + MeOBpin B2pin2 + KOMe

LCu(I)Bpin

R

R'

R' R

RAlkyl

LCu(I)X

Bpin O R' R

Cu(I)L Bpin

R' O R

RAlkyl Cu(III)L Bpin X

RAlkyl

RAlkyl

R' R

X

Cu(II)L Bpin X

O RAlkyl

CO

Fig. 11 Boracarbonylative coupling of alkynes and alkyl halides

B2pin2 under CO. The use of xantphos ligand to support the Cu catalyst was found to be critical for promoting the desired transformation, presumably due to its optimal bite angle. A wide variety of alkene substrates were tolerated under the reaction conditions. While primary alkyl iodides reacted smoothly, secondary alkyl iodides showed diminished reactivity. It is likely that the mechanism is closely related to the boracarbonylative coupling reaction of alkynes previously disclosed by Cheng et al. [31] Later in 2020, Marder, Wu, and co-workers reported a novel method for the synthesis of cyclopropyl bis(boronates) with fixed stereochemistry using CO as a C1 source (Fig. 13) [33]. Copper-catalyzed carbonylation conditions were employed with terminal alkenes and B2pin2. Extensive phosphine screening indicated xantphos as the optimal ligand. Various aliphatic alkene substrates with different steric

Cu-Catalyzed C–C Bond Formation with CO

R2 CO

R3

R1

RAlkyl

267

IPrCuCl (10 mol%) xantphos (12 mol%)

I

B2pin2 (2.0 equiv.) LiOMe (2 equiv.) DMA (0.4 M), 60oC

O N

RAlkyl Bpin

O nBu

66%

O R1 R2 R3

Bpin

O Ph

Bpin 41%

51%

OH

O

O

Ph

Ph Bpin 42%

nBu

Me

Bpin

Bpin 81%

Ph

Bpin 54%

S

Fig. 12 Boracarbonylative coupling of alkenes and alkyl iodides

profiles withstood the reaction conditions, providing moderate to good yields of the corresponding cyclopropanes. However, aromatic alkenes such as styrene delivered only trace amounts of product. Further elaboration of a cyclopropyl bis(boronates) compound was carried out to demonstrate utility. As for the mechanism, two coppercentric catalytic cycles have been proposed, with IPrCu-Bpin being a common intermediate in both cycles. One cycle accomplishes CO insertion into the B–B bond of B2pin2, generating the unusual O=C(Bpin)2 intermediate. The latter then inserts into the β-borylated alkylcopper(I) intermediate that itself is generated from borylcupration of the alkene. Intramolecular rearrangement followed by ɣ-boryloxy elimination forms the cyclopropane ring. In 2021, Wu and co-workers reported a ligand-controlled, copper-catalyzed boracarbonylative coupling of imines and alkyl iodides [34]. Use of electrondeficient phosphine ligands produced α-amino ketones selectively (Fig. 14). On the other hand, use of an electron-rich carbene ligand reversed the regioselectivity and formed α-boryl amides selectively. Scope in imine was found to be quite broad, whereas alkyl iodide scope was limited to primary derivatives.

4.3

Radical Cascade

In 2022, Wu and co-workers developed a novel method for the synthesis of 1,4-diketones via copper-catalyzed 1,2-dicarbonylative cyclization of alkyl bromides with alkenes (Fig. 15) [35]. The reaction provided efficient access to α-tetralone and 2,3-dihydroquinolin-4-one derivatives under mild conditions.

268

P. Tung and N. P. Mankad

B2pin2

CO

RAlkyl

Bpin

IPrCuCl (4 mol%) xantphos (4 mol%) NaOEt (1.5 equiv.) DMAc (0.4 M), 60 oC, 12 h

Bpin

Me

55%

53%

Bpin

Bpin S

Bpin

Bpin

Bpin 67%

Bpin

55%

70%

Bpin RAlkyl

CuCl + L

Bpin

NaOEt

pinBOBpin B2pin2

NaCl

LCu(I)OBpin Bpin RAlkyl

Bpin

O

Bpin

62%

Bpin

Bpin

Bpin

Bpin

RAlkyl

LCu(I)OEt

OBpin H

B2pin2

Cu(I)L

EtOBpin

CO

Bpin O LCu(I)Bpin

LCu(I)

Cu(I)L Bpin OBpin RAlkyl

Bpin

Bpin

B2pin2

Bpin Bpin OCu(I)L RAlkyl

RAlkyl

Cu(I)L Bpin

O

RAlkyl Bpin

Bpin

Bpin O Bpin

Bpin

Fig. 13 Alkene cyclopropanation using CO as a C1 source

Amazingly, this single transformation involves formation of four new C–C bonds, installation of two carbonyl groups, and construction of a carbocyclic or heterocyclic ring. A broad substrate scope was demonstrated with moderate yields and no significant electronic or steric influence from the aromatic substituents. A radical cascade mechanism was proposed, with the copper catalyst serving as a redox mediator.

Cu-Catalyzed C–C Bond Formation with CO

RAryl

R'Aryl

N

RAlkyl

CO

CuCl (10 mol%) P(4-C6H4CF3)3 (20 mol%) B2pin2 (3.0 equiv.)

I

O

H N

269

NaOtBu (3.0 equiv.) THF/Toluene (4:1, 0.2 M) 80 oC, 16 h, then MeOH

Ph

60%

Ph

Br

61%

O

H N

Cy

CF3 Cy

78%

O

H N

Ph

MeO

S

Ph

Br

72%

O

H N

O

H N

Ph

Ph

RAlkyl RAryl

O

H N

Me

O

H N

R'Aryl

Cy Ph

54%

79%

Fig. 14 Boracarbonylative coupling of imines and alkyl iodides

Br

RAlkyl

CO X = CR2, NR

Br

Cy

Cy

54%

tBu

47% O

O Me

40%

O RAlkyl

tBu

O

N Me

O

52%

Br

O

RAlkyl [Cu(I)L] CO

H H

O

O RAlkyl

RAlkyl O

[Cu(II)L]

H

RAlkyl

O O

RAlkyl O CO

O

P O

tBu

44%

RAlkyl

O

Cy

tBu

O

tButBu

L:

O

Me

tBu

O

O

O 57%

X

O

O

MeO

Cy

RAlkyl R

acac (20 mol%), K3PO4 (3.0 equiv.) Anisole, 70 oC, 24-36 h

O

O

O

O

CuBr.SMe2(10 mol%) DABCO (20 mol%), L (30 mol%)

X R

RAlkyl O

Fig. 15 1,2-Dicarbonylative cyclization of alkenes and alkyl bromides

O

tBu

270

P. Tung and N. P. Mankad

5 Nitrogen Nucleophiles Amides are important units in most living organisms as well as synthetic moieties. Moreover, α-keto amides are widely found in natural products and inhibitors and thus bear particular interest. In 2022, Wu developed a copper-catalyzed aminocarbonylation strategy that delivers mono- and double-carbonylated amide and α-keto amide products, respectively, from various alkyl halide reactants (Fig. 16) [36]. Alkyl bromides underwent double-carbonylation exclusively, forming α-keto amides with high yields. Alkyl iodides resulted in both mono- and double-carbonylated products. During the optimization, it was observed that a slight modification of reaction conditions (such as reaction stoichiometry, temperature, and CO pressure) could regulate the selectivity between mono- and doublecarbonylation. The observed selectivity was attributed to the relative rate of activation for different alkyl halides.

6 Oxygen Nucleophiles Among various carboxylic acid derivatives, esters are one of the most abundant compounds with important applications in numerous organic transformations and the polymer industry. Typically, they are synthesized by the esterification of carboxylic acids with alcohols or the oxidative esterification of aldehydes. Alkoxycarbonylation provides an alternative that does not require pre-installed carboxylate functionality and avoids over-oxidation. Wu and co-workers recently reported an alkoxycarbonylation strategy for synthesizing esters from alkyl halides using phenols as nucleophiles (Fig. 17) [37]. A copper catalyst and readily available reagents afforded the desired outcome with high chemoselectivity and yields under very mild reaction conditions. Interestingly, aliphatic alcohols were feasibly transformed under the standard conditions, as well. The method showed wide functional group tolerance and allowed late-stage functionalization of natural products.

7 Silicon Nucleophiles Acylsilanes are useful organic scaffolds that are widely used in materials science and various organic transformations including the Brook rearrangement. Although there are some direct syntheses available, the use of stoichiometric silylcopper or silyllithium reagents, or moisture sensitive substrates such as acyl chlorides or anhydrides, restricts their broad applicability. In 2020, Cheng et al. reported a copper-catalyzed carbonylative silylation of alkyl halides to afford acylsilanes in a single step using readily available reagents under mild conditions (Fig. 18) [38]. The

O

N

O

O

O

47%

4

H

H

4

43%

O

H

H

O

Me Me

90%

75%

O

N H

O

CO

O

61%

4

HNRR'

H N

O

O

O N

4

80%

O

H N

70%

O

O

H

MeS

1,4-Dioxane, 50-110

oC,

Fig. 16 Aminocarbonylation of alkyl halides to produce amides and α-keto amides

O

N

O

X

N H

O

RAlkyl

Cu cat. (10 mol%) bpy (10 mol%) Cs2CO3 (3.0 equiv)

H H

H

O

O

4

O N H

O

EtO 95%

O

HN

R'

O

O Cl

Me

R N

Me

O

Me

O

MeO2C

N

68%

O

RAlkyl

n-C4H9

N

n-C4H9

O

R

O

N R'

O

O

41%

N

72%

O

n-C4H9

24 h

RAlkyl

OMe

O 4

54%

O

O

N

O

Cu-Catalyzed C–C Bond Formation with CO 271

272

P. Tung and N. P. Mankad

RAlkyl

X

CuBr·SMe2 (10 mol%) bpy (10 mol%) Cs2CO3 (2.0 equiv.)

CO

R OH

Me

O Me

Toluene, 50

15 h

O RAlkyl

O

R

O

Br

O Me

O

oC,

Me

O

O

90%

93%

75% O

O

O

O

O

O 87%

63%

93%

Fig. 17 Alkoxycarbonylation of alkyl halides

RAlkyl

X

CO

R3Si

IPrCuCl (10 mol%) NaOPh (3.0 equiv.)

Bpin

O

91%

SiMe2Ph

4

SiR3

RAlkyl

O

O N

SiMe2Ph

O

1,4-dioxane, 60 oC, 12 h

50%

O SiMe2Ph

SiMe2Ph 97%

73%

IPrCu(I)X O NaOPh RAlkyl PhMe2Si

Bpin

SiMe2Ph

IPrCu(I)OPh

PhO Bpin iPr O

IPrCu(I)SiMe2Ph RAlkyl

RAlkyl

SiMe2Ph Cu(III)IPr X

iPr N

N

iPr

iPr IPr

X O

RAlkyl

IPrCu(II)SiMe2Ph RAlkyl X

CO

Fig. 18 Carbonylative silylation of alkyl halides

method is scalable and tolerated a broad range of substrates including primary, secondary, and tertiary alkyl electrophiles with very high yields. The authors demonstrated the utility of the method by conducting a late-stage functionalization

Cu-Catalyzed C–C Bond Formation with CO

273

on an estrone derivative. The transformation proceeds via an electron-rich silylcopper(I) intermediate that enables the radical carbonylation mechanism.

8 Conclusions This chapter provides a thorough overview of copper-catalyzed reactions that form C–C bonds with CO, including comprehensive coverage of cases that form two C–C bonds and selected recent developments on cases that form one C–C and one C–X bond with CO. Most transformations use readily available copper catalysts and ligand systems. The use of copper makes these processes greener and more sustainable than noble metal-catalyzed carbonylation reactions. Moreover, in many cases the copper-catalyzed carbonylation reactions access bond disconnections that are completely novel and, thus, complement the more established carbonylation catalysis of noble metals. Although reaction conditions tend to be mild, relatively high catalyst loadings required for Cu-catalyzed carbonylation reactions is a major issue to be addressed to impact industrial synthesis. Additionally, stereoselective variants of reactions that generate stereocenters are yet to be developed.

References 1. Peng JB, Geng HQ, Wu XF (2019) The chemistry of CO: carbonylation. Chem 5:526–552 2. Cornils B, Herrmann WA, Rasch M (1994) Otto Roelen, Pioneer in industrial homogeneous catalysis. Angew Chem Int Ed Engl 33:2144–2163 3. Beller M, Cornils B, Frohning CD, Kohlpaintner CW (1995) Progress in hydroformylation and carbonylation. J Mol Catal Chem 104:17–85 4. Haynes A (2006) Acetic acid synthesis by catalytic carbonylation of methanol. In: Beller M (ed) Catalytic carbonylation reactions, vol 18. Springer, Berlin, pp 179–205 5. Hebrard F, Kalck P (2009) Cobalt-catalyzed hydroformylation of alkenes: generation and recycling of the carbonyl species, and catalytic cycle. Chem Rev 109:4272–4282 6. Heck RF, Breslow DS (1963) Carboxyalkylation reactions catalyzed by cobalt carbonylate ion. J Am Chem Soc 85:2779–2782 7. Adkins H, Krsek G (1948) Preparation of aldehydes from alkenes by the addition of carbon monoxide and hydrogen with cobalt carbonyls as intermediates. J Am Chem Soc 70:383–386 8. Heck RF, Breslow DS (1961) The reaction of cobalt hydrotetracarbonyl with olefins. J Am Chem Soc 83:4023–4027 9. Brennführer A, Neumann H, Beller M (2009) Palladium-catalyzed carbonylation reactions of aryl halides and related compounds. Angew Chem Int Ed 48:4114–4133 10. Torborg C, Beller M (2009) Recent applications of palladium-catalyzed coupling reactions in the pharmaceutical, agrochemical, and fine chemical industries. Adv Synth Catal 351:3027– 3043 11. Hayler JD, Leahy DK, Simmons EM (2019) A pharmaceutical industry perspective on sustainable metal catalysis. Organometallics 38:36–46 12. Li Y, Hu Y, Wu XF (2018) Non-noble metal-catalysed carbonylative transformations. Chem Soc Rev 47:172–194

274

P. Tung and N. P. Mankad

13. Xu J-X, Wang L-C, Wu X-F (2022) Non-Noble metal-catalyzed carbonylative multicomponent reactions. Chem Asian J 17:e202200928 14. Cheng L-J, Mankad NP (2020) C–C and C–X coupling reactions of unactivated alkyl electrophiles using copper catalysis. Chem Soc Rev 49:8036–8064 15. Cheng LJ, Mankad NP (2021) Copper-catalyzed carbonylative coupling of alkyl halides. Acc Chem Res 54:2261–2274 16. Ryu I (2001) Radical carboxylations of iodoalkanes and saturated alcohols using carbon monoxide. Chem Soc Rev 30:16–25 17. Zhao S, Mankad NP (2018) Cu-catalyzed hydroxymethylation of unactivated alkyl iodides with CO to provide one-carbon-extended alcohols. Angew Chem Int Ed 57:5867–5870 18. Wu D, Taguchi J, Tanriver M, Bode JW (2020) Synthesis of acylboron compounds. Angew Chem Int Ed 59:16847–16858 19. Cheng L-J, Zhao S, Mankad NP (2021) One-step synthesis of acylboron compounds via coppercatalyzed carbonylative borylation of alkyl halides. Angew Chem Int Ed 60:2094–2098 20. Tung P, Schuhmacher A, Schilling PE, Bode JW, Mankad NP (2021) Preparation of potassium acyltrifluoroborates (KATs) from carboxylic acids by copper-catalyzed borylation of mixed anhydrides. Angew Chem Int Ed 61:e202114513 21. Wu X-F, Schranck J, Neumann H, Beller M (2012) Palladium-catalyzed carbonylative Negishitype coupling of aryl iodides with benzyl chlorides. Chem Asian J 7:40–44 22. Barnard CFJ (2008) Palladium-catalyzed carbonylation – a reaction come of age. Organometallics 27:5402–5422 23. Kang S-K, Yamaguchi T, Kim T-H, Ho P-S (1996) Copper-catalyzed cross-coupling and carbonylative cross-coupling of organostannanes and organoboranes with hypervalent iodine compounds. J Org Chem 61:9082–9083 24. Yu C-M, Kweon J-H, Ho P-S, Kang S-C, Lee GY (2006) Copper-catalyzed cross- and carbonylative coupling reactions of alkynyliodonium salts with organoboronic acids and organostannanes. ChemInform 37 25. Tambade P, Patil Y, Nandurkar N, Bhanage B (2008) Copper-catalyzed, palladium-free carbonylative Sonogashira coupling reaction of aliphatic and aromatic alkynes with iodoaryls. Synlett 2008:886–888 26. Cheng L et al (2014) Copper-catalyzed carbonylative Suzuki coupling of aryl iodides with arylboronic acids under ambient pressure of carbon monoxide. RSC Adv 4:44312–44316 27. Pye DR, Cheng L-J, Mankad NP (2017) Cu/Mn bimetallic catalysis enables carbonylative Suzuki–Miyaura coupling with unactivated alkyl electrophiles. Chem Sci 8:4750–4755 28. Cheng L-J, Mankad NP (2017) Cu-catalyzed hydrocarbonylative C–C coupling of terminal alkynes with alkyl iodides. J Am Chem Soc 139:10200–10203 29. Cheng L-J, Islam SM, Mankad NP (2018) Synthesis of allylic alcohols via Cu-catalyzed hydrocarbonylative coupling of alkynes with alkyl halides. J Am Chem Soc 140:1159–1164 30. Liu S et al (2020) The origin of regioselectivity in Cu-catalyzed hydrocarbonylative coupling of alkynes with alkyl halides. Org Chem Front 7:1137–1148 31. Cheng L, Mankad NP (2018) Copper-catalyzed borocarbonylative coupling of internal alkynes with unactivated alkyl halides: modular synthesis of tetrasubstituted β-borylenones. Angew Chem Int Ed 57:10328–10332 32. Wu F-P, Yuan Y, Schünemann C, Kamer PCJ, Wu X-F (2020) Copper-catalyzed regioselective borocarbonylative coupling of unactivated alkenes with alkyl halides: synthesis of β-boryl ketones. Angew Chem Int Ed 59:10451–10455 33. Wu F-P, Luo X, Radius U, Marder TB, Wu X-F (2020) Copper-catalyzed synthesis of stereodefined cyclopropyl bis(boronates) from alkenes with CO as the C1 source. J Am Chem Soc 142:14074–14079 34. Wu F-P, Wu X-F (2021) Ligand-controlled copper-catalyzed regiodivergent carbonylative synthesis of α-amino ketones and α-boryl amides from imines and alkyl iodides. Angew Chem Int Ed 60:695–700

Cu-Catalyzed C–C Bond Formation with CO

275

35. Zhao F, Gu X-W, Franke R, Wu X-F (2022) Copper-catalyzed 1,2-dicarbonylative cyclization of alkenes with alkyl bromides via radical Cascade process. Angew Chem Int Ed 61: e202214812 36. Zhao F, Ai H-J, Wu X-F (2022) Copper-catalyzed substrate-controlled carbonylative synthesis of α-keto amides and amides from alkyl halides. Angew Chem Int Ed 61:e202200062 37. Zhao F, Russo P, Mancuso R, Gabriele B, Wu X-F (2022) Copper-catalyzed carbonylative coupling of alkyl iodides with phenols for the synthesis of esters. J Catal 413:907–912 38. Cheng L-J, Mankad NP (2020) Cu-catalyzed carbonylative silylation of alkyl halides: efficient access to acylsilanes. J Am Chem Soc 142:80–84

Top Organomet Chem (2023) 93: 277–384 https://doi.org/10.1007/3418_2022_81 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 31 January 2023

Cu-Catalyzed C-C Coupling Reactions Manjunath S. Lokolkar, Yuvraj A. Kolekar, Prafull A. Jagtap, and Bhalchandra M. Bhanage

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Breakthrough After Ullmann Coupling Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Untapped Potential of Copper Catalysts in the Coupling Reactions . . . . . . . . . . . . . . . . . . . . . . . 3.1 Coupling with Terminal Alkynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Coupling with Grignard Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Coupling with Organozinc Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Coupling with Organoboron Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Coupling with Organotin Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Coupling with Organosilicon Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Coupling with Organoindium and Organoaluminium Reagents . . . . . . . . . . . . . . . . . . . . . 3.8 Coupling with Organomanganese Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Copper-Catalyzed Cyanations of Aryl Halides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Copper-Catalyzed Alkynylation, Alkenylation, and Allylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Copper-Catalyzed Alkynylation Reactions of Aryl Compounds . . . . . . . . . . . . . . . . . . . . 5.2 Copper-Catalyzed Alkenylation of Aryl Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Copper-Catalyzed Synthesis of Allyl–Aryl Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Copper-Catalyzed Oxidative Cross-Coupling Reaction Between Two Nucleophiles for C-C Bond Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Oxidative Cross-Coupling of Aryl Boronic Acids with Hydrocarbons/Nucleophiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Copper-Catalyzed Oxidative Decarboxylative Cross-Coupling for C-C Formation . . . 7 Copper-Catalyzed Cross-Dehydrogenative Coupling (CDC) for C-C Bond Formation . . . 7.1 Cross-Dehydrogenative C(sp3)-C(sp) Bond Formation (Alkynylation) . . . . . . . . . . . . . 7.2 Cross-Dehydrogenative C(sp3)-C(sp2) Bond Formation (Arylation) . . . . . . . . . . . . . . . . 7.3 Cross-Dehydrogenative C(sp3)-C(sp3) Bond Formation (Alkylation) . . . . . . . . . . . . . . . 7.4 Cross-Dehydrogenative C(sp2)-C(sp2) Bond Formation (Aryl-Aryl) . . . . . . . . . . . . . . . . 7.5 Cross-Dehydrogenative C(sp)-C(sp) Bond Formation (Diyenes) . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

279 280 285 285 291 298 300 309 314 317 319 319 321 321 325 331 339 340 343 346 347 352 358 360 362 366

Manjunath S. Lokolkar, Yuvraj A. Kolekar, Prafull A. Jagtap, and Bhalchandra M. Bhanage contributed equally to this work. M. S. Lokolkar, Y. A. Kolekar, P. A. Jagtap, and B. M. Bhanage (✉) Department of Chemistry, Institute of Chemical Technology, Mumbai, Maharashtra, India e-mail: [email protected]

278

M. S. Lokolkar et al.

Abstract This book chapter intends to give the reader a timely overview of significant copper-catalyzed cross-coupling reaction advancements. Carbon–carbon bond formation through cross-coupling methodologies is among the most indispensable and versatile tools in organic synthesis for constructing the carbon framework of organic molecules. The uncontested role of the expensive and lessabundant 2d and 3d row metals for organic and organometallic synthesis is evident based on their exceptional catalytic performance and high industrial demand. These applications can cause environmental and economic concerns, which can be alleviated by replacing these metals by applying the highly abundant and costeffective 1d transition metals. Copper-based catalysts are an attractive choice for emerging new synthetic methodologies due to their relatively lower toxicity, low cost, and high catalytic activity. In this context, this chapter intends to develop an understanding of novel and sustainable strategies and methodologies in organic and organometallic chemistry by utilizing the concepts elaborated in detail below for carbon–carbon bond formation, which is vital for future synthesis design. This chapter covers protocols in copper-catalyzed Csp3-Csp3, Csp3-Csp2, Csp3-Csp, Csp2-Csp2, and Csp-Csp bonds formation through several strategies such as Ullmann-type reaction, cross-coupling with organometallic reagents, cyanation, alkynylation, alkenylation, allylation reactions, and oxidative cross-coupling reactions. Moreover, a brief description of direct C-H functionalization referred to as cross-dehydrogenative coupling (CDC) for direct carbon–carbon bond formation has been summarized. Graphical Abstract

Cu-Catalyzed C-C Coupling Reactions

279

Cross-Coupling with Organometallic Reagents

Ullmann Coupling

Cu(0)

CrossDehydrogenative Coupling

Cu(I)

C Cu(II)

Oxidative CrossCoupling

Cyanation Reaction

C Cu(III)

Alkynylation Alkenylation Allylation

Keywords C-C coupling · Copper · Cross coupling · Homocoupling · Synthetic methodology

1 Introduction The transition metal-catalyzed cross-coupling strategy has contributed significantly and become a powerful and versatile tool for the construction of carbon–carbon (C-C) and carbon–heteroatom (C-X, X=O, N, S, etc.) bonds in advanced organic synthesis both in industries and academia [1–6]. These transformations have been widely utilized for the synthesis of pharmaceuticals, agrochemicals, natural products, and functional materials in the past decades [7–9]. Typically, such transformations are catalyzed with noble metal catalysts like palladium, and continuous efforts have been devised for these reactions as efficient tools in the synthesis of the functionalized C-C coupled products. The palladium catalysis for the coupling reactions has significantly contributed to the development and sharpened well in organic transformations to synthesize value-added chemicals [10–12]. The

280

M. S. Lokolkar et al.

significance and contributions of the Pd-catalyzed coupling reactions in organic transformations were recognized in 2010 with the Nobel Prize in Chemistry awarded to the three scientists, Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki [13]. These strategies have good functional group tolerance, work under mild reaction conditions, and lower air and moisture sensitivity for metal catalysts. Although these methods progressed continuously and well-sharpened in the field of synthetic organic chemistry, they have some drawbacks, such as the use of an expensive and low natural abundance of palladium and pre-functionalized coupling partners. The elemental copper (Cu) is the first transition metal to catalyze C-C and C-X bond synthesis. Tremendous efforts have been dedicated to the development of copper catalysts as an alternative to the palladium catalyst for these transformations [14–16]. Copper-based catalytic approaches for cross-coupling reactions are inspired due to their long-term sustainability, high earth abundance, low cost, air insensitive, less toxic, easy to handle, and environmentally benign. The copper-assisted coupling reaction chemistry was widely used before the advent of palladium catalysis in coupling reactions. In the early investigations in 1901, Ullmann reported the C-C bond formation using copper-catalyzed homocoupling of ortho-bromonitrobenzene for biaryl derivatives synthesis. Then the modification to the previous Ullmann coupling by Ullmann and Goldberg was reported from 1903 to 1906 using a C-X bond. However, several protocols were investigated for the C-C coupling reactions using different catalytic systems for the synthesis of organic frameworks [17]. The present chapter outlines recent developments in C-C coupling reactions through copper catalysts. These are classified into several major parts based on the precursors involved and the type of reactions. (1) The breakthrough after the Ullmann coupling reaction, (2) The untapped potential of copper catalysts in the coupling reactions includes coupling with terminal acetylenes, Grignard reagent and organozinc reagents, organotin reagents, organosilicon reagents, organoboron reagents, organoindium, and organoaluminium reagents, and organomanganese, which are described in detail, (3) The classical cyanation reaction and their modifications using a copper catalyst, (4) Aryl–aryl bond formation through coppercatalyzed alkenylation, alkynylation, and allylation reactions of aryl derivatives, (5) Copper-mediated catalytic and oxidative cross-coupling processes, and (6) Copper-catalyzed dehydrogenative C-C bond formation.

2 Breakthrough After Ullmann Coupling Reaction The foundation and investigations of copper-catalyzed C-C coupling chemistry, pioneering and noteworthy efforts of Fritz Ullmann and Irma Goldberg. Ullmann developed the C-C bond formation reaction in 1901 by using two molecules of ortho-bromonitrobenzene with copper powder to form a symmetrical biaryl homocoupled product (Scheme 1) [17].

Cu-Catalyzed C-C Coupling Reactions

281

Scheme 1 Ullmann reaction: biaryl synthesis

Ullmann, 1901 After the effective investigation of the Ullmann reaction for C-C bond formation, the Ullmann reaction was modified for the building of C-O, C-N, and C-S bonds by using aryl halides and various nucleophiles using the copper catalyst. The fascinating power of metallic copper, after 2 years of initial discovery (1903), Ullmann reported the coupling of ortho-chlorobenzoic acid and aniline (aniline derivatives) under the reflux reaction conditions by using metallic copper, which worked efficiently and smoothly by constructing corresponding diarylamines. Further, in 1905 Ullmann extended the coupling chemistry of copper for the C-O bond formation by reacting bromobenzene with potassium phenoxide for diphenyl ether synthesis. In 1906, Goldberg reported the first C-N coupling strategy using catalytic copper to synthesize N-arylated products by the reaction of aryl halides and N-nucleophiles. These C-C and C-X bond-forming strategies have become the first transition metalcatalyzed coupling reactions. Thereafter, several excellent and new reaction approaches have been developed using catalytic copper compounds contributing a wide variety of synthetic strategies for the construction of C-C and C-X bonds. The Ullmann reaction has been studied broadly and the scope and applications of the reaction are systematically described in the review articles [15, 18–20]. Therefore, only a brief outline has been given for the classical Ullmann reaction to describe the essence of this method and some newer Ullmann-type coupling reactions have been described. For most of the transition metal-catalyzed cross-coupling reactions, the reactivity order of halogens I > Br > Cl is common, while the electron-withdrawing substituents like carboxymethoxy and nitro groups at ortho position were used for some cases which promotes the reaction in comparison with the previous Ullman reaction due to the activating effects of these substituents. This activating effect dramatically affected by the position of the activating substituent and decreases in order ortho ≪ para > meta. The reaction also gets affected by substituents such as a chloro, methoxy, and methyl irrespective of their positions and no explanation has been provided. In contrast, the typical inactive substrate having labile protons such as anilines, phenols, and benzoic acid derivatives inhibits the coupling, which may preferentially undergo Ullmann–Goldberg condensation [15, 21, 22] or decarboxylation [23, 24]. The polar aprotic solvents including dimethylformamide (DMF) and N-methylpyrrolidinone (NMP) were used under milder reaction conditions, although the previous reaction was carried out with solvent-free conditions, and also nitrobenzene and aromatic solvents were utilized for the reaction. The former Ullman coupling of iodobenzene undergoes reductive arylation at higher temperatures in nitrobenzene, which results in the formation of triphenylamine by-product, and also a side reaction occurs through reductive dehalogenation in the presence of proton sources. The commercially available, powdered copper has been applied with or without activation and repeated washing with acetone solutions of iodine and

282

M. S. Lokolkar et al.

Scheme 2 Homocoupling of iodobenzenes, mediated by copper(I) thiophene-2carboxylate

hydrochloric acid. It has been found that mild reaction conditions increase the yield of the reaction. In this regard, the homocoupling of the o-bromonitrobenzene at 60°C, by using excess of activated copper bronze afforded the improvement in product yield from 76 to 99.6% in comparison with original Ullmann conditions [25]. Further, copper loading was reduced to 4 equiv and reaction rate was improved by presonication of the copper bronze with ultrasound in air [26], and the freshly synthesized copper powder by the reduction of aqueous copper sulfate with zinc powder was found to be superior to commercial copper bronze [27, 28]. In addition, γ-alumina-supported copper found to be superior to copper powder for Ullmann coupling of p-chlorotoluene [29]. Further, Cu(I) ions were applied for the Ullmanntype coupling reaction, which undergoes at milder conditions. The freshly prepared copper(I) triflate was applied for the o-iodonitrobenzene in acetone and using 20% aqueous ammonia to afford corresponding biphenyl in 92% yield at ambient temperature. Also, tetrakis(acetonitrile)copper(I) perchlorate used as catalyst showed similar effectivity [30, 31]. The copper(I)thiophene-2-carboxylate (CuTc) catalyzed an efficient intra- and intermolecular Ullmann-type coupling of aryl iodides resulting in moderate to high yields of the product at ambient temperature (Scheme 2) [32]. This method is extended for the synthesis of fluorinated oligo(para-phenylenes) and enantioselective trans-4,5,9,10-tetrahydroxy-9,10-dihydrophenanthrene [33, 34]. In the aforementioned Ullmann coupling examples, the excess of copper was generally applied; however, the copper nanoparticles were applied for the Ullmann coupling of iodobenzene at 150–200°C by using copper:iodobenzene ratio in the range 1.6:1–1:1 to result good yield of the corresponding biphenyls [35, 36]. Additionally, the supported copper (II) diamine compound, applied for Ullmann coupling [37], the immobilized copper (II) catalyst reused and easily removed from the reaction. Notably, electron-poor and electron-rich substituents bearing aryl bromides undergo homocoupling to afford biaryls in good yields (Eq. 1). Due to the wide

Cu-Catalyzed C-C Coupling Reactions

283

occurrence of axially chiral biaryls in natural products and asymmetric catalysts the atroposelective aryl–aryl coupling also attracted much interest [38–43]. Consequently, the Ullmann coupling of 2,6-disubstituted aryl halides for the synthesis of enantiomerically pure chiral biaryls forms the chiral backbone of asymmetric catalysts and later optical resolution of the racemic products [44–46]. The maximum 50% yield of the enantioenriched product was achieved by optical resolution and requires a tedious procedure. The diastereoselective coupling of the substrates with appropriate chiral auxiliary is more desirable and extensively studied for the diastereoisomer separation formed in the course of reaction. In this regard, several Ullmann coupling reactions of aryl halides by using chiral inducer were investigated. Still observed diastereoselectivity was not satisfactory and further optical resolution was required [47, 48]. Meyers and co-workers presented a chiral oxazoline as an auxiliary [49], the valinol-derived chiral oxazoline was reacted with the copper powder for the synthesis of corresponding biaryl bis(oxazoline) in refluxing DMF achieving the diastereomeric ratio 70:30 after 12 h, this was improved to 93:7 as the reaction time after 72 h. The enantiopure biaryl bis(oxazoline) product obtained in 60% yield and further this oxazoline approach was extended for the binaphthyls and various natural products [50–53].

ð1Þ

Miyano and their co-workers reported an alternative route for synthesis of (S)2,2′-di(hydroxymethyl)-1,1′-binaphthyl through intramolecular Ullmann coupling of binaphthol connected bis(1-bromo-2-naphthoate) followed by the reduction of the resulting product with lithium aluminium hydride (Eq. 2) [54, 55].

ð2Þ Tethers having in central chirality also studied well [56, 57], the chiral diol tethers linked with (o-iodophenyl)diphenylphosphine oxides involved in intramolecular coupling affording biaryl bis(phosphine oxides) in an excellent diastereoselectivity with 98% in 61–91% yields and higher yield was observed for smaller tethers (Eq. 3) [58, 59]. Also, the synthesis of ellagitannins was made by the Ullmann coupling of 2-iodo-3,4,5-trimethoxybenzoate connected by sugar moieties and the coupling products were afforded in single atropisomers in moderate yields [60, 61].

284

M. S. Lokolkar et al.

Scheme 3 Examples of cross Ullmann coupling of halobenzenes

ð3Þ

The serious disadvantage of Ullmann coupling is its less effectiveness for the cross-coupling of two different aryl halides for the synthesis of unsymmetrical biaryls. However, the Ullmann cross-coupling is possible if one of the coupling partners is more reactive than the other coupling partner, in addition most reactive aryl halides component must have an activating substituent at ortho position to the halogen group and also less reactive substrate should be used in excess. Besides, the temperatures applied for the reaction should be low at which less reactive substrate can react with the copper. The Ullmann cross-coupling of iodobenzene and 2,4-dibromonitrobenzene afforded the corresponding product moderate yield of 52% with little amount of 2,4-dibromonitrobenzene [62]. In another cross-coupling reaction, 6-bromopiperonal and highly bulkier iodoarene were coupled to form an intermediate with moderate yields in the total synthesis of steganone [63, 64]. Later protocol was developed using iodonaphthalenes as less reactive substrate resulting high yield of the product [65]. The reaction involves dropwise addition of 2-iodo-5nitrobenzoate solution in DMF to the mixture of 1-iodo-4-nitronaphthalene and copper bronze over 4 h at 140–150°C affording the corresponding cross-coupled product with 98% yield (Scheme 3), which was later converted to benzanthrone derivative. Recently, Dughera and co-workers investigated the mild and effective Ullmann protocol using diazonium salts as an alternative to classical haloarenes, by employing deep eutectic solvent as green and sustainable solvent medium. The CuCl salt was applied for the reaction under mild reaction condition resulting good yields of the products. The reported mechanism involves the oxidative addition of first equivalent of arenediazonium salt to the copper catalyst and then reduction of the intermediate by DES which further undergo C-C coupling with second

Cu-Catalyzed C-C Coupling Reactions

285

Scheme 4 Cu-catalyzed homocoupling of arenediazonium salt in DES

arenediazonium salt. The reductant property of the DES operates again by regeneration of the copper (I) catalyst (Scheme 4) [66].

3 Untapped Potential of Copper Catalysts in the Coupling Reactions This section includes the cross-coupling reaction with terminal acetylenes, Grignard reagent, organozinc reagents, organotin reagents, organosilicon reagents, organoboron reagents, organoindium reagents, organoaluminium, organomanganese, and magnesium reagents, which are described in detail.

