1
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Lee C, Kim M, Han S, Kim D, Hong S. Nickel-Catalyzed Hydrofluorination in Unactivated Alkenes: Regio- and Enantioselective C-F Bond Formation. J Am Chem Soc 2024; 146:9375-9384. [PMID: 38512796 DOI: 10.1021/jacs.4c01548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Catalytic formation of a regio- and enantioselective C-F bond chiral center from readily available alkenes is a crucial goal, yet it continues to pose significant challenges in organic synthesis. Here, we report the regioselective formation of C-F bonds facilitated by NiH catalysis and a coordination directing strategy that enables precise hydrofluorination of both terminal and internal alkenes. Notably, we have optimized this methodology to achieve high enantioselectivity in creating aliphatic C-F stereogenic centers especially with β,γ-alkenyl substrates, using a tailored chiral Bn-BOx ligand. Another pivotal finding in our research is the identification of the (+)-nonlinear effect under optimized conditions, allowing for high enantioselectivity even with moderately enantiomerically enriched chiral ligands. Given the significant role of fluorine in pharmaceuticals and synthetic materials, this research offers essential insights into the regioselective and enantioselective formation of C-F bond chiral centers, paving the way for the efficient production of valuable fluorinated compounds.
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Affiliation(s)
- Changseok Lee
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea
| | - Minseok Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea
| | - Seunghoon Han
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea
| | - Dongwook Kim
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea
| | - Sungwoo Hong
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea
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2
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Li E, Tang K, Ren Z, Liao X, Liu Q, Huang Y, Chen J. Enantioselective S N 2 Alkylation of Homoenolates by N-Heterocyclic Carbene Catalysis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303517. [PMID: 37541670 PMCID: PMC10582416 DOI: 10.1002/advs.202303517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 07/17/2023] [Indexed: 08/06/2023]
Abstract
The functionalization of the β-carbon of enals with electrophiles is a signature umpolung reactivity of N-heterocyclic carbene (NHC) derived homoenolates. However, only a limited number of electrophiles are shown to be compatible, with most of them being π-electrophiles. In this study, the successful enantioselective β-alkylation of homoenolates is reported using Csp3 electrophiles through an SN 2 strategy. The protocol shows a broad scope regarding alkyl electrophiles, delivering good yields, and excellent enantioselectivities (up to 99% ee). It enables the installation of drug-like structural motifs in either enals or alkylating agents, demonstrating its potential as a valuable tool for late-stage modification. Furthermore, a concise synthetic route is presented to chiral pyrroloindoline-type skeletons. Preliminary mechanistic studies support a direct SN 2 mechanism.
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Affiliation(s)
- En Li
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
| | - Kai Tang
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
| | - Zhuhui Ren
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
| | - Xiaoyun Liao
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
| | - Qianchen Liu
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
- College of PharmacyShenzhen Technology UniversityShenzhen518118China
| | - Yong Huang
- Department of ChemistryThe Hong Kong University of Science and TechnologyClear Water BayKowloonHong Kong SAR999077China
| | - Jiean Chen
- Pingshan Translational Medicine CenterShenzhen Bay LaboratoryShenzhen518118China
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3
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Assembly of versatile fluorine-containing structures via N-heterocyclic carbene organocatalysis. Sci China Chem 2022. [DOI: 10.1007/s11426-022-1291-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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4
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Chai H, Zhen X, Wang X, Qi L, Qin Y, Xue J, Xu Z, Zhang H, Zhu W. Catalytic Synthesis of 5-Fluoro-2-oxazolines: Using BF 3·Et 2O as the Fluorine Source and Activating Reagent. ACS OMEGA 2022; 7:19988-19996. [PMID: 35721954 PMCID: PMC9202255 DOI: 10.1021/acsomega.2c01791] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 05/16/2022] [Indexed: 06/15/2023]
Abstract
Hypervalent iodine catalyst-catalyzed nucleophilic fluorination of unsaturated amides using BF3·Et2O as the fluorine source and activating reagent was reported. Various 5-fluoro-2-oxazoline derivatives were synthesized in good to excellent yields (up to 95% isolated yield) within 10 min. The process was efficient and metal-free under mild conditions. A mechanism involving a fluorination/1,2-aryl migration/cyclization cascade was proposed on the basis of previous work and experimental results.
