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Bejarano CA, Díaz JE, Cifuentes-López A, López LV, Jaramillo-Gómez LM, Buendia-Atencio C, Lorett Velásquez VP, Mejía SM, Loaiza AE. Experimental and theoretical study of the mechanism and rate constants of the sequential 5- exo-trig spirocyclization involving vinyl, aryl and N-alkoxyaminyl radicals. Org Biomol Chem 2022; 20:4141-4154. [PMID: 35521783 DOI: 10.1039/d2ob00387b] [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
In this research the sequential generation and cyclization of N-alkoxyaminyl radicals to produce 1-azaspiro[4.4]nonane, a prominent scaffold in organic and medicinal chemistry, was studied. Competition experiments in benzene at 80 °C with brominated oxime ethers using Bu3SnH as chain transfer and AIBN as the initiator generated vinyl or aryl radicals which were captured by oxime ethers, allowing approximate 5-exo-trig cyclization constants at 4.6 × 108 s-1 and 9.9 × 108 s-1 respectively to be established. Similar results were obtained by kinetic studies using the transition state theory (TST) from ab initio calculations with density functional theory (DFT) using the M06-2X, B3LYP, mPW1PW91 and TPSSh functionals in combination with the 6-311+G(d, p) basis set. Additionally, it was found that the 5-exo-trig cyclization of the N-alkoxyaminyl radical onto CC double bonds is a reversible process whose constants were determined to be in the range of 6.2 × 100 s-1 and 3.5 × 106 s-1 at 80 °C, depending on the nature of the substituents. The calculation of the radical stabilization energy (RSE) shows that the N-alkoxyaminyl radical is a very stable species and its reactivity in the addition on alkenes is governed by its nucleophilic character and the stability of the carbon-centered radical formed after cyclization. The reduction constant of the N-alkoxyaminyl radical with Bu3SnH in the gas phase at 80 °C was also estimated to be 3.4 × 100 M-1 s-1 through computational calculations. This information facilitates the rational planning of cascades and other methodologies applied to the construction of carbocyclic and aza-heterocyclic compounds.
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Affiliation(s)
- Carlos A Bejarano
- Departamento de Química, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá 11001000, Colombia. .,Departamento de Química, Facultad de Ciencias, Universidad Antonio Nariño, Bogotá 110231, Colombia
| | - John E Díaz
- Departamento de Química, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá 11001000, Colombia.
| | | | - Lina V López
- Departamento de Química, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá 11001000, Colombia.
| | - Luz M Jaramillo-Gómez
- Departamento de Química, Facultad de Ciencias, Universidad del Valle, Cali 760032, Colombia
| | - Cristian Buendia-Atencio
- Departamento de Química, Facultad de Ciencias, Universidad Antonio Nariño, Bogotá 110231, Colombia
| | | | - Sol M Mejía
- Departamento de Química, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá 11001000, Colombia.
| | - Alix E Loaiza
- Departamento de Química, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá 11001000, Colombia.
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Ye T, Zhang FL, Xia HM, Zhou X, Yu ZX, Wang YF. Stereoselective hydrogen atom transfer to acyclic radicals: a switch enabling diastereodivergent borylative radical cascades. Nat Commun 2022; 13:426. [PMID: 35058459 PMCID: PMC8776760 DOI: 10.1038/s41467-022-28071-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 01/04/2022] [Indexed: 12/18/2022] Open
Abstract
Radical cascade reactions are powerful tools to construct structurally complex molecules. However, the stereochemical control of acyclic radical intermediates remains a persistent challenge, due to the low differentiation between the two faces of these species. This hurdle further makes stereodivergent synthesis rather more difficult to be accomplished, in particular for intermediates resulted from complex cascades. Here we report an efficient strategy for stereoselective hydrogen atom transfer (HAT) to acyclic carbon radicals, which are generated via N-heterocyclic carbene (NHC)-boryl radicals triggered addition-translocation-cyclization cascades. A synergistic control by the NHC subunit and a thiol catalyst has proved effective for one facial HAT, while a ZnI2-chelation protocol allows for the preferential reaction to the opposite face. Such a stereoselectivity switch enables diastereodivergent construction of heterocycles tethering a boron-substituted stereocenter. Mechanistic studies suggest two complementary ways to tune HAT diastereoselectivity. The stereospecific conversions of the resulting boron-handled products to diverse functionalized molecules are demonstrated.
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Affiliation(s)
- Tian Ye
- Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China
| | - Feng-Lian Zhang
- Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China
| | - Hui-Min Xia
- Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China
| | - Xi Zhou
- Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China
| | - Zhi-Xiang Yu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, 100871, Beijing, China.
| | - Yi-Feng Wang
- Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China.
- State Key Laboratory of Elemento-Organic Chemistry, Nankai University, 300071, Tianjin, China.
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Tambutet G, Guindon Y. Diastereoselective Radical Hydrogen Transfer Reactions using N-Heterocyclic Carbene Boranes. J Org Chem 2016; 81:11427-11431. [DOI: 10.1021/acs.joc.6b02066] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Guillaume Tambutet
- Bio-Organic
Chemistry Laboratory, Institut de Recherches Cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada
- Département
de Chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Yvan Guindon
- Bio-Organic
Chemistry Laboratory, Institut de Recherches Cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada
- Département
de Chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Québec H3A 2K6, Canada
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Godin F, Mochirian P, St-Pierre G, Guindon Y. Total synthesis of zincophorin methyl ester. Stereocontrol of 1,2-induction using sterically hindered enoxysilanes. Tetrahedron 2015. [DOI: 10.1016/j.tet.2014.11.061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Wang Y, Zheng L, Wei D, Tang M. A quantum mechanical study of the mechanism and stereoselectivity of the N-heterocyclic carbene catalyzed [4 + 2] annulation reaction of enals with azodicarboxylates. Org Chem Front 2015. [DOI: 10.1039/c5qo00121h] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism and stereoselectivity of the NHC-catalyzed [4 + 2] annulation reaction of enals with azodicarboxylates have been investigated using the DFT method.
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Affiliation(s)
- Yang Wang
- The College of Chemistry and Molecular Engineering
- Center of Computational Chemistry
- Zhengzhou University
- Zhengzhou
- P.R. China
| | - Linjie Zheng
- The College of Chemistry and Molecular Engineering
- Center of Computational Chemistry
- Zhengzhou University
- Zhengzhou
- P.R. China
| | - Donghui Wei
- The College of Chemistry and Molecular Engineering
- Center of Computational Chemistry
- Zhengzhou University
- Zhengzhou
- P.R. China
| | - Mingsheng Tang
- The College of Chemistry and Molecular Engineering
- Center of Computational Chemistry
- Zhengzhou University
- Zhengzhou
- P.R. China
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