3.1

Coupling with Terminal Alkynes

In 1975, Heck [67, 68], Cassar and Sonogashira independently developed the palladium- catalyzed cross-coupling reaction between terminal alkynes and SP2-C halides. For the Heck and Cassar coupling reaction of terminal alkyne with Csp2 halide is relied on Pd catalyst, whereas a Cu-catalyst was utilized in combination with Pd catalyst for Sonogashira reaction. Whereas in the Sonogashira-Hagihara reaction, the catalytic amount of Pd complex, Cu(I) salt and base was used for the cross-coupling reaction of terminal acetylene with aryl halides (OTf, I, Br, Cl) (Eq. 4). It is believed that the role of Cu is involved in the formation of copper acetylides and further through a Pd-catalyzed process which in turn react with electrophilic coupling partner. As the Castro-Stephens reaction, Cu-acetylides are themselves able to react with organic halides. ð4Þ Due to the expensive cost of Pd, the utility of Sonogashira reaction is restricted for large-scale production and thus the other substitute metal catalysts were actively searched for. Owing to the more abundance, less toxic, and cheap, Cu has become attractive in the field of research and many copper-catalyzed versions of this reaction

286

M. S. Lokolkar et al.

Scheme 5 Intra- and intermolecular crosscoupling of terminal alkynes and iodoarenes

Scheme 6 Cu-catalyzed coupling of terminal alkynes with 2,2,2-trifluoro-N(2-iodophenyl)acetamide or with 2-iodophenol

exist in the literature. Different Cu-catalyzed versions of this reaction have been developed. In 1989, the terminal alkynes reacted with haloalkenes for the synthesis of conjugated alkenynes in the presence of stoichiometric amount of CuI [69]. The similar Cu-catalyzed version of Sonogashira reaction was followed for the reaction of aryl or vinyl iodides with terminal alkynes with CuI, PPh3, K2CO3 at 120°C in DMF or DMSO as the catalytic system (Scheme 5) [70–72]. The protocol has found application in the intramolecular cyclization of terminal alkyne and vinyl iodide within the molecule under similar conditions [73]. Guo et al. reported cross-coupling of aryl and alkyl acetylenes with aryl iodides and aryl bromides using CuI-ethylenediamine as catalyst system. The reaction worked well by tolerating electron-rich and electron-deficient substituents on the aryl iodides and bromides under mild reaction condition with dioxan solvent [74]. The [Cu(phen) (PPh3)Br] catalyst was used as ligand-free protocol for coupling of electron-rich and electron-poor aryl iodides with terminal alkynes using toluene as solvent and K2CO3 base [75], while some ligand-free, supported Cu precatalysts and copper nanoclusters catalyzed methodologies have also been developed using mild reaction conditions for the synthesis of internal alkynes [76, 77]. Progress was made in these transformations by developing the C-C and C-X (X= N, O, S) bond-forming reaction. The straightforward synthetic approaches were developed using cationic Cu complex Cu(phen)(PPh3)NO3 for the synthesis of heterocycles, indoles, and benzofurans by using o-iodophenol/o-iodotrifluoroacetanilide with alkynes using toluene as non-polar solvent under mild reaction conditions [78, 79]. Lee et al. described the one-pot strategy for the synthesis of benzofurans and isobenzofurans through a 5-oxo-dig-cyclization method by reacting phenyl acetylene with 2-iodophenol and (2-iodophenyl)methanol (Scheme 6). In 2007, Liu et al. developed the cross-coupling between vinyl iodides and 1-alkynes for the synthesis of conjugated enynes using CuI/N,N-dimethylglycine catalytic system in dioxane at 80°C resulting good to excellent yield of the product. Furthermore, they extended the protocol for the conversion of indole by heating the

Cu-Catalyzed C-C Coupling Reactions

287

Scheme 7 Cross-coupling of alkynes with N-(2-bromophenyl)-2,2,2-trifluoroacetamide

Scheme 8 Cu-catalyzed cross-coupling of alkynes and aromatic o-bromoaldehyde

mixture of 1-alkyne and 2-bromotrifluoroacetanilide in the presence of catalytic amount CuI, L-proline as ligand and K2CO3 in dimethylformamide solvent. This protocol involves the Cu-mediated cross-coupling reaction between aryl bromide and 1-alkyne followed by cyclization. The presence of ortho substituent NHCOCF3 at position allows the reaction to progress under mild reaction conditions. O-protected propargyl alcohol as well as aryl acetylenes can be applied, resulting protected 2-hydroxymethyl and 5-, 6-, or 7-substituted 2-aryl indoles in good yields, for the simple aliphatic alkynes lower yield was observed (Scheme 7) [80]. Our group also demonstrated the Sonogashira cross-coupling reaction between 2-iodonitrobenzene and terminal alkynes for the 2-substituted indole synthesis through palladium catalyst, in which the reaction involves Sonogashira crosscoupling of 2-iodonitrobenzene with terminal alkynes followed by the reductive cyclization to form corresponding indole products [81]. Ray et al. disclosed one-pot methodology for the synthesis of biologically active nitrogen-containing heterocycles pyridine and isoquinoline. The Cu-catalyzed crosscoupling reaction and cyclization strategy used catalytic system as CuI catalyst, 1, 10-phenathroline ligand, Et3N and ammonia as a nitrogen source in DMF solvent. The reaction of substituted aromatic o-bromoaldehyde with terminal alkynes affords the 3-substituted isoquinoline derivative as product in good to excellent yield whereas reaction of non-aromatic b-bromoaldehyde affords pyridine and dihydroisoquinoline derivative (Scheme 8) [82]. In 2013, Wu and co-workers described the Cu-catalyzed alkynylative-cyclization approach for the conversion of pyrazolo[5,1-a]isoquinolines from 3-(2-bromophenyl)pyrazoles. The protocol proceeded with the Sonogashira-type coupling of 3-(2-bromophenyl)pyrazoles with the terminal alkynes succeeding the electrophilic cyclization in one pot to form pyrazolo[5,1-a]isoquinolines. The protocol utilizes the CuCl salt, K2CO3 base in NMP at 120°C and Ag additive is beneficial for the reaction (Eq. 5) [83].

288

M. S. Lokolkar et al.

ð5Þ

An environmentally friendly and inexpensive methodology was reported by Fu et al. for the coupling of terminal alkynes and aryl halides using CuBr as catalyst, ligand 1,10-phenanthroline and phase transfer catalyst tetrabutylammonium bromide (TBAB) in aqueous medium for the conversion of substituted alkynes (Eq. 6) [84]. ð6Þ There are several reports based on copper catalyst and different ligand system combination have been developed for the cross-coupling reaction between terminal alkynes and aryl/alkyl halides for the synthesis of internal alkynes. The catalytic systems including Cu-nitrogen, Cu-phosphorus, Cu-oxygen, and Cu-N and O bidentate ligand complexes system were successfully developed in this transformation (Eq. 7) [85–89]. ð7Þ Liu et al. reported the Sonogashira-coupling reaction in water using CuI/PPh3, KOH as base. The simple and reported protocol tolerates electron-rich and electrondeficient groups on the aryl iodides and the reaction is also suitable for the coupling of aliphatic alkynes (Eq. 8) [90]. ð8Þ The Sonogashira-coupling reaction between 2-iodobenzoic acid derivatives and terminal alkynes through 5-exodigcyclization with high regio-, stereo-, and chemoselectivities has also been reported Cu-catalyst CuI, K2CO3 in DMF solvent. The reaction further applied for the total synthesis of naturally occurring phthalides (+)-(4-methoxybenzyl)-5,7-dimethoxyphthalide and (+)-herbaric acid (Scheme 9) [91]. The new catalytic system sulfonato-Cu(II) (salen) complex was developed by Zhou et al., and this reusable Cu-catalyst used for the alkynylative cross-coupling reaction of terminal alkynes with aryl iodides under air condition in an aqueous medium. The reaction found to be effectively worked with electron-withdrawing groups on aryl halides as compared to electron-donating groups on the aryl iodide for the conversion of respective internal alkynes and with the steric effects the reaction found to be sensitive. This catalytic system further applied for the synthesis of the 2-arylindoles by the reacting aryl acetylene and 2-iodoaniline (Eq. 9) [92].

Cu-Catalyzed C-C Coupling Reactions

289

Scheme 9 Cu-catalyzed coupling between 2-iodobenzoic acid and alkynes Scheme 10 Cu-catalyzed synthesis of alkynones or acetylenic ketoesters

ð9Þ Chlorine chloride/CuCl (ChCl-CuCl) was employed as moisture stable and inexpensive effective catalytic system for the cross-coupling reaction between aryl halides and phenyl acetylene for the synthesis of different internal alkynes. Chlorine chloride acts as ligand and a quaternary ammonium salt that stabilizes Cu(I) species during the reaction [93]. The arylation of terminal alkynes was accomplished by using diaryl or alkenylphenyliodonium salts as electrophiles to be performed with CuI, NaHCO3 in a DME/H2O as a medium at room temperature to afford disubstituted acetylenes (Eq. 10) [94]. ð10Þ Another route for the synthesis of alkynones or acetylenic ketoesters has been described using cuprous iodide catalyst for the reaction of terminal alkynes with acid chlorides or monooxalyl chloride, respectively, under ligand-free and mild reaction conditions (Scheme 10) [95, 96]. Microwave-assisted rate acceleration technology has been developed as effective implement in the field of organic synthesis, due to diverse advantages including enhanced selectivity, mild reaction conditions, and faster reaction. He et al. developed copper-catalyzed cross-coupling reaction of aryl acetylenes and aryl iodides

290

M. S. Lokolkar et al.

under microwave irradiation with Cs2CO3 as base and ligand-free conditions yielding moderate to good yield of the internal alkynes (Eq. 11) [97]. ð11Þ Wang et al. reported the cross-coupling reaction between aryl iodides and aryl acetylene under microwave irradiations using copper catalyst CuI, PPh3, and K2CO3 in DMF solvent for the electron-rich and electron-poor aryl iodides and aryl acetylenes [98]. The Cu-catalyzed Sonogashira-coupling reaction developed using polyethylene glycol (PEG) as a medium under microwave irradiation, with different molecular weight PEGs was studied for the synthesis of different internal alkynes in low to moderate yields [99], while Chen and co-workers developed the Sonogashira reaction by using Cu salt in aqueous medium, stoichiometric amount of tetrabutylammonium bromide (TBAB) for the conversion of different internal alkynes with satisfactory yields [100, 101]. Vogel et al. reported Sonogashiracoupling reaction by synergic effect of Fe and Cu salt under microwave irradiation, by reacting terminal alkynes with aryl iodides using Fe(acac)3, CuI, and Cs2CO3 in DMF or NMP solvent medium [102]. Lalic and co-workers reported a Cu-catalyzed photoinduced alkylation of unactivated alkyl iodides (primary, secondary, or tertiary) with terminal alkynes for the synthesis of internal alkynes. The reaction uses the CuCl as a catalyst with a terpyridine ligand, under blue light (450 nm) irradiation and the reaction found to inhibit the formation of polymerization of alkynes. This catalytic system tolerates broad functionalities like nitrile, ester, amide, alcohol, epoxide, aryl halide, and ether by affording respective internal alkyne products (Eq. 12) [103]. ð12Þ Meija et al. developed Cu-catalyzed alkynylation method between terminal alkynes and allylic C-H to afford direct 1,4-enynes with high selectivity. The oxidative rection conditions carried out with [Cu(NCMe)4]PF6 as catalyst, ligand 4′-( p-tolyl)-2,2′:6′,2″-terpyridine, di-tert-butyl peroxide (DTBP) in DMSO solvent. The electron-donating groups on phenyl acetylene afforded good yields of the respective products [104]. They also reported the coupling reaction between terminal alkynes and cyclic alkenes for the synthesis of 1,4-enynes through Cu-catalyst. This photocatalyzed coupling reaction used the similar condition except oxidant tertbutyl hydroperoxide (TBHP) in acetonitrile solvent medium. This photocatalyzed reaction tolerates both electron-deficient and electron-rich groups on the terminal alkynes [105]. Yang et al. demonstrated the copper-catalyzed oxidative dehydrogenative coupling of terminal alkynes with 2H-chromenes. The catalyst Cu(CN)4PF6, K2CO3, additive EtOH in dichloromethane and toluene were used for this coupling reaction between terminal alkynes and 2H-chromenes. Gupta et al. employed the acridine-based (ENE) pincers copper (I) catalyst for cross-

Cu-Catalyzed C-C Coupling Reactions

291

dehydrogenative coupling (CDC) between phenyl acetylene and N, N-dimethylbenzylamine, this reaction has been discussed in cross-dehydrogenative coupling section. Zhang et al. described an effective strategy for the cross-coupling reaction between terminal alkynes and benzyl bromides through Cu(I) catalyst. The Cu-catalyzed reaction selectively provides the benzyl alkyne by coupling both primary and secondary benzylic bromides with various terminal alkynes (aryl, alkyl) and enynes in moderate to excellent yields promoted under Cu(I) catalyst, NaHMDS base in toluene solvent. Further scale-up of the reaction successfully demonstrated for this protocol [106]. Liu and co-workers recently disclosed the copper-catalyzed coupling reaction between terminal alkynes and alkyl halides under mild reaction conditions. This methodology involves the use of Cu salt, proline-based N,N,P-ligand, Cs2CO3 base in diethyl ether as solvent medium at room temperature for the conversion of substituted alkynes. The protocol works effectively with different alkyl halides including primary, secondary (hetero)benzyl bromides and chlorides, propargylic bromide and secondary and tertiary α-bromo amides for the synthesis of different internal alkynes under mild conditions (Eq. 13) [107].

ð13Þ Peng et al. developed the copper-catalyzed three-component coupling reaction with terminal alkynes, arynes, and benzenesulfonothioates. This method provides one-pot C-C and C-S bond formation for the synthesis of o-alkynyl arylsulfides under mild reaction conditions. The protocol tolerates different functional groups affording respective o-alkynyl arylsulfides (Eq. 14) [108]. ð14Þ

3.2

Coupling with Grignard Reagents

Kochi and Tamura disclosed the copper-mediated cross-coupling of alkyl halides with Grignard reagent (Scheme 11) [109, 110]. Several examples or similar approach has been reported by different groups after this methodology using Cu

Scheme 11 Copper-mediated cross-coupling of alkyl halides with Grignard reagents

292

M. S. Lokolkar et al.

Scheme 12 Cu-catalyzed cross-coupling between alkyl halides and Grignard reagents

Scheme 13 Cu-catalyzed cross-coupling of Grignard reagent with alkyl bromides/ alkynylhalides

salts. These methodologies became synthetically helpful in coupling alkyl halides with aryl, alkyl, allyl, and vinyl Grignard reagents [111–114]. The reactions were carried out by using cuprous halides such as CuI, CuBr, or CuCl or by using more soluble complexes like CuBr/HMPA, CuCl2/TMEDA, Li2CuCl4 in a THF solvent (Scheme 12) [115, 116]. However, the CuBr–Me2S–LiBr–PhSLi catalyst system in THF showed notable performance in the coupling of aliphatic, vinylic, and aromatic Grignard reagent with primary alkyl tosylates or mesylates [115]. Li2CuCl4 or CuCl-catalyzed coupling of 2° and 3° alkyl Grignard reagents with 1° alkyl halides by adding N-methyl pyrrolidone (NMP) in THF solvent has been developed by Cahiez and co-workers. The reaction tolerates functional groups like amide, ester, ketone, and nitrile by affording products in moderate to excellent yield of the product [117, 118]. In 2010, the same group reported that the excellent yield of the products could be achieved by the slow addition of the 1° Grignard reagent to the 1° alkyl halide, and for the 2° and 3° Grignard reagents, benzonitrile observed to be very effective additive for this reaction (Scheme 13). Kambe and co-workers demonstrated the first cross-coupling of various Grignard reagents with primary alkyl fluorides applying either copper or nickel catalyst. The Cu-catalyzed cross-coupling reaction worked well in the presence of additive 1,3-butadiene and in the absence of additive low yield was observed for primary and secondary alkyl Grignard reagents, whereas for the tertiary alkyl and phenyl Grignard reagent the additive 1,3-butadiene exhibited slight effect for the reaction and afforded good to high yields of the corresponding product without additive [119]. Kambe and co-workers developed Cu-catalyzed coupling of Grignard reagent with primary alkyl chlorides using 1-phenylpropyne as additive in 2007.

Cu-Catalyzed C-C Coupling Reactions

293

Scheme 14 Cu-catalyzed C-C bond formation reaction using alkyl halides with Grignard reagents

Scheme 15 Cu-catalyzed cross-coupling between secondary alkyl iodides and primary alkyl Grignard reagent

This protocol demonstrated that high yields for the electrophiles such as alkyl fluoride, mesylates, and tosylates to afford corresponding products under the same reaction conditions and also works effectively for phenyl, tertiary butyl, secondary butyl and n-butyl Grignard reagents (Scheme 14) [120]. Kambe and co-workers developed Cu-mediated cross-coupling reaction between primary alkyl Grignard reagents with unactivated secondary alkyl iodides in the presence of 1, 3-butadiene as an additive. The protocol showed enhanced selectivity and efficiency for the preparation of alkyl–alkyl coupled product by the use of additive 1,3-butadiene (Scheme 15) [121]. The same group reported that the Cu salt and 1,3-butadiene or phenylpropyne additive as a catalytic system for alkyl– alkyl cross-coupling reactions could effectively work with high turnover numbers (TONs) up to 1 × 106 and showed additive plays an important role in the reaction [122]. Hu and co-workers demonstrated an effectual cross-coupling of functionalized primary alkyl tosylates, iodides, and bromides with secondary and tertiary Grignard reagent through a copper catalyst. The protocol works well using CuCl as catalyst without any additive at room temperature with many functional group tolerance. The reaction afforded high yields of the corresponding products for the coupling of secondary and tertiary Grignard reagent with alkyl electrophiles containing variety of sensitive groups and also reaction works well for the coupling of primary alkyl Grignard reagent using the same conditions (Scheme 16) [123]. In 2008, Hintermann and co-workers developed Cu-catalyzed cross-coupling of tertiary alkyl Grignard reagents with different nitrogen-containing heterocyclic

294

M. S. Lokolkar et al.

Scheme 16 Cu-catalyzed coupling of 1°, 2°, 3° alkyl Grignard reagents with primary alkyl halides

Scheme 17 Coppercatalyzed cross-coupling with Grignard reagents

Scheme 18 Cu-catalyzed cross-coupling between secondary alkyl halides with different Grignard reagents

chlorides. The protocol afforded cross-coupled product with excellent yield without adding any ligand at or below room temperature (Scheme 17) [124]. Though, Burns and Kambe groups had demonstrated the Cu-catalyzed crosscoupling reaction of secondary alkyl electrophiles earlier [115, 121] with limited to primary Grignard reagent. Liu and co-workers disclosed novel catalytic system with Li additive containing CuI/N,N,N′,N′-tetramethylethylenediamine (TMEDA)/ LiOMe system employed for the cross-coupling between secondary alkyl tosylates and bromides with different secondary alkyl Grignard reagents. Aromatic and tertiary alkyl Grignard reagent and also less reactive primary alkyl halides were demonstrated under the same reaction conditions (Scheme 18) [125].

Cu-Catalyzed C-C Coupling Reactions

295

Scheme 19 Cu-catalyzed cross-coupling of Grignard reagents and secondary alkyl electrophiles

Scheme 20 Cu-catalyzed cross-coupling between primary, secondary alkyl halides with cyclopentadienyl Grignard reagent

To enhance the reactivity of the secondary alkyl electrophiles Liu and co-workers generally applied 12–24 h for the reaction. Kobayashi and co-workers demonstrated the Cu-catalyzed coupling between highly reactive 2-pyridinesulfonyloxy leaving group and Grignard reagent and found to be within 40 min and at 0°C reaction works effectively. The protocol uses Cu(OTf)2 as catalyst, LiOMe and TMEDA as additives for the coupling of tosylates, less reactive MeMgCl and other Grignard reagents. However, under the same reaction conditions, the reaction with chiral substrates results into complete inversion of the stereocenter was observed (Scheme 19) [126]. In 2008, Yorimitsu and Oshima developed Cu-catalyzed cross-coupling reaction between nucleophile cyclopentadienyl Grignard reagent and alkyl halides. The mixture of the two isomers was obtained and further reduced with PtO2, H2 for the simple analysis of the product formed. The protocol with Cu(OTf)2 in diisopropyl ether medium, tertiary alkyl halides (fluoride, chlorides, and bromides) electrophiles was performed by giving corresponding products (Scheme 20) [126]. In 2009, under the similar conditions they were subjected to allylic Grignard reagent as a nucleophile with secondary and tertiary alkyl halides as a suitable nucleophile [127]. Tao et al. demonstrated Cu-catalyzed cross-coupling of phenyl magnesium bromide with less reactive alkyl chlorides such as 1°, 2°, and 3° alkyl chlorides were efficiently accomplished without any additive and ligand. The 2-methyltetrahydrofuran used as solvent for the preparation of phenylmagnesium bromide is critical for the success of the reaction. The method is useful for the crosscoupling of unactivated 2° or 3° alkyl chlorides with phenyl magnesium bromides, while the unsuccessful results were observed for the cross-coupling reaction with aryl magnesium halides (Scheme 21) [128]. For the copper-catalyzed cross-coupling reaction, the addition of LiCl as an additive showed remarkable effect. In 2014, Kobayashi and co-workers established the cross-coupling reaction of Grignard reagents and 1° alky halides were found to be accelerated using LiCl as an additive [129]. In 2015, Lee and co-workers

296

M. S. Lokolkar et al.

Scheme 21 Cross-coupling of 1°, 2°, 3° alkyl halides with phenyl magnesium chlorides through copper catalyst

Scheme 22 Cu-catalyzed cross-coupling between alkyl, aryl Grignard reagents with chiral cyclic 1,2-sulfamidates

developed that the catalytic amount of LiCl was an effective additive for the Cu-catalyzed stereo- and regioselective ring opening of chiral cyclic 1,2-sulfamidates with Grignard reagents. The presence of lithium chloride as an additive was vital for the activation of C-O bond cleavage. The reaction of 1°, 2°, and 3° alkyl along with aryl Grignard as nucleophile afforded an efficient methodology for the preparation of α-branched benzylamine derivatives with high enantioselectivity in good yields. The coordination of lithium ion with bridging oxygen in sulfamidates might contribute for the stereo and regioselectivity ring opening in the course of the reaction (Scheme 22) [130]. Fu and Liu demonstrated Cu-catalyzed cross-coupling of aryl and alkyl bromides with unactivated alkyl tosylates and mesylates without using Grignard reagent instead of Grignard reagent developed in situ. Additionally, this protocol avoids the prior preparation and handling of expensive or sensitive organometallic reagents. The developed protocol involves the use of CuI as catalyst, ligand bis (diphenylphosphino)methane (DPPM), an additive LiOMe and magnesium powder as reductant for the coupling reaction under mild conditions. The cross-coupling methodology for the formation of alkyl–alkyl and aryl–alkyl C-C bonds progressed with intermolecular as well as intramolecular manner. The Grignard reagent generated in situ by reacting alkyl bromide with Mg powder then it is coupled with the alkyl sulfonates in the presence of Cu-catalyst (Scheme 23) [131]. In 2013, Feringa and co-workers provided the Cu-catalyzed enantioselective asymmetric allyl–allyl coupling reaction between allylic electrophile allyl bromide with allyl Grignard reagent. The protocol uses the phosphoramidite as effective ligand for the preparation of the chiral 1,5-diene with high enantioselectivity and good yield. The coupling of allylmagnesium bromide with different functional groups bearing allylic substrates such as protected amines, alcohols, and alkenes afforded products in exceptional enantioselectivities (Scheme 24) [132]. Shi and their co-workers disclosed the copper-catalyzed self and cross-coupling of different Grignard reagents using di-tert-butyldiaziridinone as an oxidant

Cu-Catalyzed C-C Coupling Reactions

297

Scheme 23 Cu-catalyzed cross-coupling of alkyl/aryl bromides with 1°, 2° alkyl tosylates/ mesylates Scheme 24 Cu-catalyzed cross-coupling of allyl bromides and allyl Grignard reagents

Scheme 25 Coppercatalyzed self and crosscoupling of different Grignard reagents using oxidant

affording good to moderate yields of the corresponding products under mild conditions. The protocol progressed with Aryl, alkynyl, and alkyl Grignard reagent giving homocoupled products and two different Grignard reagents providing three coupled products in which cross-coupled product in higher selectivity was observed (Scheme 25) [133]. Spring and co-workers reported homocoupling methodology for the synthesis of sterically hindered biaryl and also biaryl with higher strains which are crucial unit in the ellagitannin family of natural products. The protocol involves the oxidation of the cuprates produced from Grignard reagents, obtained under mild conditions. The reaction tolerates broad functionalities including cyclization of different aryl units, using CuBr.SMe2 and 3,5-dinitrobenzoic amide catalytic system affording products in moderate to good yields. The substrates with dihaloarenes undergo homocoupling with retaining one of the halogen atoms (Scheme 26) [134, 135].

298

M. S. Lokolkar et al.

Scheme 26 Cupratesmediated homocoupling of hindered aryl iodides

Scheme 27 Cuprate oxidation strategy for inter- and intramolecular type of homocoupling

Besides the organozinc reagents applied for the cuprate oxidation strategy, Spring and co-workers described the preparation of symmetrical biaryls in good yields by cuprates which derived from the reaction of arylzinc and CuBrSMe2 and oxidized by 3,5-dinitrobenzoic amide [136, 137]. The catalytic use of the copper catalyst was applied for the biaryl synthesis under atmospheric oxygen (Scheme 27). The zinc and magnesium cuprate based oxidative approach was also demonstrated for the synthesis of ellagitannin natural products [138, 139].

3.3

Coupling with Organozinc Reagents

The copper-catalyzed cross-coupling between alkylzinc halides with α-chloroketones ketone has been developed by Reddy et al. in 2004. The transmetalation of Grignard reagent with alkyl chlorides forms corresponding alkylzinc halides, which then react with α-chloroketone to give corresponding α-branched ketones. The several primary, secondary alkyl groups were introduced for the conversion of α-branched ketones using Cu(acac)2 as catalyst under mild conditions (Scheme 28) [140]. Menche and co-workers demonstrated the copper-catalyzed oxidative crosscoupling reaction under aerobic conditions between tetrahydroisoquinolines and

Cu-Catalyzed C-C Coupling Reactions

299

Scheme 28 Cu-catalyzed cross-coupling between organozinc reagent and α-chloroketone

Scheme 29 Cu-catalyzed oxidative cross-coupling reaction of tetrahydroisoquinolines and diorganozinc reagents

Scheme 30 Cu-catalyzed cross-coupling between heteroaryl halides with aryl, alkyl, or alkynylzinc halides

diorganozinc reagents or organozinc bromide reagents in 2015. The protocol proceeds with the tolerating wide range of functional groups including alkyl, allyl, propargyl, and benzyl groups as well as ortho- and para-susbstituted N-phenyl substrates for the formation of different C-1-alkylated tetrahydroisoquinolines (THIQ) in excellent yields (Scheme 29) [141]. Giri et al. developed copper-catalyzed cross-coupling between heteroaryl halides with aryl, alkyl, or alkynylzinc halides in 2015. The reported protocol proceeds at room temperature by using CuI, lithium chloride in DMF solvent. Various alkylzinc reagents react with heteroaryl iodides without rearrangement by affording corresponding products with good to excellent yields (Scheme 30) [142]. The same group reported copper-catalyzed ligand-free protocol for synthesis of diaryl products using aryl iodides and diarylzinc reagent. The reaction tolerates different functional groups such as ester, chloride, bromide, nitrile, and trifluoromethyl bearing aryl iodide as well as alkyl, alkoxy, and chloro on arylzinc reagent [143]. Dilman and their co-workers developed Cu-mediated coupling between 1-bromoalkynes and α,α-difluoro-substituted organozinc reagents in 2015. The reaction performed under the catalytic amount of copper iodide with ligand-free condition in dimethylformamide. Different gem-difluoro-substituted alkynes have been prepared under mild conditions (Scheme 31) [144].

300

M. S. Lokolkar et al.

Scheme 31 Cu-catalyzed coupling between 1-bromoalkynes with α,α-difluoro-substituted organozinc reagents

Scheme 32 Cross-coupling reaction between N-heterocyclic organozinc and 1-bromoalkynes

Recently, Livinghouse and co-workers demonstrated the Cu(I) catalyzed crosscoupling reaction of N-heterocyclic organozinc with 1-bromoalkynes. The reaction of N,N-dimethylhydrazinoalkenes with Et2Zn, followed by copper-catalyzed coupling with 1-bromoalkynes, afforded pyrrolidines and piperidines in good yields (Scheme 32) [145].

3.4

Coupling with Organoboron Reagents

The cross-coupling between organic halides with organoboronic acids through palladium catalyst, known as Suzuki–Miyaura coupling, turned out to be an important tool for carbon–carbon bond formation reactions. The organoboron compounds are less harmful and being readily available than the corresponding organostannanes and it is advantageous as compared to Grignard reagents due to its stability and wide functional group tolerance. In 1996, the copper-catalyzed cross-coupling was described for the first time using hypervalent iodonium reagent. Reagent arylboronic acid was coupled with diaryliodonium using copper iodide as catalyst, base sodium carbonate in dimethoxyethane, and water as solvent system for the synthesis of biaryls. The more electron-rich aryl(hetero)group of iodonium reagent selectively transferred for each case (Scheme 33) [146]. Rothenberg and co-workers described the Cu-catalyzed Suzuki–Miyaura coupling as first example in 2002 and the cross-coupling reaction using catalytic amount of copper nanocluster between phenylboronic acid and 4-iodotoluene in dimethylformamide with K2CO3 as base. Further reaction protocol was extended for various aryl iodides and aryl boronic acid derivatives for the synthesis of biaryls [147]. The same group reported the coupling reaction by replacing DMF solvent

Cu-Catalyzed C-C Coupling Reactions

301

Scheme 33 Arylboronic acid was coupled with diaryliodonium using copper iodide as catalyst Scheme 34 Cu-catalyzed Suzuki–Miyaura coupling of aryl boronic acids and aryl halides

with poly(ethylene)glycol (PEG)-400 solvent with Cu powder. The methodology tolerates electron-rich and electron-poor functionalities for the conversion of different biaryls. Further the protocol was extended for the coupling of aryl chlorides and bromides with arylboronic acids using catalytic amount of iodine as an additive (Scheme 34) [148]. The Cu(0) could be employed as catalyst in the Suzuki–Miyaura coupling as the early evidence from Rotherberg and co-workers, the CuI salts displayed to be more effective in later studies. In this regard, Li et al. demonstrated the copper-catalyzed cross-coupling reaction between variety of vinyl iodides and bromides with arylboronic acids. The protocol worked efficiently with CuI salt with 1,4-diazabicyclo[2.2.2]octane (DABCO) as ligand and in the presence of base Cs2CO3 and TBAB in DMF. The reaction also applied for the multiple arylation of di- and tri-iodobenzenes [149, 150]. Further the authors developed a similar protocol in DMSO solvent and without using DABCO. The reaction applied for aryl and heteroarylboronic acids with vinyl, aryl iodides, and bromides. However, cross-coupling between alkynyl bromides and arylboronic acids is also described by using catalytic system CuI with 8-hydroxyquinoline. A variety of electron-rich and electron-deficient functionalities tolerated afforded good to excellent yield of the products (Scheme 35) [151]. The copper-catalyzed organoboron compounds or reagents also utilized for the functionalization of nonactivated primary haloalkyl systems by Suzuki–Miyaura cross-coupling. Liu and co-workers demonstrated the copper-catalyzed cross-coupling reaction between organoboron compounds and alkyl electrophiles by using lithium tertiary butoxide as a vital base with mild reaction conditions. The method with arylboronate esters is applicable to alkyl mesylates, tosylates, bromides, iodides, and also chlorides and tolerates various functional groups in Cu-catalyzed coupling of Grignard reagents as compared to previously described methods. The

302

M. S. Lokolkar et al.

Scheme 35 Cu-mediated cross-coupling between aryl boronic acid with aryl, vinyl iodides and bromides as well as with alkynyl bromides Scheme 36 Cu-catalyzed Suzuki–Miyaura coupling of organoborons with different alkyl halides

alkyl 9-BBN reagents (9-BBN = 9-borabicyclo-[3.3.1]nonane) nucleophile were applied under same reaction condition to obtain C(sp3)-C(sp3) bond formation. The Cu-catalyzed protocol works with alkyl bromides, iodides, mesylates, tosylates and also for chlorides tolerating different functionalities accessing corresponding products (Scheme 36) [152]. In 2014, Fu and co-workers developed the cross-coupling of gem-diborylalkanes and alkyl halides under similar conditions for the conversion of alkylboronic esters as a new approach. For the reaction with gem-diborylmethane catalytic amount of copper iodide is necessary, but for substituted 1,1-diborylalkanes, a stoichiometric quantity is required [153]. In 2015, Y. Fu and H. J. Xu developed the coppercatalyzed cross-coupling reaction between allyl boronate esters with 1°, 2°, and 3° haloalkanes, where previous conditions were exploited for this reaction. The protocol exhibited good compatibility with milder reaction conditions, however adding a catalytic quantity of TMEDA and reaction under low temperature could prevent the elimination of side reaction for secondary alkyl containing hydrogen at b-position (Scheme 37) [154].

Cu-Catalyzed C-C Coupling Reactions

303

Scheme 37 Cu-catalyzed C-C bond formation reaction through crosscoupling

Scheme 38 Cu-catalyzed arylation of heterocycles with arylboronic acids

Giri and co-workers demonstrated the Cu-catalyzed cross-coupling reaction of aryl halides with aryl, heteroarylboronate esters. The method progressed by using catalytic amount of copper iodide, 2-(di-tert-butylphosphanyl)-N,Ndimethylbenzenamine as ligand and base cesium fluoride for the conversion of the product in good yields [155, 156]. In 2014, Rao et al. developed the arylation of heterocycles with arylboronic acids for the synthesis of different 4-aryl/heteroaryl4H-chromenes through sp3-sp2 coupling. The reaction proceeds with copper (II) acetate in dimethylformamide at room temperature tolerating electron-poor as well as electron-rich groups on arylboronic acids providing corresponding product in good yields. This reaction provides the first report for the coupling with a C(sp3)SMe bond [157]. The same group described the cross-coupling between 3-hydroxyisoindolinones and alkenyl, heteroaryl, or arylboronic acids through copper catalyst, both intramolecular and intermolecular version of the reaction worked smoothly in dichloroethane solvent with reflux condition. The C(sp3)-OH bond cleavage and C-C bond formation reaction occur in this protocol (Scheme 38) [158]. In 2008, Itami and co-workers demonstrated the copper-catalyzed cross-coupling between aryl boronic acid and arenes. The copper trifluoroacetate catalyzed C(sp2)H bond arylation with arylboronic acids in the presence of trifluoroacetic acid in dichloroethane under aerobic conditions with moderate yield of the products. The

304

M. S. Lokolkar et al.

Scheme 39 Cu-catalyzed oxidative cross-coupling of arenes and aryl boronic acids

Scheme 40 Cross-coupling of aryl iodides and arylboronate esters through Cu-catalyst

protocol has been extended for the π-systems like indoles and pyrroles where multiple C-H bond arylations are feasible (Scheme 39) [159]. Hoshi et al. demonstrated the cross-coupling between (trimethylsilyl) ethynyl bromide and alkenyldialkylboranes through copper catalyst. The catalytic amount of copper (II) acetylacetonate and in the presence of lithium hydroxide as a base for the synthesis of terminal enynes in moderate to good yields with milder reaction conditions (Eq. 15) [160, 161].

