1
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Song C, Bai X, Li B, Dang Y, Yu S. Photoexcited Palladium-Catalyzed Deracemization of Allenes. J Am Chem Soc 2024. [PMID: 39024194 DOI: 10.1021/jacs.4c07126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
The different enantiomers of specific chiral molecules frequently exhibit disparate biological, physiological, or pharmacological properties. Therefore, the efficient synthesis of single enantiomers is of particular importance not only to the pharmaceutical sector but also to other industrial sectors, such as agrochemical and fine chemical industries. Deracemization, a process during which a racemic mixture is converted into a nonracemic product with 100% atom economy and theoretical yield, is the most straightforward method to access enantioenriched molecules but a challenging task due to a decrease in entropy and microscopic reversibility. Axially chiral allenes bear a distinctive structure of two orthogonal cumulative π-systems and are acknowledged as synthetically versatile synthons in organic synthesis. The selective creation of axially chiral allenes with high optical purity under mild reaction conditions has always been a very popular and hot topic in organic synthesis but remains challenging. Herein, a photoexcited palladium-catalyzed deracemization of nonprefunctionalized disubstituted allenes is disclosed. This method provides an efficient and economical strategy to accommodate a broad scope of allenes with good enantioselectivities and yields (53 examples, up to 96% yield and 95% ee). The use of a suitable chiral palladium complex with visible light irradiation is an essential factor in achieving this transformation. A metal-to-ligand charge transfer mechanism was proposed based on control experiments and density functional theory calculations. Quantum mechanical studies implicate dual modes of asymmetric induction behind our new protocol: (1) sterically controlled stereoselective binding of one allene enantiomer under the ground-state and (2) facile, noncovalent interaction-driven excited-state isomerization toward the opposite enantiomer. The success of this newly established photochemical deracemization strategy should provide inspiration for expansion to other multisubstituted allenes and will open up a new mode for enantioselective excited-state palladium catalysis.
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Affiliation(s)
- Changhua Song
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xiangbin Bai
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Bo Li
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
| | - Yanfeng Dang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
| | - Shouyun Yu
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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2
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Doyle MGJ, Bsharat O, Sib A, Derdau V, Lundgren RJ. Enantioselective Carbon Isotope Exchange. J Am Chem Soc 2024; 146:18804-18810. [PMID: 38968381 DOI: 10.1021/jacs.4c03685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2024]
Abstract
The synthesis of isotopically labeled organic molecules is vital for drug and agrochemical discovery and development. Carbon isotope exchange is emerging as a leading method to generate carbon-labeled targets, which are sought over hydrogen-based labels due to their enhanced stability in biological systems. While many bioactive small molecules bear carbon-containing stereocenters, direct enantioselective carbon isotope exchange reactions have not been established. We describe the first example of an enantioselective carbon isotope exchange reaction, where (radio)labeled α-amino acids can be generated from their unlabeled precursors using a stoichiometric chiral aldehyde receptor with isotopically labeled CO2 followed by imine hydrolysis. Many proteinogenic and non-natural derivatives undergo enantioselective labeling, including the late-stage radiolabeling of complex drug targets.
