1
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Buzsaki SR, Mason SM, Kattamuri PV, Serviano JMI, Rodriguez DN, Wilson CV, Hood DM, Ellefsen JD, Lu YC, Kan J, West JG, Miller SJ, Holland PL. Fe/Thiol Cooperative Hydrogen Atom Transfer Olefin Hydrogenation: Mechanistic Insights That Inform Enantioselective Catalysis. J Am Chem Soc 2024. [PMID: 38875703 DOI: 10.1021/jacs.4c04047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2024]
Abstract
Asymmetric hydrogenation of activated olefins using transition metal catalysis is a powerful tool for the synthesis of complex molecules, but traditional metal catalysts have difficulty with enantioselective reduction of electron-neutral, electron-rich, and minimally functionalized olefins. Hydrogenation based on radical, metal-catalyzed hydrogen atom transfer (mHAT) mechanisms offers an outstanding opportunity to overcome these difficulties, enabling the mild reduction of these challenging olefins with selectivity that is complementary to traditional hydrogenations with H2. Further, mHAT presents an opportunity for asymmetric induction through cooperative hydrogen atom transfer (cHAT) using chiral thiols. Here, we report insights from a mechanistic study of an iron-catalyzed achiral cHAT reaction and leverage these insights to deliver stereocontrol from chiral thiols. Kinetic analysis and variation of silane structure point to the transfer of hydride from silane to iron as the likely rate-limiting step. The data indicate that the selectivity-determining step is quenching of the alkyl radical by thiol, which becomes a more potent H atom donor when coordinated to iron(II). The resulting iron(III)-thiolate complex is in equilibrium with other iron species, including FeII(acac)2, which is shown to be the predominant off-cycle species. The enantiodetermining nature of the thiol trapping step enables enantioselective net hydrogenation of olefins through cHAT using a commercially available glucose-derived thiol catalyst with up to 80:20 enantiomeric ratio. To the best of our knowledge, this is the first demonstration of asymmetric hydrogenation via iron-catalyzed mHAT. These findings advance our understanding of cooperative radical catalysis and act as a proof of principle for the development of enantioselective iron-catalyzed mHAT reactions.
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Affiliation(s)
- Sarah R Buzsaki
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Savannah M Mason
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | | | - Juan M I Serviano
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Dinora N Rodriguez
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Conner V Wilson
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Drew M Hood
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Jonathan D Ellefsen
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Yen-Chu Lu
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Jolie Kan
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Julian G West
- Department of Chemistry, Rice University, Houston, Texas 77030, United States
| | - Scott J Miller
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Patrick L Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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2
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Yamaguchi Y, Hirata Y, Higashida K, Yoshino T, Matsunaga S. Cobalt/Photoredox Dual-Catalyzed Cross-Radical Coupling of Alkenes via Hydrogen Atom Transfer and Homolytic Substitution. Org Lett 2024; 26:4893-4897. [PMID: 38836750 DOI: 10.1021/acs.orglett.4c01370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Cobalt-catalyzed metal hydride hydrogen atom transfer (MHAT) in combination with photoredox catalysis has emerged as a powerful synthetic method, owing to its redox nature and applicability to various radical precursors. Herein, we describe a cross-radical coupling reaction under cobalt/photoredox dual catalysis. MHAT and homolytic substitution (SH2) processes enabled Markovnikov-selective hydrobenzylation of di/trisubstituted alkenes, affording products with a quaternary carbon center in a redox-neutral manner.
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Affiliation(s)
- Yuto Yamaguchi
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0808, Japan
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yuki Hirata
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0808, Japan
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kosuke Higashida
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Tatsuhiko Yoshino
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0808, Japan
| | - Shigeki Matsunaga
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0808, Japan
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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3
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Cai Q, McWhinnie IM, Dow NW, Chan AY, MacMillan DWC. Engaging Alkenes in Metallaphotoredox: A Triple Catalytic, Radical Sorting Approach to Olefin-Alcohol Cross-Coupling. J Am Chem Soc 2024; 146:12300-12309. [PMID: 38657210 DOI: 10.1021/jacs.4c02316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Metallaphotoredox cross-coupling is a well-established strategy for generating clinically privileged aliphatic scaffolds via single-electron reactivity. Correspondingly, expanding metallaphotoredox to encompass new C(sp3)-coupling partners could provide entry to a novel, medicinally relevant chemical space. In particular, alkenes are abundant, bench-stable, and capable of versatile C(sp3)-radical reactivity via metal-hydride hydrogen atom transfer (MHAT), although metallaphotoredox methodologies invoking this strategy remain underdeveloped. Importantly, merging MHAT activation with metallaphotoredox could enable the cross-coupling of olefins with feedstock partners such as alcohols, which undergo facile open-shell activation via photocatalysis. Herein, we report the first C(sp3)-C(sp3) coupling of MHAT-activated alkenes with alcohols by performing deoxygenative hydroalkylation via triple cocatalysis. Through synergistic Ir photoredox, Mn MHAT, and Ni radical sorting pathways, this branch-selective protocol pairs diverse olefins and methanol or primary alcohols with remarkable functional group tolerance to enable the rapid construction of complex aliphatic frameworks.