ð15Þ

In 2014, Brown and co-workers described the coupling of aryl iodides and arylboronate esters through CuCl and Xantphos catalyst system for the conversion of biaryl products. The reaction tolerates different functional groups resulting corresponding product in good to excellent yields (Scheme 40) [162]. Later in 2018, the same group reported cross-coupling between aryl bromides with aryl and alkylboranes through copper catalyst. The protocol effectively applied for electron-poor and heteroaryl bromides for the synthesis of corresponding products with good to excellent yields. Additionally, the reaction also applied for aryl iodides with different substitution and also for primary as well as secondary alkylboranes (Scheme 41) [163]. Fu and co-workers demonstrated copper-catalyzed cross-coupling reaction of epoxides with arylboronates in 2015. The aliphatic and aromatic epoxides are suitable coupling partner for this reaction affording corresponding secondary and tertiary alcohols as products. The protocol proceeds with adding catalytic amount of CuI and lithium tertiary butoxide with KI as an additive in dimethylformamide as

Cu-Catalyzed C-C Coupling Reactions

305

Scheme 41 Cu-catalyzed cross-coupling between aryl bromides with aryl and alkylboranes

Scheme 42 Copper-catalyzed cross-coupling reaction of epoxides with arylboronates Scheme 43 Cross-coupling between gem-diborylalkanes and epoxides through copper catalyst

solvent tolerating various functional groups under mild reaction condition. The electrophilic reagents expanded by the reaction and also applicable for N-T aziridines for the coupling with arylboronates (Scheme 42) [164]. Later, the same group developed the approach for cross-coupling between gem-diborylalkanes and epoxides through copper catalyst. The protocol works smoothly for aliphatic, aromatic, and also with tosyl protected aziridines providing corresponding γ-pinacolboronate alcohols or amines in the presence of CuI catalyst, lithium tertiary butoxide in tetrahydrofuran solvent (Scheme 43) [165]. In 2018, Ma and co-workers demonstrated the first copper-catalyzed coupling through ring opening of vinyl epoxides with arylboronates. The protocol provides an effective approach for the preparation of aryl-substituted homoallylic alcohols under mild reaction conditions. The reaction worked well with CuCl catalyst and in the presence of pincer nitrogen ligand N,N,N′,N′-tetramethyl-ethane-1,2-diamine (TMEDA) with lithium tertiary butoxide as a base tolerating variety of functional groups (Scheme 44) [166]. In 2016, Moon et al. reported the oxidative approach for the arylation of activated methylene species through copper catalyst. The cross-coupling between organoboron species with in situ generated enolates under mild reaction conditions. The aryl boroxines found to be a better substrate than aryl boronic acids, neopentyl ester, or pinacol ester. The Cu(OTf)2-mediated reaction could be applied for tertiary

306

M. S. Lokolkar et al.

Scheme 44 Cu-catalyzed cross-coupling via ring opening of vinyl epoxides with arylboronates Scheme 45 Oxidative arylation of activated methylene species through copper catalyst

Scheme 46 Cu-mediated allyl–allyl couplings between allylic phosphates with allylboronates

malonates, amido ester substrates for the synthesis of quaternary centers (Scheme 45) [167]. In 2016, Sawamura and co-workers described the Cu(I)-phenol/N-heterocyclic carbine chiral ligand allyl–allyl enantioselective couplings of either cyclic allylic or Z-acyclic phosphates with allylboronates (Scheme 46). The reaction with exceptionally SN2 type regioselective and high enantioselective synthesis of chiral 1,5-diene derivatives were obtained with a tertiary stereogenic centre at allylic position, and for the γ-substituent reaction selectivity with γ/α>20:1 isomer ratio was observed. The reaction is noteworthy that acid and base labile functionalities also tolerated for this reaction. Previously, the same group reported the use of stoichiometric amount of alkoxide as base was essential while later found that the presence of phenolic group bearing ligand plays a significant role in the catalytic cycle [168–171]. Incorporating fluorine moieties with aromatic platforms has gained much interest due to their chemical properties. In this regard, the aryl boronic acids with Cu-catalyst combination is one of such approach, Lundgren and co-workers disclosed the copper-catalyzed decarboxylative cross-coupling of aryl boronic

Cu-Catalyzed C-C Coupling Reactions

307

Scheme 47 Cu-catalyzed cross-coupling of aryl boronic acids and ethyl bromofluoroacetate

Scheme 48 Cu-catalyzed coupling of fluorinated aryl boronate esters and aryl bromides and iodides

reagents with fluoromalonic acid derivatives for the synthesis of monofluoro aryl acetates. The oxidative protocol tolerates variety of functional groups promoted by Cu(OTf)2 as catalyst using triethyl-amine using dimethylacetamide solvent [172]. In 2019, Gouverneur and co-workers demonstrated the cross-coupling between aryl boronic acids and with ethyl bromofluoroacetate for the synthesis of 2-fluoro-2arylacetic acids. The protocol involved followed the sequential copper catalyst crosscoupling and then hydrolysis by the base to afford different 2-fluoro-2-arylacetic acids (Scheme 47) [173]. In 2019, Marder and co-workers demonstrated the Cu-catalyzed cross-coupling between fluorinated aryl boronate esters and aryl bromides and iodides. The protocol uses the combination of CuI as catalyst, 1, 10-phenanthroline as ligand and base CsF in mixture of DMF and toluene solvent to afford the fluorinated biaryl products. The protocol tolerates broad functional groups on aryl halides providing corresponding fluorinated biaryl products with good to excellent yields (Scheme 48) [174]. Several methods are developed by different scientific groups for homocoupling of arylboronic acids into the corresponding biaryls employing several homogeneous and heterogeneous catalysts. In this regard, Demir et al. described the homocoupling of arylboronic acids through copper catalyst in 2003. The reaction progressed without presence of any additive in DMF solvent resulting moderate to good yields of the products [175]. In 2009, Yamamoto and co-workers introduced Cu(II)/1,10phenanthroline as an effectual catalytic system for the homocoupling of arylboronic acids [176]. By developing three co-ordinate dinuclear copper(I)/2-hydroxy-1,10phenanthroline complex successfully, Wang et al. applied for the homocoupling reaction of arylboronic acids [177]. [Cu(cyhxn)2(H2O)2][OTf]2 complex also developed for the biaryl synthesis from homocoupling strategy by Pathak and co-workers

308

M. S. Lokolkar et al.

Scheme 49 Cu-catalyzed coupling of vinylidene cyclopropanes and allyl or allenyl boronates

using mild reaction conditions [178]. In combination with this copper complexes, simple copper salts including Cu(I)Cl, Cu(II)SO4, and Cu(II)Cl22H2O were investigated for these homocoupling reactions. Also, the copper(II)–β-cyclodextrin (Cu (II)–β-CD) complex was also described for this reaction as a water soluble complex [179–182]. On the other hand, different heterogeneous catalysts were developed and successfully employed for the homocoupling reactions. Vishwakarma and co-workers developed clay (montmorillonite-KSF) encapsulated Cu(OH)x as heterogeneous catalyst and applied for biaryl synthesis through oxidative homocoupling of aryl boronic acids in 2013. Ligand free, base free, and without use of any additive protocol worked well under atmospheric pressure at room temperature [183]. Heterogeneous catalysis using metal-organic frameworks (MOFs) has arisen to be an interesting topic in recent days. The copper terephthalate Cu(BDC) MOF developed by Pitchumani and co-workers in 2014 applied for the oxidative homocoupling of aryl boronic acids as an environmentally benign, effective, and reusable catalyst for biaryl synthesis [184]. Wang et al. developed twofold interpenetrated 3D “dia”-type framework of {[Cu(tatrz)2(H2O)2](NO3)28H2O}n (1; tatrz = 1-[9-(1H-1,2,4-triazol-1-yl)anthracene-10-yl]-1H-1,2,4-triazole) catalyst for the homocoupling of aryl boronic acids in 2016 [185]. Also, CuNPs, Cu-NHC cluster, and copper fluorapatite (CuFAP) were applied as catalysts for homocoupling of arylboronic acids to afford symmetrical biaryls [186, 187]. Recently in 2021, M. Chen reported the copper-catalyzed coupling of allyl or allenyl boronates with vinylidene cyclopropanes. The protocol proceeds using CuCl as catalyst, sodium tertiary butoxide as base in THF solvent at room temperature affording C-C bond at the terminal carbon atom of allene moiety of the vinylidene cyclopropanes and simultaneous ring opening of the cyclopropane. The intermediate copper enolate formed during the reaction could be incorporated with the external electrophile. Different poly-unsaturated derivatives were synthesized in good yields from coupling of vinylidene cyclopropane with allyl/allenyl boronates and simultaneous incorporation of Cu-enolate with external electrophile in the reaction forming two carbon–carbon bonds (Scheme 49) [188]. In 2019, Zhang and co-workers demonstrated Cu-catalyzed three-component reaction for the dicarbofunctionalization of cyclopropane with aryl boronic esters

Cu-Catalyzed C-C Coupling Reactions

309

and allylic electrophile. The protocol provides the first example for the conjugate C-C cross-coupling of cyclopropenes affording poly-carbon substituted cyclopropanes with stereoselectivity and the reactivity and the chemoselectivity of the reaction depends on the suitable ligand (Eq. 16) [189]. ð16Þ Nagib and co-workers developed the copper-catalyzed method for the selective δ C-H arylation through intramolecular hydrogen atom transfer (HAT) by N-centered radical. The reaction enables the incorporation of arenes and heteroarenes by coupling with boronic acids. The reaction tolerates broad functional group affording arylation at C-C coupled product at δ C-H bond (Eq. 17) [190]. ð17Þ Recently, Venkateswarlu and co-workers reported the copper-catalyzed crosscoupling reaction between aryl/heteroaryl halides with aryl boronic acids using water extract of pomegranate ash (WEPA) aqueous reaction medium and as biorenewable base. CuI/WEPA catalytic system found to be effective base and reaction medium among the studied CuI/WEPA/DABCO, CuI/WEPA/SPhos, CuI/WEPA catalytic systems for the Suzuki–Miyaura coupling to deliver good to high yields of the products. The protocols tolerate broad substrate scope under mild reaction condition with low loading of catalyst, low E-factor, and high chemoselectivity (Eq. 18) [191].

ð18Þ

3.5

Coupling with Organotin Reagents

The Pd-catalyzed cross-coupling of organic halides with organostannanes reagents is known as Migita–Kosugi–Stille cross-coupling reaction, and the reaction found several advantages in organic synthesis [192]. The homocoupling of organostannanes reagent was accomplished using stoichiometric amount of copper (II) nitrate. The developed method afforded symmetrical biaryl by treating o-tolyl-, p-tolyl-, or p-anisyl-stannanes with 1 equivalent of Cu(NO3)23H2O in THF solvent obtaining 45–67% yields. The method was also extended for the synthesis of cyclic oligophenylenes [193]. Further, copper-catalyzed homocoupling reaction yield and scope improved for the synthesis of different biaryls, and crossover experiment also

310

M. S. Lokolkar et al.

Scheme 50 Copper(I)mediated biaryl synthesis using diaryltin reagents

Scheme 51 Copper(II)mediated biaryl synthesis using diaryltin reagents

Scheme 52 Cu(I)-catalyzed coupling of allyl iodides and chlorides with vinyl stannanes

performed between two different diarylstannanes which afforded both crosscoupling and homocoupling products (Scheme 50) [194]. Kang and co-workers disclosed the homocoupling of organostannanes using copper catalyst for the synthesis of biaryls, 1,3-diynes, and 1,3-dienes using iodine molecule as an oxidant. The protocol employed CuCl2 as catalyst, molecular iodine as an oxidant in dimethylformamide at 100°C to obtain symmetrical biaryls in good yields (Scheme 51) [195]. The seven-membered ring compounds have been synthesized by employing copper-catalyzed intramolecular homocoupling strategy, the protocol is applied for the preparation of tubulin-binding agents [196, 197]. In 1995, Takeda and co-workers demonstrated Cu-catalyzed coupling of vinylstannanes and allyl halides in DMSO-THF solvent medium. The protocol displays the α-regioselectivity for the reaction with allyl chlorides as compared to allyl iodides, the reaction affording vinyl-allyl adduct. The stereochemistry of the product is affected by the structural variation and the type of leaving present. However, the stereospecificity could be enhanced by the presence of metal salts and protodestannylated side product generation can be suppressed by the addition of carbonate (Scheme 52) [198]. In 1998, Campbell, Lipshutz, and co-workers demonstrated that vinylstannanes could undergo transmetalation with higher order cyanocuprates [199, 200]. Subsequently, several groups independently reported the copper-catalyzed cross-coupling reactions of organotin by the research groups Liebeskind, Piers and Falck [201–

Cu-Catalyzed C-C Coupling Reactions

311

Scheme 53 Coupling of alkynyl bromides and vinyl iodides with α-substituted alkyltin reagents Scheme 54 Coupling of organoiodides with organotin reagents

203]. The reported methods developed the catalytic systems using stoichiometric amount of CuI, CuCl, and CuTc(Tc = thiophene-2-carboxylate) catalysts for the coupling of vinyl iodides and alkynyl bromides with vinyl, aryl, and alkynyl bromides (Scheme 53). Falck and co-workers demonstrated the cross-coupling reaction of iodo/ bromobenzenes with α-heteroatom-substituted alkyltributylstannanes through copper catalyst in THF medium in 1995. Though protocol shows low yields of the products, this serves as first potential example of copper-catalyzed cross-coupling [204]. Kang and co-workers reported the Cu-catalyzed cross-coupling reaction between organic halides and organostannanes using NMP solvent at 90°C and NaCl as an additive resulting improved yields of the protocols. The method disclosed could be employed for vinyl and aryl iodides coupling with different aryl, vinyl, heteroaryl, and alkyltin reagents providing good to excellent yield of the products. Also, the reaction successfully applied for the diarylation of 1,4-diiodobenzene with organotin reagent [205]. In 2006, Li and Zhang developed an effective and reusable copper-catalyzed Stille-coupling reaction between organotin reagents and organohalides. The catalytic system with Cu2Onanoparticles/p(o-tol)3/TBAB) could be successfully applied to aryl halides such as less active aryl chlorides for the coupling with vinyl, aryl, and alkynyltin reagents. The protocol tolerates different functionality bearing aryl ring providing good to excellent yield of the corresponding products using potassium fluoride KF (Scheme 54) [206]. In 2003, Falck and co-workers contributed copper-catalyzed stereospecific crosscoupling of organohalides with heteroatom-substituted enantioenriched α-alkoxy-β-amino and α,β-dialkoxystannanes (Scheme 55). The Cu(I)-catalyzed approach progressed with stereochemical retention, resulting good yields of the product when coupled with corresponding substrates vinylic iodides and allylic,

312

M. S. Lokolkar et al.

Scheme 55 Stereospecific coupling of thionocarbamates with organohalides

Scheme 56 CuTC as an effective catalyst for synthesis of α-amino-α’-alkoxy ketones

acetylenic, cinnamylic, and propargylic bromides [201]. Flack and co-workers then explored the scope of Cu(I) salts in cross-coupling of the organic iodides with α-thiocarbamo-substituted stannanes. This stereospecific reaction method focused on the coupling of both scalemic and racemic pyrrolidinylthiocarbamoyl (PTC)protected α-hydroxystannanes with aryl, heteroaryl, and alkenyl iodides using Liebeskind promoter (CuTC)-assisted system [207]. In 2011, Liebeskind and co-workers developed copper(I) thiophene-2-carboxylate (CuTC) as neutral catalyst for synthesis of stereocontrolled α-amino-α’-alkoxy ketones by coupling reaction between chiral nonracemic α-alkoxyalkylstannanes and amino acid thiol esters. The reaction coupling of N-protected α-amino acid thiol esters and chiral scalemic α-alkoxyalkylstannanes generates chiral adduct with retention of configuration at the stereogenic centers of both the coupling partners with moderate to high yields. The protocol tolerates different functional groups including free indole, acetal, thioether, ester, and carbamate groups on the electrophile (Scheme 56) [208]. Abarbri and co-workers developed Cu(I)-catalyzed cross-coupling of aliphatic/ aromatic alkynyl bromides with β-tributylstannyl β-trifluoromethyl α,β-unsaturated ester as an effectual method for the synthesis of (E)-3-trifluoromethylbut-2-en-3ynoates in 2012. The protocol progressed by utilizing CuBr/CuI with excellent stereoselectivity of 2,3-enynoates and good functional group tolerance on the electrophile with moderate to good yields. In the presence of electron-rich substituent on the aryl ring no or very less effect was observed while for the electron-poor groups yield of the product is lowered. The double-bond partial isomerization (E/Z = 60:40) was observed in the case of some aromatic electrophiles bearing electron-rich groups

Cu-Catalyzed C-C Coupling Reactions

313

Scheme 57 Scope of nanocopper catalyst in the synthesis of biphenyls

[209]. Wang and Falck disclosed the cross-coupling reaction for the enantioselective synthesis of biologically significant 4(S)-11 dihydroxydocosahexaenoic acid (diHDHA) through CuTC-catalyst in 2015. The coupling of conjugated bromides with chiral α-hydroxystannanes for the generation essential Csp-Csp3-bonded motifs of diHDHA was described under mild reaction conditions (Eq. 19) [210].

ð19Þ Rajabi and co-workers developed new Schiff base-alumoxane-reinforced mesoporous Cu nano-catalyst (SBA-Cu2+) and applied as catalyst for coupling of aryl/heteroaryl halides with triphenyltin chloride. The reaction worked with low loading of the catalyst, base sodium carbonate in polyethylene glycol (PEG) as solvent medium to afford biphenyls in good yields. The protocol tolerates electronrich as well as electron-poor functionalities on the aryl ring, however for the reaction with aryl chloride, it is slow as compared to aryl bromides and iodides. The reaction worked well for aryltin substrates and heteroaryl coupling providing decent yields and the heterogeneous copper catalyst has been recycled with negligible leaching (Scheme 57) [211]. Recently, Ghosh and co-workers demonstrated the cross-coupling of functionalized furanyl stannyl derivative with allyl bromide by employing CuI and Cs2CO3 additive as an effectual catalytic system with low loading of catalyst at ambient temperature. The formation of the by-products such as ketone and protodestannylated product reduced by the addition of carbonates, affording dioxalane adduct in moderate to good yields. The protocol described for the synthesis of furan bearing sensitive functionalities. The mixture of E and Z isomers γ-alkylated and protodestannylated obtained in the ratio 20:1:1:1, for the coupling reaction of functionalized furanyl stannyl derivative with (E)-5-bromo-3-methylpenta-1,3-diene when acetonitrile solvent is used under same condition. The E isomer obtained with 94% in excellent yield which has significance in the synthesis of anticancer therapeutic, spliceostatin derivatives [212].

314

3.6

M. S. Lokolkar et al.

Coupling with Organosilicon Reagents

The cross-coupling of organic halides with organosilicon reagents through palladium catalyst is known as Hiyama cross-coupling reaction [213, 214]. Though, low toxicity and easy handling of organosilicon compounds are less explored in comparison with organotin and organoboron reagents (Migita–Kosugi–Stille coupling and Suzuki–Miyaura coupling), due to less efficiency for transmetalation from silicon to palladium from those of tin or boron reagents and typically requires fluoride anion for the activation of silicon–carbon bond and enables transmetalation. However by using silanols [215] or 2-(hydroxymethyl)phenylsilanes [216, 217], the coupling efficiency improved. A number of palladium-free, copper-catalyzed Hiyama-type cross-coupling approaches were developed. Ito and co-workers developed copper-catalyzed cross-coupling between aryl halides and aryl or heteroarylsilanes in 1997. The catalyst copper(I) pentafluorophenoxide acts as effective promoter which is generated in situ from copper iodide and sodium pentafluorophenoxide and reaction worked without fluoride ion. The reaction of iodobenzene with trimethylsilylthiazole accomplished in dimethylimidazolidinone (DMI) to access the coupling product with 93% yield. The reaction of phenyltrimethylsilane with p-iodotoluene was failed under same reaction condition, however this cross-coupling reaction was enabled using methoxydimethylsilyl analogue under same condition which undergoes the transmetalation (Scheme 58) [218]. Kang and co-workers developed the copper-catalyzed homocoupling strategy for arylsilanes, by applying tetrabutylammonium fluoride (TBAF) at ambient temperature. The homocoupling coupling of aryls, alkenyl, and alkynyldimethylhalosilanes afforded moderate to good yields of corresponding biaryls, dienes, and diynes [219]. However, Nishihara et al. described the homocoupling of alkenyl and aryl fluorosilanes using copper catalyst and presence of fluoride halide on silicon shows slight superior ligand to chloride in terms of yield and homocoupling of arylethyldifluorosilane has also been reported using stoichiometric amount of copper chloride [220]. In 2013, Giri and co-workers developed the copper-catalyzed crosscoupling of aryl and heteroaryl iodides with aryl and heteroaryltriethoxysilanes affording cross-coupled product. The reaction utilizes copper iodide as catalyst, under ligand-free condition and cesium fluoride as fluoride source for accessing heteroaryl-heteroaryl and aryl-heteroaryl coupling products and tolerates broad functionalities with good to excellent yield of the corresponding product (Scheme 59) [221]. When the ligand-free condition has been applied for the aryl–aryl

Scheme 58 Copper(I)-mediated cross-coupling between arylsilanes and aryl iodides

Cu-Catalyzed C-C Coupling Reactions

315

Scheme 59 Coupling of aryl-, heteroarylsilicon reagents and aryl and heteroaryl iodides

Scheme 60 Coupling of alkynyl bromides with vinylsilicon reagents

coupling, low yields of the products were observed, however employing 2-(diphenylphosphino)-N,N-dimethylaniline (PN-1) in combination with CuI yield was improved and also allowed the cross-coupling between aryl bromide and aryltriethoxysilanes. The highly sterically hindered and electron-rich ligand 2-(di-tert-butylphosphino)-N,N-dimethylaniline (PN-2) was applied for the crosscoupling between aryl bromides and aryltriethoxysilanes by using copper iodide in stoichiometric amount under same conditions [222]. Riant and co-workers described similar reaction for the cross-coupling of alkynyl bromides with vinyltriethoxysilanes using cationic copper complex, Cu(MeCN)PF6 as catalyst, and tetrabutylammonium difluorotriphenylsilicate (TBAT). The reaction protocol works effectively for both aromatic and aliphatic alkynyl bromides affording corresponding products in 2014 (Scheme 60) [223]. Takeda and co-workers demonstrated the intramolecular coordination of aryl and alkenylsilanes bearing alkoxide group which undergoes alkylation with benzyl chlorides and alkyl iodides by using NHC-bound Cu, catalyst [(IPr)CuCl] [224, 225]. Later the same group demonstrated the coupling of primary alkyl and benzyl halides with vinylsilicon reagents using a stoichiometric amount of catalyst CuIP(OEt)3, and fluoride source Bu4NF(tBuOH)4 in dimethylformamide (Scheme 61) [226]. They also developed the coupling reaction of organic halides having sp3 carbon–halogen bond with the organo(hydro)silane, that is aryldimethylsilane with benzyl, allyl, and alkyl halides through copper catalyst. The organocopper formed in the reaction by the copper salt, ethylene glycol, and a base which in turn reacts with organic halides [227]. Also, Riant and co-workers described the coupling of alkynyl bromide with vinyltriethoxysilanes and benzyl bromides as electrophile also applied (Eq. 20) [228].

316

M. S. Lokolkar et al.

Scheme 61 Cu-catalyzed coupling of aryldimethylsilane with benzyl, allyl, and alkyl halides

ð20Þ

In 2016, Hartwig and co-workers disclosed the cross-coupling of various haloarenes with difluoro(trimethylsilyl)acetamide in the presence of copper catalyst. The coupling reaction of difluoro(trimethylsilyl)acetamide with 2-bromo-5ethylpyridine by using CuOAc catalyst afforded the difluoro(2-pyridyl)acetamide which is transferred to difluoro pioglitazone analogue (Eq. 21) [229].

ð21Þ

In 2016, Hiyama and co-workers disclosed the Cu(II) catalyzed cross-coupling reaction of arylhalides and aryl- and heteroaryl(triethyl)silanes. The method progresses smoothly with catalytic amount of CuBr2 and Ph-Davephos and using stoichiometric quantity of base cesium fluoride to afford biaryls or teraryls with high yields. The C-H silylation of aromatic substrates provides silicon reagents which allows the coupling with haloarenes [230]. Later, the same group disclosed the copper-catalyzed coupling reaction of n-alkyl halides with aryl(trialkyl)silanes. The catalytic system using CuI as catalyst and 1,10-phenanthroline as ligand is observed to be effective for this alkylation reaction. For example, 2-hexylated product was formed by the coupling of 2-triethylsilylbenzo[b]thiophene with hexyl iodide in good yields. The protocol tolerates bulky triisopropylsilyl groups and trimethylsilyl, tert-butyldimethylsilyl affording coupled products in good yields under same condition. Similarly, aryl bromides, chloride, and tosylates also applied for this alkylation reaction resulting aryl–alkyl coupling (Scheme 62) [231].

Cu-Catalyzed C-C Coupling Reactions

317

Scheme 62 Cu-catalyzed cross-coupling of arylsilanes with iodoarenes and alkylation of 2-trialkylsilylbenzo[b] thiophene

3.7

Coupling with Organoindium and Organoaluminium Reagents

Giri and co-workers disclosed for the first time the Cu-catalyzed cross-coupling of triorganoindium reagents with aryl halides in 2014. They found that triorganoindium reagents serve as an exceptional coupling partner for the reaction by transferring all three organic nucleophiles for the product formation through sequential transmetalation and require only one third equivalent of the organometallic reagent. Protocol works for both alkyl and arylindoium reagents with the presence of PN-2 ligand sodium methoxide as a base in dimethylformamide. The different functional groups and steric effect were tolerated for aryl iodides as electrophiles and reaction also applied for the electron-poor and heteroaryl bromide electrophiles. The reaction for heteroaryl iodides with organoindium reagents allowed without presence of the external PN-2 ligand (Scheme 63) [232]. In the following year, Giri and co-workers developed first the copper-catalyzed cross-coupling of organohalides and organoaluminium reagents. The reported protocol proceeds by using catalytic quantity of CuI and 2-(diphenylphosphino)-N,Ndimethylaniline (PN-1) as a ligand and LiCl as an additive in dimethylformamide showing wide substrate scope for organohalides as well as organoaluminium reagents. The coupling reaction of aryl, heteroaryl iodides and vinyl bromides, aryl, heteroaryl bromides and heteroaryl chlorides coupling with aryl, alkyl, and

Scheme 63 Cu-catalyzed triarylindium reagents and aryl iodides cross-coupling through three consecutive transmetalations

318

M. S. Lokolkar et al.

Scheme 64 Coupling of triorganoaluminium reagents with aryl and heteroaryl, alkenyl halides

Scheme 65 Coupling of triarylaluminum reagents with alkyl iodides and bromides

alkynylaluminium reagents afforded corresponding products in moderate to excellent yields. Both 1° and 2° alkylaluminium reagents are allowed as coupling partner in the reaction resulting good yields. For the coupling reaction products such as aryl– vinyl, alkyl–aryl and aryl–aryl it requires catalytic amount of PN-1 ligand to afford good yields. Nevertheless, without presence of PN-1 ligand reaction proceeds for heteroaryl halides and even for coupling of 1° and 2° alkylaluminium reagents with heterohalides. The reaction likely to be proceeded through oxidative additionreductive elimination way (Scheme 64) [233]. The same group reported the copper-catalyzed cross-coupling of alkyl halides with triarylaluminium reagent for the preparation of arylalkanes. The protocol uses the CuI salt, N,N,N′,N′-tetramethyl-o-phenylenediamine (NN-1) ligand. The reaction of electron-rich, electron-neutral triarylaluminium reagents couples with various 1° alkyl bromides and iodides containing functionalities like nitriles, olefins and resulting good to excellent yields of the products (Scheme 65) [234].

Cu-Catalyzed C-C Coupling Reactions

319

Scheme 66 Cu-catalyzed coupling of 1° alkyl bromides with 2° and 3° alkyl Grignard reagents

3.8

Coupling with Organomanganese Reagents

Cahiez and Marquais developed the copper-catalyzed cross-coupling of alkyl halides and phenylsulfonates with organomanganese chloride in 1993. The reaction utilizes NMP as co-solvent which enhances the reaction, resulting corresponding product in good to excellent yields. The protocol tolerates different functionalities including esters and ketones and reaction could be applied to 1°, 2°, and 3° alkyl and also allyl, aryl, and vinyl manganese reagents which are coupled with phenylsulfonates and primary alkyl iodides and bromides [235]. The same group later extended the scope of the method for the coupling of free carboxyl and hydroxyl groups containing alkyl bromides and also for vinyl iodides (Scheme 66) [236].

4 Copper-Catalyzed Cyanations of Aryl Halides Initially, Scheele (Fill) invented hydrogen cyanide in 1782 and died later while trying to isolate the anhydrous material. After that, Wohler and Liebig reported the first nitrile compound in 1832 when they prepared benzoyl cyanide and benzonitrile, and Pelouze also obtained propionitrile in 1834. There are numerous applications of nitrile compounds in the field of synthetic chemistry like acrylonitrile (for the synthesis of rubber, fiber, and plastic), trichloroacetonitrile used in fumigants and phthalonitrile for the dyestuffs, etc. widely applicable in synthetic resin as well as used as solvents, especially, as a chemical intermediate in the synthesis of pharmaceuticals, and insecticide and dyestuffs [237]. In 1913, Meister, Lucius, and Bruning patented work on cyanation reaction. For example, the chloro- and bromo anthraquinones were treated with CuCN in pyridine by prolonged heating conditions to form corresponding nitrile derivatives (Scheme 67). In 1927, Alfred Pongraz also demonstrated an aromatic halide or benzenoid reaction with copper(I) cyanide to the corresponding nitrile [238]. He achieved a 95% yield of perylene-3.9-dicarbonitrile from dibromide (1) and copper (I) cyanide under the heating condition. Later, Braun and Manz also prepared fluoranthene derivatives (Scheme 68).

320

M. S. Lokolkar et al.

Scheme 67 Cu-mediated cyanations of haloanthraquinones by the Meister, Lucius, and Brüning

Scheme 68 Cyanation of aryl halide reported by Alfred Pongraz

The attention to copper-mediated cyanation of aryl halides led to the following significant advancement in this field. Fritz Ullmann and Irma Goldberg laid the groundwork for contemporary copper catalysis. In the roughly 30 years that followed this groundbreaking work, more significant papers emerged that further illustrated the potential of copper-catalyzed cross-coupling reactions. After Ullmann and Goldberg’s key articles, there was a surge in interest in the Cu-mediated cyanation of aryl halide compounds, which led to the next significant advancement in this field. Under extremely hot reaction conditions (150–250°C), the stoichiometric amount of copper(I) cyanide was treated with aryl halides for the preparation of nitrile compounds. Nowadays, this classical reaction of aryl bromide with CuCN at high temperature to give aryl nitriles is known as Rosenmund–von Braun reaction [15]. For example, the stoichiometric amount of cuprous salt precursor (CuCl, CuBr, CuI, or CuCN) is used to exchange the halide group of arylhalides in the presence of excess sodium cyanide in ionic liquid at high temperature (Eq. 22). ð22Þ But under the same reaction condition cyanation of aryl bromide does not give satisfactory conversation. To overcome this lack of reactivity for activating aryl bromides, an alternative approach based on the Cu-catalysed aromatic Finkelstein reaction were developed [239, 240]. In this domino halide exchange in one-pot process, the first bromide was exchanged by the iodide to form aryl iodide in the presence of CuI/KI catalytic system, and followed by the cyanation of aryl iodide using sodium cyanide salt (Eq. 23).

Cu-Catalyzed C-C Coupling Reactions

321

Scheme 69 Cu (II)mediated aerobic oxidative cyanation of 2-aryl heterocycles

Scheme 70 Copper(I)mediated regioselectivity oxidative cyanation reaction of heterocycles

ð23Þ

Besides, direct cyanation via C-H bond activation is more appealing since it uses easily available reactants. Direct cyanation of heterocyclic compounds can be achieved using effective oxidants like I2, air, and oxygen. Recently, Wang and their co-workers disclosed the aerobic oxidative cyanation of 2-arylheteroaromatics applying CuBr as catalyst with benzyl cyanide as a cyanide source. In parallel, they also use Cu (II) as a catalyst for the cyanation reaction (Scheme.69) [241]. Most recently, the Daugulis research group reported a Cu-mediated regioselective cyanation of heterocyclic compounds by using CuCN as a catalyst and iodide as an oxidant with sodium cyanide as a cyanide source (Scheme 70) [242–244].

5 Copper-Catalyzed Alkynylation, Alkenylation, and Allylation 5.1

Copper-Catalyzed Alkynylation Reactions of Aryl Compounds

Cu-mediated C-C bond formation reactions via cross-coupling of alkynylation and alkenylation reactions of aromatic compounds represent the most useful approaches in synthetic chemistry. Consequently, a variety of processes have been investigated

322

M. S. Lokolkar et al.

and published in the literature. Copper is the first transition metal used as a catalyst for the formation of C-C bonds. In 1975 Cassar and Sonogashira described the Pd-catalyzed cross-coupling reaction between an aryl halide and terminal alkyne, while Sonogashira employed a combination of Pd/Cu-catalysts. Because of the high cost of carbon–carbon bond reaction utilization in large-scale production, researchers are interested in developing Cu-catalytic systems due to its greater availability, lower cost, and lack of toxicity. In 1901, Fritz Ullman proposed the first report on copper-mediated C-C bond formation reaction. In this case, we discuss copper-catalyzed aryl alkynes and aryl alkenes syntheses via Sonogashira-, Suzuki– Miyaura-, and Stille-type cross-coupling reactions and also disclosed coppermediated allylation. Alkynes are adaptable intermediates widely existing in synthetic chemistry, pharmaceutical chemistry, natural products, and bioactive compounds. Therefore, incorporating the alkynyl group into organic compounds has a much more important objective in the chemical research community. The most efficient and simple processes for the synthesis of aryl alkynes include the Sonogashiracoupling reaction, Stille-coupling reaction, and direct C-H bonds functionalization, these processes have all received a great deal of attention.

5.1.1

Copper-Catalyzed Preparation of Aryl–Ynes via Stille-Type Cross-Coupling Reactions

The transition metal-catalyzed Stille cross-coupling reaction is one of the most important representative cross-coupling transformations in organic synthesis. In 1977, John Kenneth Stille and David Milstein developed an enormously prevailing tool for carbon–carbon bond formation, and these reactions continue to be exploited industrially, particularly for pharmaceuticals. This Pd-catalyzed coupling reaction is carried out in an inert atmospheric condition, using a dried solvent. Without maintaining inert conditions oxygen can oxidize the palladium catalyst to endorse the homocoupling reaction of stannylated compounds and the yield of the desired cross-coupling product is frequently reduced due to side reactions. In 1994, L. Liebeskind and co-workers report the Stille-coupling reaction between iodobenzene and vinyl tributyltin in dioxane at ambient temperature. In this protocol, they use Cu(I) salt cocatalyst and Pd (0) as a catalyst (Eq. 24) [245]. ð24Þ In 2006, M. Zhang and their co-workers extended a Cu-catalyzed Stille-type cross-coupling reaction. Aryl iodides and aryl bromides can be activated using the Cu2O/P(o-tol)3/TBAB system and it can be used three times without a loss of catalytic activity (Scheme 71) [206]. The Stille cross-coupling reaction of 1-bromo-4-nitrobenzene (1a) with tributyl(phenyl)stannane (2a) performed in ionic liquids was conducted as a model to screen the optimized reaction conditions. The

Cu-Catalyzed C-C Coupling Reactions

323

Scheme 71 Cu-catalyzed Stille-type couplings of alkynyltin derivatives with aryl halides

Stille-type coupling reaction demonstrated the arylated alkynes employing alkynyltin derivatives and aryl halides under the Cu2O nanoparticles/P(o-tol)3 (L7)/TBAB system and KF as additive (Scheme 71).

5.1.2

Copper-Catalyzed Preparation of Aryl–Ynes via Sonogashira-Type Cross-Coupling Reaction

Decarboxylative copper-catalyzed cross-coupling reactions have received a great deal of consideration. Various alkynyl groups have been used as reaction partners for the various transformations of alkynylative molecules. Initially, in 2010 Y. Xue and their research groups report that alkynyl carboxylic acids and aryl halides are decarboxylative coupled with the assistance of copper catalyst under mild conditions [246]. Here they study a wide variety of aryl iodides and aryl bromides by reacting with a different alkynyl carboxylic acids, using Cs2CO3 as a base, phenanthroline (10 mol%), and CuI (10 mol%) in DMF at 130°C for 24 h (Scheme 72). A year later, the Mao and Jiao groups illustrated a protocol for synthesis of alkynylative derivatives using Cu-catalyzed decarboxylative coupling of alkynyl carboxylic acids with various aryl and alkyl halides under mild conditions, it is an alternative approach for the palladium-catalyzed cross-coupling reactions [247, 248]. This method also extends the decarbonylative alkynylation of diiodobenzene under the same reaction conditions. More recently, S. Lee demonstrated the aluminosilicate framework of zeolite-based copper (II) catalyst for decarboxylative Sonogashira-type cross-coupling reactions of alkynyl carboxylic

Scheme 72 Cu-catalyzed decarboxylative cross-coupling reaction

324

M. S. Lokolkar et al.

Scheme 73 Cu-catalyzed cross-coupling of alkynyl silanes with aryl iodides Scheme 74 Preparation of steroidal enynes

acids and aryl iodides [249]. The microporous size of the zeolites is uniformly distributed on Cu metal to increase the activity of the catalyst, due to this protocol providing an excellent yield of the diarylalkynes. The copper-catalyzed synthesis of aryl–ynes mostly employed aryl acetylene molecule with an electrophilic coupling partner. Recently various alkyne precursors as partners for coupling reactions to transform organic-ynes compounds such as propiolic acids, ethynylsilanes, and propargyl alcohol were utilized for the Cu-mediated Sonogashira reactions due to its internal attached leaving groups being easily removable. In 2011, N. Yasushi et al. disclosed the Cu-catalyzed cross-coupling reaction between aryl iodides and alkynyl silanes [250]. This methodology is more tolerant, useful, and significantly inexpensive than the palladium-catalyzed Sonogashira-coupling reaction (Scheme 73). Most recently, I. Beletskaya and their co-workers demonstrate the new Cu-mediated deacetonative Sonogashira-coupling reaction from propargyl alcohols and (het)aryl halides [251]. They use propargyl alcohol as an alternative source for the terminal alkyne, the synthesis of some natural product by applying the same reaction conditions (Scheme 74) [252, 253].

5.1.3

Synthesis of Aryl–Ynes by Direct C–H

In the last decade, interest in C-H bond activations may have increased. During this time a number of groundbreaking experiments were conducted to demonstrate the

Cu-Catalyzed C-C Coupling Reactions

325

usefulness of cross-couplings. Various practical synthetic techniques for the synthesis of organic compounds, including the formation of C-C and C-heteroatom bonds through cross-dehydrogenative C-H bond functionalization using a Cu-catalyzed system were developed. In 2010, M. Miura disclosed the intramolecular direct dehydrogenative C-H functionalization to C-C coupling using copper salt media. Cu-catalyzed oxidative cross-coupling reaction of heteroaryl with terminal alkyne synthesized the alkynylazoles derivative (Eq. 25) [254].