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Affiliation(s)
- Michael G J Doyle
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
- Integrated Drug Discovery, Isotope Chemistry, R&D, Sanofi Germany, Industriepark Höchst, 65926 Frankfurt, Germany
| | - Odey Bsharat
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Anna Sib
- Integrated Drug Discovery, Isotope Chemistry, R&D, Sanofi Germany, Industriepark Höchst, 65926 Frankfurt, Germany
| | - Volker Derdau
- Integrated Drug Discovery, Isotope Chemistry, R&D, Sanofi Germany, Industriepark Höchst, 65926 Frankfurt, Germany
| | - Rylan J Lundgren
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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3
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Lin A, Lee S, Knowles RR. Organic Synthesis Away from Equilibrium: Contrathermodynamic Transformations Enabled by Excited-State Electron Transfer. Acc Chem Res 2024; 57:1827-1838. [PMID: 38905487 DOI: 10.1021/acs.accounts.4c00227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/23/2024]
Abstract
ConspectusChemists have long been inspired by biological photosynthesis, wherein a series of excited-state electron transfer (ET) events facilitate the conversion of low energy starting materials such as H2O and CO2 into higher energy products in the form of carbohydrates and O2. While this model for utilizing light-driven charge transfer to drive catalytic reactions thermodynamically "uphill" has been extensively adapted for small molecule activation, molecular machines, photoswitches, and solar fuel chemistry, its application in organic synthesis has been less systematically developed. However, the potential benefits of these approaches are significant, both in enabling transformations that cannot be readily achieved using conventional thermal chemistry and in accessing distinct selectivity regimes that are uniquely enabled by excited-state mechanisms. In this Account, we present work from our group that highlights the ability of visible light photoredox catalysis to drive useful organic transformations away from their equilibrium positions, addressing a number of long-standing synthetic challenges.We first discuss how excited-state ET enabled the first general methods for the catalytic anti-Markovnikov hydroamination of unactivated alkenes with alkyl amines. In these reactions, an excited-state iridium(III) photocatalyst reversibly oxidizes secondary amine substrates to their corresponding aminium radical cations (ARCs). These electrophilic N-centered radicals can then react with olefins to furnish valuable tertiary amine products with complete anti-Markovnikov regioselectivity. Notably, some of these products are less thermodynamically stable than their corresponding amine and alkene starting materials. We next present a strategy for light-driven C-C bond cleavage within various aliphatic alcohols mediated by homolytic activation of alcohol O-H bonds by excited-state proton-coupled electron transfer (PCET). The resulting alkoxy radical intermediates then undergo C-C β-scission to ultimately provide isomeric linear carbonyl products that are often higher in energy than their cyclic alcohol precursors. Applications of this chemistry for the light-driven depolymerization of lignin biomass, commercial phenoxy resin, hydroxylated polyolefin derivatives, and thermoset polymers are presented as well. We then describe a method for the contrathermodynamic positional isomerization of highly substituted olefins by means of cooperative photoredox and chromium(II) catalysis. In this work, generation of an allylchromium(III) species that can undergo highly regioselective in situ protodemetalation enables access to a less substituted and thermodynamically less stable positional isomer. Product selectivity in this reaction is determined by the large differential in oxidation potentials between differently substituted olefin isomers. Lastly, we discuss a light-driven deracemization reaction developed in collaboration with the Miller group, wherein a racemic urea substrate undergoes spontaneous optical enrichment upon visible light irradiation in the presence of an iridium(III) chromophore, a chiral Brønsted base, and a chiral peptide thiol. Excellent levels of enantioselectivity are achieved via sequential and synergistic proton transfer (PT) and H atom transfer (HAT) steps. Taken together, these examples highlight the ability of excited-state ET events to enable access to nonequilibrium product distributions across a wide range of catalytic, redox-neutral transformations in which photons are the only stoichiometric reagents.
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Affiliation(s)
- Angela Lin
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sumin Lee
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Robert R Knowles
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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4
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Ding B, Xue Q, Wei H, Chen J, Liu ZS, Cheng HG, Cong H, Tang J, Zhou Q. Enantioconvergent synthesis of chiral fluorenols from racemic secondary alcohols via Pd(ii)/chiral norbornene cooperative catalysis. Chem Sci 2024; 15:7975-7981. [PMID: 38817591 PMCID: PMC11134410 DOI: 10.1039/d4sc01004c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 04/18/2024] [Indexed: 06/01/2024] Open
Abstract
An efficient protocol for the asymmetric synthesis of fluorenols has been developed through an enantioconvergent process enabled by Pd(ii)/chiral norbornene cooperative catalysis. This approach allows facile access to diverse functionalized chiral fluorenols with constantly excellent enantioselectivities, applying readily available racemic secondary ortho-bromobenzyl alcohols and aryl iodides as the starting materials.