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Affiliation(s)
- Qinyan Cai
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - Iona M McWhinnie
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - Nathan W Dow
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - Amy Y Chan
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
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4
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Cong F, Sun GQ, Ye SH, Hu R, Rao W, Koh MJ. A Bimolecular Homolytic Substitution-Enabled Platform for Multicomponent Cross-Coupling of Unactivated Alkenes. J Am Chem Soc 2024; 146:10274-10280. [PMID: 38568080 DOI: 10.1021/jacs.4c02284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/18/2024]
Abstract
The construction of C(sp3)-C(sp3) bonds remains one of the most difficult challenges in cross-coupling chemistry. Here, we report a photoredox/nickel dual catalytic approach that enables the simultaneous formation of two C(sp3)-C(sp3) linkages via trimolecular cross-coupling of alkenes with alkyl halides and hypervalent iodine-based reagents. The reaction harnesses a bimolecular homolytic substitution (SH2) mechanism and chemoselective halogen-atom transfer (XAT) to orchestrate the regioselective addition of electrophilic and nucleophilic alkyl radicals across unactivated alkenes without the need for a directing auxiliary. Utility is highlighted through late-stage (fluoro)alkylation and (trideutero)methylation of C═C bonds bearing different substitution patterns, offering straightforward access to drug-like molecules comprising sp3-hybridized carbon scaffolds.
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Affiliation(s)
- Fei Cong
- Department of Chemistry, National University of Singapore, 4 Science Drive 2, Republic of Singapore, 117544
| | - Guo-Quan Sun
- Department of Chemistry, National University of Singapore, 4 Science Drive 2, Republic of Singapore, 117544
| | - Si-Han Ye
- Department of Chemistry, National University of Singapore, 4 Science Drive 2, Republic of Singapore, 117544
| | - Rui Hu
- Department of Chemistry, National University of Singapore, 4 Science Drive 2, Republic of Singapore, 117544
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Weidong Rao
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Ming Joo Koh
- Department of Chemistry, National University of Singapore, 4 Science Drive 2, Republic of Singapore, 117544
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5
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Gan XC, Zhang B, Dao N, Bi C, Pokle M, Kan L, Collins MR, Tyrol CC, Bolduc PN, Nicastri M, Kawamata Y, Baran PS, Shenvi R. Carbon quaternization of redox active esters and olefins by decarboxylative coupling. Science 2024; 384:113-118. [PMID: 38574151 DOI: 10.1126/science.adn5619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 02/28/2024] [Indexed: 04/06/2024]
Abstract
The synthesis of quaternary carbons often requires numerous steps and complex conditions or harsh reagents that act on heavily engineered substrates. This is largely a consequence of conventional polar-bond retrosynthetic disconnections that in turn require multiple functional group interconversions, redox manipulations, and protecting group chemistry. Here, we report a simple catalyst and reductant combination that converts two types of feedstock chemicals, carboxylic acids and olefins, into tetrasubstituted carbons through quaternization of radical intermediates. An iron porphyrin catalyst activates each substrate by electron transfer or hydrogen atom transfer, and then combines the fragments using a bimolecular homolytic substitution (SH2) reaction. This cross-coupling reduces the synthetic burden to procure numerous quaternary carbon---containing products from simple chemical feedstocks.