ð25Þ In the same year Su and their co-workers also disclosed the Cu-catalyzed alkynylative C-C bond formation from perfluoroarenes and terminal alkynes [255]. The alkynylation reaction was constructed between electron-deficient 2,3,5,6-tetrafluorobenzotrifluoride and various terminal alkynes in DMSO with CuCl2 (20 mol%) catalyst and 15 mol% of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) under the 1 atm O2 at ambient temperature. This reaction worked smoothly and tolerates a variety of functional teams (Eq. 26).

ð26Þ

Recently, J. Yu and their co-workers disclosed the copper-mediated o-alkylation of arenes and heteroarenes with a variety of terminal alkynes via the dehydrogenation process [256]. This technique provides an alternative synthetic route to Sonogashira coupling, the variety of terminal alkynes and arenes were tolerated under mild conditions. They also achieve the alkylation of a number of heteroarenes such as benzofuran, imidazole pyrrole, pyrazole, and indole to demonstrate corresponding products in 30–67% yield (Scheme 75).

5.2

Copper-Catalyzed Alkenylation of Aryl Derivatives

Copper-catalyzed Heck, Stille, and Suzuki–Miyaura-type cross-coupling reactions of alkenylation of electrophilic aryl and alkene are the most effective method for the synthesis of carbon–carbon bonds including compounds.

326

M. S. Lokolkar et al.

Scheme 75 Cu-mediated o-alkynylation of arenes and heteroarenes

5.2.1

Copper-Catalyzed Preparation of Aryl–Enes via Stille-Type Cross-Coupling Reaction

LS. Liebeskind et al. first reported the function of copper metal in a Stille-coupling reaction in 1990. Here they carried out the cross-coupling reaction between organic iodide and vinyl trifluoromethanesulfonate esters in the presence of Pd/Cu catalytic system to form substituted cyclobutenediones. The Cl(C6H5CH2) Pd (PPh3)2] catalyst with CuI as cocatalyst were applied for the cross coupling reaction of iodobenzene and stannylcyclobutenedione at room temperature (Eq. 27) [257, [258]]. ð27Þ In 1997, the same scientist LS. Liebeskind and their co-workers disclosed the Cu-mediated Stille alkenylation reaction of organic iodides with organostannanes at room temperature [203, 257]. The cross-coupling of various organostannanes like vinyl, aryl and heteroarylstannanes with vinyl iodides and some aryl iodide compounds was investigated using (2-thienyl) COOCu (CuTC) in NMP solvent. They also studied thermally sensitive compounds. Despite the stoichiometric amount of copper was used for the process, this procedure is inexpensive and competitive with conventional palladium-catalyzed methods in many circumstances (Scheme 76). More recently, M. Jurica and co-workers demonstrated a Pd-free Stille-type cross-coupling reaction between organostannylfuran derivatives and allylic bromides under different reaction conditions. However, they studied different types of copper salts as well as additives with a variety of solvents. Initially, they synthesize functionalized furanyl stannane derivatives from commercially available

Cu-Catalyzed C-C Coupling Reactions

327

Scheme 76 Cu-mediated Stille-type coupling of the organotin reagents with aryl iodides

2-acetalylfuran and ethylene glycol by adding a catalytic amount of para-toluene sulphonic acid and refluxing with toluene. Then obtained derivatives react with nBuLi in THF at -78°C. Copper-mediated cross-coupling reaction was performed by adding a mixture of DMSO and THF (3:1) at room temperature. CuI (0.5 equiv) and inorganic base (0.1 equiv) were added to this mixture, followed by allyl bromide (2.0 equiv) (Eq. 28) [212].

ð28Þ

5.2.2

Copper-Catalyzed Preparation of Aryl–Enes via Heck-Type Cross-Coupling

Traditional Heck couplings are performed by Pd(0) catalysts, which are primarily stabilized by phosphine ligands. In 1997, P. Wadgaonkar and their co-workers for the first time reported Cu-mediated Heck-type reactions were carried out with CuI or CuBr as a catalyst to promote cross-coupling reactions for the synthesis of carbon– carbon bond compounds [259]. They also explore the alkenylative Cu-catalyzed Heck coupling reaction of inter- as well as intra-molecular compounds (Scheme 77). X. Zheng and their co-workers have been synthesized novel silica-supported Cu-catalyst for alkenylation of various aryl iodide derivatives with olefins [260]. This Scheme 77 Cu-Catalyzed Heck-type inter- and intramolecular crosscoupling reactions

328

M. S. Lokolkar et al.

Scheme 78 Silica-supported Cu-catalyzed Heck-type cross-coupling reaction

silica-supported Cu-catalysts are very active and stereoselective for alkenylative Hecktype coupling reaction of olefins with aryl iodide under high temperatures (130–150°C) and recyclable without loss of catalytic activity (Scheme 78). J. Li et al. have established an effective catalytic method using CuI/DABCO for alkenylation of aryl halides. The alkenylation of various aryl iodide and bromide using CuI (10 mol%), DABCO (20 mol%), and K2CO3 as a base in polar protic solvent ethanol with various alkene derivatives. This catalytic system provides a good to excellent yield of desired products [261]. In the same year, N. Cioffi and co-workers developed a novel catalytic method for alkenylation by using copper bronze with tetrabutylammonium acetate base in ionic liquid TBAB (tetrabutylammonium bromide). Copper nanocolloids are remarkably stabilized by tetraalkylammonium salts and their high reusability and effectiveness without losing catalytical activity. The copper-bronze catalyst was used for the alkenylation of various aryl iodide and activated bromides with acrylates under the ionic liquid as solvent [262]. In 2018 Houcine and their co-workers used a new supramolecular mononuclear complex [Cu(C5H6N2)4]2Br-2(C3H7NO) to produce the Cu-catalyzed Heck coupling reaction under the ultrasonic irradiation condition [263]. The reaction between aryl bromides and olefins was carried out with Cu-4AP-Br catalysts under different solvents like DMSO, ACN, and DMF, where DMSO is good for the Heck coupling reactions. Recently, I. Yavari et al. designed a magnetically separable copper catalyst and it was investigated for Heck-type cross-coupling reactions [264]. The established heterogeneous catalyst was used to examine Heck-type coupling as well as Ullmann coupling reactions of various aryl halide derivatives. The Heck-type cross coupling reaction of aryl halides and alkene using silicasupported copper catalyst in an environmental-friendly aqueous medium at 100 ̊C. According to studies, a number of aryl halide derivatives with both electrondonating and electron-deficient substituents were successful in producing the desired products in good to excellent yields (Scheme 79). Most recently, different types of carbon–carbon bond formation reactions using CuI in reusable solvent dimethyl sulfone (DMSN) without use of any ligand were reported by S. Cheng et al in 2020 [265]. The C-C bond formation reactions via Sonogashira, Heck, and Suzuki cross-coupling were proposed using a copper catalyst in environmentally benign solvent dimethyl sulfone giving moderate to good yield. Finally, dimethyl sulfone (DMSN) was separated by using a recrystallization

Cu-Catalyzed C-C Coupling Reactions

329

Scheme 79 Fe3O4@SiO2@PrNCu-catalyzed Heck-type cross-coupling reactions of variety of aryl halides and olefins

method from the reaction mixture. Heck cross-coupling reaction of aryl halide derivatives with olefins was accomplished with a yield of 54–90%. When compared to aryl chlorides and bromide, aryl iodides are revealed to be superior substrates and have a good conversion with withdrawing substituents.

5.2.3

Copper-Catalyzed Preparation of Aryl–Enes via Suzuki– Miyaura-Type Cross-Coupling

The synthesis of carbon–carbon bond formation reactions by using Heck, Suzuki– Miyaura, and Sonogashira, cross-coupling is exposed to signify the transformations. Conventionally, this transformation uses palladium catalysts. Recently, incredible work has been developing alternative sources for the synthesis of C-C bond compounds. The copper-catalytic system is the alternative source to the palladiumcatalyzed system due to being inexpensive and easily available. Li and their co-workers have disclosed the copper-catalyzed alkenylation via Suzuki–Miyauratype cross-coupling of a variety of vinyl halides and aryl halides using aryl boronic acids which shows good conversation of corresponding yields. The reaction of vinyl halides with different boronic acids has been described using 10 mol% CuI, 20 mol% DABCO, Cs2CO3 (2 equiv), and TBAI (1 equiv) in DMF at 125–130°C for 16–24 h. In comparison with the palladium/ligand catalytic methods, the affordable

Scheme 80 Cu-mediated Suzuki–Miyaura-type crosscoupling of aryl boronic acids and vinyl halides

330

M. S. Lokolkar et al.

CuI/DABCO system has become a popular choice for this reaction (Scheme 80) [150].

5.2.4

Copper-Catalyzed Preparation of Aryl–Enes via Direct C–H Activation of Arenes

The C-H functionalization of substituted aryl oxazoles and other connected heterocyclic compounds like benzothiazole, oxazole, and benzoxazole with bromoalkene derivatives using copper-catalyzed systems was reported by M. Betzer and D. Grierson in 2008. The synthesis of various 2-E-vinyl oxazoles has been described with the smooth conversion of the corresponding product yields. This copper-catalytic system allows for the synthesize of both regio- and stereoselective compounds and the tolerance of different functionalities (Scheme 81) [266]. Lan and their co-workers performed copper-catalyzed C-H functionalization of azoles utilizing gem-dihaloolefins for the synthesis of benzofused heteroaryl azole. This reaction is convenient to synthesize the bezofused heteroaryl azole derivatives via tandem C-hetero atoms coupling or C-H functionalization [267]. In this content, this method is not only suitable for the synthesis of different benzofused heterocycles but also relevant to the various azoles like imidazoles, oxazoles, thiazoles, etc. Subsequently, there is reaction of imidazoles with 1,4-dihalo-1,3-dienes in the presence of Cu-catalyst (Eq. 29). ð29Þ K. Rousée also reported the direct C-H functionalization of hetero azoles by using different gem-bromofluoroalkene compounds [268]. This effective protocol is economically relevant. The C-H functionalization of 5-phenyl-oxazole with (E)-gem-

Scheme 81 Cu-catalyzed C-H functionalization of substituted aryl oxazoles

Cu-Catalyzed C-C Coupling Reactions

331

bromofluoroalkene used (10 mol%) CuI, (20 mol%) dppe, and (3 equiv.) t-BuOLi in dioxane at 110°C. Furthermore, the alternatively phosphorous ligand was used to improve the yield of products. While azole C-H activations were used to accomplish a lot of C-H alkenylations, Charette and co-workers disclosed copper-mediated C2 selective direct alkenylation of pyridines [269]. This protocol describes the reaction of N-iminopyridinium ylides with alkenyl iodides using copper bromide and K2CO3 as weak base in chlorobenzene solvent. After carrying out some control experiments the alkenylation goes through CuI/CuIII catalytic run to obtain the range of yields of products from good to excellent (Eq. 30). ð30Þ

5.2.5

Copper-Catalyzed Synthesis of Aryl–Enes via Decarboxylative Cross-Coupling

L. Liu demonstrated the Cu-mediated alkenylative cross-coupling by decarboxylative potassium polyfluorobenzoates with vinyl bromides and the synthesis of polyfluorostilbene in high yields from potassium polyfluorobenzoate and vinyl bromide in the presence of CuI and phenanthroline (10 mol%) in diglyme at high temperature conditions (Eq. 31) [270].

ð31Þ

5.3

Copper-Catalyzed Synthesis of Allyl–Aryl Bonds

The allylation process is one of the essential and significant transformations in synthetic chemistry and medicinal chemistry, the ally groups can be easily transformed to a variety of functional groups. Numerous types of transition metalcatalyzed systems are used to introduce the allyl groups to aromatic metal complex. In this constant, the Cu-catalyzed allylation or aryl boron coupling partners are highlighted. The M. Sawamura group has demonstrated an effective coppermediated coupling reaction between allylic phosphate and aryl boronates to form the allyl-aryl coupling products through transfer chirality. They first reported crosscoupling between acyclic and cyclic allyl phosphates and boron ester (Eq. 32) [271].

332

M. S. Lokolkar et al.

Scheme 82 Cu-catalyzed selective allylation of aryl boron ester nucleophiles using allylchloride

ð32Þ In the same year, G. Lalic and co-workers reported copper-catalyzed selective allylation of aryl boron ester nucleophiles using allylchloride [272]. Advantageously, they also studied the aryl boron nucleophiles can also be used for the alkenylation as well as alkylation of various allylic compounds. In this methodology, the wide range of substrate scope is tolerated. M. Miura groups disclosed the copper-catalyzed direct C-H functionalization or allylation of arenes compounds using allyl phosphates in 2011 [273]. Furthermore, the stereospecificity of the reaction was also studied. After the screening of different reaction conditions, the allylation of arenes with allyl phosphate used (10 mol%) copper acetylacetonate, (10 mol%) Phen, and base LiOtBu in dioxane solvent at room temperature (Scheme 82). On the other hand, T. Hayashi and co-workers have reported the copper-catalyzed asymmetric allylation of organic boronates [274]. This group also investigated the stereo- and enantioselective synthesis of the products, showing that the selectivity was dependant on the nature of the catalyst, the effect of ligands, and a portion of the ester of the arylboronate. Alkenyl- and heteroarylboronates can also be used to produce high yields of products. Additionally, the potential catalytic cycle for this process was proposed to describe the observed influence of reaction parameters (Eq. 33).

ð33Þ

Recently, M. Sawamura and their co-workers proposed the Cu-mediated enantioselective allylation of azoles by using allylic phosphates in presence of a chiral ligand (N-heterocyclic carbene ligand) [275]. This methodology contains both branches of regioselectivity and enantioselectivity excellently resulting due to the carbon quaternary stereogenic center location in the heteroaromatic ring. The allylic

Cu-Catalyzed C-C Coupling Reactions

333

alkylation process tolerates various azole derivatives containing chiral centers. Some molecules are also synthesized via Sharpless asymmetric epoxidation. The stoichiometric amount of base is used for this catalytic system (Eq. 34).

ð34Þ

5.3.1

Copper-Catalyzed Synthesis of Diynes Through Alkylation of Alkyl Derivatives

Synthesis of diynes is one of the most vital classes in synthetic chemistry because it is not only an essential structural motif in synthetic chemistry but also plays an important role in pharmaceutical chemistry. Therefore, various types of diynes are synthesized by employing transition-metal catalysts. In the last 10 years, the synthesis of C-C or carbon–heteroatom bond used copper salt with or without external ligands. The dimerization of terminal alkyne via direct C-H functionalization was discussed in detail in cross-dehydrogenative coupling section. The copper (I) or copper (II) catalyzed synthesis of diynes having structural units is divided into two classes, which are studied in this chapter.

5.3.2

Copper-Catalyzed Synthesis of Symmetric and Unsymmetric 1,3 Diynes

The copper-catalyzed self and heterocoupling of alkynes is one of the most effective directions for the synthesis of symmetrical and unsymmetrical diynes. Nishihara and co-workers reported the synthesis of symmetrical 1,3 diynes via self-coupling of alkynyl boronates using stoichiometric amounts of Cu(I) or Cu (II)-catalysts with polar aprotic solvent (DMI) in aerobic condition at ambient temperature. The formation of 1,3 diynes using alkynylborates gives an excellent yield of corresponding self-coupled compounds under mild reaction conditions. This method tolerates various functional groups in the absence of additive or moisture-sensitive ligands (Scheme 83) [276]. H. Stefani reported the copper-mediated aerobic dimerization of potassium alkynyltrifluoroborates using a stoichiometric amount of copper salts, under the polar aprotic solvent (DMSO). Both the Cu(I) and Cu (II) salts used with polar solvents are effective for the alkynylative homocoupling of organic borates. The alkynylative homocoupling reaction demonstrates toleration of various substrate scope, which makes this method feasible, cost-effective, and efficient to employ in

334

M. S. Lokolkar et al.

Scheme 83 Coppercatalyzed self-coupling reaction of alkynylboronates

Scheme 84 Alkynylative dimerization from propargyl alcohol under oxidative conditions

industrial processes. They also studied various applications of Cu(OAc)/DMSO catalytic systems to coupling reactions of a variety of alkynyltrifluoroborates [277]. H. Jang and their co-workers demonstrated alkynylative dimerization from propargyl alcohol under oxidative conditions followed by in situ generations of hemiaminal intermediates in 2015 [278]. The aerobic alkynylative homocoupling of aryl propargyl alcohol was developed by using 5 mol% Cu (OAc) and 5 mol% 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) at 100°C for 18 h. However, under the same optimized reaction condition the alkynylation of phenylpropiolaldehyde to gives dimerized phenylacetylene compounds (Scheme 84). N. Jiao group demonstrated the copper-mediated aerobic alkynylative crosscoupled dimerization via decarboxylation of propiolic acids with terminal alkynes. This protocol achieved the Csp-Csp bond formation by decarbonylative crosscoupling to transform 1,3 diynes, CO2 as a by-product generated. This synthetic process is an alternative to the organic halides. Diynes functionality of structural motifs is most important in natural products and biological active compounds. Here the reaction was catalyzed by 10 mol% CuBr, 10 mol% phenanthroline with 2 equiv. base, in polar solvent DMF under air (Scheme 85) [279]. D.-X. Liu et al. disclosed the same as above Cu-catalyzed oxidative decarboxylative self/inter-dimerization of aryl propiolic acids in DMSO. Under this catalytic condition the 1,3 and 1,4 dialkynes are formed without using any ligands. But this methodology worked smoothly with various bearing groups of aryl propylic acids to give good to excellent yields of corresponding products. This approach illustrates various symmetrical as well as unsymmetrical 1,3 diynes in mild reaction conditions. Here the catalytic reaction was carried out in 10 mol%

Cu-Catalyzed C-C Coupling Reactions

335

Scheme 85 Cu-mediated alkynylative dimerization via decarboxylation of propiolic acids with terminal alkynes

Scheme 86 Cu-catalyzed oxidative decarboxylative dimerization of aryl propiolic acids Scheme 87 Dimerization of alkynyl halides with alkynyl oranoboronates using CuFe2O4 catalyst

CuBr with 10 mol%phenanthroline ligands and 2 equiv. triethyl-amine as a base under the aerobic condition at 120°C for 20 h (Scheme 86) [280, 281]. C. Ranu and their co-workers proved an effective dimerization of alkynyl halides with alkynyl oranoboronates using CuFe2O4 catalyst in environment-friendly dimethyl carbonate to transform the unsymmetrical 1, 3 diynes derivatives. This research group also explores the Csp-Csp as well as Csp-Csp2 cross-coupling of alkynyl bromide and alkynyl/alkenyl boronic acids to form 1,3 diynes. This protocol tolerates a variety of aromatic, aliphatic, and hetero alkynes coupled with different organoboronates to give 1,3 diynes/enynes in good to excellent yields (Scheme 87) [282]. In 1998, Y. Nishihara et al. have reported a convenient method for the formation of cross-coupled unsymmetrical 1,3 diynes using alkynylsilanes and 1-chloroalkynes under copper catalyst. Firstly, he investigated the cross-coupling to dimerized alkynyl compounds [283]. After 20 years, A. Mori and T. Hiyama reported practical method for synthesizing diynes by oxidative homocoupling of alkynyltrimethylsilanes with copper(I) salt in DMF. In reaction, the alkynyl group is transmetalated from silicon to copper, via oxidative dimerization to produce the homocoupled diyne. Generally, for the coupling reactions trimethylsilyl groups are

336

M. S. Lokolkar et al.

used as compounds which is alternate to the aryl silicon compounds that need heteroatomic substituent on silicon. The synthesis of cross-coupled reaction of organosilanes was achieved in a one-pot manner, generally, unsymmetric alkynylation organosilane produced by initially cross-coupling reaction of aryl halide and 1-trimethylsilyl ethyne and then desilylation the arylethynyl trimethylsilane and convert it into terminal alkyne [284]. Recently, Q. Miao reported copper-catalyzed synthesized s-heterocycloarenes from phenanthrylene ethynylene macrocycle via oxidative alkynylation of silyl-protected polyne to homocoupling macrocyclic molecule. S-heterocycloarene exhibited p-type semiconductor behavior (Eq. 35) [285].

ð35Þ

Cadiot and Chodkiewicz published the groundbreaking work on the synthesis of unsymmetrical 1,3-diynes in the 1950s by using the reaction of an alkynyl halide with a cuprous acetylide. This cross-coupling reaction also requires a base, often an amine. To reduce cupric ions in the reaction, additive hydroxylamine needed. According to the hypothesized mechanism, the haloalkyne is added oxidatively to Cu(I) to create a Cu(III) intermediate, which is then eliminated reductively to produce 1,3-diyne. Anilkumar and co-workers reported the Cu-catalyzed Cadiot– Chodkiewicz coupling reaction for the synthesis of 1,3-diynes under mild reaction conditions. The protocol involves the coupling of terminal alkynes and alkynyl halide in the presence of CuI as catalyst, K2CO3 as a base in methanol solvent and under aerobic conditions (Scheme 88) [286].

5.3.3

Copper-Catalyzed Synthesis of 1,4 Diynes

In 1965, Cadiot and co-workers demonstrated an effective technique for the synthesis of corresponding 1,4-diyne established by the cross-coupling of a terminal alkyne with a propargyl halide under the influence of copper. But this methodology has limited scope [287]. Linstrumelle group expanded this work by employing various propargylic halides or triplet and terminal alkynes with inorganic base sodium carbonates, tetrabutylammonium in polar aprotic solvents like DMF or MeCN (Scheme 89) [288].

Cu-Catalyzed C-C Coupling Reactions

337

Scheme 88 Plausible mechanism for Cadiot– Chodkiewicz cross-coupling reaction

Scheme 89 Cu-mediated cross-coupling of a terminal alkyne with a propargyl halide

5.3.4

Copper-Catalyzed Synthesis of Dienes via Alkenylation of Alkynyl Derivatives

In 1989, Suzuki and co-workers published the first examples of the copper-mediated direct cross-coupling reaction between terminal and alkynes vinyl halides. It is found that the addition of copper iodide in hexamethylphosphoric triamide solvent is most effective for vinylic halide derivatives. They also utilize other haloalkenes for stereospecific cross-coupling reaction with terminal alkynes under same reaction conditions [69]. There is no polymeric side product formed. Three years later, Miura and co-workers published the cross-coupling reaction of vinyl halides and organic alkynes under copper media to produce conjugated 1,3 enynes in moderate to good yield. For this transformation, the stoichiometric amount of copper iodide, triphenylphosphine as ligand and potassium carbonate as inorganic base were used [70]. Okuro et al. also reported same type of reaction by using copper-catalyzed cross-coupling reaction of electrophilic vinyl iodide and terminal alkyne in polar dioxane solvent to obtain the conjugated 1,3 dienynes in good to excellent yield. Other copper catalysts such as CuI/1,10-phenanthroline, CuI/8-hydroxyquinoline were also good for the cross-coupling reaction to synthesize 1,3 enynes (Scheme 90) [71]. Recently, N. Tsukada and co-workers disclosed new catalytic approach for the synthesis of 1,3 dienyne from terminal alkyne and allyl, benzyl, and aryl halides. The synthesis of dinuclear Cu complex was characterized by X-ray analysis and both copper atoms bridged by amidinates and oxo or hydroxo ligands. This dinuclear copper-catalyzed system is used to accomplish cross-coupling reaction between allyl

338

M. S. Lokolkar et al.

Scheme 90 Coppermediated alkenylation of terminal alkynes

halides with terminal alkyne in the presence of additive tetraalkylammonium salts (Eq. 36). ð36Þ More recently, W. Li et al. have developed copper-catalyzed cross intramolecular Castro-Stephens coupling of vinyl iodide with terminal alkyne. The synthesis of conjugated E, Z-diene macrocycle was obtained, by the in situ semireduction of intermediate enyne. Stereoselectivity of macrocycle was dependent upon ring strain, numerous macrocyclic compounds with various ring sizes and functions were created. In this methodology a variety of macrocycles using Cu(OAc)2 (0.33 equiv), rac-BINAP base (1.5 equiv), and HCOONa (4 equiv) were used (Eq. 37) [289]. ð37Þ D. Venkataraman and co-workers proposed copper-catalyzed synthesis of 1,3 dienynes using vinyl iodide and acetylene. Different types of copper complex have been used to study the variety of 1,3-enynes, for the trans vinyl halides they use [Cu (phen)(PPh3)2]NO3 as a catalyst with base cesium carbonate, while most of other vinyl halides they use [Cu(bipy)-PPh3Br] as the catalyst and potassium carbonate as a base. One of the significant advantages of this catalytic system is the retained stereochemistry of alkene conformation. This catalytic system tolerates a wide variety of substrates to transform the corresponding desired 1,3-enynes in excellent yields (Scheme 91) [290]. A similar type of copper-catalyzed cross-coupling reactions was done by using Stille-type and Suzuki-type cross-coupling reaction also demonstrated 1,3-enynes. K. Zine et al. disclosed the alternative approach for the Pd-catalyzed dienynes formation. The copper catalysed cross-coupling reaction of organostannanes with alkynyl bromides was proposed under mild reaction condition. This catalytic process provides easy to access to various 2,3-enynoate containing trifluoromethyl groups with retention stereoselectivity to give excellent yields of corresponding compounds. They explore a cross-coupling reaction of vinylstannane with terminal alkyne

Cu-Catalyzed C-C Coupling Reactions

339

Scheme 91 Coppercatalyzed synthesis of 1,3-enynes

Scheme 92 CuI-mediated coupling of vinyltin with alkynyl bromide

bromides using 10 mol% CuI, the retention of stereoselectivity of double bond indicates the formation of copper intermediate after the transmetalation of vinyltin. In this context, the Suzuki–Miyaura-type cross-coupling reaction has also been examined (Scheme 92) [209].

6 Copper-Catalyzed Oxidative Cross-Coupling Reaction Between Two Nucleophiles for C-C Bond Formation Traditional cross-coupling reactions for C-C bond formation based on the construction process between electrophiles and nucleophiles have long been discovered. As a result, developing a cross-coupling reaction between two different nucleophiles appears to be another challenging method [291]. Molecular oxygen is atom-efficient, environment-friendly, and easily available, making it ideal oxidant. On the other hand, organocopper in the modern era has received much attention since copper is affordable and relatively less toxic than expensive heavy metals. The chemistry of copper catalysis expands with molecular oxygen because oxygen can serve as an electron sink (oxidase activity). Oxidation of copper using oxygen is a simple process that allows to increase the catalytic activity in net oxidative processes and it can access the higher oxidation states of Cu, enabling a variety of prevailing transformations [292].

340

6.1

M. S. Lokolkar et al.

Oxidative Cross-Coupling of Aryl Boronic Acids with Hydrocarbons/Nucleophiles

In this context, Demir and group published the first methodology for oxidative dimerization of aryl boronic acid in 2003 [175]. Here, homocoupling of arylsubstituted boronic acid with Cu(OAc)2 in DMF as solvent performed admirably. However, this developed transformation offers good results for certain substrates, it is sensitive to steric factors around the active site (Eq. 38).

ð38Þ Internal alkynes as intermediates are a useful building block for biologically active natural products [293, 294] and materials like polymers and liquid crystals [295–297]. The well-known Sonogashira-type cross-coupling reactions are a traditional technique for constructing C(sp)-C(sp2) bonds between aryl boronic acids and aryl halides with terminal alkynes by using palladium and/or copper catalyst [298, 299]. In 2010, Fu’s group developed Cu2O-catalyzed Sonogashira-type cross-coupling reaction. Cross-coupling was carried out between aryl boronic acid and terminal alkyne using molecular oxygen as an oxidant under mild reaction conditions, in pyridine and methanol-containing media [300]. The coupling protocol tolerates different substituents containing nitro, ether, aldehyde, substitution on aryl boronic acids, as well as hydroxy, esters, amino groups in terminal alkynes. The developed methodology generated well to excellent yields of corresponding internal alkyne (Scheme 93). Yasukawa and co-workers reported low copper catalyst loading (0.15–3 mol%) and oxidative cross-coupling of boronic acids with alkynes in methanol and 2,6-lutidine media [301]. Various copper salts were screened in the presence of 2,6-lutidine. Cu(II) salt also screened for this reaction; however, the yield was reduced as compared to Cu(I) salt. Cuprous oxide also employed for this reaction, but it was not completely dissolved, affording a 35% yield of diphenylacetylene. Phenylacetylenes with ortho-, meta-, and para-substitution afforded good yields of corresponding products. Electron-deactivating groups attached to aromatic and aliphatic alkynes gave moderate yields (Scheme 94).

Scheme 93 Cu-catalyzed oxidative couplings of aryl boronic acids with terminal alkynes

Cu-Catalyzed C-C Coupling Reactions

341

Scheme 94 Cu-catalyzed oxidative couplings of terminal alkynes with aryl boronic acids

Scheme 95 Cross-coupling of aryl boronic acids with arenes

Oxidative functionalization of arenes occurs in certain cases, where arene acts as a nucleophile. In this regard, Ban and co-workers developed Cu-mediated coupling of nucleophilic arenes with aryl boronic acids [159]. Under the influence of Cu (OCOCF3)2-catalyst, the authors found that the reaction is selective for crosscoupling. However, no homocoupled products were observed for both arene and boronic acid substrates. The C-H arylation of boronic acid derivatives having electron-rich and electron-deficient substituents afforded good yields of the products. Besides, multiple C-H arylations are possible for nitrogen heterocycles (Scheme 95). Gui et al. employed Cu/DMSO as catalyst for ortho selective C-H arylation of benzamide derivatives with aryl boronic acids [302]. Various boronic acid derivatives were examined under the optimized reaction conditions. The substrates containing both electron-deficient and electron-rich groups were well tolerated, afforded the coupling products at 68–81% and 82–95%, respectively (Scheme 96). Interestingly, Wang et al. established copper(II)-mediated oxidative coupling reaction between organoboronic acids and arenes C-H bond for functionalizing azacalixaromatics [303]. The discovered methodology involves Cu (ClO4)26H2O-catalyzed oxidative coupling of aryl, alkenyl, and alkyl boronic acids with arene C-H bond of macrocyclic azacalix[1]arene[3]pyridines. The reaction was carried out smoothly with optimized reaction conditions, the various functional groups were tolerated affording good to excellent yields of desired products. The involvement of arylcopper(II) rather than arylcopper(III) species in catalysis was confirmed by using stoichiometric reactions with aryl boronic acids. Two years later, in 2018, the same group described Cu(II)-catalyzed mechanistic

342

M. S. Lokolkar et al.

Scheme 96 Cu-mediated ortho-arylation of various aromatic amides

Scheme 97 Oxidative cross-coupling between arene C-H bond and boronic acids

Scheme 98 Oxidative cross-coupling of aryl boronic acids with potassium alkyl trifluoroborates

study on cross-coupling of arenes with boronic acids under aerobic conditions [304]. The experimental and computational investigation of the reaction mechanism of copper catalysis was reported (Scheme 97). Oxidative C(sp2)-C(sp3) cross-coupling between aryl boronic acids and potassium alkyl trifluoroborates involving single-electron transmetalation was described by Ding and co-workers [305]. This strategy circumvents the issues associated with the classical cross-coupling reactions of alkyl boronates and offers a complementary way for formation of C(sp2)-C(sp3) bonds. Under mild reaction conditions using copper(II) acetate and silver oxide (oxidant), a variety of boronic acid derivatives and primary and secondary potassium alkyl trifluoroborates were screened; here, decent yields were obtained (Scheme 98).

Cu-Catalyzed C-C Coupling Reactions

6.2

343

Copper-Catalyzed Oxidative Decarboxylative Cross-Coupling for C-C Formation

Carboxylic acids are readily available, simple to store and handle, and they can serve as leaving group in cross-coupling reactions. Thus, utilizing carboxylic acids to realize functionalization reactions is a good synthesis strategy. The decarboxylation of benzoic acid derivatives promoted by transition metal was first observed in 1930 [306]. When Shepard and co-workers noted in the presence of copper, furan-2carboxylic acid derivatives were more susceptible to protodecarboxylation than upon heating alone. During the 1970s the groups of Nilsson, Sheppard, and Cohenmade made a remarkable evolution in protodecarboxylation [307– 309]. Until 2002 the field remained relatively unexplored. Then Myers et al. displayed Heck-type decarboxylative coupling between olefins and benzoic acid derivatives catalyzed by palladium and a stoichiometric amount of silver salt additive (Eq. 39). Recently, we developed a Xantphos-coordinated palladium dithiolates complex for cross-coupling reactions. The efficiency of this palladium-complex was described for decarboxylative Sonogashira reaction [310, 311].

ð39Þ In 2007, Gooßen and co-workers developed copper-catalyzed protodecarboxylation [24]. Various copper salts were screened for this transformation, halide-free species gave the best results, indicates the counter-ion must not be too strongly coordinating. On the other hand, a combination of NMP and quinoline is more effective. Using Cu2O as a catalyst with 1,10-phenanthroline as a ligand afforded good decarboxylated yields (Scheme 99). Shang and co-workers displayed copper catalyzes the decarboxylative crosscoupling of potassium polyfluorobenzoates with aryl bromides and iodides [312]. They suggested the reaction pathway based on DFT calculations where the initially produced copper(II) carboxylates exclude CO2 with the formation of polyfluorophenylcopper(I) species under oxidative addition/reductive elimination sequentially with aryl halides yielding the unsymmetrical biaryls (Eq. 40).

Scheme 99 Coppercatalyzed protodecarboxyation

344

M. S. Lokolkar et al.

ð40Þ

For decarboxylative cross-coupling, not only arenes and heteroarenes but also alkynes as a substrate of carboxylic acid have successfully been used. Thus, the decarboxylative cross-coupling of propiolic acids and terminal alkynes for the synthesis of unsymmetric diynes using copper as a catalyst was established by Jiao et al. [279]. In this approach decarboxylative sp-sp bond formation takes place and carbon dioxide produced as a by-product (Eq. 41).

ð41Þ Marder and co-workers reported copper-catalyzed cross-coupling between terminal alkynes and electron-deficient polyfluorophenylboronate esters. The reaction promoted by using Cu(OAc)2 as catalyst, phenanthroline as ligand, Ag2O as oxidant. The reaction tolerates broad functional groups by affording products in encouraging yields of alkynyl(fluoro)arene (Eq. 42) [313].

ð42Þ On the other hand, the CuI-catalyzed cross-coupling of aryl halides and alkynyl carboxylic acids was demonstrated by Zhao et al. with optimized reaction conditions CuI (10 mol%), 1,10-phenanthroline (10 mol%), in the presence of Cs2CO3, at 130° C, the aryl iodides and alkynyl carboxylic acids with electron-rich, electron-poor, or sterically bulky, all of them afforded good to excellent yields [246]. The authors expanded the scope of this developed methodology for preparing benzofurans directly from 2-iodophenols by the sequential one-pot reaction. The reaction involves decarboxylative coupling and subsequent intramolecular hydroalkoxylation to yield benzofuran moieties with good yields (Eq. 43).

ð43Þ

Most recently, copper-mediated coupling of pyrazolones and 3-indoleacetic acids has been developed by Wen et al. [314]. The developed protocol involves direct functionalization of pyrazolones with decarboxylative coupling of 3-indoleacetic acids with 2 equiv. of Cu(OAc)2H2O acts as both catalyst and an oxidant in DMF at

Cu-Catalyzed C-C Coupling Reactions

345

Scheme 100 Decarboxylative coupling of 3-indoleacetic acids with pyrazolones

Scheme 101 Cu-catalyzed C-3 functionalization of imidazo[1,2-a]pyridines

90°C under an inert atmosphere which afforded the corresponding product (Scheme 100). The substrates having EDG (CH3, OCH3, OBn), weak EWG (Br, F, Cl), and strong electron-withdrawing group (NO2) at the 5th-position of 3-indoleacetic acids are suitable and produced the yields in 65–97%. Subsequently, the substrate screening for pyrazolones with substituents (CH3, OCH3, F, Cl, Br, CN, SO2Me) at the para-position of the phenyl ring afforded moderate to good yields. Wu and co-workers investigated Cu-catalyzed aerobic oxidative decarboxylative C-3 functionalization of imidazo[1,2-a]pyridines with 3-indoleacetic acids [315]. The developed protocol provides a series of 3-(1H-indol-3-ylmethyl)imidazo[1,2-a]pyridines good yields. In addition, some derived products exhibited potent antiproliferative activity in cancer cell lines (Scheme 101).

