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Xu W, Xu T. Dual Nickel- and Photoredox-Catalyzed Asymmetric Reductive Cross-Couplings: Just a Change of the Reduction System? Acc Chem Res 2024; 57:1997-2011. [PMID: 38961540 DOI: 10.1021/acs.accounts.4c00309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
ConspectusIn recent years, nickel-catalyzed asymmetric coupling reactions have emerged as efficient methods for constructing chiral C(sp3) carbon centers. Numerous novel approaches have been reported to rapidly construct chiral carbon-carbon bonds through nickel-catalyzed asymmetric couplings between electrophiles and nucleophiles or asymmetric reductive cross-couplings of two different electrophiles. Building upon these advances, our group has been devoted to interrogating dual nickel- and photoredox-catalyzed asymmetric reductive cross-coupling reactions.In our endeavors over the past few years, we have successfully developed several dual Ni-/photoredox-catalyzed asymmetric reductive cross-coupling reactions involving organohalides. While some probably think that this system is just a change of the reduction system from traditional metal reductants to a photocatalysis system, a question that we also pondered at the beginning of our studies, both the achievable reaction types and mechanisms suggest a different conclusion: that this dual catalysis system has its own advantages in the chiral carbon-carbon bond formation. Even in certain asymmetric reactions where the photocatalysis regime functions only as a reducing system, the robust reducing capability of photocatalysts can effectively accelerate the regeneration of low-valent nickel species, thus expanding the selectable scope of chiral ligands. More importantly, in many transformations, besides reducing nickel catalysts, the photocatalysis system can also undertake the responsibility of alkyl radical formation, thereby establishing two coordinated, yet independent catalytic cycles. This catalytic mode has been proven to play a crucial role in achieving diverse asymmetric coupling reactions with great challenges.In this Account, we elucidate our understanding of this system based on our experience and findings. In the Introduction, we provide an overview of the main distinctions between this system and traditional Ni-catalyzed asymmetric reductive cross-couplings with metal reductants and the potential opportunities arising from these differences. Subsequently, we outline various chiral carbon-carbon bond-forming types obtained by this dual Ni/photoredox catalysis system and their mechanisms. In terms of chiral C(sp3)-C(sp2) bond formation, extensive discussion focuses on the asymmetric arylations of α-chloroboronates, α-trifluoromethyl alkyl bromides, α-bromophosphonates, and so on. In the realm of chiral C(sp3)-C(sp) bond formation, asymmetric alkynylations of α-bromophosphonates and α-trifluoromethyl alkyl bromides have been presented herein. Regarding C(sp3)-C(sp3) bond formation, we take the asymmetric alkylation of α-chloroboronates as a compelling example to illustrate the great efficiency of this dual catalysis system. This summary would enable a better grasp of the advantages of this dual catalysis system and clarify how the photocatalysis regime facilitates enantioselective transformations. We anticipate that this Account will offer valuable insights and contribute to the development of new methodologies in this field.
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Affiliation(s)
- Wenhao Xu
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China
| | - Tao Xu
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China
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Sonawane SC, Gourkhede R, Saini P, Ramakrishnan S, Balakrishna MS. Cu I-amidobis(phosphine) catalyzed C(sp 3)-C(sp 3) direct homo- and hetero-coupling of unactivated alkanes via C(sp 3)-H activation. Chem Commun (Camb) 2024; 60:6055-6058. [PMID: 38780035 DOI: 10.1039/d4cc01119h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Herein, we present a CuI-dimer, [CuI{Ph2PC6H4C(O)NC6H4PPh2-o}]2, which catalyzed direct C(sp3)-H homocoupling of benzyl and cycloalkane derivatives with excellent yields and regio-selectivity. The method is very simple and tolerates various functionalities. Synergistic metal-ligand cooperativity was observed in Cu-N bond cleavage and protonation of nitrogen, and facilitates a bifunctional pathway, minimising the free energy corrugation for catalytic intermediates.