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Affiliation(s)
- Hongli Chai
- Key
Laboratory of Preclinical Study for New Drugs of Gansu Province, School
of Basic Medical Science, Lanzhou University, Lanzhou 730000, China
| | - Xiang Zhen
- Key
Laboratory of Preclinical Study for New Drugs of Gansu Province, School
of Basic Medical Science, Lanzhou University, Lanzhou 730000, China
| | - Xueqing Wang
- Department
of Pharmacy, College of Life Sciences, China
Jiliang University, Hangzhou 310018, China
| | - Liang Qi
- Department
of Pharmacy, College of Life Sciences, China
Jiliang University, Hangzhou 310018, China
| | - Yuji Qin
- School
of Pharmaceutical Sciences, Sun Yat-Sen
University, Guangzhou 510006, China
| | - Jijun Xue
- Key
Laboratory of Preclinical Study for New Drugs of Gansu Province, School
of Basic Medical Science, Lanzhou University, Lanzhou 730000, China
| | - Zhaoqing Xu
- Key
Laboratory of Preclinical Study for New Drugs of Gansu Province, School
of Basic Medical Science, Lanzhou University, Lanzhou 730000, China
| | - Hongrui Zhang
- Key
Laboratory of Preclinical Study for New Drugs of Gansu Province, School
of Basic Medical Science, Lanzhou University, Lanzhou 730000, China
| | - Weiwei Zhu
- School
of Pharmaceutical Sciences, Sun Yat-Sen
University, Guangzhou 510006, China
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5
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Mondal S, Ghosh A, Biju AT. N-Heterocyclic Carbene (NHC)-Catalyzed Transformations Involving Azolium Enolates. CHEM REC 2022; 22:e202200054. [PMID: 35562645 DOI: 10.1002/tcr.202200054] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/19/2022] [Indexed: 11/08/2022]
Abstract
The recent advances in the N-heterocyclic carbene (NHC)-organocatalyzed generation of azolium enolate intermediates and their subsequent interception with electrophiles are highlighted. The NHC-bound azolium intermediates are generated by the addition of NHCs to suitably substituted aldehydes, acid derivatives or ketenes. A broad range of coupling partners can intercept the azolium enolates to form [2+n] cycloadducts (n=2,3,4) and various α-functionalized compounds. The enantioselective synthesis of the target compounds are achieved with the use of chiral NHCs. Herein, we summarized the development that occurred in this subclass of NHC catalysis.
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Affiliation(s)
- Santigopal Mondal
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560012
| | - Arghya Ghosh
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560012
| | - Akkattu T Biju
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560012
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6
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Liu W, Zhang L, Liao X, Chen J, Huang Y. An NHC-Catalyzed [3+2] Cyclization of β-Disubstituted Enals with Benzoyl Cyanides. Chem Commun (Camb) 2022; 58:9742-9745. [DOI: 10.1039/d2cc04025e] [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
The NHC-catalyzed asymmetric [3+2] cyclization of benzoyl cyanides to homoenolate generated in-situ from enals was reported. This methodology leads to the efficient construction of a series of chiral cyclic compounds...
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7
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Yuan S, Zheng WH. Enantioselective Construction of Tertiary α-Alkyl Fluoride via BTM-Catalyzed Fluorination of α-Alkynyl-Substituted Acetic Acids. J Org Chem 2021; 87:713-720. [PMID: 34927437 DOI: 10.1021/acs.joc.1c02710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The isothiourea-catalyzed enantioselective construction of tertiary α-fluoro stereogenic centers has been demonstrated by using branched alkynyl-substituted acetic acids as starting materials, providing a broad range of optically active tertiary α-alkyl fluorides in high enantioselectivity (up to 97% ee). Furthermore, this methodology was proven to be scaled up to a Gram scale without loss of enantioselectivity.