346

M. S. Lokolkar et al.

7 Copper-Catalyzed Cross-Dehydrogenative Coupling (CDC) for C-C Bond Formation The selective formation of novel C-C and C-heteroatom bonds through transition metals as catalysts has proven to be a handy and integral tool for the scientific community. The easily predicted regioselectivity of the C-C or C-heteroatom bond formation is one of the reasons for the coupling reactions’ great success [316]. Transition-metal catalysts, notably those from group VIII-X metals, exhibit great efficiency in achieving these transformations through reactions between nucleophiles and electrophilic partners. Nowadays, the focus of the scientific community has shifted toward first row transition metals, which offer competitive performance, albeit at harsh reaction conditions, compared to expensive and hard-to-acquire noble transition metals. Lately, the emergence of copper-catalyzed cross-coupling is undergoing tremendous growth [317]. In 1869, copper-driven coupling processes were firstly reported by Glaser through homocoupling of metallic acetylides. Glaser elaborated on the aerobic dimerization of copper and silver phenylacetylide to yield diphenyl diacetylene [318]. The new C(sp)-C(sp) bond formation was applied heavily during the following decades by the synthetic community for the synthesis of valuable acetylenic compounds (Eq. 44) [319]. ð44Þ Impressively, in 1882, by using the Glaser coupling, Scientist Baeyer reported the indigo synthesis (Scheme 102) [320]. Later, Rosenmund and Struck developed the synthesis of benzoic acid using copper(I) cyanide in combination with potassium cyanide [321]. Then copper (I) thiocyanate was used in pyridine to prepare aryl thiocyanate from aryl bromides, yielded the nitrile products at 180°C. Many chemists pursued the development of this reaction simultaneously [237]. In 1929, Hurtley, influenced by this work, reported copper-catalyzed C-arylation of some CH-acids with o-bromobenzoic acid with sodium ethoxide at reflux condition (Eq. 45) [322].

Scheme 102 Baeyer’s synthesis of indigo

Cu-Catalyzed C-C Coupling Reactions

347

ð45Þ In the mid-twentieth century, multiple Pd-catalyzed cross-coupling reactions emerged such as Sonogashira, Suzuki, Stille, Negishi, Hiyama, and Heck coupling. For the Sonogashira and Stille reactions, copper was only used as a cocatalyst. Over the past two decades, several modified versions of cross-coupling reactions have been discovered. The use of pre-functionalized arenes sought to be a significant drawback of this methodology. In this context, direct C–H functionalization by connecting two fragments through a dehydrogenation pathway is an ideal, straightforward, and atom-economical approach to cross-coupling and has emerged as an efficient tool in constructing C-C bonds. Direct C–H functionalization omits the use of pre-functionalized arenes, thus reflecting its superiority over traditional crosscoupling strategies. On the other hand, using expensive, low-abundance 4d and 5d transition metals for organic synthesis is almost inevitable, and they are in high demand. This will be a cause of concern; hence, it is essential to develop methods based on 3d transition metals, which are widely present in the earth’s crust. In particular, the carbon–carbon bond formation via the cross-dehydrogenative coupling process has attracted much attention because it generally increases the overall efficiency and improves atom economy. The construction of C-C bonds without prefunctionalization from only C-H bonds can be achieved back almost 150 years ago when Glaser reported the homocoupling of terminal alkyne through oxidative dimerization using a stoichiometric amount of copper as an oxidant (Eq. 44).

7.1

Cross-Dehydrogenative C(sp3)-C(sp) Bond Formation (Alkynylation)

Alkynylation, or the synthesis of alkynes, has long been a central concern in organic synthesis [323]. Alkynes are often employed in synthetic chemistry, biology, and materials research and are among the most fundamentally significant organic molecules. Therefore, a key concern in organic synthesis has been developing an effective and sustainable method to manufacture alkynes. Cross-dehydrogenative coupling is one of the simplest ways for C-C coupling by utilizing C(sp3)-H and C (sp)-H bonds of two different molecules to avoid the necessity of prefunctionalization of starting materials. In 2004, Li and co-workers described the first catalytic alkynylation reaction to synthesize propargylic amines [324]. Leonard and Murahashi described the direct C-H bond activation adjacent to nitrogen atom from amines to provide iminium ions through SET process or by using transition metals [325, 326]. The cross-coupling was carried out for the N,N-dimethylaniline with phenylacetylene as starting material and copper salts as catalyst with TBHP as oxidant. With the optimal reaction conditions, it was found that when using CuBr as

348

M. S. Lokolkar et al.

the catalyst and TBHP as the oxidant, the reaction could give the tertiary amine alkynylated products with good yields at 100°C while still being able to react with less reactive aliphatic-terminal alkynes. Under the oxidation of copper catalyst and peroxide, the tertiary amine readily generates copper-coordinated iminium intermediates; at the same time, copper can activate the terminal alkynes to form copper intermediates to enhance their nucleophilicity, and the intermediates undergo nucleophilic addition to the former to give the alkynylated products, with the copper catalyst being regenerated for the next catalytic cycle (Eq. 46).

ð46Þ

In the same year (2004), the authors demonstrated an enantioselective CDC of tetrahydroisoquinolines with alkynes; they put in much effort to achieve the enantioselective alkynylation of prochiral C(sp3)-H bonds adjacent to a nitrogen atom. The chiral tetrahydroisoquinoline derivatives, which are essential structural natural products, and pharmaceuticals, were obtained by the asymmetric method. For asymmetric Cu-mediated CDC reaction, a wide range of ligands were chosen based on prior literature and tested with copper-catalyzed reactions. Cu(I) and Cu (II) salts influence the reactions, in which the combination of copper(I) triflate and phenyl bisoxazoline ligand provided highest ee selectivity with enantioenriched products in the low to moderate ee (5–74%) range as shown (Eq. 47) [327].

ð47Þ

Later, Su’s group demonstrated alkynylation of tetrahydroisoquinolines with oxidant DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) in high-speed ball-milling process [328]. Using copper rather than stainless steel balls at 30 Hz results in 78% of alkynylated product in 20 min. The reaction went well with wide range of alkynes, preferably aromatic substrates (Scheme 103). In 2008, Zhao developed an NBS-driven copper(I) catalyst for reacting C(sp3)-H adjacent to nitrogen with C(sp)-H bonds to form propargyl amines, only applicable to 3̊ aliphatic amines [329]. The authors investigated a variety of copper(I) and (II) salts to catalyze the coupling, out of which copper(I) bromide showed the best catalytic performance. Different catalytic loadings were tested with 40 mol% of the “catalyst” showing improved yields (52%) and shorter reaction times were obtained. Steric factor resulted in reduced product yield for tertiary amines with bulky

Cu-Catalyzed C-C Coupling Reactions

349

Scheme 103 C(sp3)-H & C(sp)-H alkynation under ball-milling condition

Scheme 104 Cu-catalyzed coupling of N, N-dimethylbenzylamine with phenylacetylene

substituents. The developed alkylation is selective toward the N-methyl substituents than the benzylic carbon. Steric effects resulted in alkylation of just tertiary amines. Aromatic alkynes performed better compared to aliphatic ones (Eq. 48).

ð48Þ

Recently Jain and colleagues demonstrated C(sp3)-C(sp) bond formation using [Cu] complexes with acridine-based ligands [330]. They synthesized propargylamine derivatives using Cu-pincer complex and oxidant TBHP involving tertiary amines and terminal alkynes. The reaction of widely substituted benzylamine and alkyne substrates including electron-donating and halo-substituted substrates gave decent to appreciable yields. The catalyst recyclability was tested with encouraging results, making these complexes an attractive process with promising industrial potential (Scheme 104). Li’s group pioneered the CDC process in the form of cross-dehydrogenative alkynylation process (Eq. 49) [331]. At room temperature, CuBr, in combination with TBHP, catalyzes the reaction. Various protected glycine derivatives showed successful conversion paired with aromatic alkynes. However, steric hinderance was

350

M. S. Lokolkar et al.

observed with the bulky aromatic alkynes, exhibiting low yields. Furthermore, the process was shown to convert secondary and tertiary amides in high yields. This scheme was also shown to functionalize simple peptides. The parameters were re-optimized for dipeptide coupling, and alkynylation occurred regiospecifically at the protected glycine site in DCE at 70°C in inert conditions with product yields up to 63% yield.

ð49Þ

In 2018, Yang and co-workers showcased the Cu-catalyzed crossdehydrogenative coupling of 2H-chromenes and terminal alkynes with ethanol as an additive, DDQ as oxidant. This conversion is intriguing as the involvement of the copper site in the redox step is non-existent. The first step involved formation of the 2H-chromene acetal, followed by oxidation of 2H-chromene with DDQ with ethanol acting as a nucleophile to attack the oxocarbenium intermediate. The coppercatalyzed alkynylation of the 2H-chromene acetal is completed in the final step. Here, different aryl acetylenes substrates were well tolerated and afforded excellent yields (Eq. 50) [332].

ð50Þ Under CDC conditions, Almasalma and Meija reported alkynylation of allylic compounds with terminal alkynes. The tridentate pyridine ligand proved to be critical in controlling the selectivity of desired product over additional by-products. Cyclic alkenes and linear aliphatic alkenes proved to be good substrates, which produced linear products. Furthermore, kinetic isotopic studies revealed that the cleavage of alkene C-H bond is vital in the rate-determining step (Eq. 51) [104].

ð51Þ

One year later, Meija et al. achieved the room-temperature allylic alkynylation of cyclic alkenes by exploiting Cu-(I) terpyridyl complex, which was applied as a cross-dehydrogenative coupling catalyst for the synthesis of substituted 1,4-enynes [105]. Under the similar reaction conditions, using TBHP (tert-butyl hydroperoxide) as oxidant instead of DTBP in acetonitrile solvent, and light as an energy source for the reaction. Terminal alkynes bearing electron-donating substituents

Cu-Catalyzed C-C Coupling Reactions

351

Scheme 105 Copper-photocatalyzed allylic C-H alkynylation

(1-ethynyl4-methoxy-2-methylbenzene) gave higher yields at 90%, where the electron-deficient substituent (1-ethynyl-4-fluorobenzene) gave lower yields at 44% (Scheme 105). The alkynylation of benzylic C(sp3)-H bonds with no adjacent heteroatoms was reported by Li and co-workers [333]. Several alkynes and diphenylmethane derivatives have been successfully coupled, using CuOTf toluene complex with DDQ (Eq. 52). Aromatic alkynes showed smooth conversion with electron-rich substrates exhibiting better yields. The authors explained this observation by citing the substrates’ nucleophilicity. However, this method could not convert aliphatic alkynes (for example, n-hexyne). The authors proposed a mechanism involving the formation of radical intermediates. DDQ acting as a radical initiator, a benzylic cation is formed via two successive SET process. The resulting hydroquinone then accepts the acidic proton of the alkyne to create the copper acetylide, coupling with benzylic cation to form the product.

ð52Þ

Shaikh et al. explored C(sp3)-H of 4-thiazolidinone alkynylation with terminal alkynes by cross-dehydrogenative coupling reaction. The reaction involves coupling C(sp3) adjacent to the sulfur of 4-thiazolidinone with C(sp) of terminal alkyne under CDC strategy using CuBr and TBHP. The 4-thiazolidinone showed decent tolerance for substituent-based electronic effects (Eq. 53) [334].

ð53Þ

352

7.2

M. S. Lokolkar et al.

Cross-Dehydrogenative C(sp3)-C(sp2) Bond Formation (Arylation)

The formation of a Csp3-Csp2 bond in organic synthesis is of great value. Despite the success of traditional cross-coupling reactions, the cross-dehydrogenative coupling between inert C(sp3)-H and C(sp2)-H bonds constitutes an adequate substitute for new C(sp3)-C(sp2) bonds. Friedel-Crafts alkylation reaction is one of the most essential processes, which includes the classical electrophilic substitution reaction of aromatic compounds (SAr2). Li and his colleagues used copper bromide as a catalyst for the Friedel-Crafts-type cross-dehydrogenative coupling reaction of the nitrogen atom in the α-position of tetrahydroisoquinolines with indoles in the presence of TBHP as an oxidant to afford the indole alkylation product [335] (Eq. 54).

ð54Þ

After the successful development of Friedel-Crafts-type alkylation with indoles, Li’s group moved toward investigating this developed strategy. They found that tetrahydroisoquinolines could undergo CDC with naphthols in the presence of a copper catalyst. For the Friedel–Crafts reaction, naphthols are less reactive than indoles, but due to a reactive hydroxyl group, the reaction produced both homo and cross-coupled products [336]. Self-coupled by-products were reduced after optimized reaction conditions, and the CDC alkylation product of naphthol was obtained in good yield. Next, they combined the CDC strategy using tetrahydroisoquinoline with olefins or acrylates in the presence of TBHP and DABCO as catalysts to afford the final alkenylated products (Eq. 55).

ð55Þ

Chandrasekharam and co-workers achieved a one-step α-functionalization of tetrahydroquinoline under mild conditions [337]. In an aqueous and open-air medium, the direct oxidative copper-catalyzed dehydrogenative cross C(sp3)-C (sp2) couplings of tetrahydroquinolines and indoles were carried out to produce the coupling product (Scheme 106). Zhang and co-workers reported Cu(OTf)2-catalyzed dehydrogenative crosscoupling reactions of N-para-tolylamides for the synthesis of 4H-3,1-benzoxazine through the N-para-tolylamides intermolecular C-H coupling between benzylic

Cu-Catalyzed C-C Coupling Reactions

353

Scheme 106 CDC of C(sp3)-H of tetrahydroquinoline and C(sp2)-H of indoles

methyl C(sp3)-H and aromatic C(sp2)-H bond [338]. The catalytic amount of H2O played an essential role in the in situ formation of the copper hydroxy complex. Therefore, 0.1 equivalent of H2O was used for this intramolecular annulation. Other copper salts were also examined for this coupling, where CuF2 and CuI were less effective and gave 43% and 27% yield of 4H-3,1-benzoxazine, respectively. The products containing different substituents could be obtained in good to high yields (Eq. 56).

ð56Þ

Mukhopadhyay et al. developed a novel and convenient strategy for synthesizing 3-hydroxy-2-pyrrolidinone derivatives featuring regioselective C-C coupling. The Cu-catalyzed CDC involves enamino-ketones of benzyl amines and dialkyl acetylenedicarboxylate (DMAD), followed by cyclization by primary amines to afford the corresponding product (Scheme 6). The reaction was also carried out at a gram-scale level using 3-(benzylamino)cyclohex-2-enone, DMAD, and 3-methyl aniline, resulting in a 69% yield (Scheme 107) [339]. In 2020, Zhao and co-workers showcased copper/silver cocatalyzed crossdehydrogenative coupling to achieve remote C5-H of 8 aminoquinoline amides with methylenic C(sp3)-H bond of 1,3-dicarbonyl compounds under mild conditions [340]. Preliminary experiments revealed that free radicals might be involved in this catalytic transformation. Further investigation revealed that MeCN: H2O (1:1 v/v) mixed solvent system afforded the corresponding product. Initially, N-(quinolin-8yl)pivalamide, 2,4-pentanedione, potassium persulfate (1.5 equiv.) as the oxidant, silver acetate (10 mol%) as the catalyst in DCE (1 ml) was chosen as model reaction conditions but resulted in the formation of low yield (10%). As from previously reported C5-H bond functionalization of 8-aminoquinoline amides, the catalytic amount of copper salts was investigated. Surprisingly yields were improved to 35% with 10 mol% of Cu(OTf)2. Then by adjusting the amount of oxidant

354

M. S. Lokolkar et al.

Scheme 107 Synthesis of 3-hydroxy-2-pyrrolidinones via regioselective C-(sp3)-C(sp2)

K2S2O8, the isolated yield of desired product was increased to 62%. With the optimized reaction conditions, different quinoline amides were screened to examine the effectiveness of the reaction with various 1,3-dicarbonyl compounds. Here, moderate to good yields were obtained (Eq. 57).

ð57Þ

Zhu et al. described Cu-mediated CDC reaction of N-arylglycine esters with imidazo[1,2-a]pyridines [341]. For this coupling reaction, N-(4-methyl phenyl)glycine ethyl ester and 2-phenylimidazo[1,2-a]pyridine were chosen as a model substrate with catalytic amount of Cu(OTf)2 (10 mol%) in MeCN in air, exhibiting desired products in decent yields. With the optimized condition, Arylimidazo[1,2-a] pyridine and N-arylglycine substrates showed good yields for both substitutionbased electronic effects. However, the stronger electron-withdrawing groups on the N-phenyl ring of N-arylglycine esters resulted in no reaction (Scheme 108). The reaction pathway reveals that the oxidation of N-arylglycine ester via single-electron transfer (SET) by two molecules of Cu(OTf)2, imine intermediate, and Cu(OTf) is generated within the reaction. Concurrently, molecular oxygen oxidizes the Cu(OTf) to Cu(OTf)2. Further the intermediate reacts with 2-phenylimidazo[1,2-a]pyridine to provide the desired product. Interestingly, Zhu et al. have established a mild and convenient visible-lightdriven CDC reaction between imidazo[1,2-a]pyridines and N-arylglycine esters to afford α-heteroaryl substituted α-amino acid products. The light promoted CDC reaction proceeds with the presence of Cu(II)salt as catalyst under room temperature in acetonitrile solvent medium, resulting in good to excellent yields of the corresponding product. Evaluation of the substrate screening shows that the process for 2-arylimidazo[1,2-a]pyridines for both electron-rich or electron-deficient

Cu-Catalyzed C-C Coupling Reactions

355

Scheme 108 Cu-catalyzed reaction of N-arylglycine esters and 2-arylimidazo[1,2-a]pyridines

Scheme 109 Visible-light promoted CDC for C(sp3)-C(sp2) formation

substituents is very efficient and provides the coupled products with good yields. The substituted electron-donating substituent at m- or p- position of the N-benzene ring of the N-arylglycine ester gave the products good to excellent yields (Scheme 109) [342]. The ideal strategy for cross-dehydrogenative C(sp3)-C(sp2) construction was developed by Yu et al. [343], inspired by Mannich reaction. Here, the authors developed Cu(II)/phenanthroline complex-catalyzed selective orthoaminomethylation of phenols with N-methyl aniline derivatives through direct intramolecular CDC. The proposed radical mechanism involves the generation of tert-butoxy radical through SET from Cu(II) and DTBP oxidant. Further this radical removes a hydrogen radical from phenol or N-methyl aniline. Copper phenolate intermediates would eventually form within the metal coordination sphere and undergo ortho-C-C coupling with a methyl aniline radical. The reaction was also found to be scalable up to the gram level (Eq. 58).

356

M. S. Lokolkar et al.

ð58Þ Baruah and colleagues reported one-pot coupling of C(sp3)-N and C(sp3)-C(sp2) bonds for the multicomponent synthesis of 1,3-oxazines by using methanol as one-carbon source. The protocol utilizes methanol as solvent as well as a methylene carbon source for the oxazine ring formation, to circumventing the use of carcinogenic formaldehyde. For this reaction Cu(II) salt was applied as catalyst and in the presence of TBHP as an oxidant under room temperature (Eq. 59) [344].

ð59Þ

Ding and co-workers demonstrated oxidative vinylic Cβ-H bond functionalization of enamides by using cupric oxide as the catalyst. Under standard reaction conditions, acyclic and cyclic enamides were screened with cyclic ethers providing corresponding multi-substituted alkene products with good yields. Radical-trapping experiments with the scavenger TEMPO completely inhibited the CDC reaction and resulting only TEMPO adducts of the ether substrate. Thus, the involvement of Cu (II) and Cur(III) was proposed by a radical mechanism (Eq. 60) [345].

ð60Þ Cu-catalyzed C(sp3)-H arylation or the construction of C(sp3)-C(sp2) bond by CDC of benzofuranones with heteroaryl, quinolines, indoles, carbazoles, and thiophene was demonstrated by Tang et al. [346]. Here, the authors demonstrated the first example of a Cu-mediated cross-dehydrogenative coupling reaction for constructing triaryl quaternary carbon centers via intermolecular arylation with various heteroarenes. The reaction was conducted in acetonitrile using CuBr as the catalyst, K2S2O8 as an oxidant, base KH2PO4 and reacted at 80°C for 12 h under an N2 atmosphere. With the enormous range of substrate scope, the developed protocol offered moderate to good yield (Scheme 110). In 2020, Xie et al. established Cu-catalyzed cross-dehydrogenative coupling of polyfluoroarenes with alkanes under mild conditions [347]. The relatively weak sp3 C-H bonds in the benzyl or allyl positions and unactivated hydrocarbons could be alkylated by newly developed catalytic system. Under mild reaction conditions CuBr SMe2 (10 mol%), Ligand (15 mol%) DTBP (4 equiv.), tBuONa (80 mol%), C6H6 at 60–80°C for 24 h afforded moderate to high yields (Scheme 111). They provided possible mechanistic pathways and computational studies for this C(sp3)-C(sp2)

Cu-Catalyzed C-C Coupling Reactions

357

Scheme 110 CDC of tertiary C(sp3)-H bonds with heteroaryl C(sp2)–H

Scheme 111 Cu-mediated C-H alkylation of polyfluoroarenes

coupling. The substrate scope indicated that the developed methodology applies to various hydrocarbons and polyfluoroarenes. Zhou et al. reported C(sp3)-H arylation via CDC of N-heteroaromatics with hydrogen donor for the construction of the C(sp2)-C(sp3) bond [348]. Various alkanes and ethers reacted with isoquinoline, quinolines, benzoxazole, pyridines, and benzothiazole to give the C(sp2)–H alkylation products. The reaction was carried out using (5 mol%) CuBr catalyst, H2SO4 (1 equiv.), Selectfluor (2 equiv.), in MeCN at 50°C for 4 h. The coupling reaction of quinoline and cyclohexane afforded the coupling products in excellent yields (Scheme 112). Additionally, they also proposed the coupling of ether instead of cyclohexane resulting the desired product in good yields. For this method, they used TfOH (1 equiv.) as an additive. Next, the reaction was carried out with substituted quinolines, isoquinolines or pyridines, and cyclic ethers using CuBr (5 mol%), Selectfluor (2 equiv.), TfOH

358

M. S. Lokolkar et al.

Scheme 112 Cu-catalyzed C(sp3)-H arylation of Nheteroaromatics

(1 equiv.) in MeCN at 50°C for 4 h. For this reaction, various substitutions on quinoline afforded products with good yields. Most recently, in 2022, Alkylpolyfluoroarylation of styrene by copper-catalyzed C(sp3)–H and C(sp2)–H double activation was achieved by Zheng et al. [349]. The developed method provides a regioselective route to highly functionalized polyfluoroaryl compounds. According to mechanistic studies, the copper intermediate and the carbon-based radicals are involved in the reaction. The reaction tolerates broad substrate scope and the gram-scale experiment also presented for this reaction (Eq. 61). ð61Þ

7.3

Cross-Dehydrogenative C(sp3)-C(sp3) Bond Formation (Alkylation)

After the success of the cross-dehydrogenative C(sp3)-C(sp) and C(sp3)-C(sp2) coupling, we are now focusing on the CDC of C(sp3)-C(sp3) bonds. Li’s group first reported the CDC-type aza-Henry reaction in 2005 [350]. The reaction of different tertiary amines and nitroalkanes as the two coupling partners utilizes cuprous bromide catalyst and TBHP oxidant as catalytic system to result desired products in good yields. The Csp3-H bond at the nitrogen atom’s α-position coupled with the Csp3-H bond at the nitro group’s α-position. The authors then screened different tertiary amines (tetrahydroisoquinoline and N, N-dimethyl aniline) for reaction coupling with nitromethane and nitroethane to yield the expected products in 30–75% yields (Eq. 62).

Cu-Catalyzed C-C Coupling Reactions

359

ð62Þ

By extending the CDC reaction to Mannich-type-reaction, Li and co-workers successfully developed the first cross-dehydrogenative Mannich-type reaction to synthesize β-carbonylamines by coupling tetrahydroisoquinoline with malonic acid esters. For this transformation, 5 mol% CuBr as catalyst and 1 equivalent of TBHP as an oxidant were used at room temperature, affording good yields of the products (Eq. 63) [351].

ð63Þ

Inspired by previously reported CDC between tertiary amines with a nitroalkane and malonate esters to generate β-nitroamines and β-carbonylamines, respectively, Li and co-workers examined the β-nitroamines synthesis in aqueous medium along with oxygen gas which afforded 45% of CDC product in 18 h. After successfully optimizing the reaction condition, ns 85% of the desired product was obtained in 24 h. In addition to nitroalkanes, this strategy was also applied to the dialkyl malonate derivative. The reaction of 2-phenyl-1,2,3,4-tetrahydroisoquinoline with dimethyl and diethyl malonate generated β-diester products in good yields in water and with oxygen gas (Eq. 64) [352]. Wei et al. [353] developed Cu-mediated alkylation of α-amino carbonyl compounds with ethers for the synthesis of α-etherized α-amino carbonyl compounds under oxidative condition. This crossdehydrogenative alkylation was accomplished by dual C(sp3)-H bonds coupling using TBHP. Then the scope of this reaction extended to α-amino esters, α-amino ketones, and α-amino amides. All the screened ethers and thioether substrates acted as excellent substrates to react with 1-phenyl-2-(phenylamino)ethanone, CuCl2, and TBHP delivering the related products in moderate to good yields. Cu-driven CDC reactions between simple ketones and unactivated ethers have also been described by Huang et al. [354]. This transformation was also carried out with a Cu-catalyst using tert-butyl hydrogen peroxide as an oxidant. The proposed radical mechanism is involved in this reaction.

ð64Þ

Asymmetric CDC reaction via Csp3-H bond activation by using catalytic amount of Cu(OTf)2 was established by Zhang et al. The authors demonstrated cross-

360

M. S. Lokolkar et al.

dehydrogenative coupling of C-H bond adjacent to a nitrogen atom and construction of C(sp3)-C(sp3) bonds for the numerous complex chiral molecules, including optically active α-alkyl α-amino acids and C1-alkylated tetrahydroisoquinolines (Eq. 65) [355]. ð65Þ Scheidt and group described an enantioselective tetrahydropyrans synthesis via CDC [356]. The oxidative methodology involves the in situ Lewis acid activation of the nucleophile and transient oxocarbenium electrophile generation for highly enantioselective reaction. For this transformation, they used DDQ as the oxidant and Cu(II)-bisoxazoline (BOX) complex as the catalyst. Electron-donating substituents bearing aromatic cinnamyl ethers at ortho, meta, and para positions afforded high enantioselective yields. However, for the esters containing steric crowding, no further improvement observed for stereoselectivity of the reaction, whereas the enantioselectivity was not observed in the absence of β-ketoesters, which reveals the vital role of this substrate as chelating ligand in the reaction.

7.4

Cross-Dehydrogenative C(sp2)-C(sp2) Bond Formation (Aryl-Aryl)

Historically, it has been challenging to derivatize C-H bonds at the sp2 position. The sp2-H bonds are relatively inactive compared to sp3-H bonds mostly because of their high bond dissociation energies and pKa values. The Cu-catalyzed CDC reactions are significant in overcoming these challenges. In this context, Pandit et al. have prepared copper-catalyzed functionalized 3-indolylbenzoxazine-2-ones under aerobic oxidative conditions. Here, the C(sp2)-C(sp2) coupling of benzoxazine-2-one and indoles was carried out using molecular oxygen as the sole oxidant. Electronwithdrawing and donating groups presence on indole derivatives worked smoothly affording corresponding products with decent yields. They also synthesized natural alkaloid cephalandole-A up to the gram scale (Eq. 66) [357]. Yin and co-workers reported the synthesis of 4-(indol-3-yl)quinazolines from indoles and quinazoline-3oxides applying same Cu-catalyst under aerobic cross-dehydrogenative conditions [358].

ð66Þ

Cu-Catalyzed C-C Coupling Reactions

361

Scheme 113 C(sp2)-C(sp2) annulation of 2-arylbenzaldehyde and N-(2′-arylphenyl) formamides

Singh and group established a novel strategy for the preparation of polycyclic systems via intramolecular site-selective C(sp2)-C(sp2) coupling of 3- and 3,4-disubstituted pyrrole-azole substrates. Silver/copper-based ligand-free catalytic system was used for achieving this transformation, where copper core serves as the active catalyst, involving Cu(I)–(II)–(III) cycle and silver Ag(I) acts as an oxidant (Eq. 67) [359].

ð67Þ

Another elegant intramolecular catalytic C(sp2)-C(sp2) cross-dehydrogenative coupling of 2-aryl benzaldehyde was demonstrated by Bao et al. [360]. For this reaction, the Cu(0)/Selectfluor catalytic system was used in the presence of acetonitrile as medium at 100°C for 24 h. Radical scavenger TEMPO was used for mechanistic investigation. In addition, the CDC annulation of N-(2′-arylphenyl) formamides was also tolerated, which resulted in the corresponding phenanthridinones affording moderate yields (Scheme 113). The majority of enantioenriched biphenol and binaphthol derivatives have been prepared using Cu-mediated C(sp2)-C(sp2) oxidative coupling approach. Sekar and co-workers developed new catalytic system CuCl/(R)-BINAM (1,1′-binaphthyl2,2′-diamine) for asymmetric oxidative coupling of 2-naphthol [361]. The rate and selectivity of the C-C coupling surprisingly increase when TEMPO in a catalytic amount is combined with oxygen. It was suggested that the active catalyst might be regenerated by using TEMPO. In contrast, good to excellent yields for the oxidative coupling of 2-naphthol were obtained using a straightforward Cu(OAc)2/1,5diazabicyclo[4.3.0]non-5-ene (DBN) system. The presence of an additive is required to deliver good results for this reaction. By replacing the use of external additives with air, Lee explored a hexanuclear Cu(II) system for the oxidative C(sp2)-C(sp2) homocoupling reaction of 2-naphthols [362]. Two copper centers are coordinated by

362

M. S. Lokolkar et al.

Scheme 114 Copper/(BINAM) and copper/(DBN)-catalyzed synthesis of BINOL derivatives

the N, N, N, N-tetra(pyridine-2-ylmethyl)-m-xylene diamine ligand in this system (Scheme 114).

7.5

Cross-Dehydrogenative C(sp)-C(sp) Bond Formation (Diyenes)

The homocoupling reaction of terminal alkynes is a precious reaction for constructing functional molecules containing buta-1,3-diyne fragments. It has been widely used in many fields of the chemistry, including polymer, natural product synthesis, supramolecular chemistry, and materials science, as they can be converted into a wide range of structural entities [363]. Almost 150 years ago, Glaser discovered the first report on the dimerization of phenylacetylene. The original system employed by Glaser comprised cuprous chloride salt, ammonium hydroxide as a base, and oxygen as an oxidant. The phenylacetylene readily reacted with CuCl in NH4OH/EtOH, forming copper(I)phenylacetylide, which when exposed to air underwent oxidative dimerization to afford diphenylacetylene in an open flask [364]. Although the initial strategy involved the isolation of copper acetylene intermediate as potentially explosive, the synthetic community recognized the benefits of this new sp-sp bond-forming reaction for the construction of various acetylenic compounds. S. Yin and co-workers developed the Cu-catalyzed oxidative cross-coupling of terminal alkynes under mild conditions. This reaction provides selective heterocoupling of two different alkynes by using Cu(0) as catalyst, N1,N1, N2,N2-tetramethylethylenediamine (TMEDA) as a ligand, chloroform medium under aerobic conditions. This Cu-catalyzed heterocoupling provides the synthesis of wide range of unsymmetrical aryl–aryl, alkyl–alkyl, and aryl–alkyl 1,3-diynes in good to excellent yield of the products. This protocol used heterocoupling of terminal alkynes using Glaser–Hay-type reaction for the conversion of unsymmetrical 1,3-diynes (Eq. 68) [365].

Cu-Catalyzed C-C Coupling Reactions

363

ð68Þ

The dimerization of terminal alkynes to give 1,3-diynes through oxidative homocoupling is one of the significant methods for C-C bond formation. As a result, much effort has been devoted for synthesizing diyne derivatives implementing different methodologies. One of the most commonly used procedures for synthesizing symmetrical diyne derivatives is an oxidative alkyne-alkyne homocoupling reaction. Li et al. developed homocoupling of two symmetrical alkynes by using 1 equiv. of copper iodide as a catalyst, molecular iodine (1 equiv.), with 2 equiv. Na2CO3 as a base in DMF at 80°C for 3 h to afford the corresponding diyene [366]. Various terminal alkynes, including aliphatic acetylene, produced the homocoupled 1,3-diyenes in good to excellent yields (Table 1 entry-1). For this particular transformation, Nador and co-workers prepared copper(0) nanoparticles [367]. The reaction of various aryl and alkyl terminal alkynes with 4 equiv. of CuNPs was carried out in the absence of an oxidant, additive, and ligands in THF (7 mL). Under this mild reaction conditions, a variety of alkyne substrates afforded 65–90% yields (Table 1 entry-2). The influence of various bases and ligands on the outcome of the homocoupling of terminal alkynes to afford 1,3-diyenes by copper (I)-catalyzed oxidative transformation using molecular oxygen as the sole oxidant was reported by Adimurthy and co-workers [368]. The reaction was carried out with various bases such as triethyl-amine (TEA) (Table 1, entry 5), diisopropylethylamine (DIPEA), N-methylpyrrolidine (NMP), 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo non-5-ene (DBN), 1,4-diaza-bicyclo-octane (DABCO), and 1,5-naphthyridine. The best result was obtained with sterically hindered amine bases such as DBU and DABCO. The optimized reaction condition were applied as CuCl (2 mol%), base DBU (12.5 mol%), and TMEDA (1.5 mol%) under aerobic condition which delivered 34–97% yield of the corresponding diyenes, whereas 55–99% yield of the product 1,3-diyenes was achieved for 1 equiv. of DBU (Table 1 entry-3). Oishi and co-workers developed heterogeneous catalyzed alkyne–alkyne homocoupling by supported copper hydroxide on titanium oxide (Cu(OH)x/TiO2) [369]. For this homocoupling reaction, the catalytic amount of copper catalyst was used in toluene as solvent under one atmosphere of O2 to get resulting homocoupled products with excellent yields. Various aliphatic and aromatic alkynes were well tolerated (Table 1 entry-4). Lu et al. developed the recyclable Cu/PEG catalytic system for the homocoupling reaction of terminal alkynes [370]. The mixture of PEG 6000 and Cu(OAc)2 and the base NaOAc was used as catalytic system for this transformation. Even alkylacetylenes, which are usually relatively unreactive substrates in these types of reactions, were obtained in excellent yields. The Cu/PEG system was recycled with an acetic acid wash and reused five times without significantly lower yields (Table 1 entry-5). Jiang and Li explored homocoupling

364

M. S. Lokolkar et al.

Table 1 Cross-dehydrogenative C(sp)-C(sp) coupling of terminal alkynes a

Entry 1 2

3

4

5 6 7

8

9

10

11

12

13

14

15

a b

Substrates R = Ph, p-Me-Ph, p-MeO-Ph, p -F-Ph, nBu, n-Pent, n-Hex, HOCH2 R = Ph, p-NH2-Ph, 3,5-bis(CF3)-Ph, n-Bu, n-Decyl, THPOCH2, HOCH2, 1-Cyclohexenyl R = Ph, p-Et-Ph, p-OMe-Ph, p-Me-Ph, 2,4,5-Me-Ph, p-F-Ph, 1-cyclohexyne, nHex R = Ph, o-Me-Ph, m-Me-Ph, m-OMe-Ph, p-Me-Ph, p-F-Ph, 1-cyclohexenyl, n-Hex, n-Bu, n-Oct, i-Pr3Si R = Ph, p-Et-Ph, p-Me-Ph, p-F-Ph, c-Hex, n-Hex, n-Bu, CH2OH R = p-Me-Ph, p-OMe-Ph, p-F-Ph, c-Hex, n-Hex, n-Bu R = Ph, p-OMe-Ph, p-F-Ph, m-Thiophenyl, o-Pyridinyl, n-Bu, BrCH2, HOC(CH3)2, HOCH2, Ferrocenyl R = n-Hex, Me2(OH)C, Cl(CH2)3, NC (CH2)3, p-Me-Ph, o-Me-Ph, p-OMe-Ph, o-CF3-Ph R = p-Me-Ph, p-OMe-Ph, p-COMe-Ph mMe-Ph, m-Me-Ph, o-Me-Ph, n-Bu, BrCH2, HOC(CH3)2, HOCH2 R = Ph, p-Me-Ph, p-Et-Ph, p-Pr-Ph, p-BuPh, p-F-Ph m-Me-Ph, n-Pen, n-Oct, pOMe-Ph m-NH2-Ph R = Ph, p -Me-Ph, p-tBu-Ph, p-CF3-Ph, pF-Ph, m-Cl-Ph, o-Cl-Ph, o-CF3-Ph, n-Hex, p-ph-CO-Ph R = Ph, o-Me-Ph, m-Me-Ph, p-Me-Ph, pF-Ph, p-n-pentyl-Ph, m-NH2-Ph, Thienyl2-, n-Butyl, n-Hex, t-Butyl R = Ph R’ = p-diMe-N-Ph, R’ = m-OHPh, R’ = p-OMe-Ph, R’ = p-tBu-Ph, R’ = p-F-Ph, R’ = p-CN-Ph, R’ = m-NO2-Ph, R = p-Et-Ph, R’ = OH(CH2)2, R = p-OMe-Ph, R’ = p-Ac-Ph R = Ph, p-Br-Ph, m-Cl-Ph, p-Cl-Ph, o-ClPh, o-F-Ph, p-F-Ph, p-Ph-Ph, p-CO2MePh, p-OMe-Ph, p-Et-Ph n-Hep R = Ph, p-Ethnyl-Ph, p-OMe-Ph, p-tBuPh, p-F-Ph, m-Cl-Ph, p-Cl-Ph, m-Br-Ph, pBr-Ph, m-NO2-Ph