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Affiliation(s)
- Bo Ding
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Qilin Xue
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Han Wei
- The Institute for Advanced Studies, Wuhan University Wuhan 430072 China
| | - Jiangwei Chen
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Ze-Shui Liu
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Hong-Gang Cheng
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Hengjiang Cong
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
| | - Jianting Tang
- Key Laboratory of Water Environment Evolution and Pollution Control in Three Gorges Reservoir, School of Environmental and Chemical Engineering, Chongqing Three Gorges University Chongqing 404100 China
| | - Qianghui Zhou
- Engineering Research Center of Organosilicon Compounds & Materials (Ministry of Education), Hubei Key Lab on Organic and Polymeric OptoElectronic Materials, College of Chemistry and Molecular Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University Wuhan 430072 China
- The Institute for Advanced Studies, Wuhan University Wuhan 430072 China
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5
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Pecchini P, Fochi M, Bartoccini F, Piersanti G, Bernardi L. Enantioselective organocatalytic strategies to access noncanonical α-amino acids. Chem Sci 2024; 15:5832-5868. [PMID: 38665517 PMCID: PMC11041364 DOI: 10.1039/d4sc01081g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 03/23/2024] [Indexed: 04/28/2024] Open
Abstract
Organocatalytic asymmetric synthesis has evolved over the years and continues to attract the interest of many researchers worldwide. Enantiopure noncanonical amino acids (ncAAs) are valuable building blocks in organic synthesis, medicinal chemistry, and chemical biology. They are employed in the elaboration of peptides and proteins with enhanced activities and/or improved properties compared to their natural counterparts, as chiral catalysts, in chiral ligand design, and as chiral building blocks for asymmetric syntheses of complex molecules, including natural products. The linkage of ncAA synthesis and enantioselective organocatalysis, the subject of this perspective, tries to imitate the natural biosynthetic process. Herein, we present contemporary and earlier developments in the field of organocatalytic activation of simple feedstock materials, providing potential ncAAs with diverse side chains, unique three-dimensional structures, and a high degree of functionality. These asymmetric organocatalytic strategies, useful for forging a wide range of C-C, C-H, and C-N bonds and/or combinations thereof, vary from classical name reactions, such as Ugi, Strecker, and Mannich reactions, to the most advanced concepts such as deracemisation, transamination, and carbene N-H insertion. Concurrently, we present some interesting mechanistic studies/models, providing information on the chirality transfer process. Finally, this perspective highlights, through the diversity of the amino acids (AAs) not selected by nature for protein incorporation, the most generic modes of activation, induction, and reactivity commonly used, such as chiral enamine, hydrogen bonding, Brønsted acids/bases, and phase-transfer organocatalysis, reflecting their increasingly important role in organic and applied chemistry.
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Affiliation(s)
- Pietro Pecchini
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
| | - Mariafrancesca Fochi
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
| | - Francesca Bartoccini
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Piazza Rinascimento 6 61029 Urbino PU Italy
| | - Giovanni Piersanti
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Piazza Rinascimento 6 61029 Urbino PU Italy
| | - Luca Bernardi
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
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6
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Xu Y, Dong G. Deracemization through C-C bond manipulation. Sci Bull (Beijing) 2024; 69:285-287. [PMID: 38105162 DOI: 10.1016/j.scib.2023.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Affiliation(s)
- Yan Xu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Guangbin Dong
- Department of Chemistry, University of Chicago, Chicago IL 60637, USA.
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7
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Xu GQ, Wang WD, Xu PF. Photocatalyzed Enantioselective Functionalization of C(sp 3)-H Bonds. J Am Chem Soc 2024; 146:1209-1223. [PMID: 38170467 DOI: 10.1021/jacs.3c06169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Owing to its diverse activation processes including single-electron transfer (SET) and hydrogen-atom transfer (HAT), visible-light photocatalysis has emerged as a sustainable and efficient platform for organic synthesis. These processes provide a powerful avenue for the direct functionalization of C(sp3)-H bonds under mild conditions. Over the past decade, there have been remarkable advances in the enantioselective functionalization of the C(sp3)-H bond via photocatalysis combined with conventional asymmetric catalysis. Herein, we summarize the advances in asymmetric C(sp3)-H functionalization involving visible-light photocatalysis and discuss two main pathways in this emerging field: (a) SET-driven carbocation intermediates are followed by stereospecific nucleophile attacks; and (b) photodriven alkyl radical intermediates are further enantioselectively captured by (i) chiral π-SOMOphile reagents, (ii) stereoselective transition-metal complexes, and (iii) another distinct stereoscopic radical species. We aim to summarize key advances in reaction design, catalyst development, and mechanistic understanding, to provide new insights into this rapidly evolving area of research.