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Affiliation(s)
- Shiru Yuan
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Wen-Hua Zheng
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, Jiangsu 210023, China
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8
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Remete AM, Nonn M, Escorihuela J, Fustero S, Kiss L. Asymmetric Methods for Carbon‐Fluorine Bond Formation. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101094] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Attila M. Remete
- Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
- Interdisciplinary Excellence Centre Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
| | - Melinda Nonn
- Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
- Interdisciplinary Excellence Centre Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
| | - Jorge Escorihuela
- Department of Organic Chemistry University of Valencia Pharmacy Faculty 46100- Burjassot Valencia Spain
| | - Santos Fustero
- Department of Organic Chemistry University of Valencia Pharmacy Faculty 46100- Burjassot Valencia Spain
| | - Loránd Kiss
- Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
- Interdisciplinary Excellence Centre Institute of Pharmaceutical Chemistry University of Szeged 6720 Szeged Eötvös u. 6 Hungary
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9
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10
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Zhu W, Zhen X, Wu J, Cheng Y, An J, Ma X, Liu J, Qin Y, Zhu H, Xue J, Jiang X. Catalytic asymmetric nucleophilic fluorination using BF 3·Et 2O as fluorine source and activating reagent. Nat Commun 2021; 12:3957. [PMID: 34172752 PMCID: PMC8233348 DOI: 10.1038/s41467-021-24278-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 06/09/2021] [Indexed: 01/16/2023] Open
Abstract
Fluorination using chiral catalytic methods could result in a direct access to asymmetric fluorine chemistry. However, challenges in catalytic asymmetric fluorinations, especially the longstanding stereochemical challenges existed in BF3·Et2O-based fluorinations, have not yet been addressed. Here we report the catalytic asymmetric nucleophilic fluorination using BF3·Et2O as the fluorine reagent in the presence of chiral iodine catalyst. Various chiral fluorinated oxazine products were obtained with good to excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >20:1 dr). Control experiments (the desired fluoro-oxazines could not be obtained when Py·HF or Et3N·3HF were employed as the fluorine source) indicated that BF3·Et2O acted not only as a fluorine reagent but also as the activating reagent for activation of iodosylbenzene. Catalytic asymmetric fluorination remains elusive, especially the longstanding stereochemical challenges which exist in BF3Et2O-based fluorinations. Here the authors show a catalytic asymmetric nucleophilic fluorination using BF3·Et2O as the fluorine reagent in the presence of chiral iodine catalyst.
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Affiliation(s)
- Weiwei Zhu
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Xiang Zhen
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China
| | - Jingyuan Wu
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Yaping Cheng
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Junkai An
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China
| | - Xingyu Ma
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Jikun Liu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China
| | - Yuji Qin
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Hao Zhu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China
| | - Jijun Xue
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China
| | - Xianxing Jiang
- Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China.
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11
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Zhao C, Blaszczyk SA, Wang J. Asymmetric reactions of N-heterocyclic carbene (NHC)-based chiral acyl azoliums and azolium enolates. GREEN SYNTHESIS AND CATALYSIS 2021. [DOI: 10.1016/j.gresc.2021.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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12
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Bertrand X, Chabaud L, Paquin JF. Hydrofluorination of Alkenes: A Review. Chem Asian J 2021; 16:563-574. [PMID: 33502810 DOI: 10.1002/asia.202001403] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/13/2021] [Indexed: 11/12/2022]
Abstract
In this minireview, we explore the different approaches used to perform the hydrofluorination reaction of alkenes. Contrary to other hydrohalogenation reactions, the hydrofluorination requires specific conditions due to the lower reactivity of HF. Over the years, many different approaches have been explored among which the use of HF complexes has particularly proved to be useful as these reagents are easier to handle. The enantioselective hydrofluorination has been demonstrated using electrophilic sources of fluorine, while radical fluorination proved compatible with a vast range of functional groups that are generally problematic with strong acids and some fluoride sources. This review will cover the different conditions developed through the years, starting with the first reported addition using gaseous HF, up to the most recent method described in October 2020.
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Affiliation(s)
- Xavier Bertrand
- CCVC, PROTEO, Département de chimie, Université Laval, 1045 Avenue de la Médecine, Québec, QC, G1V 0A6, Canada
| | - Laurent Chabaud
- Institut des Sciences Moléculaires, UMR, 5255, CNRS, Université de Bordeaux, 33405, Talence, France
| | - Jean-François Paquin
- CCVC, PROTEO, Département de chimie, Université Laval, 1045 Avenue de la Médecine, Québec, QC, G1V 0A6, Canada
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13
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Cao J, Zhu SF. Catalytic Enantioselective Proton Transfer Reactions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200350] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jin Cao
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China
| | - Shou-Fei Zhu
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China
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14
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Jiang X, Li E, Chen J, Huang Y. Photo-induced energy transfer relay of N-heterocyclic carbene catalysis: an asymmetric α-fluorination/isomerization cascade. Chem Commun (Camb) 2021; 57:729-732. [PMID: 33346284 DOI: 10.1039/d0cc07264h] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The geometric configuration of olefin products is often driven by thermodynamic control in synthesis. Methods enabling switching of cis/trans selectivity are rare. Recently, photosensitized approaches have emerged as a powerful tool for accomplishing this task. In this report, we report an in situ isomerization of an N-heterocyclic carbene (NHC)-bound intermediate by a photo-induced energy transfer process that leads to selective access of chiral allylic fluorides with a cis-olefin geometry. In the absence of a photocatalyst or light, the reaction proceeds smoothly to give (E)-olefin products, while the (Z)-isomer can be obtained under photosensitizing conditions. Preliminary mechanistic experiments suggest that an energy transfer process might be operative.
