1
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Fang J, Ren H, Xu S, Huang C, Jiang Y, Zhang W, You S, Qin B. Asymmetric Synthesis of β-Hydroxyphosphonates via a Chemoenzymatic Cascade. Org Lett 2024. [PMID: 38899921 DOI: 10.1021/acs.orglett.4c01716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Chiral β-hydroxyphosphonates are essential building blocks for organophosphorus compounds. However, the asymmetric synthesis of these units remains a significant challenge. Herein, we describe a one-pot chemoenzymatic cascade process to access chiral β-hydroxyphosphonates, which combines photo-oxidative chemical reactions and bioreductions. The incorporation of photooxidation in the chemical reaction resulted in up to 92% yield and >99% enantiomeric excess (ee) of β-hydroxyphosphonates in the cascade. In addition, the scale-up of diethyl (S)-(2-hydroxy-2-phenylethyl)phosphonate demonstrates the potential application of this strategy.
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Affiliation(s)
- Jiali Fang
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Hanwen Ren
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Shaowu Xu
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Chenming Huang
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Yingqian Jiang
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Wenhe Zhang
- School of Life Sciences and Biopharmaceutical Sciences, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Song You
- School of Life Sciences and Biopharmaceutical Sciences, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
| | - Bin Qin
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe, Shenyang 110016, People's Republic of China
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2
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Borsley S, Leigh DA, Roberts BMW. Molecular Ratchets and Kinetic Asymmetry: Giving Chemistry Direction. Angew Chem Int Ed Engl 2024; 63:e202400495. [PMID: 38568047 DOI: 10.1002/anie.202400495] [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: 01/12/2024] [Indexed: 05/03/2024]
Abstract
Over the last two decades ratchet mechanisms have transformed the understanding and design of stochastic molecular systems-biological, chemical and physical-in a move away from the mechanical macroscopic analogies that dominated thinking regarding molecular dynamics in the 1990s and early 2000s (e.g. pistons, springs, etc), to the more scale-relevant concepts that underpin out-of-equilibrium research in the molecular sciences today. Ratcheting has established molecular nanotechnology as a research frontier for energy transduction and metabolism, and has enabled the reverse engineering of biomolecular machinery, delivering insights into how molecules 'walk' and track-based synthesisers operate, how the acceleration of chemical reactions enables energy to be transduced by catalysts (both motor proteins and synthetic catalysts), and how dynamic systems can be driven away from equilibrium through catalysis. The recognition of molecular ratchet mechanisms in biology, and their invention in synthetic systems, is proving significant in areas as diverse as supramolecular chemistry, systems chemistry, dynamic covalent chemistry, DNA nanotechnology, polymer and materials science, molecular biology, heterogeneous catalysis, endergonic synthesis, the origin of life, and many other branches of chemical science. Put simply, ratchet mechanisms give chemistry direction. Kinetic asymmetry, the key feature of ratcheting, is the dynamic counterpart of structural asymmetry (i.e. chirality). Given the ubiquity of ratchet mechanisms in endergonic chemical processes in biology, and their significance for behaviour and function from systems to synthesis, it is surely just as fundamentally important. This Review charts the recognition, invention and development of molecular ratchets, focussing particularly on the role for which they were originally envisaged in chemistry, as design elements for molecular machinery. Different kinetically asymmetric systems are compared, and the consequences of their dynamic behaviour discussed. These archetypal examples demonstrate how chemical systems can be driven inexorably away from equilibrium, rather than relax towards it.