Yields of corresponding symmetrical 1,3-diyenes Yields of corresponding unsymmetrical 1,3-diyenes

Reaction conditions CuI (1 equiv.), I2 (1 equiv.) Na2CO3 (2 equiv.), DMF CuNPs, THF

CuCl (2 mol%), DBU, TMEDA (1.5 mol%), O2, MeCN, rt Cu(OH)x/TiO2, Toluene, O2, 100°C, 0.5 h

Yield range 70–99% 65–90%

34–97%

80–99%

Cu(OAc)2.PEG-6000, NaOAc, 120°C CuCl2, NaOAc, MeOH/scCO2

96–100%

CuCl2 (3 mol%), TEA (3 mol %), “Solvent free”

40–99% 32–72%b

CuCl (2 mol%), piperidine (10 mol%), Toluene, air, 60° C, 5–8 h CuSO4.5H2O (5 mol%), KOAc, I2, H2O, 120°C, 24 h

77–96% 21–51%b

A-21.CuI (5 mol%), nbutylamine (0.5 equiv.), rt, air, “Solvent free” CuBr (5–10 mol%), di-tertbutyldiaziridinone, MeCN, rt, 2–7 h CuI (0.5 mol%), benzylamine (5 mol%), rt, O2

85–98%

86–98%

11–90%

64–83%

63–99%

CuCl (5 mol%), Blue LEDs, MeCN, O2, rt

64–95%b

Cu(OTf)2 (5 mol%), DBU (1 equiv.), Acetone, rt CuCl (5 mol%), npropylamine (1 equiv.), air, 60°C “Solvent free”

63–92%

70–95%

Cu-Catalyzed C-C Coupling Reactions

365

reactions in supercritical carbon dioxide (scCO2) as solvent medium [371]. The use of this solvent is very attractive due to its physical and toxicological properties and the fact that it is far superior to conventional solvents in terms of environmental impact. The authors demonstrated a Glaser-type coupling reaction using scCO2 and an inorganic base for this transformation. The absence of amines, usually serving the purpose of ligand and base, did not affect the reaction drastically resulting in appreciable yields (Table 1 entry-6). In 2010, an efficient and environmentally friendly protocol for synthesis of symmetrical 1,3-diynes under “solvent-free” conditions was developed [372]. In CuCl2 and triethyl-amine catalytic system, aromatic and aliphatic alkynes with a wide range of functional groups were oxidatively homocoupled. The catalyst was shown to be recycled five times with slight decline in catalytic activity. The symmetrical as well as unsymmetrical 1,3-diyenes was synthesized with 40–99% and 32–72% yields, respectively (Table 1 entry-7). Taking advantage of this methodology, 1,3-diynes were synthesized in the air at 60° C with CuCl and piperidine as an additive [373]. This process has also been applied to terminal alkynes’ symmetrical and unsymmetrical coupling (Table 1 entry-8). In 2010, Wu et al. developed a reusable CuSO4/2,2′-bipyridyl pair-driven homocoupling for 1,3-diyenes synthesis from alkynes in water [374]. A variety of substituted terminal alkynes were screened with this catalytic system and produced good to high yields (Table 1 entry-9). The reusable copper/polymer composite catalyst for similar reactions at ambient conditions without solvent media was developed by He et al. in 2012 [375]. Here, A-21-CuI, a polymer-supported catalyst, was prepared by reacting the Amberlyst A-21 with CuI in acetonitrile stirred at ambient temperature for 24 h in inert conditions. The homocoupling reaction using 5 mol% of this A-21-CuI catalyst and base n-butylamine (0.5 equiv.) under solventfree conditions at room temperature proceeded smoothly. It generated the corresponding 1,3-diyene in high yields within 10–20 min (Table 1 entry-10). Zhu and co-workers developed oxidative homocoupling of terminal alkynes with diaziridione as an oxidant under mild conditions [376]. A catalytic amount of CuBr was used with di-tert-butyldiaziridinone under base-free conditions. Various terminal alkynes can be effectively homocoupled to give 1,3-diynes products in good yields (Table 1 entry-11). In 2013, Cheng et al. reported a CuI-catalyzed homocoupling reaction. Here, using 5 mol% of benzylamine as a ligand under solvent and base-free conditions using oxygen as the oxidant produced excellent yields of up to 99%. The transformation is mild and general and can involve aliphatic and heteroaromatic alkynes (Table 1 entry-12) [377]. Under photoredox conditions, the CDC reaction of two alkynes also proceeds well. In 2016, constructed the Csp-Csp bond of two alkynes with a simple copper catalyst under visible-light irradiation [378]. Under mild reaction conditions, a series of non-symmetrical conjugated diynes were synthesized. Furthermore, the authors inferred that the mechanism proceeded by forming stable ground-state bipolar heterodimeric Cu(I)-acetylide complexes that were photoexcited to promote the cross-coupling reaction of the complex’s dimeric alkyne ligand (Table 1 entry-13). Cu(OTf)2-catalyzed homocoupling and heterocoupling were established by Holganza and colleagues (2019) [379]. In the presence of organic base DBU, at

366

M. S. Lokolkar et al.

Scheme 115 Copper-catalyzed C(sp)-C(sp) coupling of terminal alkynes

room temperature, a variety of 1,3-diyenes were prepared in good to excellent yields within a short reaction time (Table 1 entry-14). Recently, in 2021, Xiao et al. reported CuCl-catalyzed homocoupling of terminal alkynes under solvent-free conditions [380]. The developed methodology provides environmental-friendly preparation of 1,3-diyenes in short reaction time. The phenylacetylene substrates bearing electron-donating and electron-withdrawing substitutions were well tolerated under the identified conditions to afford the desired product in 70–95% yields (Table 1 entry-15) (Scheme 115).

References 1. Miyaura N, Suzuki A (1995) Palladium-catalyzed cross-coupling reactions of organoboron compounds. Chem Rev 95:2457–2483 2. Ruiz-Castillo P, Buchwald SL (2016) Applications of palladium-catalyzed C–N crosscoupling reactions. Chem Rev 116:12564–12649 3. Schlummer B, Scholz U (2004) Palladium-catalyzed C–N and C–O coupling – a practical guide from an industrial vantage point {. Adv Synth Catal 346:1599–1626 4. Jana R, Pathak TP, Sigman MS (2011) Advances in transition metal (Pd,Ni,Fe)-catalyzed cross-coupling reactions using alkyl-organometallics as reaction partners. Chem Rev 111: 1417–1492 5. Beletskaya IP, Ananikov VP (2011) Transition-metal-catalyzed C-S, C-Se, and C-Te bond formation via cross-coupling and atom-economic addition reactions. Chem Rev 111:1596– 1636 6. Tang X, Wu W, Zeng W, Jiang H (2018) Copper-catalyzed oxidative carbon–carbon and/or carbon–heteroatom bond formation with O2 or internal oxidants. Acc Chem Res 51:1092– 1105 7. de Vries JG (2012) Palladium-catalysed coupling reactions. pp 1–34 8. Torborg C, Beller M (2009) Recent applications of palladium-catalyzed coupling reactions in the pharmaceutical, agrochemical, and fine chemical industries. Adv Synth Catal 351:3027– 3043 9. Devendar P, Qu R-Y, Kang W-M et al (2018) Palladium-catalyzed cross-coupling reactions: a powerful tool for the synthesis of agrochemicals. J Agric Food Chem 66:8914–8934 10. Buchwald SL, Mauger C, Mignani G, Scholz U (2006) Industrial-scale palladium-catalyzed coupling of aryl halides and amines – a personal account. Adv Synth Catal 348:23–39 11. Magano J, Dunetz JR (2011) Large-scale applications of transition metal-catalyzed couplings for the synthesis of pharmaceuticals. Chem Rev 111:2177–2250 12. Wang D, Weinstein AB, White PB, Stahl SS (2018) Ligand-promoted palladium-catalyzed aerobic oxidation reactions. Chem Rev 118:2636–2679 13. Gildner PG, Colacot TJ (2015) Reactions of the 21st century: two decades of innovative catalyst design for palladium-catalyzed cross-couplings. Organometallics 34:5497–5508

Cu-Catalyzed C-C Coupling Reactions

367

14. Ley SV, Thomas AW (2003) Modern synthetic methods for copper-mediated C(aryl)–O, C (aryl)–N, and C(aryl)–S bond formation. Angew Chem Int Ed Engl 42:5400–5449 15. Evano G, Blanchard N, Toumi M (2008) Copper-mediated coupling reactions and their applications in natural products and designed biomolecules synthesis. Chem Rev 108:3054– 3131 16. Thapa S, Shrestha B, Gurung SK, Giri R (2015) Copper-catalysed cross-coupling: an untapped potential. Org Biomol Chem 13:4816–4827 17. Cai Q, Zhou W (2020) Ullmann-Ma reaction: development, scope and applications in organic synthesis {. Chin J Chem 38:879–893 18. Beletskaya IP, Cheprakov AV (2004) Copper in cross-coupling reactions. Coord Chem Rev 248:2337–2364 19. Nelson TD, Crouch RD (2004) Cu, Ni, and Pd mediated homocoupling reactions in biaryl syntheses: the Ullmann reaction. In: Organic reactions. Wiley, Hoboken, pp 265–555 20. Goshaev M, Otroshchenko OS, Sadykov AS (1972) The Ullmann reaction. Russ Chem Rev 41:1046–1059 21. Monnier F, Taillefer M (2009) Catalytic C–C, C–N, and C–O Ullmann-type coupling reactions. Angew Chem Int Ed Engl 48:6954–6971 22. Qiao J, Lam P (2011) Copper-promoted carbon-heteroatom bond cross-coupling with boronic acids and derivatives. Synthesis (Stuttg) 2011:829–856 23. Goossen LJ, Manjolinho F, Khan BA, Rodríguez N (2009) Microwave-assisted Cu-catalyzed protodecarboxylation of aromatic carboxylic acids. J Org Chem 74:2620–2623 24. Gooßen LJ, Thiel WR, Rodríguez N et al (2007) Copper-catalyzed protodecarboxylation of aromatic carboxylic acids. Adv Synth Catal 349:2241–2246 25. RAUSCH MD (1961) Ferrocene and related organometallic π-complexes. IV. Some Ullmann reactions of Haloferrocenes 1. J Org Chem 26:1802–1805 26. Lindley J, Mason TJ, Lorimer JP (1987) Sonochemically enhanced Ullmann reactions. Ultrasonics 25:45–48 27. Ebert G, Rieke RD (1984) Direct formation of organocopper compounds by oxidative addition of zerovalent copper to organic halides. J Org Chem 49:5280–5282 28. Rieke RD, Rhyne LD (1979) Preparation of highly reactive metal powders. Activated copper and uranium. The Ullmann coupling and preparation of organometallic species. J Org Chem 44:3445–3446 29. Roberge DM, Hölderich WF (2000) Catalytic and non-catalytic formation of 4,4′-dimethylbiphenyl using p-chlorotoluene. Appl Catal A Gen 194–195:341–357 30. Cohen T, Tirpak JG (1975) Rapid, room-temperature Ullman-type coupling and ammonolyses of activated aryl halides in homogeneous solutions containing copper(I) ions. Tetrahedron Lett 16:143–146 31. Cohen T, Cristea I (1975) Copper(I)-induced reductive dehalogenation, hydrolysis, or coupling of some aryl and vinyl halides at room temperature. J Org Chem 40:3649–3651 32. Zhang S, Zhang D, Liebeskind LS (1997) Ambient temperature, Ullmann-like reductive coupling of aryl, heteroaryl, and alkenyl halides. J Org Chem 62:2312–2313 33. Babudri F, Cardone A, Farinola GM, Naso F (1998) A versatile copper-induced synthesis of fluorinated oligo(para-phenylenes). Tetrahedron 54:14609–14616 34. Stavrakov G, Keller M, Breit B (2007) From central to axial to central chirality: enantioselective construction of thetrans-4,5,9,10-tetrahydroxy-9,10-dihydrophenanthrene system. Eur J Org Chem 2007:5726–5733 35. Dhas NA, Raj CP, Gedanken A (1998) Synthesis, characterization, and properties of metallic copper nanoparticles. Chem Mater 10:1446–1452 36. Ponce AA, Klabunde KJ (2005) Chemical and catalytic activity of copper nanoparticles prepared via metal vapor synthesis. J Mol Catal A Chem 225:1–6 37. Wu Q, Wang L (2008) Immobilization of copper(II) in organic-inorganic hybrid materials: a highly efficient and reusable catalyst for the classic Ullmann reaction. Synthesis (Stuttg) 2008: 2007–2012

368

M. S. Lokolkar et al.

38. Bringmann G, Gulder T, Gulder TAM, Breuning M (2011) Atroposelective total synthesis of axially chiral biaryl natural products. Chem Rev 111:563–639 39. Tasler S, Bringmann G (2002) Biarylic biscarbazole alkaloids: occurrence, stereochemistry, synthesis, and bioactivity. Chem Rec 2:113–126 40. Schenker S, Zamfir A, Freund M, Tsogoeva SB (2011) Developments in chiral binaphthylderived Brønsted/Lewis acids and hydrogen-bond-donor organocatalysis. Eur J Org Chem 2011:2209–2222 41. Li Y, Kwong F, Yu W, Chan A (2007) Recent advances in developing new axially chiral phosphine ligands for asymmetric catalysis. Coord Chem Rev 251:2119–2144 42. Kozlowski MC, Morgan BJ, Linton EC (2009) Total synthesis of chiral biaryl natural products by asymmetric biaryl coupling. Chem Soc Rev 38:3193 43. Wallace TW (2006) Biaryl synthesis with control of axial chirality. Org Biomol Chem 4:3197 44. Zhang YJ, Wei H, Zhang W (2009) Synthesis of atropisomeric 5,5′-linked biphenyl bisaminophosphine ligands and their applications in asymmetric catalysis. Tetrahedron 65: 1281–1286 45. Wei H, Zhang YJ, Wang F, Zhang W (2008) Novel atropisomeric bisphosphine ligands with a bridge across the 5,5′-position of the biphenyl for asymmetric catalysis. Tetrahedron Asymmetry 19:482–488 46. Pai C-C, Lin C-W, Lin C-C et al (2000) Highly effective chiral dipyridylphosphine ligands: synthesis, structural determination, and applications in the Ru-catalyzed asymmetric hydrogenation reactions. J Am Chem Soc 122:11513–11514 47. Rankic D, Hopkins J, Parvez M, Keay B (2009) Synthesis and resolution of 3,3′-disubstituted xylBINAP derivatives and their application in rhodium-catalyzed asymmetric hydrogenation. Synlett 2009:2513–2517 48. Gorobets E, Wheatley BMM, Hopkins JM et al (2005) Avoiding the classical resolution during the synthesis of MeO-BIPHEP and 3,3′-disubstituted derivatives. Tetrahedron Lett 46:3843– 3846 49. Nelson TD, Meyers AI (1993) The synthesis of a useful chiral biaryl catalyst. An oxazolinemediated Ullmann reaction. Tetrahedron Lett 34:3061–3062 50. Nelson TD, Meyers AI (1994) A rapid total synthesis of an ellagitannin. J Org Chem 59:2577– 2580 51. Meyers AI, Willemsen JJ (1997) The synthesis of (S)-(+)-gossypol via an asymmetric Ullmann coupling. Chem Commun:1573–1574 52. Meyers A, Nelson TD, Moorlag H et al (2004) Chiral oxazoline route to enantiomerically pure biphenyls: magnesio and copper mediated asymmetric hetero- and homo-coupling reactions. Tetrahedron 60:4459–4473 53. Li Y, Wang Q, Dong L et al (2009) Asymmetric synthesis of (+)- and (-)-Wuweizisu C stereoisomers and their chemosensitizing effects on multidrug-resistant cancer cells. Synthesis (Stuttg) 2009:3383–3390 54. Miyano S, Tobita M, Hashimoto H (1981) Asymmetric synthesis of axially dissymmetric 1,1′-binaphthyls via an intramolecular Ullmann coupling reaction of ( R )- and ( S )-2,2′-bis (1-bromo-2-naphthylcarbonyloxy)-1,1′-binaphthyl. Bull Chem Soc Jpn 54:3522–3526 55. Miyano S, Fukushima H, Handa S et al (1988) Asymmetric synthesis of axially chiral, unsymmetrical diphenic acids via intramolecular Ullmann coupling reaction. Bull Chem Soc Jpn 61:3249–3254 56. Miyano S, Handa S, Shimizu K et al (1984) The asymmetric Ullmann coupling reaction of chiral diol diesters of 1-bromo-2-naphthoic acid and 2-Halo-3-nitrobenzoic acids: highly diastereoselective synthesis of atropisomeric 6,6′-dinitrodiphenic acids. Bull Chem Soc Jpn 57:1943–1947 57. Wang C-J, Xu Z-P, Wang X, Teng H-L (2010) Axial [6,6′-(2,4-pentadioxy)]-1,1′-biphenyl2,2′-diamine (PD-BIPHAM): practical synthesis and applications in asymmetric hydrogenation. Tetrahedron 66:3702–3706

Cu-Catalyzed C-C Coupling Reactions

369

58. Qiu L, Wu J, Chan S et al (2004) Remarkably diastereoselective synthesis of a chiral biphenyl diphosphine ligand and its application in asymmetric hydrogenation. Proc Natl Acad Sci 101: 5815–5820 59. Qiu L, Kwong FY, Wu J et al (2006) A new class of versatile chiral-bridged atropisomeric diphosphine ligands: remarkably efficient ligand syntheses and their applications in highly enantioselective hydrogenation reactions. J Am Chem Soc 128:5955–5965 60. Dai D, Martin OR (1998) Studies relevant to ellagitannin chemistry: highly diastereoselective intramolecular biaryl coupling in bis(iodotrimethoxybenzoyl) hexopyranose derivatives. J Org Chem 63:7628–7633 61. Ikeda Y, Nagao K, Tanigakiuchi K et al (2004) The first construction of a 3,6-bridged ellagitannin skeleton with 1C4/B glucose core; synthesis of nonamethylcorilagin. Tetrahedron Lett 45:487–489 62. Forrest J (1960) 122. The Ullmann biaryl synthesis. Part VI. The scope and mechanism of the reaction. J Chem Soc 594 63. Brown E, Robin J-P (1977) Application de la reaction d’ulimann a la synthese de diaryles encombres precurseurs de lignanes bis-benzocyclootadieniques. Tetrahedron Lett 18:2015– 2018 64. Brown E, Robin J-P, Dhal R (1982) Syntheses totales et etudes de lignanes biologiquement actifs – I. Tetrahedron 38:2569–2579 65. Suzuki H, Enya T, Hisamatsu Y (1997) Synthesis and characterization of some nitrobenzanthrones: suspected new mutagens in atmospheric environment. Synthesis (Stuttg) 1997:1273–1276 66. Ghigo G, Bonomo M, Antenucci A et al (2022) Ullmann homocoupling of arenediazonium salts in a deep eutectic solvent. Synthetic and mechanistic aspects. RSC Adv 12:26640–26647 67. Dieck HA, Heck FR (1975) Palladium catalyzed synthesis of aryl, heterocyclic and vinylic acetylene derivatives. J Organomet Chem 93:259–263 68. Cassar L (1975) Synthesis of aryl- and vinyl-substituted acetylene derivatives by the use of nickel and palladium complexes. J Organomet Chem 93:253–257 69. Ogawa T, Kusume K, Tanaka M et al (1989) An alternative method for the stereospecific synthesis of conjugated alkenynes via the copper (I) iodide assisted cross-coupling reaction of 1-akyens with haloalkenes. Synth Commun 19:2199–2207 70. Okuro K, Furuune M, Miura M, Nomura M (1992) Copper-catalyzed coupling reaction of aryl and vinyl halides with terminal alkynes. Tetrahedron Lett 33:5363–5364 71. Okuro K, Furuune M, Enna M et al (1993) Synthesis of aryl- and vinylacetylene derivatives by copper-catalyzed reaction of aryl and vinyl iodides with terminal alkynes. J Org Chem 58: 4716–4721 72. Okuro K, Furuune M, Miura M, Nomura M (1993) Copper-catalyzed reaction of aryl iodides with active methylene compounds. J Org Chem 58:7606–7607 73. Coleman RS, Garg R (2001) Stereocontrolled synthesis of the diene and triene macrolactones of Oximidines I and II: organometallic coupling versus standard macrolactonization. Org Lett 3:3487–3490 74. Liu Y, Yang J, Bao W (2009) Palladium-free synthesis of conjugated enynes by direct olefination of terminal alkynes using vinyl bromides. Eur J Org Chem 2009:5317–5320 75. Gujadhur RK, Bates CG, Venkataraman D (2001) Formation of aryl-nitrogen, aryl-oxygen, and aryl-carbon bonds using well-defined copper(I)-based catalysts. Org Lett 3:4315–4317 76. Biffis A, Scattolin E, Ravasio N, Zaccheria F (2007) Supported copper precatalysts for ligandfree, palladium-free Sonogashira coupling reactions. Tetrahedron Lett 48:8761–8764 77. Thathagar MB, Beckers J, Rothenberg G (2004) Palladium-free and ligand-free Sonogashira cross-coupling. Green Chem 6:215 78. Bates CG, Saejueng P, Murphy JM, Venkataraman D (2002) Synthesis of 2-arylbenzo[b] furans via copper(I)-catalyzed coupling of o -iodophenols and aryl acetylenes. Org Lett 4: 4727–4729

370

M. S. Lokolkar et al.

79. Cacchi S, Fabrizi G, Parisi LM (2003) 2-Aryl and 2-heteroaryl indoles from 1-alkynes and o-iodotrifluoroacetanilide through a domino copper-catalyzed coupling-cyclization process. Org Lett 5:3843–3846 80. Liu F, Ma D (2007) Assembly of conjugated enynes and substituted indoles via CuI/amino acid-catalyzed coupling of 1-alkynes with vinyl iodides and 2-bromotrifluoroacetanilides. J Org Chem 72:4844–4850 81. Lokolkar MS, Mane PA, Dey S, Bhanage BM (2022) Synthesis of 2-substituted indoles by Pd-catalyzed reductive cyclization of 1-Halo-2-nitrobenzene with alkynes. Eur J Org Chem 82. Dhara S, Singha R, Nuree Y, Ray JK (2014) One-pot synthesis of isoquinoline and related compounds via Cu-mediated tandem cross-coupling and cyclization. Tetrahedron Lett 55: 795–798 83. Yang Y, Ren H, Wang D et al (2013) Cu-catalyzed alkynylation–cyclization cascade for the construction of the pyrazolo[5,1-a]isoquinoline skeleton. RSC Adv 3:10434 84. Yang D, Li B, Yang H et al (2011) Efficient copper-catalyzed Sonogashira couplings of aryl halides with terminal alkynes in water. Synlett 2011:702–706 85. Deng C-L, Xie Y-X, Yin D-L, Li J-H (2006) Copper(II) acetate/1,4-diphenyl-1,4-diazabuta1,3-diene catalyzed Sonogashira cross-coupling of aryl halides with terminal alkynes under aerobic and solvent-free conditions. Synthesis (Stuttg) 2006:3370–3376 86. Thakur KG, Jaseer EA, Naidu AB, Sekar G (2009) An efficient copper(I) complex catalyzed Sonogashira type cross-coupling of aryl halides with terminal alkynes. Tetrahedron Lett 50: 2865–2869 87. Monnier F, Turtaut F, Duroure L, Taillefer M (2008) Copper-catalyzed Sonogashira-type reactions under mild palladium-free conditions. Org Lett 10:3203–3206 88. Wu M, Mao J, Guo J, Ji S (2008) The use of a bifunctional copper catalyst in the crosscoupling reactions of aryl and heteroaryl halides with terminal alkynes. Eur J Org Chem 2008: 4050–4054 89. Lin C-H, Wang Y-J, Lee C-F (2010) Efficient copper-catalyzed cross-coupling reaction of alkynes with aryl iodides. Eur J Org Chem 90. Guan JT, Yu G-A, Chen L et al (2009) CuI/PPh 3-catalyzed Sonogashira coupling reaction of aryl iodides with terminal alkynes in water in the absence of palladium. Appl Organomet Chem 23:75–77 91. Petrignet J, Inack Ngi S, Abarbri M, Thibonnet J (2014) Short and convenient synthesis of two natural phthalides by a copper(I) catalysed Sonogashira/oxacyclisation copper(I) process. Tetrahedron Lett 55:982–984 92. Yu L, Jiang X, Wang L et al (2010) Catalytic alkynylation coupling reactions by copper (II) complex in water and its applications to domino synthesis of 2-arylindoles. Eur J Org Chem 2010:5560–5562 93. Hajipour AR, Nazemzadeh SH, Mohammadsaleh F (2014) Choline chloride/CuCl as an effective homogeneous catalyst for palladium-free Sonogashira cross-coupling reactions. Tetrahedron Lett 55:654–656 94. Kang S-K, Yoon S-K, Kim Y-M (2001) Copper-catalyzed coupling reaction of terminal alkynes with aryl- and alkenyliodonium salts. Org Lett 3:2697–2699 95. Chowdhury C, Kundu NG (1999) Studies on copper(I) catalysed cross-coupling reactions: a convenient and facile method for the synthesis of diversely substituted α,β-acetylenic ketones. Tetrahedron 55:7011–7016 96. Guo M, Li D, Zhang Z (2003) Novel synthesis of 2-Oxo-3-butynoates by copper-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride. J Org Chem 68:10172– 10174 97. He H, Wu Y-J (2004) Copper-catalyzed cross-coupling of aryl iodides and aryl acetylenes using microwave heating. Tetrahedron Lett 45:3237–3239 98. Wang J-X, Liu Z, Hu Y et al (2002) Microwave-assisted copper catalyzed coupling reaction of aryl halides with terminal alkynes. Synth Commun 32:1937–1945

Cu-Catalyzed C-C Coupling Reactions

371

99. Colacino E, Daïch L, Martinez J, Lamaty F (2007) Microwave-assisted copper-catalyzed Sonogashira reaction in PEG solvent. Synlett 2007:1279–1283 100. Chen G, Zhu X, Cai J, Wan Y (2007) Palladium-free copper-catalyzed coupling reaction of aryl iodides and terminal acetylenes in water. Synth Commun 37:1355–1361. https://doi.org/ 10.1080/00397910701227416 101. Chen G, Xie J, Weng J et al (2011) CuI/PPh 3 /PEG–water: an efficient catalytic system for cross-coupling reaction of aryl iodides and alkynes. Synth Commun 41:3123–3133 102. Rao Volla CM, Vogel P (2008) Iron/copper-catalyzed C–C cross-coupling of aryl iodides with terminal alkynes. Tetrahedron Lett 49:5961–5964 103. Hazra A, Lee MT, Chiu JF, Lalic G (2018) Photoinduced copper-catalyzed coupling of terminal alkynes and alkyl iodides. Angew Chem 130:5590–5594 104. Almasalma AA, Mejía E (2018) Copper-catalyzed allylic C-H alkynylation by crossdehydrogenative coupling. Chem A Eur J 24:12269–12273 105. Almasalma AA, Mejía E (2020) Allylic C–H alkynylation via copper-photocatalyzed crossdehydrogenative coupling. Synthesis (Stuttg) 52:529–536 106. Zhang H, Sun N, Hu B et al (2019) Copper-catalyzed direct couplings of terminal alkynes with primary and secondary benzyl bromides. Org Chem Front 6:1983–1988 107. Cao Y, Dong X, Yang J et al (2020) A copper-catalyzed Sonogashira coupling reaction of diverse activated alkyl halides with terminal alkynes under ambient conditions. Adv Synth Catal 362:2280–2284 108. Peng X, Ma C, Tung C-H, Xu Z (2016) Cu-catalyzed three-component coupling of aryne, alkyne, and benzenesulfonothioate: modular synthesis of o -alkynyl arylsulfides. Org Lett 18: 4154–4157 109. Tamura M, Kochi J (1971) Coupling of Grignard reagents with organic halides. Synthesis (Stuttg) 1971:303–305 110. Kochi JK, Tamura M (1971) Alkylcopper(I) in the coupling of Grignard reagents with alkyl halides. J Am Chem Soc 93:1485–1487 111. Fleming FF, Jiang T (1997) Unsaturated nitriles: optimized coupling of the chloroprene Grignard reagent 1 with ω-bromonitriles. J Org Chem 62:7890–7891 112. Nunomoto S, Kawakami Y, Yamashita Y (1981) Synthesis of 2-substituted 1,3-butadienes by cross-coupling reaction of 2-(1,3-butadienyl)magnesium chloride with alkyl or aryl iodides. Bull Chem Soc Jpn 54:2831–2832 113. Johnson DK, Ciavarri JP, Ishmael FT et al (1995) A novel copper (I) mediated, symmetrical coupling procedure for alkyl, aryl, benzyl, and thiophenyl dihalides. Tetrahedron Lett 36: 8565–8568 114. Onuma K, Hashimoto H (1972) N, N, N′, N′-tetramethylethylenediamine-copper saltcatalysed coupling of aryl grignard reagents with alkyl and aralkyl halides. Bull Chem Soc Jpn 45:2582–2586 115. Burns DH, Miller JD, Chan H-K, Delaney MO (1997) Scope and utility of a new soluble copper catalyst [CuBr-LiSPh-LiBr-THF]: a comparison with other copper catalysts in their ability to couple one equivalent of a Grignard reagent with an alkyl sulfonate. J Am Chem Soc 119:2125–2133 116. Burns DH, Chan H, Miller JD et al (2000) Synthesis, modification, and characterization of a family of homologues of exo -Calix[4]arene: exo -[n.m.n.m]Metacyclophanes, n, m ≥ 3. J Org Chem 65:5185–5196 117. Cahiez G, Chaboche C, Jézéquel M (2000) Cu-catalyzed alkylation of Grignard reagents: a new efficient procedure. Tetrahedron 56:2733–2737 118. Cahiez G, Gager O, Buendia J (2010) Copper-catalyzed cross-coupling of alkyl and aryl Grignard reagents with alkynyl halides. Angew Chem 122:1300–1303 119. Terao J, Ikumi A, Kuniyasu H, Kambe N (2003) Ni- or Cu-catalyzed cross-coupling reaction of alkyl fluorides with Grignard reagents. J Am Chem Soc 125:5646–5647

372

M. S. Lokolkar et al.

120. Terao J, Todo H, Begum SA et al (2007) Copper-catalyzed cross-coupling reaction of Grignard reagents with primary-alkyl halides: remarkable effect of 1-phenylpropyne. Angew Chem Int Ed 46:2086–2089 121. Shen R, Iwasaki T, Terao J, Kambe N (2012) Copper-catalyzed coupling reaction of unactivated secondary alkyl iodides with alkyl Grignard reagents in the presence of 1,3-butadiene as an effective additive. Chem Commun 48:9313 122. Iwasaki T, Imanishi R, Shimizu R et al (2014) Copper-catalyzed alkyl–alkyl cross-coupling reactions using hydrocarbon additives: efficiency of catalyst and roles of additives. J Org Chem 79:8522–8532 123. Ren P, Stern L-A, Hu X (2012) Copper-catalyzed cross-coupling of functionalized alkyl halides and tosylates with secondary and tertiary alkyl Grignard reagents. Angew Chem Int Ed 51:9110–9113 124. Hintermann L, Xiao L, Labonne A (2008) A general and selective copper-catalyzed crosscoupling of tertiary Grignard reagents with azacyclic electrophiles. Angew Chem Int Ed 47: 8246–8250 125. Yang C-T, Zhang Z-Q, Liang J et al (2012) Copper-catalyzed cross-coupling of nonactivated secondary alkyl halides and tosylates with secondary alkyl Grignard reagents. J Am Chem Soc 134:11124–11127 126. Shinohara R, Morita M, Ogawa N, Kobayashi Y (2019) Use of the 2-pyridinesulfonyloxy leaving group for the fast copper-catalyzed coupling reaction at secondary alkyl carbons with Grignard reagents. Org Lett 21:3247–3251 127. Sai M, Yorimitsu H, Oshima K (2009) Copper-catalyzed allylation of alkyl halides with allylic Grignard reagents. Bull Chem Soc Jpn 82:1194–1196 128. Tao C, Sun L, Wang B et al (2017) Copper-catalyzed cross-coupling reactions of non-activated primary, secondary or tertiary alkyl chlorides with phenylmagnesium bromide. Tetrahedron Lett 58:305–308 129. Nakata K, Feng C, Tojo T, Kobayashi Y (2014) Acceleration of CuI-catalyzed coupling reaction of alkyl halides with aryl Grignard reagents using lithium chloride. Tetrahedron Lett 55:5774–5777 130. Arigala P, Sadu VS, Hwang I-T et al (2015) Copper-catalyzed regio- and stereoselective ringopening of cyclic sulfamidates with Grignard reagents assisted by lithium chloride. Adv Synth Catal 357:2027–2032 131. Liu J-H, Yang C-T, Lu X-Y et al (2014) Copper-catalyzed reductive cross-coupling of nonactivated alkyl tosylates and mesylates with alkyl and aryl bromides. Chem A Eur J 20: 15334–15338 132. Hornillos V, Pérez M, Fañanás-Mastral M, Feringa BL (2013) Copper-catalyzed enantioselective allyl–allyl cross-coupling. J Am Chem Soc 135:2140–2143 133. Zhu Y, Xiong T, Han W, Shi Y (2014) Copper-catalyzed oxidative homo- and cross-coupling of Grignard reagents using diaziridinone. Org Lett 16:6144–6147 134. Surry DS, Su X, Fox DJ et al (2005) Synthesis of medium-ring and iodinated biaryl compounds by organocuprate oxidation. Angew Chem 117:1904–1907 135. Surry DS, Fox DJ, Macdonald SJF, Spring DR (2005) Aryl–aryl coupling via directed lithiation and oxidation. Chem Commun (Camb):2589 136. Su X, Fox DJ, Blackwell DT et al (2006) Copper catalyzed oxidation of organozinc halides. Chem Commun:3883 137. Humayun Kabir SM, Hasegawa M, Kuwatani Y et al (2001) Synthesis of biphenylenes and tetraphenylenes using copper-catalyzed coupling of arylzinc intermediates. J Chem Soc Perkin Trans 1:159–165 138. Zheng S, Laraia L, O’Connor CJ et al (2012) Synthesis and biological profiling of tellimagrandin I and analogues reveals that the medium ring can significantly modulate biological activity. Org Biomol Chem 10:2590

Cu-Catalyzed C-C Coupling Reactions

373

139. Su X, Thomas G, Galloway W et al (2009) Synthesis of biaryl-containing medium-ring systems by organocuprate oxidation: applications in the total synthesis of ellagitannin natural products. Synthesis (Stuttg) 2009:3880–3896 140. Malosh CF, Ready JM (2004) Catalytic cross-coupling of alkylzinc halides with α-chloroketones. J Am Chem Soc 126:10240–10241 141. Wang T, Schrempp M, Berndhäuser A et al (2015) Efficient and general aerobic oxidative cross-coupling of THIQs with organozinc reagents catalyzed by CuCl 2: proof of a radical intermediate. Org Lett 17:3982–3985 142. Thapa S, Kafle A, Gurung SK et al (2015) Ligand-free copper-catalyzed Negishi coupling of alkyl-, aryl-, and alkynylzinc reagents with heteroaryl iodides. Angew Chem Int Ed 54:8236– 8240 143. Thapa S, Vangala A, Giri R (2016) Copper-catalyzed Negishi coupling of diarylzinc reagents with aryl iodides. Synthesis (Stuttg) 48:504–511 144. Zemtsov AA, Volodin AD, Levin VV et al (2015) Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes. Beilstein J Org Chem 11:2145–2149 145. Frabitore C, Lépeule J, Livinghouse T (2022) Copper(I)-catalyzed cross-coupling of 1-bromoalkynes with N-heterocyclic organozinc reagents. Molecules 27:4561 146. Kang S-K, Yamaguchi T, Kim T-H, Ho P-S (1996) Copper-catalyzed cross-coupling and carbonylative cross-coupling of organostannanes and organoboranes with hypervalent iodine compounds. J Org Chem 61:9082–9083 147. Thathagar MB, Beckers J, Rothenberg G (2003) Combinatorial design of copper-based mixed nanoclusters: new catalysts for Suzuki cross-coupling. Adv Synth Catal 345:979–985 148. Mao J, Guo J, Fang F, Ji S-J (2008) Highly efficient copper(0)-catalyzed Suzuki–Miyaura cross-coupling reactions in reusable PEG-400. Tetrahedron 64:3905–3911 149. Li J-H, Li J-L, Xie Y-X (2007) TBAB-promoted ligand-free copper-catalyzed cross-coupling reactions of aryl halides with arylboronic acids. Synthesis (Stuttg) 2007:984–988 150. Li J-H, Li J-L, Wang D-P et al (2007) CuI-catalyzed Suzuki-Miyaura and Sonogashira crosscoupling reactions using DABCO as ligand. J Org Chem 72:2053–2057 151. Wang S, Wang M, Wang L et al (2011) CuI-catalyzed Suzuki coupling reaction of organoboronic acids with alkynyl bromides. Tetrahedron 67:4800–4806 152. Yang C-T, Zhang Z-Q, Liu Y-C, Liu L (2011) Copper-catalyzed cross-coupling reaction of organoboron compounds with primary alkyl halides and pseudohalides. Angew Chem Int Ed 50:3904–3907 153. Zhang Z-Q, Yang C-T, Liang L-J et al (2014) Copper-catalyzed/promoted cross-coupling of gem-diborylalkanes with nonactivated primary alkyl halides: an alternative route to alkylboronic esters. Org Lett 16:6342–6345 154. Wang G-Z, Jiang J, Bu X-S et al (2015) Copper-catalyzed cross-coupling reaction of allyl boron ester with 1°/2°/3°-halogenated alkanes. Org Lett 17:3682–3685 155. Gurung SK, Thapa S, Kafle A et al (2014) Copper-catalyzed Suzuki–Miyaura coupling of arylboronate esters: transmetalation with (PN)CuF and identification of intermediates. Org Lett 16:1264–1267 156. Gurung SK, Thapa S, Shrestha B, Giri R (2015) Copper-catalysed cross-couplings of arylboronate esters with aryl and heteroaryl iodides and bromides. Org Chem Front 2:649–653 157. Rao HSP, Rao AVB (2014) Copper-catalyzed C(sp 3)-C(sp 2) cross-coupling: synthesis of 4-aryl-2-alkyl-amino-3-nitro-4 H-chromenes. Eur J Org Chem 2014:3646–3655 158. Rao HSP, Rao AVB (2015) Copper-catalyzed C(sp 3)–OH cleavage with concomitant C–C coupling: synthesis of 3-substituted isoindolinones. J Org Chem 80:1506–1516 159. Ban I, Sudo T, Taniguchi T, Itami K (2008) Copper-mediated C-H bond arylation of arenes with arylboronic acids. Org Lett 10:3607–3609 160. Hoshi M, Kawamura N, Shirakawa K (2006) Construction of terminal conjugated enynes: Cu-mediated cross-coupling reaction of alkenyldialkylborane with (trimethylsilyl)ethynyl bromide. Synthesis (Stuttg) 2006:1961–1970