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Affiliation(s)
- Xu-Cheng Gan
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Benxiang Zhang
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Nathan Dao
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Cheng Bi
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Maithili Pokle
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Liyan Kan
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
- College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Michael R Collins
- Oncology Medicinal Chemistry Department, Pfizer Pharmaceuticals, San Diego, CA 92122, USA
| | | | | | | | - Yu Kawamata
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Phil S Baran
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
| | - Ryan Shenvi
- Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA
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6
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Li LJ, Zhang JC, Li WP, Zhang D, Duanmu K, Yu H, Ping Q, Yang ZP. Enantioselective Construction of Quaternary Stereocenters via Cooperative Photoredox/Fe/Chiral Primary Amine Triple Catalysis. J Am Chem Soc 2024; 146:9404-9412. [PMID: 38504578 DOI: 10.1021/jacs.4c01842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
The catalytic and enantioselective construction of quaternary (all-carbon substituents) stereocenters poses a formidable challenge in organic synthesis due to the hindrance caused by steric factors. One conceptually viable and potentially versatile approach is the coupling of a C-C bond through an outer-sphere mechanism, accompanied by the realization of enantiocontrol through cooperative catalysis; however, examples of such processes are yet to be identified. Herein, we present such a method for creating different compounds with quaternary stereocenters by photoredox/Fe/chiral primary amine triple catalysis. This approach facilitates the connection of an unactivated alkyl source with a tertiary alkyl moiety, which is also rare. The scalable process exhibits mild conditions, does not necessitate the use of a base, and possesses a good functional-group tolerance. Preliminary investigations into the underlying mechanisms have provided valuable insights into the reaction pathway.
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Affiliation(s)
- Lian-Jie Li
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Jun-Chun Zhang
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Wei-Peng Li
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Dan Zhang
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Kaining Duanmu
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Hui Yu
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, 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
- Shanghai Key Laboratory of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
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7
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Clark KF, Murphy JA. Trio of radicals choreographed for versatile chemical reaction. Nature 2024; 628:42-43. [PMID: 38570714 DOI: 10.1038/d41586-024-00735-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
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8
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Wang JZ, Lyon WL, MacMillan DWC. Alkene dialkylation by triple radical sorting. Nature 2024; 628:104-109. [PMID: 38350601 DOI: 10.1038/s41586-024-07165-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/05/2024] [Indexed: 02/15/2024]
Abstract
The development of bimolecular homolytic substitution (SH2) catalysis has expanded cross-coupling chemistries by enabling the selective combination of any primary radical with any secondary or tertiary radical through a radical sorting mechanism1-8. Biomimetic9,10 SH2 catalysis can be used to merge common feedstock chemicals-such as alcohols, acids and halides-in various permutations for the construction of a single C(sp3)-C(sp3) bond. The ability to sort these two distinct radicals across commercially available alkenes in a three-component manner would enable the simultaneous construction of two C(sp3)-C(sp3) bonds, greatly accelerating access to complex molecules and drug-like chemical space11. However, the simultaneous in situ formation of electrophilic and primary nucleophilic radicals in the presence of unactivated alkenes is problematic, typically leading to statistical radical recombination, hydrogen atom transfer, disproportionation and other deleterious pathways12,13. Here we report the use of bimolecular homolytic substitution catalysis to sort an electrophilic radical and a nucleophilic radical across an unactivated alkene. This reaction involves the in situ formation of three distinct radical species, which are then differentiated by size and electronics, allowing for regioselective formation of the desired dialkylated products. This work accelerates access to pharmaceutically relevant C(sp3)-rich molecules and defines a distinct mechanistic approach for alkene dialkylation.
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Affiliation(s)
- Johnny Z Wang
- Merck Center for Catalysis at Princeton University, Princeton, NJ, USA
| | - William L Lyon
- Merck Center for Catalysis at Princeton University, Princeton, NJ, USA
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9
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Chen R, Intermaggio NE, Xie J, Rossi-Ashton JA, Gould CA, Martin RT, Alcázar J, MacMillan DWC. Alcohol-alcohol cross-coupling enabled by S H2 radical sorting. Science 2024; 383:1350-1357. [PMID: 38513032 DOI: 10.1126/science.adl5890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 02/15/2024] [Indexed: 03/23/2024]
Abstract
Alcohols represent a functional group class with unparalleled abundance and structural diversity. In an era of chemical synthesis that prioritizes reducing time to target and maximizing exploration of chemical space, harnessing these building blocks for carbon-carbon bond-forming reactions is a key goal in organic chemistry. In particular, leveraging a single activation mode to form a new C(sp3)-C(sp3) bond from two alcohol subunits would enable access to an extraordinary level of structural diversity. In this work, we report a nickel radical sorting-mediated cross-alcohol coupling wherein two alcohol fragments are deoxygenated and coupled in one reaction vessel, open to air.