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Affiliation(s)
- Sachin C Sonawane
- Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
| | - Rani Gourkhede
- Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
| | - Prateek Saini
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
| | - Srinivasan Ramakrishnan
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
| | - Maravanji S Balakrishna
- Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
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Zeng XW, Lin JN, Shu W. Hydrogen Source Tuned Regiodivergent Asymmetric Hydroalkylations of 2-Substituted 1,3-Dienes with Aldehydes by Cobalt-Catalysis. Angew Chem Int Ed Engl 2024; 63:e202403073. [PMID: 38567830 DOI: 10.1002/anie.202403073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Indexed: 05/03/2024]
Abstract
Catalytic methods allowing for the reliable prediction and control of diverse regioselectivity along with the control of enantioselectivity to access different regio- and enantiomers by switching the least reaction parameters are one of the most attractive ways in organic synthesis, which provide access to diverse enantioenriched architectures from identical starting materials. Herein, a Co-catalyzed regiodivergent and enantioselective reductive hydroalkylation of 1,3-dienes with aldehydes has been achieved, furnishing different enantioenriched homoallylic alcohol architectures in good levels of enantioselectivity. The reaction features the switch of regioselectivity tuned by the selection of proton source. The use of an acid as proton source provided asymmetric 1,2-hydroalkylation products under reductive conditions, yet asymmetric 4,3-hydroalkylation products were obtained with silane as hydride source. This catalytic protocol allows for the access of homoallylic alcohols with two continuous saturated carbon centers in good levels of regio-, diastereo-, and enantioselectivity.
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Affiliation(s)
- Xian-Wang Zeng
- Department of Chemistry, Guangming Advanced Research Institute and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, P. R. China
| | - Jia-Ni Lin
- Department of Chemistry, Guangming Advanced Research Institute and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, P. R. China
| | - Wei Shu
- Department of Chemistry, Guangming Advanced Research Institute and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, P. R. China
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Fu H, Hyster TK. From Ground-State to Excited-State Activation Modes: Flavin-Dependent "Ene"-Reductases Catalyzed Non-natural Radical Reactions. Acc Chem Res 2024; 57:1446-1457. [PMID: 38603772 DOI: 10.1021/acs.accounts.4c00129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
Enzymes are desired catalysts for chemical synthesis, because they can be engineered to provide unparalleled levels of efficiency and selectivity. Yet, despite the astonishing array of reactions catalyzed by natural enzymes, many reactivity patterns found in small molecule catalysts have no counterpart in the living world. With a detailed understanding of the mechanisms utilized by small molecule catalysts, we can identify existing enzymes with the potential to catalyze reactions that are currently unknown in nature. Over the past eight years, our group has demonstrated that flavin-dependent "ene"-reductases (EREDs) can catalyze various radical-mediated reactions with unparalleled levels of selectivity, solving long-standing challenges in asymmetric synthesis.This Account presents our development of EREDs as general catalysts for asymmetric radical reactions. While we have developed multiple mechanisms for generating radicals within protein active sites, this account will focus on examples where flavin mononucleotide hydroquinone (FMNhq) serves as an electron transfer radical initiator. While our initial mechanistic hypotheses were rooted in electron-transfer-based radical initiation mechanisms commonly used by synthetic organic chemists, we ultimately uncovered emergent mechanisms of radical initiation that are unique to the protein active site. We will begin by covering intramolecular reactions and discussing how the protein activates the substrate for reduction by altering the redox-potential of alkyl halides and templating the charge transfer complex between the substrate and flavin-cofactor. Protein engineering has been used to modify the fundamental photophysics of these reactions, highlighting the opportunity to tune these systems further by using directed evolution. This section highlights the range of coupling partners and radical termination mechanisms available to intramolecular reactions.The next section will focus on intermolecular reactions and the role of enzyme-templated ternary charge transfer complexes among the cofactor, alkyl halide, and coupling partner in gating electron transfer to ensure that it only occurs when both substrates are bound within the protein active site. We will highlight the synthetic applications available to this activation mode, including olefin hydroalkylation, carbohydroxylation, arene functionalization, and nitronate alkylation. This section also discusses how the protein can favor mechanistic steps that are elusive in solution for the asymmetric reductive coupling of alkyl halides and nitroalkanes. We are aware of several recent EREDs-catalyzed photoenzymatic transformations from other groups. We will discuss results from these papers in the context of understanding the nuances of radical initiation with various substrates.These biocatalytic asymmetric radical reactions often complement the state-of-the-art small-molecule-catalyzed reactions, making EREDs a valuable addition to a chemist's synthetic toolbox. Moreover, the underlying principles studied with these systems are potentially operative with other cofactor-dependent proteins, opening the door to different types of enzyme-catalyzed radical reactions. We anticipate that this Account will serve as a guide and inspire broad interest in repurposing existing enzymes to access new transformations.