374

M. S. Lokolkar et al.

161. Hoshi M, Iizawa T, Okimoto M, Shirakawa K (2008) One-pot synthesis of internal conjugated (Z)-enynyltrimethylsilanes possessing aryl, cycloalkenyl, (E)- or (Z)-Alk-1-enyl moieties on the sp carbon atom via two types of cross-coupling reaction. Synthesis (Stuttg) 2008:3591– 3600 162. Zhou Y, You W, Smith KB, Brown MK (2014) Copper-catalyzed cross-coupling of boronic esters with aryl iodides and application to the carboboration of alkynes and allenes. Angew Chem 126:3543–3547 163. Bergmann AM, Oldham AM, You W, Brown MK (2018) Copper-catalyzed cross-coupling of aryl-, primary alkyl-, and secondary alkylboranes with heteroaryl bromides. Chem Commun 54:5381–5384 164. Lu X-Y, Yang C-T, Liu J-H et al (2015) Cu-catalyzed cross-coupling reactions of epoxides with organoboron compounds. Chem Commun 51:2388–2391 165. Ebrahim-Alkhalil A, Zhang Z-Q, Gong T-J et al (2016) Copper-catalyzed cross-coupling reactions of epoxides with gem-diborylmethane: access to γ-hydroxyl boronic esters. Chem Commun 52:4891–4893 166. Lu X-Y, Li J-S, Wang J-Y et al (2018) Cu-catalyzed cross-coupling reactions of vinyl epoxide with organoboron compounds: access to homoallylic alcohols. RSC Adv 8:41561–41565 167. Moon PJ, Halperin HM, Lundgren RJ (2016) Oxidative coupling of aryl boron reagents with sp 3 -carbon nucleophiles: the enolate Chan-Evans-Lam reaction. Angew Chem Int Ed 55: 1894–1898 168. Ohmiya H, Yokobori U, Makida Y, Sawamura M (2010) Copper-catalyzed γ-selective allylalkyl coupling between allylic phosphates and alkylboranes. J Am Chem Soc 132:2895–2897 169. Yasuda Y, Ohmiya H, Sawamura M (2016) Copper-catalyzed enantioselective allyl-allyl coupling between allylic boronates and phosphates with a phenol/N-heterocyclic carbene chiral ligand. Angew Chem Int Ed 55:10816–10820 170. Shido Y, Yoshida M, Tanabe M et al (2012) Copper-catalyzed enantioselective allylic substitution with alkylboranes. J Am Chem Soc 134:18573–18576 171. Hojoh K, Shido Y, Ohmiya H, Sawamura M (2014) Construction of quaternary stereogenic carbon centers through copper-catalyzed enantioselective allylic cross-coupling with alkylboranes. Angew Chem Int Ed 53:4954–4958 172. Fahandej-Sadi A, Lundgren R (2017) Copper-mediated synthesis of monofluoro aryl acetates via decarboxylative cross-coupling. Synlett 28:2886–2890 173. Sap JBI, Wilson TC, Kee CW et al (2019) Synthesis of 18 F-difluoromethylarenes using aryl boronic acids, ethyl bromofluoroacetate and [18 F]fluoride. Chem Sci 10:3237–3241 174. Budiman YP, Friedrich A, Radius U, Marder TB (2019) Copper-catalysed Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters with aryl iodides and bromides and fluoroarene-arene π-stacking interactions in the products. ChemCatChem 11:5387–5396 175. Demir AS, Reis Ö, Emrullahoglu M (2003) Role of copper species in the oxidative dimerization of arylboronic acids: synthesis of symmetrical biaryls. J Org Chem 68:10130–10134 176. Kirai N, Yamamoto Y (2009) Homocoupling of arylboronic acids catalyzed by 1,10phenanthroline-ligated copper complexes in air. Eur J Org Chem 2009:1864–1867 177. Wang Y-H, Xu M-C, Liu J et al (2015) Three-coordinate copper(I) 2-hydroxy-1,10phenanthroline dinuclear complex catalyzed homocoupling of arylboronic acids towards biphenyls under air condition. Tetrahedron 71:9598–9601 178. Agrahari B, Layek S, Kumari S et al (2017) Synthesis, characterization and crystal structure of Cu(II) complex of trans-cyclohexane-1,2-diamine: application in synthesis of symmetrical biaryls. J Mol Struct 1134:85–90 179. Kaboudin B, Haruki T, Yokomatsu T (2011) CuSO4-mediated homocoupling of arylboronic acids under ligand- and base-free conditions in air. Synthesis (Stuttg) 2011:91–96 180. Cheng G, Luo M (2011) Homocoupling of arylboronic acids catalyzed by CuCl in air at room temperature. Eur J Org Chem 2011:2519–2523 181. Kaboudin B, Abedi Y, Yokomatsu T (2011) CuII-β-cyclodextrin complex as a nanocatalyst for the homo- and cross-coupling of arylboronic acids under ligand- and base-free conditions

Cu-Catalyzed C-C Coupling Reactions

375

in air: chemoselective cross-coupling of arylboronic acids in water. Eur J Org Chem 2011: 6656–6662 182. Kaboudin B, Mostafalu R, Yokomatsu T (2013) Fe3O4 nanoparticle-supported Cu (II)-β-cyclodextrin complex as a magnetically recoverable and reusable catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from aryl boronic acids. Green Chem 15:2266 183. Dar BA, Singh S, Pandey N et al (2014) Clay encapsulated Cu(OH)x promoted homocoupling of arylboronic acids: an efficient and eco-friendly protocol. Appl Catal A Gen 470:232–238 184. Puthiaraj P, Suresh P, Pitchumani K (2014) Aerobic homocoupling of arylboronic acids catalysed by copper terephthalate metal–organic frameworks. Green Chem 16:2865 185. Wang Y, Meng S-S, Lin P-X, et al (2016) Solvent-induced single crystal–single crystal transformation of an interpenetrated three-dimensional copper triazole catalytic framework. Inorg Chem 55:4069–4071 186. Mulla SAR, Chavan SS, Pathan MY et al (2015) Ligand-, base-, co-catalyst-free copper fluorapatite (CuFAP) as a versatile, ecofriendly, heterogeneous and reusable catalyst for an efficient homocoupling of arylboronic acid at ambient reaction conditions. RSC Adv 5:24675– 24680 187. Lin C-N, Huang C-Y, Yu C-C et al (2015) Iron carbonyl cluster-incorporated Cu(I) NHC complexes in homocoupling of arylboronic acids: an effective [TeFe3 (CO)9]2- ligand. Dalton Trans 44:16675–16679 188. Chen M (2021) Cu-catalyzed coupling of vinylidene cyclopropanes with allyl and allenyl boronates. Chem Commun 57:9212–9215 189. Li H, Zhang M, Mehfooz H et al (2019) Highly convergent modular access to poly-carbon substituted cyclopropanes via Cu(I)-catalyzed three-component cyclopropene carboallylation. Org Chem Front 6:3387–3391 190. Zhang Z, Stateman LM, Nagib DA (2019) δ C–H (hetero)arylation via Cu-catalyzed radical relay. Chem Sci 10:1207–1211 191. Lakshmidevi J, Naidu BR, Venkateswarlu K (2022) CuI in biorenewable basic medium: three novel and low E-factor Suzuki-Miyaura cross-coupling reactions. Mol Catal 522:112237 192. Stille JK (1986) The palladium-catalyzed cross-coupling reactions of organotin reagents with organic electrophiles[new synthetic methods(58)]. Angew Chem Int Ed Engl 25:508–524 193. Iyoda M, Kondo T, Nakao K et al (2000) A cyclic oligophenylene containing two 1,8-naphthalene units bridged by two face-to-face biphenyl linkages exhibiting unusual strain and π-π interaction. Org Lett 2:2081–2083 194. Harada G, Yoshida M, Iyoda M (2000) Synthesis of biaryls using the coupling reaction of diaryldimethyltins with copper(II) nitrate. Chem Lett 29:160–161 195. Kang S-K, Baik T-G, Jiao XH, Lee Y-T (1999) Copper- and manganese-catalyzed homocoupling of organostannanes in the presence of iodine. Tetrahedron Lett 40:2383–2384 196. Piers E, Yee JGK, Gladstone PL (2000) CuCl-mediated intramolecular oxidative coupling of aryl- and alkenyltrimethylstannane functions. Org Lett 2:481–484 197. Edwards DJ, Hadfield JA, Wallace TW, Ducki S (2011) Tubulin-binding dibenz[c,e]oxepines as colchinol analogues for targeting tumour vasculature. Org Biomol Chem 9:219–231 198. Takeda T, Matsunaga K, Kabasawa Y, Fujiwara T (1995) The copper(I) iodide-promoted allylation of vinylstannanes with allylic halides. Chem Lett 24:771–772 199. Behling JR, Ng JS, Babiak KA et al (1989) The synthesis of β-hydroxy-(E)-vinylstannanes using an “in-situ” generated cuprate reagent derived from (E)-bis-(tributylstannyl)ethylene. Tetrahedron Lett 30:27–30 200. Behling JR, Babiak KA, Ng JS et al (1988) In situ cuprate formation via transmetalation between vinylstannanes and higher order cyanocuprates. J Am Chem Soc 110:2641–2643 201. Mohapatra S, Bandyopadhyay A, Barma DK et al (2003) Chiral α,β-dialkoxy- and α-alkoxy-β-aminostannanes: preparation and copper-mediated cross-coupling. Org Lett 5: 4759–4762

376

M. S. Lokolkar et al.

202. Piers E, Wong T (1993) Copper(I) chloride-mediated intramolecular coupling of vinyltrimethylstannane and vinyl halide functions. J Org Chem 58:3609–3610 203. Allred GD, Liebeskind LS (1996) Copper-mediated cross-coupling of organostannanes with organic iodides at or below room temperature. J Am Chem Soc 118:2748–2749 204. Falck JR, Bhatt RK, Ye J (1995) Tin-copper transmetalation: cross-coupling of .alpha.heteroatom-substituted alkyltributylstannanes with organohalides. J Am Chem Soc 117: 5973–5982 205. Kang S-K, Kim J-S, Choi S-C (1997) Copper- and manganese-catalyzed cross-coupling of organostannanes with organic iodides in the presence of sodium chloride. J Org Chem 62: 4208–4209 206. Li J-H, Tang B-X, Tao L-M et al (2006) Reusable copper-catalyzed cross-coupling reactions of aryl halides with organotins in inexpensive ionic liquids. J Org Chem 71:7488–7490 207. Falck JR, Patel PK, Bandyopadhyay A (2007) Stereospecific cross-coupling of α-(thiocarbamoyl)organostannanes with alkenyl, aryl, and heteroaryl iodides. J Am Chem Soc 129:790–793 208. Li H, He A, Falck JR, Liebeskind LS (2011) Stereocontrolled synthesis of α-amino-α′-alkoxy ketones by a copper-catalyzed cross-coupling of peptidic thiol esters and α-alkoxyalkylstannanes. Org Lett 13:3682–3685 209. Zine K, Petrignet J, Thibonnet J, Abarbri M (2012) An easy stereoselective copper(I)catalyzed synthesis of (E)-3-trifluoromethylbut-2-en-3-ynoate via palladium-free Stille coupling reaction. Synlett 23:755–759 210. Wang R, Falck JR (2015) Studies towards asymmetric synthesis of 4(S)-11dihydroxydocosahexaenoic acid (diHDHA) featuring cross-coupling of chiral stannane under mild conditions. Org Biomol Chem 13:1624–1628 211. Ghorbani-Choghamarani A, Derakhshan AA, Hajjami M, Rajabi L (2016) Copper–Schiff base alumoxane: a new and reusable mesoporous nano catalyst for Suzuki–Miyaura and Stille C–C cross-coupling reactions. RSC Adv 6:94314–94324 212. Ghosh AK, Born JR, Veitschegger AM, Jurica MS (2020) Copper-catalyzed Stille crosscoupling reaction and application in the synthesis of the spliceostatin Core structure. J Org Chem 85:8111–8120 213. Hatanaka Y, Hiyama T (1991) Highly selective cross-coupling reactions of organosilicon compounds mediated by fluoride ion and a palladium catalyst. Synlett 1991:845–853 214. Hiyama T, Shirakawa E (2002) Organosilicon compounds, pp 61–85 215. Denmark SE, Liu JH-C (2010) Silicon-based cross-coupling reactions in the total synthesis of natural products. Angew Chem Int Ed 49:2978–2986 216. Nakao Y, Sahoo AK, Imanaka H et al (2006) Alkenyl- and aryl[2-(hydroxymethyl)phenyl] dimethylsilanes: Tetraorganosilanes for the practical cross-coupling reaction. Pure Appl Chem 78:435–440 217. Chen J, Tanaka M, Sahoo AK et al (2010) Synthesis of biaryls and oligoarenes using aryl [2-(hydroxymethyl)phenyl]dimethylsilanes. Bull Chem Soc Jpn 83:554–569 218. Ito H, Sensui H, Arimoto K et al (1997) New access to cross-coupling reaction between arylsilanes or heteroarylsilanes and aryl halides mediated by a copper(I) salt. Chem Lett 26: 639–640 219. Kang S-K, Kim T-H, Pyun S-J (1997) Copper(I)-catalysed homocoupling of organosilicon compounds: synthesis of biaryls, dienes and diynes. J Chem Soc Perkin Trans 1:797–798 220. Nishihara Y, Ikegashira K, Toriyama F et al (2000) Homo-coupling reactions of alkenyl- and arylfluorosilanes mediated by a copper(I) salt. Bull Chem Soc Jpn 73:985–990 221. Gurung SK, Thapa S, Vangala AS, Giri R (2013) Copper-catalyzed Hiyama coupling of (hetero)aryltriethoxysilanes with (hetero)aryl iodides. Org Lett 15:5378–5381 222. Gurung S, Thapa S, Shrestha B, Giri R (2014) Copper-catalyzed cross-coupling of aryl- and heteroaryltriethoxysilanes with aryl and heteroaryl iodides and bromides. Synthesis (Stuttg) 46:1933–1937

Cu-Catalyzed C-C Coupling Reactions

377

223. Cornelissen L, Lefrancq M, Riant O (2014) Copper-catalyzed cross-coupling of vinylsiloxanes with bromoalkynes: synthesis of enynes. Org Lett 16:3024–3027 224. Tsubouchi A, Muramatsu D, Takeda T (2013) Copper(I)-catalyzed alkylation of aryl- and alkenylsilanes activated by intramolecular coordination of an alkoxide. Angew Chem Int Ed 52:12719–12722 225. Taguchi H, Tsubouchi A, Takeda T (2003) Copper(I) tert-butoxide-promoted stereospecific alkylation of β-hydroxymethylvinylsilanes with alkyl halides. Tetrahedron Lett 44:5205–5207 226. Takeda T, Matsumura R, Wasa H, Tsubouchi A (2014) Copper(I)-promoted alkylation of alkenylbenzyldimethylsilanes. Asian J Org Chem 3:838–841 227. Takeda T, Takeda Y, Tsubouchi A (2015) Cross-coupling between aryl- and alkenyldimethylsilanes and organic halides promoted by a copper(I) iodide/sodium hydride/ ethylene glycol system. Chem Lett 44:809–811 228. Cornelissen L, Cirriez V, Vercruysse S, Riant O (2014) Copper-catalyzed Hiyama crosscoupling using vinylsilanes and benzylic electrophiles. Chem Commun 50:8018–8020 229. Arlow SI, Hartwig JF (2016) Synthesis of aryldifluoroamides by copper-catalyzed crosscoupling. Angew Chem Int Ed 55:4567–4572 230. Komiyama T, Minami Y, Hiyama T (2016) Aryl(triethyl)silanes for biaryl and teraryl synthesis by copper(II)-catalyzed cross-coupling reaction. Angew Chem Int Ed 55:15787–15791 231. Komiyama T, Minami Y, Hiyama T (2018) Copper-catalyzed cross-coupling reaction between aryl(trialkyl)silanes and alkyl halides. Chem Lett 47:1048–1050 232. Thapa S, Gurung SK, Dickie DA, Giri R (2014) Copper-catalyzed coupling of triaryl- and trialkylindium reagents with aryl iodides and bromides through consecutive transmetalations. Angew Chem 126:11804–11808 233. Shrestha B, Thapa S, Gurung SK et al (2016) General copper-catalyzed coupling of alkyl-, aryl-, and alkynylaluminum reagents with organohalides. J Org Chem 81:787–802 234. Shrestha B, Giri R (2015) Copper-catalyzed arylation of alkyl halides with arylaluminum reagents. Beilstein J Org Chem 11:2400–2407 235. Cahiez G, Marquais S (1993) Copper-catalyzed alkylation of organomanganese chloride reagents 1. Synlett 1993:45–47 236. Cahiez G, Marquais S (1996) Cu-catalyzed alkylation and Fe catalyzed alkenylation of organomanganese reagents. Pure Appl Chem 68:53–60 237. Mowry DT (1948) The preparation of nitriles. Chem Rev 42:189–283 238. Ellis GP, Romney-Alexander TM (1987) Cyanation of aromatic halides. Chem Rev 87:779– 794 239. Amal Joseph PJ, Priyadarshini S (2017) Copper-mediated C–X functionalization of aryl halides. Org Process Res Dev 21:1889–1924 240. Penn L, Gelman D (2011) Copper-mediated cross-coupling reactions. In: PATAI’S chemistry of functional groups. Wiley, Chichester 241. Schareina T, Beller M (2013) Copper-catalyzed cyanations of aryl halides and related compounds. In: Copper-mediated cross-coupling reactions. Wiley, Hoboken, pp 313–334 242. Do H-Q, Daugulis O (2010) Copper-catalyzed cyanation of heterocycle carbon-hydrogen bonds. Org Lett 12:2517–2519 243. Wen Q, Jin J, Zhang L et al (2014) Copper-mediated cyanation reactions. Tetrahedron Lett 55: 1271–1280 244. Najam T, Shah SSA, Mehmood K et al (2018) An overview on the progress and development on metals/non-metal catalyzed cyanation reactions. Inorg Chim Acta 469:408–423 245. Farina V, Kapadia S, Krishnan B et al (1994) On the nature of the “Copper Effect” in the Stille cross-coupling. J Org Chem 59:5905–5911 246. Zhao D, Gao C, Su X et al (2010) Copper-catalyzed decarboxylative cross-coupling of alkynyl carboxylic acids with aryl halides. Chem Commun 46:9049 247. Li T, Sun P, Yang H et al (2012) Copper-catalyzed decarboxylative coupling of aryl halides with alkynyl carboxylic acids performed in water. Tetrahedron 68:6413–6419

378

M. S. Lokolkar et al.

248. Qu X, Li T, Sun P et al (2011) Highly effective copper-catalyzed decarboxylative coupling of aryl halides with alkynyl carboxylic acids. Org Biomol Chem 9:6938 249. Park J, Jung D, Kim H-S et al (2017) Zeolite-based copper catalyst for decarboxylative coupling of alkynyl carboxylic acids with aryl iodides. Catal Commun 99:83–88 250. Nishihara Y, Noyori S, Okamoto T et al (2011) Copper-catalyzed Sila-Sonogashira–Hagihara cross-coupling reactions of alkynylsilanes with aryl iodides under palladium-free conditions. Chem Lett 40:972–974 251. Kotovshchikov YN, Binyakovsky AA, Latyshev GV et al (2022) Copper-catalyzed deacetonative Sonogashira coupling. Org Biomol Chem 20:7650–7657 252. Kotovshchikov YN, Latyshev GV, Lukashev NV, Beletskaya IP (2015) Alkynylation of steroids via Pd-free Sonogashira coupling. Org Biomol Chem 13:5542–5555 253. Kotovshchikov YN, Latyshev GV, Lukashev NV, Beletskaya IP (2013) An efficient approach to azolyl-substituted steroids through copper-catalyzed Ullmann C-N coupling. Eur J Org Chem 2013:7823–7832 254. Hirano K, Miura M (2012) Copper-mediated oxidative direct C–C (hetero) aromatic crosscoupling. Chem Commun 48(87):10704–10714. https://doi.org/10.1039/C2CC34659A 255. Wei Y, Zhao H, Kan J et al (2010) Copper-catalyzed direct alkynylation of electron-deficient polyfluoroarenes with terminal alkynes using O2 as an oxidant. J Am Chem Soc 132:2522– 2523 256. Shang M, Wang H-L, Sun S-Z et al (2014) Cu(II)-mediated ortho C–H alkynylation of (hetero)arenes with terminal alkynes. J Am Chem Soc 136:11590–11593 257. Liebeskind LS, Fengl RW (1990) 3-Stannylcyclobutenediones as nucleophilic cyclobutenedione equivalents. Synthesis of substituted cyclobutenediones and cyclobutenedione monoacetals and the beneficial effect of catalytic copper iodide on the Stille reaction. J Org Chem 55:5359–5364 258. Wang M, Lin Z (2010) Stille cross-coupling reactions of alkenylstannanes with alkenyl iodides mediated by copper(I) thiophene-2-carboxylate: a density functional study. Organometallics 29:3077–3084 259. Iyer S, Ramesh C, Sarkar A, Wadgaonkar PP (1997) The vinylation of aryl and vinyl halides catalyzed by copper salts. Tetrahedron Lett 38:8113–8116 260. Yang Y, Zhou R, Zhao S et al (2003) Silica-supported poly-γ-aminopropylsilane Ni2+, Cu2+, Co2+ complexes: efficient catalysts for Heck vinylation reaction. J Mol Catal A Chem 192: 303–306 261. Li J-H, Wang D-P, Xie Y-X (2005) CuI/Dabco as a highly active catalytic system for the Heck-type reaction. Tetrahedron Lett 46:4941–4944 262. Calò V, Nacci A, Monopoli A et al (2005) Copper bronze catalyzed Heck reaction in ionic liquids. Org Lett 7:617–620 263. Hfidhi N, Bkhairia I, Atoui D et al (2019) Catalytic and biological valorization of a supramolecular mononuclear copper complex based 4-aminopyridine. Appl Organomet Chem 33: e4793 264. Yavari I, Mobaraki A, Hosseinzadeh Z, Sakhaee N (2019) Copper-catalyzed Mizoroki-Heck coupling reaction using an efficient and magnetically reusable Fe3O4@SiO2@PrNCu catalyst. J Organomet Chem 897:236–246 265. Cheng S, Wei W, Zhang X et al (2020) A new approach to large scale production of dimethyl sulfone: a promising and strong recyclable solvent for ligand-free Cu-catalyzed C–C crosscoupling reactions. Green Chem 22:2069–2076 266. Besselievre F, Piguel S, Mahuteau-Betzer F, Grierson DS (2008) Stereoselective direct copper-catalyzed alkenylation of oxazoles with bromoalkenes. Org Lett 10(18):4029–4032. https://doi.org/10.1021/ol801512q 267. Qin X, Cong X, Zhao D et al (2011) One-pot synthesis of benzofused heteroaryl azoles via tandem C-heteroatom coupling/C–H activation of azoles. Chem Commun 47:5611–5613

Cu-Catalyzed C-C Coupling Reactions

379

268. Rousée K, Schneider C, Bouillon J-P et al (2016) Copper-catalyzed direct C–H fluoroalkenylation of heteroarenes. Org Biomol Chem 14:353–357 269. Mousseau JJ, Bull JA, Charette AB (2010) Copper-catalyzed direct alkenylation of N-iminopyridinium ylides. Angew Chem 122:1133–1136 270. Shang R, Fu Y, Wang Y, Xu Q, Yu HZ, Liu L (2009) Copper-catalyzed decarboxylative crosscoupling of potassium polyfluorobenzoates with aryl iodides and bromides. Angew Chem Int Ed 48(49):9350–9354. https://doi.org/10.1002/anie.200904916 271. Ohmiya H, Yokokawa N, Sawamura M (2010) Copper-catalyzed γ-selective and stereospecific allyl-aryl coupling between (Z)-acyclic and cyclic allylic phosphates and arylboronates. Org Lett 12:2438–2440 272. Whittaker AM, Rucker RP, Lalic G (2010) Catalytic S N 2′-selective substitution of allylic chlorides with arylboronic esters. Org Lett 12:3216–3218 273. Yao T, Hirano K, Satoh T, Miura M (2011) Stereospecific copper-catalyzed C–H allylation of electron-deficient arenes with allyl phosphates. Angew Chem Int Ed 50:2990–2994 274. Shintani R, Takatsu K, Takeda M, Hayashi T (2011) Copper-catalyzed asymmetric allylic substitution of allyl phosphates with aryl- and alkenylboronates. Angew Chem Int Ed 50: 8656–8659 275. Ohmiya H, Zhang H, Shibata S et al (2016) Construction of quaternary stereogenic carbon centers through copper-catalyzed enantioselective allylic alkylation of azoles. Angew Chem Int Ed 55:4777–4780 276. Nishihara Y, Okamoto M, Inoue Y et al (2005) Synthesis of symmetrical 1,3-butadiynes by homocoupling reactions of alkynylboronates mediated by a copper salt. Tetrahedron Lett 46: 8661–8664 277. Paixão MW, Weber M, Braga AL et al (2008) Copper salt-catalyzed homo-coupling reaction of potassium alkynyltrifluoroborates: a simple and efficient synthesis of symmetrical 1,3-diynes. Tetrahedron Lett 49:2366–2370 278. Kang Y-W, Cho YJ, Ko K-Y, Jang H-Y (2015) Copper-catalyzed carbon–carbon bond cleavage of primary propargyl alcohols: β-carbon elimination of hemiaminal intermediates. Cat Sci Technol 5:3931–3934 279. Yu M, Pan D, Jia W et al (2010) Copper-catalyzed decarboxylative cross-coupling of propiolic acids and terminal alkynes. Tetrahedron Lett 51:1287–1290 280. Liu D-X, Li F-L, Li H-X et al (2014) Synthesis of 1,4-diarylsubstituted 1,3-diynes through ligand-free copper-catalyzed oxidative decarboxylative homocoupling of aryl propiolic acids. Tetrahedron 70:2416–2421 281. Liu D-X, Li F-L, Li H-X et al (2014) Efficient and reusable CuI/1,10-phenanthroline-catalyzed oxidative decarboxylative homocoupling of arylpropiolic acids in aqueous DMF. Eur J Org Chem 2014:4817–4822 282. Ahammed S, Kundu D, Ranu BC (2014) Cu-catalyzed Fe-driven C sp –C sp and C sp –C sp2 cross-coupling: an access to 1,3-diynes and 1,3-enynes. J Org Chem 79:7391–7398 283. Nishihara Y, Ikegashira K, Mori A, Hiyama T (1998) Copper(I)-catalyzed cross-coupling reaction of alkynylsilanes with 1-chloroalkynes. Tetrahedron Lett 39:4075–4078 284. Nishihara Y, Ikegashira K, Hirabayashi K et al (2000) Coupling reactions of alkynylsilanes mediated by a Cu(I) salt: novel syntheses of conjugate diynes and disubstituted ethynes. J Org Chem 65:1780–1787 285. Yang Y, Chu M, Miao Q (2018) From phenanthrylene butadiynylene macrocycles to S-heterocycloarenes. Org Lett 20:4259–4262 286. Asha S, Anjana S, Thomas AM et al (2019) A convenient route to 1,3-diynes using ligand-free Cadiot-Chodkiewicz coupling reaction at room temperature under aerobic conditions. Synth Commun 49:256–265 287. Jeffery T, Gueugnot S, Linstrumelle G (1992) An efficient route to skipped diynes and triynes, (Z,Z) dienes and (Z,Z,Z) trienes. Tetrahedron Lett 33:5757–5760

380

M. S. Lokolkar et al.

288. Dasse O, Mahadevan A, Han L et al (2000) The synthesis of N-vanillyl-arachidonoyl-amide (Arvanil) and its analogs: an improved procedure for the synthesis of the key synthon methyl 14-hydroxy-(all-cis)-5,8,11-tetradecatrienoate. Tetrahedron 56:9195–9202 289. Li W, Schneider CM, Georg GI (2015) Synthesis of strained 1,3-diene macrocycles via copper-mediated Castro–Stephens coupling/alkyne reduction tandem reactions. Org Lett 17: 3902–3905 290. Saejueng P, Bates CG, Venkataraman D (2005) Copper(I)-catalyzed coupling of terminal acetylenes with aryl or vinyl halides. Synthesis (Stuttg):1706–1712 291. Lu L, Li H, Lei A (2022) Oxidative cross-coupling reactions between two nucleophiles{. Chin J Chem 40:256–266 292. Allen SE, Walvoord RR, Padilla-Salinas R, Kozlowski MC (2013) Aerobic copper-catalyzed organic reactions. Chem Rev 113:6234–6458 293. Nicolaou KC, Bulger PG, Sarlah D (2005) Palladium-catalyzed cross-coupling reactions in total synthesis. Angew Chem Int Ed 44:4442–4489 294. Grissom JW, Gunawardena GU, Klingberg D, Huang D (1996) The chemistry of enediynes, enyne allenes and related compounds. Tetrahedron 52:6453–6518 295. Chinchilla R, Nájera C (2007) The Sonogashira reaction: a booming methodology in synthetic organic chemistry. Chem Rev 107:874–922 296. Tour JM (1996) Conjugated macromolecules of precise length and constitution. Organic synthesis for the construction of nanoarchitectures. Chem Rev 96:537–554 297. Bunz UHF (2000) Poly(aryleneethynylene)s: syntheses, properties, structures, and applications. Chem Rev 100:1605–1644 298. Zou G, Zhu J, Tang J (2003) Cross-coupling of arylboronic acids with terminal alkynes in air. Tetrahedron Lett 44:8709–8711 299. Yang F, Wu Y (2007) Facile synthesis of substituted alkynes by cyclopalladated ferrocenylimine catalyzed cross-coupling of arylboronic acids/esters with terminal alkynes. Eur J Org Chem 2007:3476–3479 300. Rao H, Fu H, Jiang Y, Zhao Y (2010) Highly efficient copper-catalyzed synthesis of internal alkynes via aerobic oxidative arylation of terminal alkynes. Adv Synth Catal 352:458–462 301. Yasukawa T, Miyamura H, Kobayashi S (2011) Copper-catalyzed, aerobic oxidative crosscoupling of alkynes with arylboronic acids: remarkable selectivity in 2,6-lutidine media. Org Biomol Chem 9:6208 302. Gui Q, Chen X, Hu L et al (2016) Copper-mediated ortho -arylation of benzamides with arylboronic acid. Adv Synth Catal 358:509–514 303. Liu Y, Long C, Zhao L, Wang M-X (2016) Functionalization of azacalixaromatics by Cu(II)catalyzed oxidative cross-coupling reaction between the arene C–H bond and boronic acids. Org Lett 18:5078–5081 304. Zhang Q, Liu Y, Wang T et al (2018) Mechanistic study on Cu(II)-catalyzed oxidative crosscoupling reaction between arenes and boronic acids under aerobic conditions. J Am Chem Soc 140:5579–5587 305. Ding S, Xu L, Li P (2016) Copper-catalyzed boron-selective C(sp 2)–C(sp 3) oxidative crosscoupling of arylboronic acids and alkyltrifluoroborates involving a single-electron transmetalation process. ACS Catal 6:1329–1333 306. Shepard AF, Winslow NR, Johnson JR (1930) The simple halogen derivatives of furan. J Am Chem Soc 52:2083–2090 307. Nilsson M, Kulonen E, Sunner S et al (1966) A new biaryl synthesis illustrating a connection between the Ullmann biaryl synthesis and copper-catalysed decarboxylation. Acta Chem Scand 20:423–426 308. Cairncross A, Roland JR, Henderson RM, Sheppard WA (1970) Organocopper intermediates via decarboxylation of cuprous carboxylates. J Am Chem Soc 92:3187–3189 309. Cohen T, Berninger RW, Wood JT (1978) Products and kinetics of decarboxylation of activated and unactivated aromatic cuprous carboxylates in pyridine and in quinoline. J Org Chem 43:837–848

Cu-Catalyzed C-C Coupling Reactions

381

310. Myers AG, Tanaka D, Mannion MR (2002) Development of a decarboxylative palladation reaction and its use in a Heck-type olefination of arene carboxylates. J Am Chem Soc 124: 11250–11251 311. Lokolkar MS, Mane PA, Dey S, Bhanage BM (2021) Xantphos-coordinated palladium dithiolates: highly efficient catalyst for decarboxylative Sonogashira reaction into corresponding alkynes. Appl Organomet Chem 35 312. Shang R, Fu Y, Wang Y et al (2009) Copper-catalyzed decarboxylative cross-coupling of potassium polyfluorobenzoates with aryl iodides and bromides. Angew Chem 121:9514–9518 313. Liu Z, Budiman YP, Tian Y et al (2020) Copper-catalyzed oxidative cross-coupling of electron-deficient polyfluorophenylboronate esters with terminal alkynes. Chem A Eur J 26: 17267–17274 314. Wen K, Wu Y, Chen J et al (2022) Copper-mediated decarboxylative coupling of 3-indoleacetic acids with pyrazolones. ACS Omega 7:5274–5282 315. Wu Y, Li L, Wen K et al (2021) Copper-catalyzed C-3 functionalization of imidazo[1,2-a] pyridines with 3-indoleacetic acids. J Org Chem 86:12394–12402 316. Girard SA, Knauber T, Li C-J (2014) The cross-dehydrogenative coupling of C sp 3–H bonds: a versatile strategy for C–C bond formations. Angew Chem Int Ed 53:74–100 317. Maaliki C, Thiery E, Thibonnet J (2017) Emergence of copper-mediated formation of C-C bonds. Eur J Org Chem 2017:209–228 318. Glaser C (1869) Beiträge zur Kenntniss des Acetenylbenzols. Berichte der Dtsch Chem Gesellschaft 2:422–424 319. Johansson Seechurn CCC, Kitching MO, Colacot TJ, Snieckus V (2012) Palladium-catalyzed cross-coupling: a historical contextual perspective to the 2010 Nobel prize. Angew Chem Int Ed 51:5062–5085 320. Baeyer A (1882) Ueber die Verbindungen der Indigogruppe. Berichte der Dtsch Chem Gesellschaft 15:50–56 321. Rosenmund KW, Struck E (1919) Das am Ringkohlenstoff gebundene Halogen und sein Ersatz durch andere Substituenten. I. Mitteilung: Ersatz des Halogens durch die Carboxylgruppe. Berichte der Dtsch Chem Gesellschaft (A B Ser) 52:1749–1756 322. Hurtley WRH (1929) CCXLIV – replacement of halogen in orthobromo-benzoic acid. J Chem Soc:1870–1873 323. Zhang J, Liu L, Chen T, Han L (2020) Cross-dehydrogenative alkynylation: a powerful tool for the synthesis of internal alkynes. ChemSusChem 13:4776–4794 324. Li Z, Li C-J (2004) CuBr-catalyzed efficient alkynylation of sp 3 C-H bonds adjacent to a nitrogen atom. J Am Chem Soc 126:11810–11811 325. Leonard NJ, Leubner GW (1949) Reactions of nitroparaffins with pseudo bases related to dihydroisoquinolinium hydroxide. J Am Chem Soc 71:3408–3411 326. Murahashi S-I, Komiya N, Terai H (2005) Ruthenium-catalyzed oxidative cyanation of tertiary amines with hydrogen peroxide and sodium cyanide. Angew Chem Int Ed 44:6931– 6933 327. Li Z, Li C-J (2004) Catalytic enantioselective alkynylation of prochiral sp 3 C-H bonds adjacent to a nitrogen atom. Org Lett 6:4997–4999 328. Su W, Yu J, Li Z, Jiang Z (2011) Solvent-free cross-dehydrogenative coupling reactions under high speed ball-milling conditions applied to the synthesis of functionalized tetrahydroisoquinolines. J Org Chem 76:9144–9150 329. Niu M, Yin Z, Fu H et al (2008) Copper-catalyzed coupling of tertiary aliphatic amines with terminal alkynes to propargylamines via C-H activation. J Org Chem 73:3961–3963 330. Gupta S, Dubey P, Singh AK, Jain N (2019) Oxidative C–C bond formation and C–N bond cleavage catalyzed by complexes of copper(I) with acridine based (E N E) pincers (E = S/Se), recyclable as a catalyst. Dalton Trans 48:10129–10137 331. Zhao L, Li C-J (2008) Functionalizing glycine derivatives by direct C–C bond formation. Angew Chem 120:7183–7186