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Affiliation(s)
- Xinhang Jiang
- State Key Laboratory of Chemical Oncogenomics, Peking University Shenzhen Graduate School, Shenzhen, 518055, China and Shenzhen Public Platform of Drug Screening and Preclinical Evaluation, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
| | - En Li
- State Key Laboratory of Chemical Oncogenomics, Peking University Shenzhen Graduate School, Shenzhen, 518055, China and Shenzhen Public Platform of Drug Screening and Preclinical Evaluation, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
| | - Jiean Chen
- Pingshan Translational Medicine Center, Shenzhen Bay Laboratory, Shenzhen, 518055, China and Shenzhen Public Platform of Drug Screening and Preclinical Evaluation, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
| | - Yong Huang
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
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15
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Buchsteiner M, Martinez‐Rodriguez L, Jerabek P, Pozo I, Patzer M, Nöthling N, Lehmann CW, Fürstner A. Catalytic Asymmetric Fluorination of Copper Carbene Complexes: Preparative Advances and a Mechanistic Rationale. Chemistry 2020; 26:2509-2515. [PMID: 31916634 PMCID: PMC7065061 DOI: 10.1002/chem.202000081] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Indexed: 01/21/2023]
Abstract
The Cu-catalyzed reaction of substituted α-diazoesters with fluoride gives α-fluoroesters with ee values of up to 95 %, provided that chiral indane-derived bis(oxazoline) ligands are used that carry bulky benzyl substituents at the bridge and moderately bulky isopropyl groups on their core. The apparently homogeneous solution of CsF in C6 F6 /hexafluoroisopropanol (HFIP) is the best reaction medium, but CsF in the biphasic mixture CH2 Cl2 /HFIP also provides good results. DFT studies suggest that fluoride initially attacks the Cu- rather than the C-atom of the transient donor/acceptor carbene intermediate. This unusual step is followed by 1,2-fluoride shift; for this migratory insertion to occur, the carbene must rotate about the Cu-C bond to ensure orbital overlap. The directionality of this rotatory movement within the C2 -symmetric binding site determines the sense of induction. This model is in excellent accord with the absolute configuration of the resulting product as determined by X-ray diffraction using single crystals of this a priori wax-like material grown by capillary crystallization.
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Affiliation(s)
| | | | - Paul Jerabek
- Max-Planck-Institut für Kohlenforschung45470Mülheim/RuhrGermany
- Present Address: Nanotechnology DepartmentHelmholtz-Zentrum Geesthacht21502GeesthachtGermany
| | - Iago Pozo
- Max-Planck-Institut für Kohlenforschung45470Mülheim/RuhrGermany
| | - Michael Patzer
- Max-Planck-Institut für Kohlenforschung45470Mülheim/RuhrGermany
| | - Nils Nöthling
- Max-Planck-Institut für Kohlenforschung45470Mülheim/RuhrGermany
| | | | - Alois Fürstner
- Max-Planck-Institut für Kohlenforschung45470Mülheim/RuhrGermany
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16
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Hutchinson SM, Ardón-Muñoz LG, Ratliff ML, Bolliger JL. Catalytic Preparation of 1-Aryl-Substituted 1,2,4-Triazolium Salts. ACS OMEGA 2019; 4:17923-17933. [PMID: 31681902 PMCID: PMC6822220 DOI: 10.1021/acsomega.9b03109] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Accepted: 10/09/2019] [Indexed: 05/10/2023]
Abstract
1,4-Diaryl- and 1-aryl-4-alkyl-substituted 1,2,4-triazolium salts are convenient air-stable precursors to carbenes used both as organocatalysts or as ligands for transition metal complexes. Traditionally, they are prepared via a multistep synthetic pathway with the low-yielding formation of the triazolium ring occurring in the last step. We have developed an alternative two-step synthesis involving the conversion of a primary amine or aniline derivative to the corresponding 4-substituted triazole followed by a copper-catalyzed arylation with diaryliodonium salts. This transition metal-catalyzed arylation can be carried out under mild conditions in acetonitrile and is tolerant toward both water and oxygen. Additionally, the high functional group tolerance of the protocol described here gives easy access to triazolium salts containing heterocyclic substituents or sulfides.
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