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Affiliation(s)
- Ruizhe Chen
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | | | - Jiaxin Xie
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | | | - Colin A Gould
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | - Robert T Martin
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
| | - Jesús Alcázar
- Discovery Chemistry, Janssen Research and Development, Janssen-Cilag, S.A., C/Jarama 75A, 45007 Toledo, Spain
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, NJ 08544, USA
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10
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Kong L, Gan XC, van der Puyl Lovett VA, Shenvi RA. Alkene Hydrobenzylation by a Single Catalyst That Mediates Iterative Outer-Sphere Steps. J Am Chem Soc 2024; 146:2351-2357. [PMID: 38232310 DOI: 10.1021/jacs.3c13398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Cross-coupling catalysts typically react and unite functionally distinct partners via sequential inner-sphere elementary steps: coordination, migratory insertion, reductive elimination, etc. Here, we report a single catalyst that cross-couples styrenes and benzyl bromides via iterative outer-sphere steps: metal-ligand-carbon interactions. Each partner forms a stabilized radical intermediate, yet heterocoupled products predominate. The system is redox-neutral and, thus, avoids exogenous oxidants, resulting in simple and scalable conditions. Numerous variations of alkene hydrobenzylation are made possible, including access to the privileged heterodibenzyl (1,2-diarylethane) motif and challenging quaternary carbon variants.
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Affiliation(s)
- Lingran Kong
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
| | - Xu-Cheng Gan
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
| | - Vincent A van der Puyl Lovett
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
- Graduate School of Chemical and Biological Sciences, Scripps Research, La Jolla, California 92037, United States
| | - Ryan A Shenvi
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
- Graduate School of Chemical and Biological Sciences, Scripps Research, La Jolla, California 92037, United States
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11
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Mayerhofer VJ, Lippolis M, Teskey CJ. Dual-Catalysed Intermolecular Reductive Coupling of Dienes and Ketones. Angew Chem Int Ed Engl 2024; 63:e202314870. [PMID: 37947372 DOI: 10.1002/anie.202314870] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 11/09/2023] [Accepted: 11/10/2023] [Indexed: 11/12/2023]
Abstract
We report a mild, catalytic method for the intermolecular reductive coupling of feedstock dienes and styrenes with ketones. Our conditions allow concomitant formation of a cobalt hydride species and single-electron reduction of ketones. Subsequent selective hydrogen-atom transfer from the cobalt hydride generates an allylic radical which can selectively couple with the persistent radical-anion of the ketone. This radical-radical coupling negates unfavourable steric interactions of ionic pathways and avoids the unstable alkoxy radical of previous radical olefin-carbonyl couplings, which were limited, as a result, to aldehydes. Applications of this novel and straightforward approach include the efficient synthesis of drug molecules, key intermediates in drug synthesis and site-selective late-stage functionalisation.
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Affiliation(s)
- Victor J Mayerhofer
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Martina Lippolis
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Christopher J Teskey
- Institute of Organic Chemistry, TU Braunschweig, Hagenring 30, 38106, Braunschweig, Germany
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12
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Kotesova S, Shenvi RA. Inner- and Outer-Sphere Cross-Coupling of High F sp3 Fragments. Acc Chem Res 2023; 56:3089-3098. [PMID: 37889168 PMCID: PMC10979517 DOI: 10.1021/acs.accounts.3c00543] [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: 10/28/2023]
Abstract
Natural product research originates from a desire to explore, understand, and perturb biological function with atomic precision. To reach these goals at all, let alone efficiently, requires thoughtful and creative problem solving. Often this means bold disconnections that would simplify access to complex structures, if only the methods existed to bridge these theoretical gaps. Whereas biological interrogations provide long-term intellectual value and impetus, methods come as attractive fringe benefits of natural product synthesis. This Account describes strategic, methodological solutions to the syntheses of natural products [(-)-eugenial C, Galbulimima alkaloids GB18, GB22, GB13, and himgaline] featuring new, convergent disconnections as important problem-solving steps, which themselves were inspired by recent methods that arose from our group. Each target required the invention of first-row transition metal-catalyzed cross-coupling procedures to satisfy the biological goals of the project. In these cases, synthetic strategy identified the methodological gap (the absence of stereo- and chemoselective couplings of appropriate fragments), but the tactical advantage conferred by first-row metals met the challenge. These methods were competent to handle the dense, sterically encumbered motifs common to natural products due to, in many cases, elementary steps that did not require bond formation between the hindered substrate and the metal center. Instead, these sterically lenient reactions appeared to involve metal-ligand-substrate reactions (i.e., outer-sphere steps), in contrast to the metal-substrate, coordinative reactions of precious metals (i.e., inner-sphere steps). Key observations from our previous studies, combined with the observations in seminal publications from other laboratories (Mattay, Weix, and MacMillan), led to the optimization of ligand-controlled, stereoselective reactions and the introduction of complementary catalytic cycles that revealed new modes of reactivity and generated novel structural motifs. Optimized access to bioactive natural product space accelerated our timeline of biological characterization, fulfilling a common premise of natural products research. The integration of methodology, complex natural product synthesis, diversification, and bioassay into a single Ph.D. dissertation would have been unmanageable in a prior era. The unique ability of first-row transition metals to effect Csp3-Csp3 cross-coupling with high chemo- and stereoselectivity has significantly lowered the barrier to reach the avowed goal of natural product synthesis and reduced the burden (real or perceived) of integrating natural products into functional campaigns.