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Affiliation(s)
- Guo-Qiang Xu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, MOE Frontiers Science Center for Rare Isotopes, Lanzhou Magnetic Resonance Center, Lanzhou University, Lanzhou 730000, P.R. China
| | - Wei David Wang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, MOE Frontiers Science Center for Rare Isotopes, Lanzhou Magnetic Resonance Center, Lanzhou University, Lanzhou 730000, P.R. China
| | - Peng-Fei Xu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, MOE Frontiers Science Center for Rare Isotopes, Lanzhou Magnetic Resonance Center, Lanzhou University, Lanzhou 730000, P.R. China
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8
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Großkopf J, Bach T. Catalytic Photochemical Deracemization via Short-Lived Intermediates. Angew Chem Int Ed Engl 2023; 62:e202308241. [PMID: 37428113 DOI: 10.1002/anie.202308241] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 07/04/2023] [Accepted: 07/05/2023] [Indexed: 07/11/2023]
Abstract
Upon irradiation in the presence of a suitable chiral catalyst, racemic compound mixtures can be converted into enantiomerically pure compounds with the same constitution. The process is called photochemical deracemization and involves the formation of short-lived intermediates. By opening different reaction channels for the forward reaction to the intermediate and for the re-constitution of the chiral molecule, the entropically disfavored process becomes feasible. Since the discovery of the first photochemical deracemization in 2018, the field has been growing rapidly. This review comprehensively covers the research performed in the area and discusses current developments. It is subdivided according to the mode of action and the respective substrate classes. The focus of this review is on the scope of the individual reactions and on a discussion of the mechanistic details underlying the presented reaction.
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Affiliation(s)
- Johannes Großkopf
- School of Natural Sciences, Technische Universität München, Department Chemie and Catalysis Research Center (CRC), Lichtenbergstr. 4, 85747, Garching, Germany
| | - Thorsten Bach
- School of Natural Sciences, Technische Universität München, Department Chemie and Catalysis Research Center (CRC), Lichtenbergstr. 4, 85747, Garching, Germany
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9
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Großkopf J, Plaza M, Kutta RJ, Nuernberger P, Bach T. Creating a Defined Chirality in Amino Acids and Cyclic Dipeptides by Photochemical Deracemization. Angew Chem Int Ed Engl 2023; 62:e202313606. [PMID: 37793026 DOI: 10.1002/anie.202313606] [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: 09/13/2023] [Revised: 09/30/2023] [Accepted: 10/02/2023] [Indexed: 10/06/2023]
Abstract
2,5-Diketopiperazines are cyclic dipeptides displaying a wide range of applications. Their enantioselective preparation has now been found possible from the respective racemates by a photochemical deracemization (53 examples, 74 % to quantitative yield, 71-99 % ee). A chiral benzophenone catalyst in concert with irradiation at λ=366 nm enables to establish the configuration at the stereogenic carbon atom C6 at will. If other stereogenic centers are present in the diketopiperazines they remain unaffected and a stereochemical editing is possible at a single position. Consecutive reactions, including the conversion into N-aryl or N-alkyl amino acids or the reduction to piperazines, occur without compromising the newly created stereogenic center. Transient absorption spectroscopy revealed that the benzophenone catalyst processes one enantiomer of the 2,5-diketopiperazines preferentially and enables a reversible hydrogen atom transfer that is responsible for the deracemization process. The remarkably long lifetime of the protonated ketyl radical implies a yet unprecedented mode of action.