382

M. S. Lokolkar et al.

332. Yang F, Li Y, Floreancig PE et al (2018) Copper-catalyzed oxidative cross-dehydrogenative coupling of 2 H -chromenes and terminal alkynes. Org Biomol Chem 16:5144–5149 333. Correia CA, Li C-J (2010) Copper-catalyzed cross-dehydrogenative coupling (CDC) of alkynes and benzylic C–H bonds. Adv Synth Catal 352:1446–1450 334. Shaikh MM, Patel AP, Chikhalia KH (2019) Copper catalysed cross-dehydrogenative coupling (CDC) reaction of 4-thiazolidinone with terminal alkyne. Tetrahedron 75:475–485 335. Li Z, Li C-J (2005) CuBr-catalyzed direct indolation of tetrahydroisoquinolines via crossdehydrogenative coupling between sp 3 C-H and sp 2 C-H bonds. J Am Chem Soc 127: 6968–6969 336. Li Z, Bohle DS, Li C-J (2006) Cu-catalyzed cross-dehydrogenative coupling: a versatile strategy for C–C bond formations via the oxidative activation of sp 3 C–H bonds. Proc Natl Acad Sci 103:8928–8933 337. Ramana DV, Chandrasekharam M (2018) Copper-catalyzed direct oxidative α-functionalization of tetrahydroquinoline in water under mild conditions. Adv Synth Catal 360:4080–4083 338. Xiong T, Li Y, Bi X et al (2011) Copper-catalyzed dehydrogenative cross-coupling reactions of N-para-tolylamides through successive C–H activation: synthesis of 4H-3,1-benzoxazines. Angew Chem 123:7278–7281 339. Sarkar R, Mukhopadhyay C (2018) Cu catalyzed cross-dehydrogenative coupling reaction for the synthesis of 3-hydroxy-2-pyrrolidinones. Tetrahedron Lett 59:3069–3076 340. Zhan F, Zhang W, Zhao H (2020) Copper/silver cocatalyzed regioselective C5–H functionalization of 8-aminoquinoline amides with 1,3-dicarbonyl compounds. Synthesis (Stuttg) 52:1007–1014 341. Zhu Z-Q, Xiao L-J, Chen Y et al (2018) A highly efficient copper(II)-catalyzed crossdehydrogenative-coupling reaction of N-arylglycine esters with 2-arylimidazo[1,2-a]pyridines. Synthesis (Stuttg) 50:2775–2783 342. Zhu Z-Q, Xiao L-J, Zhou C-C et al (2018) A visible-light-promoted cross-dehydrogenativecoupling reaction of N-arylglycine esters with imidazo[1,2-a]pyridines. Tetrahedron Lett 59: 3326–3331 343. Yu C, Patureau FW (2018) Cu-catalyzed cross-dehydrogenative ortho-aminomethylation of phenols. Angew Chem Int Ed 57:11807–11811 344. Borpatra P, Deb M, Baruah P (2018) Copper-catalyzed tandem multi-component approach to 1,3-oxazines at room temperature by cross-dehydrogenative coupling using methanol as C1 feedstock. Synlett 29:1171–1175 345. Ding R, Lu W, Ci H et al (2019) Copper-catalyzed oxidative alkylation of vinylic C β -H of enamides with cyclic ethers. ChemistrySelect 4:6954–6957 346. Tang Z, Liu Z, Tong Z et al (2019) Cu-catalyzed cross-dehydrogenative coupling of heteroaryl C(sp 2)–H and tertiary C(sp 3)–H bonds for the construction of all-carbon triaryl quaternary centers. Org Lett 21:5152–5156 347. Xie W, Heo J, Kim D, Chang S (2020) Copper-catalyzed direct C–H alkylation of polyfluoroarenes by using hydrocarbons as an alkylating source. J Am Chem Soc 142: 7487–7496 348. Zhou J, Zou Y, Zhou P et al (2019) Copper-catalyzed versatile C(sp 3 )–H arylation: synthetic scope and regioselectivity investigations. Org Chem Front 6:1594–1598 349. Zheng C, Yan F, Liu Y et al (2022) Regioselective alkylpolyfluoroarylation of styrenes by copper-catalyzed C(sp 3)–H and C(sp 2)–H double activation. Org Lett 24:5462–5467 350. Li Z, Li C-J (2005) Highly efficient copper-catalyzed nitro-Mannich type reaction: crossdehydrogenative-coupling between sp 3 C-H bond and sp 3 C-H bond. J Am Chem Soc 127: 3672–3673

Cu-Catalyzed C-C Coupling Reactions

383

351. Li Z, Li C-J (2005) Highly efficient CuBr-catalyzed cross-dehydrogenative coupling (CDC) between tetrahydroisoquinolines and activated methylene compounds. Eur J Org Chem 2005: 3173–3176 352. Baslé O, Li C-J (2007) Copper catalyzed oxidative alkylation of sp3 C–H bond adjacent to a nitrogen atom using molecular oxygen in water. Green Chem 9:1047 353. Wei W-T, Song R-J, Li J-H (2014) Copper-catalyzed oxidative α-alkylation of α-amino carbonyl compounds with ethers via dual C(sp 3)-H oxidative cross-coupling. Adv Synth Catal 356:1703–1707 354. Huang X-F, Zhu Z-Q, Huang Z-Z (2013) Copper-catalyzed dehydrogenative cross-coupling reaction between unactivated ethers and simple ketones mediated by pyrrolidine. Tetrahedron 69:8579–8582 355. Zhang G, Zhang Y, Wang R (2011) Catalytic asymmetric activation of a C sp 3–H bond adjacent to a nitrogen atom: a versatile approach to optically active α-alkyl α-amino acids and C1-alkylated tetrahydroisoquinoline derivatives. Angew Chem 123:10613–10616 356. Lee A, Betori RC, Crane EA, Scheidt KA (2018) An enantioselective cross-dehydrogenative coupling catalysis approach to substituted tetrahydropyrans. J Am Chem Soc 140:6212–6216 357. Pandit RP, Shim J-J, Kim SH, Lee YR (2017) Copper-catalyzed direct coupling of benzoxazin-2-ones with indoles for the synthesis of diverse 3-indolylbenzoxazin-2-ones: access to natural cephalandole A. RSC Adv 7:55288–55295 358. Yang Q, Yin Z, Zheng L et al (2019) Copper-catalyzed cross-dehydrogenative coupling between quinazoline-3-oxides and indoles. RSC Adv 9:5870–5877 359. Tripathi KN, Ray D, Singh RP (2017) Synthesis of pyrrole-annulated heterocycles through copper-catalyzed site-selective dehydrogenative cross-coupling. Eur J Org Chem 2017:5809– 5813 360. Bao H, Hu X, Zhang J, Liu Y (2019) Cu(0)/Selectfluor system-catalyzed intramolecular Csp2H/Csp2-H cross-dehydrogenative coupling (CDC). Tetrahedron 75:130533 361. Alamsetti SK, Poonguzhali E, Ganapathy D, Sekar G (2013) Enantioselective oxidative coupling of 2-naphthol derivatives by copper-(R)-1,1′-binaphthyl-2,2′-diamine-TEMPO catalyst. Adv Synth Catal 355:2803–2808 362. Kim HY, Takizawa S, Oh K (2016) Copper-catalyzed divergent oxidative pathways of 2-naphthol derivatives: ortho-naphthoquinones versus 2-BINOLs. Org Biomol Chem 14: 7191–7196 363. Siemsen P, Livingston RC, Diederich F (2000) Acetylenic coupling: a powerful tool in molecular construction. Angew Chem Int Ed 39:2632–2657 364. Glaser C (1870) Untersuchungen über einige Derivate der Zimmtsäure. Ann der Chemie und Pharm 154:137–171 365. Su L, Dong J, Liu L et al (2016) Copper catalysis for selective heterocoupling of terminal alkynes. J Am Chem Soc 138:12348–12351 366. Li D, Yin K, Li J, Jia X (2008) CuI/iodine-mediated homocoupling reaction of terminal alkynes to 1,3-diynes. Tetrahedron Lett 49:5918–5919 367. Nador F, Fortunato L, Moglie Y et al (2009) A simple one-pot procedure for the direct homocoupling of terminal alkynes promoted by copper nanoparticles. Synthesis (Stuttg) 2009:4027–4031 368. Adimurthy S, Malakar CC, Beifuss U (2009) Influence of bases and ligands on the outcome of the Cu(I)-catalyzed oxidative homocoupling of terminal alkynes to 1,4-disubstituted 1,3-diynes using oxygen as an oxidant. J Org Chem 74:5648–5651 369. Oishi T, Katayama T, Yamaguchi K, Mizuno N (2009) Heterogeneously catalyzed efficient alkyne-alkyne homocoupling by supported copper hydroxide on titanium oxide. Chem A Eur J 15:7539–7542 370. Lu X, Zhang Y, Luo C, Wang Y (2006) Efficient and recyclable reaction system for the homocoupling of terminal acetylenes. Synth Commun 36:2503–2511 371. Jiang H-F, Tang J-Y, Wang A-Z et al (2006) Cu(II)-promoted oxidative homocoupling reaction of terminal alkynes in supercritical carbon dioxide. Synthesis (Stuttg):1155–1161

384

M. S. Lokolkar et al.

372. Wang D, Li J, Li N et al (2010) An efficient approach to homocoupling of terminal alkynes: solvent-free synthesis of 1,3-diynes using catalyticCu(II) and base. Green Chem 12:45–48 373. Zheng Q, Hua R, Wan Y (2009) An alternative CuCl–piperidine-catalyzed oxidative homocoupling of terminal alkynes affording 1,3-diynes in air. Appl Organomet Chem 374. Wu T-M, Huang S-H, Tsai F-Y (2011) A reusable CuSO4  5H2O/cationic 2,2′-bipyridyl system catalyzed homocoupling of terminal alkynes in water. Appl Organomet Chem 25:395– 399 375. He Y, Cai C (2012) Terminal alkyne homocoupling reactions catalyzed by an efficient and recyclable polymer-supported copper catalyst at room temperature under solvent-free conditions. Cat Sci Technol 2:1126 376. Zhu Y, Shi Y (2013) A facile copper(I)-catalyzed homocoupling of terminal alkynes to 1,3-diynes with diaziridinone under mild conditions. Org Biomol Chem 11:7451 377. Cheng G, Zhang H, Cui X (2014) Copper(I)-catalyzed homo-coupling of terminal alkynes at room temperature under solvent and base free conditions using O 2 as an oxidant. RSC Adv 4: 1849–1852 378. Sagadevan A, Lyu P-C, Hwang KC (2016) Visible-light-activated copper(I) catalyzed oxidative Csp–Csp cross-coupling reaction: efficient synthesis of unsymmetrical conjugated diynes without ligands and base. Green Chem 18:4526–4530 379. Holganza MK, Trigoura L, Elfarra S et al (2019) Copper (II) catalyzed homocoupling and heterocoupling of terminal alkynes. Tetrahedron Lett 60:1179–1181 380. Xiao Y, Gao J, Chen P et al (2021) Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions. J Chem Res 45:928–933

Top Organomet Chem (2023) 93: 385–400 https://doi.org/10.1007/3418_2023_87 # The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Published online: 30 March 2023

Zinc-Catalyzed C-C Coupling Reactions C. M. A. Afsina, Thaipparambil Aneeja, and Gopinathan Anilkumar

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Sonogashira Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Suzuki Type Cross-coupling Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Cadiot–Chodkiewicz Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Cross-Dehydrogenative Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Cross-Coupling Using Organotin Reagent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Cross-Coupling Using Grignard Reagent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Synthesis of α,β-Acetylenic Ketones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Synthesis of Conjugated Dienoate Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

385 386 388 389 389 393 395 395 396 397 398

Abstract Cross-coupling reactions have emerged as one of the most powerful tools for the formation of carbon–carbon and carbon–heteroatom bonds. In the past few years, enormous efforts have been made in developing efficient 3d transition metal catalyzed cross-coupling reactions. Among the different metals, zinc has great potential owing to its non-toxicity, earth abundance, eco-friendly, and inexpensive characteristics. During the last three decades, large number of reports have been disclosed employing zinc salts as catalysts. In view of the great interest in crosscoupling reactions, in this chapter, we summarize the chemistry to give an overview of zinc-catalyzed C-C cross-coupling reactions. Keywords Aryl iodide · Cross-coupling reaction · Diethyl zinc · Zinc · Zinc halide

C. M. A. Afsina, T. Aneeja, and G. Anilkumar (✉) School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, India e-mail: [email protected]

386

C. M. A. Afsina et al.

1 Introduction Transition metal catalyzed cross-coupling reactions are one of the most straightforward approaches for the construction of carbon–carbon (C–C) and carbon–heteroatom (C–X) bonds. Cross-coupling reactions have wide application in agrochemistry [1], material science [2], medicinal chemistry [3], and natural product synthesis [4]. Although initially, transition metal catalyzed reaction of vinyl or aryl halide or pseudohalide with organometallic reagent was referred to as cross-coupling reaction, nowadays this area became more general and includes other components and synthetic transformations [5]. Classical cross-coupling reactions such as Stille [6], Suzuki-Miyaura [7], Negishi [8], and Hiyama [9] use nucleophilic organometallic partners based on tin, boron, zinc, and silicon, respectively. In the past few years, tremendous amount of research has been progressing to expand the scope of these reactions by including a wide range of electrophiles like amides, esters, and sp3-hybridized substrates [10]. Although palladium has gained a dominance over other transition metals, recently much efforts have been devoted in exploring the efficiency of other earth abundant first row transition metals in cross-coupling reactions [11]. Nowadays, zinc has been widely employed as a catalyst in organic synthesis due to its less-toxic, earth abundant, environmentally benign, and cost-effective nature [12]. Zinc has tendency to form bonds with high degree of covalency, and the ability to form stable complexes with S- and N-donors [13]. The organozinc compounds have significant application in different reactions like Frankland–Duppa reaction [14], Reformatskii reaction [15], Negishi [5] reaction, and Fukuyama reaction [16]. The first report on diethyl zinc as a synthetic reagent was disclosed in 1848 [17]. Thereafter, studies on zinc chemistry has gradually and constantly intensified, and is still continuing. Considering the astonishing efficiency of zinc as a catalyst, it has been widely employed in different organic reactions. Even though reports on zinc-catalyzed Sonogashira reaction, Suzuki reaction, Cadiot–Chodkiewicz reaction, etc., are available, it is surprising that the potential of zinc as a catalyst in C-C cross-coupling reactions has not been explored sufficiently. Thus, it is interesting to get an idea about the zinc-catalyzed cross-coupling reactions reported so far. This chapter gives an overview of zinc-catalyzed C-C coupling reactions and is arranged based on the type of reactions.

2 Sonogashira Reaction In 2015, Anilkumar and co-workers reported the first zinc-catalyzed Sonogashira C (sp2)-C(sp) cross-coupling of alkynes with aryl iodides [18, 19]. They carried out the initial reaction using 4-iodoacetophenone and phenylacetylene as the model substrates and the optimized condition includes diethyl zinc (10 mol%), DMEDA

Zinc-Catalyzed C-C Coupling Reactions

387

Scheme 1 Synthesis of disubstituted alkynes through zinc-catalyzed Sonogashira C(sp2)-C (sp) cross-coupling

Scheme 2 Nanomagnetic zinc-catalyzed Sonogashira reaction for the synthesis of disubstituted alkynes

(10 mol%), and K3PO4 in 1,4-dioxane at 125°C for 48 h under inert condition (Scheme 1). This method was found efficient towards the synthesis of heterocyclic alkynes. The major highlights of this method include higher yield, mild reaction condition, and the use of less toxic catalyst. Later in 2022, a novel nanomagnetic zinc-catalyzed synthesis of disubstituted alkynes was established by Sharma and co-workers [20]. This novel and environment friendly Sonogashira reaction was achieved through C(sp2)-C(sp) crosscoupling reactions of aryl iodides with alkynes (Scheme 2). This is the first report of Sonogashira reaction catalyzed by nanomagnetic zinc catalyst devoid of palladium and copper. This method has many advantages such as simple procedure for the preparation of catalyst, high chemo selectivity, recyclability, and reusability of the catalyst.

388

C. M. A. Afsina et al.

3 Suzuki Type Cross-coupling Reaction Zinc-catalyzed C(sp3)-C(sp2) Suzuki–Miyaura cross-coupling reaction was first reported by Ingelson and co-workers [21]. The reaction disclosed the construction of C–C bond from benzyl bromides and aryl borates (Scheme 3). The reaction was carried out using less toxic and cost-effective ZnBr2 in 2-methyltetrahydrofuran (2-MeTHF) as solvent for 24 h without using any ligand and base. Pharmaceutically and industrially important internal alkynes were synthesized through Suzuki-type cross-coupling reaction using various transition metal catalysts such as palladium and copper. Anilkumar and co-workers developed zinc-catalyzed protocol for the construction of symmetrical and unsymmetrical alkynes through such type of cross-coupling reaction [22]. The coupling reaction initiated with phenylboronic acid and 1-bromotolyl acetylene afforded excellent yield of the diaryl acetylene product when the reaction was carried out in the presence of bidentate N, N-ligand, i.e., DMEDA (N,N-dimethyl ethylenediamine) under inert atmosphere (Scheme 4). In this reaction the possibility of formation of phenol as byproduct via the hydrolysis of phenylboronic acid was avoided by the use of 3 Å molecular sieves.

Scheme 3 Zinc-catalyzed coupling reaction of benzyl bromides and aryl borates

Zinc-Catalyzed C-C Coupling Reactions

389

Scheme 4 Suzuki-type coupling reaction towards the synthesis of symmetrical and unsymmetrical alkynes using diethyl zinc catalyst

Scheme 5 Zinc-catalyzed Cadiot–Chodkiewicz type reaction for the synthesis of conjugated diynes

4 Cadiot–Chodkiewicz Reaction Anilkumar and co-workers established zinc-catalyzed Cadiot–Chodkiewicz type reaction for the synthesis of symmetrical and unsymmetrical conjugated diynes [23]. In this reaction, terminal alkyne and 1-haloalkyne act as the nucleophile and electrophile, respectively, (Scheme 5). The reaction performed well in the presence of ligand, base, and solvent under inert condition, and afforded excellent yield of desired product.

5 Cross-Dehydrogenative Coupling A zinc triflate catalyzed methodology for the synthesis of alkynylated nitrones from nitrones and terminal alkynes via cross-dehydrogenative coupling was established by Studer and co-workers [24]. This method utilized cost-effective and easily available dioxygen and 3,3′,5,5′-tetra-tert-butyldipheno-quinone (1) as oxidants (Scheme 6). Aryl acetylenes with electron-withdrawing and electron-donating substituents participated well in this reaction. Aromatic nitrones failed to achieve the

390

C. M. A. Afsina et al.

Scheme 6 Zinc triflate catalyzed synthesis of alkynylated nitrones from nitrones and terminal alkynes

Scheme 7 Synthesis of N-tethered 1,6-enynes via redox cross-dehydrogenative coupling

required product via this method. The conversion of this alkynylated nitrones to 3,5-disubstituted isoxazoles further enhances the significance of this methodology. An efficient scheme for N-tethered 1,6-enyne synthesis via redox crossdehydrogenative coupling was reported [25]. The reaction between propargylic amines and terminal alkynes was catalyzed by ZnBr2 in toluene at 100°C which exhibited high atom economy (Scheme 7). This method avoids the usage of external oxidant as tertiary amine with C-C triple bond serving as an internal oxidant.

Zinc-Catalyzed C-C Coupling Reactions

391

Scheme 8 Visible light mediated synthesis of ynones from terminal alkynes and aldehydes

Scheme 9 Synthesis of propargylamines via cross dehydrogenative coupling reaction of terminal alkynes and tertiary amines

Bhalla et al. developed a visible light mediated methodology for the synthesis of ynones from terminal alkynes and aldehydes via dehydrogenative cross-coupling [26]. Supramolecular polymer perylene bisimide (PBI): ZnO NPs have been employed as an efficient photocatalytic system for this reaction (Scheme 8). Mild reaction condition, wide substrate scope, and the high recyclability of the catalyst are the main peculiarities of this reaction. Another cross-dehydrogenative coupling reaction for the preparation of propargylamines from terminal alkynes and tertiary amines under aerobic condition was designed [27]. Here, ZnBr2 and manganese oxide-based octahedral molecular sieve (OMS-2) were employed as the combined catalyst in cyclopentyl methyl ether (CPME) (Scheme 9). The steric effects of the substituents did not influence much in

392

C. M. A. Afsina et al.

Scheme 10 Zinc-catalyzed dehydrogenative cross-coupling between terminal alkynes and aldehydes

the yield of the reaction. The major advantages of this reaction include catalyst recyclability and the use of molecular oxygen as the terminal oxidant. A straightforward atom economic strategy towards the synthesis of ynones was disclosed by the same group in 2015 [28]. This dehydrogenative C(sp2)-H/C(sp)-H cross-coupling between terminal alkynes and aldehydes was proceeded well at 80°C when Zn(OTf)2 and α,α,α-trifluoroacetophenone are utilized as catalyst and oxidant, respectively (Scheme 10). Mild reaction condition, easy availability of starting materials, excellent selectivity, and high yields are the major characteristics of this method. Li and co-workers established a synthetic pathway towards 2-substituted tetrahydroquinolines via zinc-catalyzed intramolecular hydroarylation-redox crossdehydrogenative coupling of N-propargylanilines [29]. They performed this reaction with two types of carbon pronucleophiles such as nitromethane (sp3 carbon pronucleophile) and phenylacetylene (sp carbon pronucleophile) (Schemes 11 and 12). The substrate scope was found to be wide with 100% atomic utilization without adding any external oxidant. Zinc(II)-catalyzed protocol for the synthesis of 2-indolyltetrahydroquinolines from N-propargylanilines and indoles was reported by Li and co-workers [30]. This dehydrogenative cross-coupling reaction provided good to excellent yield of the desired product with the aid of dichloroethane as solvent under nitrogen atmosphere (Scheme 13). In this reaction, the three C–H bonds, i.e., one sp3 and two sp2 C–H bonds were activated at the same time and these H atoms were captured by a propargylic triple bond and which then undergo intramolecular hydroarylation redox reaction.

Zinc-Catalyzed C-C Coupling Reactions

393

Scheme 11 Intramolecular nitromethane

hydroarylation-redox

cross-dehydrogenative

coupling

using

Scheme 12 Intramolecular phenylacetylene

hydroarylation-redox

cross-dehydrogenative

coupling

using

6 Cross-Coupling Using Organotin Reagent A new methodology towards the synthesis of γ-diketones by the reaction between tin enolates and α-chloro- or bromoketone in the presence of zinc halides was developed (Scheme 14) [31]. The major steps involved in this strategy include the formation of an aldol-type species via the precondensation between α-haloketone and tin enolates and the formation of 1,4-diketones through the rearrangement of oxoalkyl group with leaving halogen. This method was found even suitable to sterically hindered

394

C. M. A. Afsina et al.

Scheme 13 Synthesis of 2-indolyltetrahydroquinolines from N-propargylanilines and indoles Scheme 14 Synthesis of γ-diketones from tin enolates and α-chloro- or bromoketone

chloroketones. Both electron-donating and electron-withdrawing tin enolates exhibit similar reactivity in this reaction. Stille and co-workers developed a novel method for the synthesis of myrcene, β-farnesene, and vitamin K1 through the cross-coupling reaction between allyl bromide and organotin reagents using zinc chloride as the catalyst [32]. This coupling reaction yielded 1,5-dienes in the presence of THF at 65°C (Schemes 15 and 16).

Scheme 15 Synthesis of myrcene via cross-coupling reaction between allyl bromide and organotin reagents

Zinc-Catalyzed C-C Coupling Reactions

395

Scheme 16 Synthesis of β-farnesene via cross-coupling reaction between allyl bromide and organotin reagents

7 Cross-Coupling Using Grignard Reagent Breit and Studte put forward the first enantiospecific zinc-catalyzed sp3–sp3 crosscoupling using Grignard reagents [33]. Easily accessible α-hydroxy esters were utilized as the electrophilic coupling partners in this protocol (Scheme 17). Synthesis of compounds with sterically hindered tertiary carbon centers in high yield and excellent enantioselectivity is the major feature of this reaction.

8 Synthesis of α,β-Acetylenic Ketones Due to the bifunctional electrophilicity, α,β-acetylenic ketones have more importance in organic synthesis as synthetic intermediates. Keivanloo and co-workers introduced a reusable heterogeneous catalyst to synthesize α,β-acetylenic ketones in 2010 [34]. The major advantage of this catalyst is that it reduces the byproduct formation in coupling reaction. The coupling reaction between acyl chloride and terminal alkyne in the presence of 6 mol% polystyrene-supported zinc bromide ethylenediamine complex [PS-en-ZnBr2] under air in toluene afforded the required product in good yield (Scheme 18).

Scheme 17 Zinc-catalyzed enantiospecific cross-coupling using Grignard reagents

396

C. M. A. Afsina et al.

Scheme 18 Synthesis of α,β-acetylenic ketones using polystyrene-supported zinc bromide ethylenediamine complex catalyst

Scheme 19 Zinc bromide (ZnBr2/SiO2) catalyzed synthesis of α,β-acetylenic ketones

In 2011, the same group put forward another synthetic method for the preparation of α,β-acetylenic ketones or ynones under neat condition [35]. In this reaction, they utilized silica-supported zinc bromide (ZnBr2/SiO2) as the catalyst and DIPEA as the base and obtained the desired product in excellent yield under mild reaction condition (Scheme 19).

9 Synthesis of Conjugated Dienoate Derivatives Vicente et al. designed a new protocol towards the synthesis of conjugated dienoate derivatives via the selective cross-coupling of vinyl diazo compounds and enynones (Scheme 20) [36]. This method involves the in situ generation of Zinc carbenes from

Zinc-Catalyzed C-C Coupling Reactions

397

Scheme 20 Synthesis of conjugated dienoate derivatives from vinyl diazo compounds and enynones

enynones and the unexpected cross-coupling of this carbene with vinyl diazo compound at the γ-carbon. Less toxic ZnCl2 was the catalyst of choice for this reaction. Inexpensive and atom-economic synthetic protocol towards 2-alkenylfuran through cross-coupling reaction using ZnCl2 was developed by Gonzalez and co-workers [37]. The reaction between enynones and diazo compounds in the presence of CH2Cl2 at room temperature furnished good to excellent yield of the product (Scheme 21).

10

Conclusion

Transition metal catalyzed cross-coupling reactions play a pivotal role in pharmaceuticals, natural product synthesis, and industrial field. Even though palladium is the most commonly used metal catalyst for coupling reactions, recently other earth abundant first row transition metals have been widely exploited in these crosscouplings. In the past few years, zinc-catalyzed organic transformations have achieved astonishing developments owing to its low-toxicity, cost effectiveness, and earth abundance. From our discussion it is clear that zinc has the ability to catalyze various cross-coupling reactions like Sonogashira reaction, Suzuki reaction, dehydrogenative cross-coupling, Cadiot–Chodkiewicz reaction, etc.

398

C. M. A. Afsina et al.

Scheme 21 Synthesis of 2-alkenylfuran via zinc-catalyzed cross-coupling reaction

Most of the reported methods prefer zinc halide as the catalyst. In addition, some of the methods disclosed the efficiency of diethyl zinc in cross-couplings. Coupling reactions with heterogeneous zinc catalyst having high recyclability are rare and need much attention in future. Detailed mechanistic studies are still missing in some of the reported works. Although zinc is widely exploited in organic transformations, zinc-catalyzed cross-coupling is still in its infancy. The scientific community are still trying their best to expand the potential of zinc in cross-couplings and to bring out the more environment-friendly and reliable zinc-catalyzed cross-coupling reactions.

References 1. Devendar P, Qu R-Y, Kang W-M, He B, Yang G-F (2018) Palladium-catalyzed cross-coupling reactions: a powerful tool for the synthesis of agrochemicals. J Agric Food Chem 66(34): 8914–8934 2. Buchwald SL (2008) Cross coupling. Acc Chem Res 41(11):1439 3. Zhang R, Li G, Wismer M, Vachal P, Colletti SL, Shi Z-C (2018) Profiling and application of photoredox C(sp3)-C(sp2) cross-coupling in medicinal chemistry. ACS Med Chem Lett 9(7): 773–777 4. Tabassum S, Zahoor AF, Ahmad S, Noreen R, Khan SG, Ahmad H (2021) Cross coupling reactions towards the synthesis of natural products. Mol Divers 26:647–668 5. Sestelo JP, Sarandeses LA (2020) Advances in cross-coupling reactions. Molecules 25(19): 4500–4504

Zinc-Catalyzed C-C Coupling Reactions

399

6. Kosugi M, Fugami K (2002) A historical note of the Stille reaction. J Organomet Chem 653(1): 50–53 7. Beletskaya IP, Alonso F, Tyurin V (2019) The Suzuki-Miyaura reaction after the Nobel prize. Coord Chem Rev 385:137–173 8. Phapale VB, Cardenas DJ (2009) Nickel-catalysed Negishi cross-coupling reactions: scope and mechanisms. Chem Soc Rev 38(6):1598–1607 9. Nakao Y, Hiyama T (2011) Silicon-based cross-coupling reaction: an environmentally benign version. Chem Soc Rev 40(10):4893–4901 10. Zeng H, Qiu Z, Domínguez-Huerta A, Hearne Z, Chen Z, Li C-J (2017) An adventure in sustainable cross-coupling of phenols and derivatives via carbon–oxygen bond cleavage. ACS Catal 7(1):510–519 11. Su B, Cao Z-C, Shi Z-J (2015) Exploration of earth-abundant transition metals (Fe, Co, and Ni) as catalysts in unreactive chemical bond activations. Acc Chem Res 48(3):886–896 12. Wu X-F, Neumann H (2012) Zinc-catalyzed organic synthesis: C-C, C-N, C-O bond formation reactions. Adv Synth Catal 354(17):3141–3160 13. Greenwood NN, Earnshaw A (1997) Chemistry of the elements.2nd edn. ButterworthHeinemann, Oxford 14. Frankland FRS, Duppa BF (1864) On a new reaction for the production of the zinc-compounds of the alcohol-radicles. J Chem Soc 17:29–36 15. Choppin S, Ferreiro-Medeiros L, Barbarotto M, Colobert F (2012) Recent advances in the diastereoselective Reformatsky-type reaction. Chem Soc Rev 42(3):937–949 16. Kunchithapatham K, Eichman CF, Stambuli JP (2011) Synthesis of diaryl ketones via a phosphine-free Fukuyama reaction. Chem Commun 47(47):12679–12681 17. Frankland E (1849) Ueber die Isolirung der organischen Radicale. Ann Chem Pharm 71(2): 171–213 18. Thankachan AP, Sindhu KS, Krishnan KK, Anilkumar G (2015) An efficient zinc-catalyzed cross-coupling reaction of aryl iodides with terminal aromatic alkynes. Tetrahedron Lett 56(41): 5525–5528 19. Thankachan AP, Abi TG, Sindhu KS, Anilkumar G (2016) Experimental and mechanistic exploration of Zn-catalyzed Sonogashira–type cross-coupling reactions. ChemistrySelect 1(13): 3405–3412 20. Raya I, Jasim SA, Abdulkadhim AH, Abbud LH, Sharma H (2022) Zinc (II) complex immobilized on the surface of magnetic nanoparticles modified with phenanthroline: a novel and efficient nanomagnetic reusable catalyst for cross-coupling reaction of aryl iodides with terminal aromatic alkynes. Synth Commun 52(15):1602–1613 21. Procter RJ, Dunsford JJ, Rushworth PJ, Hulcoop DG, Layfield RA, Ingleson MJ (2017) A zinc catalyzed C(sp3)-C(sp2) Suzuki–Miyaura cross-coupling reaction mediated by aryl-zincates. Chem A Eur J 23:15889–15893 22. Krishnan KK, Saranya S, Rohit KR, Anilkumar G (2019) A novel zinc-catalyzed Suzuki-type cross-coupling reaction of aryl boronic acids with alkynyl bromides. J Catal 372:266–271 23. Krishnan KK, Ujwaldev SM, Thankachan AP, Harry NA, Anilkumar G (2017) A novel zinccatalyzed Cadiot-Chodkiewicz cross-coupling reaction of terminal alkynes with 1-bromoalkynes in ethanol solvent. Mol Catal 440:140–147 24. Murarka S, Studer A (2011) Zinc triflate catalyzed aerobic CrossDehydrogenative coupling (CDC) of alkynes with nitrones: a new entry to isoxazoles. Org Lett 13(10):2746–2749 25. Sugiishi T, Nakamura H (2012) Zinc(II)-catalyzed redox cross-dehydrogenative coupling of propargylic amines and terminal alkynes for synthesis of N-tethered 1,6-enynes. J Am Chem Soc 134(5):2504–2507 26. Kataria M, Deol H, Singh G, Kumar M, Bhalla V (2018) Visible-light-mediated dehydrogenative cross-coupling between terminal alkynes and aldehydes by employing a supramolecular polymeric ensemble of PBI derivative. New J Chem 42(2):822–826

400

C. M. A. Afsina et al.

27. Jin X, Yamaguchi K, Mizuno N (2014) Aerobic cross-dehydrogenative coupling of terminal alkynes and tertiary amines by a combined catalyst of Zn2+ and OMS-2. RSC Adv 4(65): 34712–34715 28. Tang S, Zeng L, Liu Y, Lei A (2015) Zinc-catalyzed dehydrogenative cross-coupling of terminal alkynes with aldehydes: access to Ynones. Angew Chem Int Ed 54(52):15850–11583 29. Li G, Wang C, Li Y, Shao K, Yu G, Wang S, Guo X, Zhao W, Nakamura H (2020) Zinc(II)catalyzed intramolecular hydroarylation-redox cross dehydrogenative coupling of N-propargylanilines with diverse carbon pronucleophiles: facile access to functionalized tetrahydroquinolines. Chem Commun 56(53):7333–7336 30. Li G, Nakamura H (2016) Synthesis of 2-indolyltetrahydroquinolines by zinc(II)-catalyzed intramolecular hydroarylation-redox cross-dehydrogenative coupling of N-propargylanilines with indoles. Angew Chem Int Ed 55(23):6758–6761 31. Yasuda M, Tsuji S, Shigeyoshi Y, Baba A (2002) Cross-coupling reaction of α-chloroketones and organotin enolates catalyzed by zinc halides for synthesis of γ-diketones. J Am Chem Soc 124(25):7440–7447 32. Godschalx JP, Stille JK (1983) Cross-coupling reaction of allyl bromides with organotin reagents catalyzed by zinc chloride. Tetrahedron Lett 24(18):1905–1908 33. Studte C, Breit B (2008) Zinc-catalyzed enantiospecific sp3–sp3 cross-coupling of α-hydroxy ester triflates with Grignard reagents. Angew Chem Int Ed 47(29):5451–5455 34. Keivanloo A, Bakherad M, Bahramian B, Rahmani M, Taheri SAN (2011) Polystyrenesupported zinc bromide–ethylenediamine complex as a reusable and highly efficient heterogeneous catalyst for the synthesis of α,β-acetylenic ketones. Synthesis 2:325–329 35. Keivanloo A, Bakherad M, Bahramian B, Baratnia S (2011) Silica-supported zinc bromide (ZnBr2/SiO2): a highly efficient heterogeneous catalyst for coupling acid chlorides with terminal alkynes. Tetrahedron Lett 52(13):1498–1502 36. Mata S, González MJ, González J, López LA, Vicente R (2016) Zinc-catalyzed synthesis of conjugated dienoates via unusual cross-couplings of zinc carbenes with diazo compounds. Chem A Eur J 23(5):1013–1017 37. Gonza’lez J, Lo’pez LA, Vicente R (2014) Zinc-catalyzed synthesis of 2-alkenylfurans via cross-coupling of enynones and diazo compounds. Chem Commun 50(62):8536–8538