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Affiliation(s)
- Simona Kotesova
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
- Graduate School of Chemical and Biological Sciences, Scripps Research, La Jolla, California 92037, United States
| | - Ryan A. Shenvi
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
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13
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Qin J, Barday M, Jana S, Sanosa N, Funes-Ardoiz I, Teskey CJ. Photoinduced Cobalt Catalysis for the Reductive Coupling of Pyridines and Dienes Enabled by Paired Single-Electron Transfer. Angew Chem Int Ed Engl 2023; 62:e202310639. [PMID: 37676106 DOI: 10.1002/anie.202310639] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 09/07/2023] [Accepted: 09/07/2023] [Indexed: 09/08/2023]
Abstract
Selective hydroarylation of dienes has potential to provide swift access to useful building blocks. However, most existing methods rely on dienes stabilised by an aromatic group and transmetallation or nucleophilic attack steps require electron-rich aryl coupling partners. As such, there are few examples which tolerate wide-spread heteroarenes such as pyridine. Whilst allylic C-H functionalisation could be considered an alternative approach, the positional selectivity of unsymmetrical substrates is hard to control. Here, we report a general approach for selective hydropyridylation of dienes under mild conditions using metal catalysed hydrogen-atom transfer. Photoinduced, reductive conditions enable simultaneous formation of a cobalt-hydride catalyst and the persistent radical of easily-synthesised pyridyl phosphonium salts. This facilitates selective coupling of dienes in a traceless manner at the C4-position of a wide-range of pyridine substrates. The mildness of the method is underscored by its functional-group tolerance and demonstrated by applications in late-stage functionalisation. Based on a combination of experimental and computational studies, we propose a mechanistic pathway which proceeds through non-reversible hydrogen-atom transfer (HAT) from a cobalt hydride species which is uniquely selective for dienes in the presence of other olefins due to a much higher relative barrier associated with olefin HAT.
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Affiliation(s)
- Jingyang Qin
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Manuel Barday
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Samikshan Jana
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Nil Sanosa
- Department of Chemistry, Centro de Investigación en Síntesis Química (CISQ), Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
| | - Ignacio Funes-Ardoiz
- Department of Chemistry, Centro de Investigación en Síntesis Química (CISQ), Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
| | - Christopher J Teskey
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
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14
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Ricca M, Yao S, Le T, White JM, Donnelly PS, Rizzacasa MA. A cis-β-iron(III) SALPN catalyst for hydrogen atom transfer reductions and olefin cross couplings. Org Biomol Chem 2023; 21:6789-6793. [PMID: 37566401 DOI: 10.1039/d3ob01085f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
An inexpensive Fe(III) SALPN catalyst for MHAT reactions such as reductions of α,β-unsaturated carbonyl compounds and olefin cross couplings is reported. The majority of these reactions proceeded in good yields and high stereoselectivities with low catalyst loadings at room temperature.
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Affiliation(s)
- Michael Ricca
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
| | - Shaolei Yao
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
| | - Tommy Le
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
| | - Jonathan M White
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
| | - Paul S Donnelly
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
| | - Mark A Rizzacasa
- School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
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