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Affiliation(s)
- Johannes Großkopf
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747, Garching, Germany
| | - Manuel Plaza
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747, Garching, Germany
| | - Roger Jan Kutta
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747, Garching, Germany
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10
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Wen L, Ding J, Duan L, Wang S, An Q, Wang H, Zuo Z. Multiplicative enhancement of stereoenrichment by a single catalyst for deracemization of alcohols. Science 2023; 382:458-464. [PMID: 37883537 DOI: 10.1126/science.adj0040] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 09/04/2023] [Indexed: 10/28/2023]
Abstract
Stereochemical enrichment of a racemic mixture by deracemization must overcome unfavorable entropic effects as well as the principle of microscopic reversibility; recently, photochemical reaction pathways unveiled by the energetic input of light have led to innovations toward this end, most often by ablation of a stereogenic C(sp3)-H bond. We report a photochemically driven deracemization protocol in which a single chiral catalyst effects two mechanistically different steps, C-C bond cleavage and C-C bond formation, to achieve multiplicative enhancement of stereoinduction, which leads to high levels of stereoselectivity. Ligand-to-metal charge transfer excitation of a titanium catalyst coordinated by a chiral phosphoric acid or bisoxazoline efficiently enriches racemic alcohols that feature adjacent and fully substituted stereogenic centers to enantiomeric ratios up to 99:1. Mechanistic investigations support a pathway of sequential radical-mediated bond scission and bond formation through a common prochiral intermediate and reveal that, although the overall stereoenrichment is high, the selectivity in each individual step is moderate.
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Affiliation(s)
- Lu Wen
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jia Ding
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Lingfei Duan
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shun Wang
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Qing An
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Hexiang Wang
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Zhiwei Zuo
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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11
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Kim SF, Sarpong R. Interconverting mirror-image molecules. Science 2023; 382:373-374. [PMID: 37883536 DOI: 10.1126/science.adk7116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
A light-driven multitasking catalyst enhances chirality in molecular mixtures.
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Affiliation(s)
- Sojung F Kim
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
| | - Richmond Sarpong
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
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12
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Ričko S, Bitsch RS, Kaasik M, Otevřel J, Højgaard Madsen M, Keimer A, Jørgensen KA. Enantioconvergent 6π Electrocyclization Enabled by Photoredox Racemization. J Am Chem Soc 2023; 145:20913-20926. [PMID: 37753541 DOI: 10.1021/jacs.3c06227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2023]
Abstract
This study presents a novel photoredox-enabled enantioconvergent catalytic strategy used to construct chiral 2H-1,3-benzoxazines via an unprecedented oxa-6π electrocyclization utilizing racemic α-substituted glycinates as substrates. The approach leverages a cobalt-based chiral Lewis acid catalyst, which promotes the transformation under thermal or photoredox conditions. While the thermal reaction selectively converts only the (S)-configured glycinates into enantioenriched 2H-1,3-benzoxazines (up to 96:4 e.r.), the addition of 0.5 mol % of a commercially available iridium photocatalyst under visible light irradiation transforms the reaction into an enantioconvergent process. Detailed mechanistic and time course studies of optically pure α-deuterated substrates revealed the presence of an enantiospecific kinetic isotope effect, which helped to clarify the role of both the photo- and chiral Lewis acid catalyst in the reaction sequence. In this dual catalytic system, the photocatalyst promotes a dynamic interconversion between the substrate enantiomers─a process not accessible via ground-state chemistry─while the chiral Lewis acid selectively transforms only the (S)-configured substrates. Further mechanistic evidence for the proposed mechanism is provided by linear free energy relationship analysis, which suggests that the stereodetermining step involves a 6π electrocyclization under both thermal and photoredox conditions.
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Affiliation(s)
- Sebastijan Ričko
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
- Aarhus Institute of Advanced Studies, Aarhus University, DK-8000 Aarhus C, Denmark
| | - René Slot Bitsch
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Mikk Kaasik
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Jan Otevřel
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | | | - Anna Keimer
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
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