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Affiliation(s)
- Stefan Borsley
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
| | - David A Leigh
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
| | - Benjamin M W Roberts
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
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3
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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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4
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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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5
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Borsley S, Gallagher JM, Leigh DA, Roberts BMW. Ratcheting synthesis. Nat Rev Chem 2024; 8:8-29. [PMID: 38102412 DOI: 10.1038/s41570-023-00558-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2023] [Indexed: 12/17/2023]
Abstract
Synthetic chemistry has traditionally relied on reactions between reactants of high chemical potential and transformations that proceed energetically downhill to either a global or local minimum (thermodynamic or kinetic control). Catalysts can be used to manipulate kinetic control, lowering activation energies to influence reaction outcomes. However, such chemistry is still constrained by the shape of one-dimensional reaction coordinates. Coupling synthesis to an orthogonal energy input can allow ratcheting of chemical reaction outcomes, reminiscent of the ways that molecular machines ratchet random thermal motion to bias conformational dynamics. This fundamentally distinct approach to synthesis allows multi-dimensional potential energy surfaces to be navigated, enabling reaction outcomes that cannot be achieved under conventional kinetic or thermodynamic control. In this Review, we discuss how ratcheted synthesis is ubiquitous throughout biology and consider how chemists might harness ratchet mechanisms to accelerate catalysis, drive chemical reactions uphill and programme complex reaction sequences.
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Affiliation(s)
- Stefan Borsley
- Department of Chemistry, University of Manchester, Manchester, UK
| | | | - David A Leigh
- Department of Chemistry, University of Manchester, Manchester, UK.
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6
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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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7
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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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8
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Tian J, Meng X, Sun H, Chen Q, Xu Q, Dai P, Li L, Zhang L, Li C. Cinchona-Alkaloid-Derived NN Ligands and Achiral Phosphines for Iridium-Catalyzed Asymmetric Hydrogenation of Heteroaromatic and α-Chloroheteroaryl Ketones. J Org Chem 2023; 88:9213-9224. [PMID: 37226800 DOI: 10.1021/acs.joc.3c00786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A concise synthesis of cinchona-alkaloid-derived NN ligands bearing alkyl substituents on chiral nitrogen atoms was described. Iridium catalysts containing new chiral NN ligands and achiral phosphines were effective for the asymmetric hydrogenation of heteroaromatic ketones, which afforded corresponding alcohols in up to 99.9% ee. The same protocol was applicable to the asymmetric hydrogenation of α-chloroheteroaryl ketones. Most importantly, the gram-scale asymmetric hydrogenation of 2-acetylthiophene and 2-acetylfuran proceeded smoothly even under 1 MPa of H2.
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Affiliation(s)
- Jie Tian
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Xin Meng
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Hao Sun
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Qian Chen
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Qian Xu
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Pinli Dai
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Linlin Li
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Lin Zhang
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
| | - Chun Li
- State Key Laboratory of Functions and Applications of Medicinal Plants and School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang 550004, People's Republic of China
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9
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Abstract
Deracemization, which converts a racemate into its single enantiomer without separation of the intermediate, has gained renewed interest in asymmetric synthesis with its inherent atomic economy and high efficiency. However, this ideal process requires selective energy input and delicate reaction design to surmount the thermodynamical and kinetical constraints. With the rapid development of asymmetric catalysis, many catalytic strategies in concert with exogenous energy input have been exploited to facilitate this nonspontaneous enantioenrichment. In this perspective, we will discuss the basic ideas to accomplish catalytic deracemization, categorized by the three major exogenous energy sources including chemical (redox)-, photo- and mechanical energy from attrition. Emphasis will be given to the catalytic features and the underlying deracemization mechanism together with perspectives on future development.
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Affiliation(s)
- Mouxin Huang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
- Department of Medicinal Chemistry, Third Military of Medical University, Chongqing 400038, China
| | - Tianrun Pan
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Xieyang Jiang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Sanzhong Luo
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
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10
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Tan G, Glorius F. Stereochemical Editing. Angew Chem Int Ed Engl 2023; 62:e202217840. [PMID: 36576752 DOI: 10.1002/anie.202217840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 12/22/2022] [Accepted: 12/28/2022] [Indexed: 12/29/2022]
Abstract
Stereochemical editing has recently risen to prominence, allowing the direct editing of organic molecules with stereocenter(s) to adjust their relative stereochemistry at a late-stage. Several seminal light-driven stereochemical editing reactions such as deracemization and epimerization have been successively developed. Recently, Wendlandt and co-workers reported a versatile photochemical epimerization of unactivated tertiary stereogenic centers to rapidly prepare the stereoisomers that were previously challenging to access.