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Affiliation(s)
- Haigen Fu
- NHC Key Laboratory of Biotechnology for Microbial Drugs, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China
| | - Todd K Hyster
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Zhang LL, Gao YZ, Cai SH, Yu H, Shen SJ, Ping Q, Yang ZP. Ni-catalyzed enantioconvergent deoxygenative reductive cross-coupling of unactivated alkyl alcohols and aryl bromides. Nat Commun 2024; 15:2733. [PMID: 38548758 PMCID: PMC10979021 DOI: 10.1038/s41467-024-46713-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 03/07/2024] [Indexed: 04/01/2024] Open
Abstract
Transition metal-catalyzed enantioconvergent cross-coupling of an alkyl precursor presents a promising method for producing enantioenriched C(sp3) molecules. Because alkyl alcohol is a ubiquitous and abundant family of feedstock in nature, the direct reductive coupling of alkyl alcohol and aryl halide enables efficient access to valuable compounds. Although several strategies have been developed to overcome the high bond dissociation energy of the C - O bond, the asymmetric pattern remains unknown. In this report, we describe the realization of an enantioconvergent deoxygenative reductive cross-coupling of unactivated alkyl alcohol (β-hydroxy ketone) and aryl bromide in the presence of an NHC activating agent. The approach can accommodate substituents of various sizes and functional groups, and its synthetic potency is demonstrated through a gram scale reaction and derivatizations into other compound families. Finally, we apply our convergent method to the efficient asymmetric synthesis of four β-aryl ketones that are natural products or bioactive compounds.
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Affiliation(s)
- Li-Li Zhang
- School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Yu-Zhong Gao
- Key Laboratory of Magnetic Molecules, Magnetic Information Materials Ministry of Education, The School of Chemical and Material Science, Shanxi Normal University, Taiyuan, 030031, People's Republic of China
| | - Sheng-Han Cai
- School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Hui Yu
- School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Shou-Jie Shen
- Key Laboratory of Magnetic Molecules, Magnetic Information Materials Ministry of Education, The School of Chemical and Material Science, Shanxi Normal University, Taiyuan, 030031, People's Republic of China
| | - Qian Ping
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Ze-Peng Yang
- School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China.
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Wen S, Bu J, Shen K. Dual Nickel- and Photoredox-Catalyzed Asymmetric Reductive Cross-Coupling To Access Chiral Secondary Benzylic Alcohols. J Org Chem 2024. [PMID: 38327084 DOI: 10.1021/acs.joc.3c02293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Transition-metal-catalyzed asymmetric cross-coupling represents a powerful strategy for C-C bond formation and the synthesis of enantiomerically pure molecules. Here, we report a dual nickel/photoredox-catalyzed enantioselective reductive cross-coupling of aryl halides with α-bromobenzoates, readily generated from aliphatic aldehydes, to provide diverse chiral secondary benzylic alcohols that are important motifs in bioactive natural products and pharmaceuticals. This dual catalytic system features mild conditions, good functional group tolerance, broad substrate scope, excellent enantiocontrol, and avoidance of stoichiometric metal reductants, presenting great potential for late-stage functionalization of complex molecules.
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Affiliation(s)
- Shun Wen
- Department of Radiology, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Jie Bu
- Department of Radiology, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Kun Shen
- Department of Radiology, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
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