Study of the Mechanism of 7-exo-trig Cyclizations of Aryl, Vinyl, and Alkyl Radicals on Oxime Ethers
Por:
Bejarano C.A., Díaz J.E., Camacho J., Flores-Bernal G.G., Miranda L.D., Mejía S.M., Loaiza A.E.
Publicada:
1 ene 2024
Ahead of Print:
1 ene 2024
Resumen:
In this work, we conducted a study of 7-exo-trig cyclizations mechanism involving aryl, vinyl, and alkyl radicals on oxime ethers. Initially, the reaction of brominated oxime ether 9 a with (TMS)3SiH and AIBN gave rise to aryl radicals that underwent a 7-exo-trig cyclization on the oxime ether, yielding dibenzoxepine 10 a, and the ipso reaction and reduction products were obtained as well. Approximate rate constants at 80 °C for the 7-exo-trig (1.0×108 s-1) and the ipso cyclization (4.3×107 s-1) were determined by competition experiments. DFT calculations showed good agreement with the experimental results. The reduction rate constant of the N-alkoxyaminyl radical with (TMS)3SiH was calculated to be 4.1×10-1 M-1 s-1; while the rate constants for the 7-exo-trig cyclizations of vinyl and alkyl radicals on the oxime ether were estimated in the ranges of 106 s-1–108 s-1 and 103 s-1–108 s-1, respectively. The 7-exo-trig cyclization reactions involving aryl, vinyl, and alkyl radicals with oxime ethers were found to be an exothermic and irreversible process, with the oximic carbon showing a preference for nucleophilic alkyl radicals. This kinetic study contributes to the deeper understanding of radical-mediated cyclizations, enabling the efficient design of complex synthetic routes. © 2023 The Authors. European Journal of Organic Chemistry published by Wiley-VCH GmbH.
Filiaciones:
Bejarano C.A.:
Department of Chemistry, Facultad de Ciencias, Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Edificio Carlos Ortiz, Bogotá, 110231, Colombia
Department of Chemistry, Facultad de Ciencias, Universidad Antonio Nariño, Cra. 3 Este No. 47 A-15, Bogotá, 110231, Colombia
Díaz J.E.:
Department of Chemistry, Facultad de Ciencias, Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Edificio Carlos Ortiz, Bogotá, 110231, Colombia
Camacho J.:
Department of Chemistry, Facultad de Ciencias, Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Edificio Carlos Ortiz, Bogotá, 110231, Colombia
Programa de Ingeniería Industrial, Facultad de Ingeniería, Corporación Universitaria Minuto de Dios – UNIMINUTO, Calle 81b No. 72b-70, Bogotá, 111021, Colombia
Flores-Bernal G.G.:
Department of Organic Chemistry, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior S. N., Ciudad Universitaria, Mexico, 04510, Mexico
Miranda L.D.:
Department of Organic Chemistry, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior S. N., Ciudad Universitaria, Mexico, 04510, Mexico
Mejía S.M.:
Department of Chemistry, Facultad de Ciencias, Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Edificio Carlos Ortiz, Bogotá, 110231, Colombia
Loaiza A.E.:
Department of Chemistry, Facultad de Ciencias, Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Edificio Carlos Ortiz, Bogotá, 110231, Colombia
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