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Affiliation(s)
- Guangying Tan
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstraße 36, 48149, Münster, Germany
| | - Frank Glorius
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstraße 36, 48149, Münster, Germany
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11
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Kutta RJ, Großkopf J, van Staalduinen N, Seitz A, Pracht P, Breitenlechner S, Bannwarth C, Nuernberger P, Bach T. Multifaceted View on the Mechanism of a Photochemical Deracemization Reaction. J Am Chem Soc 2023; 145:2354-2363. [PMID: 36660908 DOI: 10.1021/jacs.2c11265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Upon irradiation in the presence of a chiral benzophenone catalyst (5 mol %), a racemic mixture of a given chiral imidazolidine-2,4-dione (hydantoin) can be converted almost quantitatively into the same compound with high enantiomeric excess (80-99% ee). The mechanism of this photochemical deracemization reaction was elucidated by a suite of mechanistic experiments. It was corroborated by nuclear magnetic resonance titration that the catalyst binds the two enantiomers by two-point hydrogen bonding. In one of the diastereomeric complexes, the hydrogen atom at the stereogenic carbon atom is ideally positioned for hydrogen atom transfer (HAT) to the photoexcited benzophenone. Detection of the protonated ketyl radical by transient absorption revealed hydrogen abstraction to occur from only one but not from the other hydantoin enantiomer. Quantum chemical calculations allowed us to visualize the HAT within this complex and, more importantly, showed that the back HAT does not occur to the carbon atom of the hydantoin radical but to its oxygen atom. The achiral enol formed in this process could be directly monitored by its characteristic transient absorption signal at λ ≅ 330 nm. Subsequent tautomerization leads to both hydantoin enantiomers, but only one of them returns to the catalytic cycle, thus leading to an enrichment of the other enantiomer. The data are fully consistent with deuterium labeling experiments and deliver a detailed picture of a synthetically useful photochemical deracemization reaction.
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Affiliation(s)
- Roger Jan Kutta
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstr. 31, RegensburgD-93053, Germany
| | - Johannes Großkopf
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747Garching, Germany
| | - Nils van Staalduinen
- Institut für Physikalische Chemie, RWTH Aachen University, D-52074Aachen, Germany
| | - Antonia Seitz
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747Garching, Germany
| | - Philipp Pracht
- Institut für Physikalische Chemie, RWTH Aachen University, D-52074Aachen, Germany.,Yusuf Hamied Department of Chemistry, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Stefan Breitenlechner
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747Garching, Germany
| | - Christoph Bannwarth
- Institut für Physikalische Chemie, RWTH Aachen University, D-52074Aachen, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstr. 31, RegensburgD-93053, Germany
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, D-85747Garching, Germany
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12
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Abstract
Creating, conserving and modifying the stereochemistry of organic compounds has been the subject of significant research efforts in synthetic chemistry. Most synthetic routes are designed according to the stereoselectivity-determining step. Stereochemical editing is an alternative strategy, wherein the chiral-defining or geometry-defining steps are independent of the construction of the major scaffold or complexity. It enables late-stage alterations of stereochemistry and can generate isomers from a single compound. However, in many instances, stereochemical editing processes are contra-thermodynamic, meaning the transformation is unfavourable. To overcome this barrier, photocatalysis uses photogenerated radical species and introduces thermochemical biases. A range of synthetically valuable contra-thermodynamic stereochemical editing processes have been invented, including deracemization of chiral molecules, positional alkene isomerization and dynamic epimerization of sugars and diols. In this Review, we highlight the fundamental mechanisms of visible-light photocatalysis and the general reactivity modes of the photogenerated radical intermediates towards contra-thermodynamic stereochemical editing processes.
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13
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Shen Z, Vargas-Rivera MA, Rigby EL, Chen S, Ellman JA. Visible Light-Mediated, Diastereoselective Epimerization of Morpholines and Piperazines to More Stable Isomers. ACS Catal 2022; 12:12860-12868. [PMID: 36406894 PMCID: PMC9668057 DOI: 10.1021/acscatal.2c03672] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report a photocatalyzed epimerization of morpholines and piperazines that proceeds by reversible hydrogen atom transfer (HAT) and provides an efficient strategy for editing the stereochemical configurations of these saturated nitrogen heterocycles, which are prevalent in drugs. The more stable morpholine and piperazine isomers are obtained from the more synthetically accessible but less stable stereoisomers, and a broad scope is demonstrated in terms of substitution patterns and functional group compatibility. The observed distributions of diastereomers correlate well with the relative energies of the diastereomer pairs as determined by density functional theory (DFT) calculations. Mechanistic studies, including luminescence quenching, deuterium labeling reactions, and determination of reversibility support a thiyl radical mediated HAT pathway for the epimerization of morpholines. Investigation of piperazine epimerization established that the mechanism is more complex and led to the development of thiol free conditions for the highly stereoselective epimerization of N,N'-dialkyl piperazines for which a previously unrecognized radical chain HAT mechanism is proposed.
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Affiliation(s)
- Zican Shen
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | | | - Elizabeth L. Rigby
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Shuming Chen
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Jonathan A. Ellman
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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14
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Wang J, Peng Y, Xu J, Wu Q. Deracemization of racemic alcohols combining photooxidation and biocatalytic reduction. Org Biomol Chem 2022; 20:7765-7769. [PMID: 36165209 DOI: 10.1039/d2ob01386j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We described a cascade reaction for deracemization of racemic alcohols combining photooxidation and enzymatic reduction under mild conditions without the isolation of intermediate ketones. Using different ketoreductases, a variety of racemic alcohols can be successfully converted into (R)- or (S)-enantiomers in high yields (up to 95%) and stereoselectivity (up to 99%).
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Affiliation(s)
- Jianfeng Wang
- Xingzhi College, Zhejiang Normal University, Lanxi 321100, China. .,Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
| | - Yongzhen Peng
- Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
| | - Jian Xu
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Qi Wu
- Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
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15
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Wang H, Tian YM, König B. Energy- and atom-efficient chemical synthesis with endergonic photocatalysis. Nat Rev Chem 2022; 6:745-755. [PMID: 37117495 DOI: 10.1038/s41570-022-00421-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2022] [Indexed: 11/09/2022]
Abstract
Endergonic photocatalysis is the use of light to perform catalytic reactions that are thermodynamically unfavourable. While photocatalysis has become a powerful tool in facilitating chemical transformations, the light-energy efficiency of these processes has not gathered much attention. Exergonic photocatalysis does not take full advantage of the light energy input, producing low-energy products and heat, whereas endergonic photocatalysis incorporates a portion of the photon energy into the reaction, yielding products that are higher in free energy than the reactants. Such processes can enable catalytic, atom-economic syntheses of reactive compounds from bench-stable materials. With respect to environmental friendliness and carbon neutrality, endergonic photocatalysis is also of interest to large-scale industrial manufacturing, where better energy efficiency, less waste and value addition are highly sought. We therefore assess here the thermochemistry of several classes of reported photocatalytic transformations to showcase current advances in endergonic photocatalysis and point to their industrial potential.
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16
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Su Y, Zou Y, Xiao W. Recent Advances in Photocatalytic Deracemization. CHINESE J ORG CHEM 2022. [DOI: 10.6023/cjoc202207046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Zhang Z, Hu X. Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols. Angew Chem Int Ed Engl 2021; 60:22833-22838. [PMID: 34397164 PMCID: PMC8519112 DOI: 10.1002/anie.202107570] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/14/2021] [Indexed: 11/18/2022]
Abstract
Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.
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Affiliation(s)
- Zhikun Zhang
- Laboratory of Inorganic Synthesis and CatalysisInstitute of Chemical Sciences and EngineeringEcole Poly-technique Fédérale de Lausanne (EPFL)ISIC-LSCI, BCH 3305Lausanne1015Switzerland
| | - Xile Hu
- Laboratory of Inorganic Synthesis and CatalysisInstitute of Chemical Sciences and EngineeringEcole Poly-technique Fédérale de Lausanne (EPFL)ISIC-LSCI, BCH 3305Lausanne1015Switzerland
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