Mechanistic Aspects on [3+2] Cycloaddition (32CA) Reactions of Azides to Nitroolefins: A Computational and Kinetic Study

Autor(es)

Kawamura, Meire Y. ; Alegre-Requena, Juan, V ; Barbosa, Thais M. ; Tormena, Claudio F. ; Paton, Robert S. ; Ferreira, Marco A. B.

• Tipo de documento: Artigo Científico
• Fonte: CHEMISTRY-A EUROPEAN JOURNAL; v. 28, n. 69, p. 9-pg., 2022-10-19.

Resumo

[3+2] cycloadditions of nitroolefins have emerged as a selective and catalyst-free alternative for the synthesis of 1,2,3-triazoles from azides. We describe mechanistic studies into the cycloaddition/rearomatization reaction sequence. DFT calculations revealed a rate-limiting cycloaddition step proceeding via an asynchronous TS with high kinetic selectivity for the 1,5-triazole. Kinetic studies reveal a second-order rate law, and C-13 kinetic isotopic effects at natural abundance were measured with a significant normal effect at the conjugated olefinic centers of 1.0158 and 1.0216 at the alpha and beta-carbons of beta-nitrostyrene. Distortion/interaction-activation strain and energy decomposition analyses revealed that the major regioisomeric pathway benefits from an earlier and less-distorted TS, while intermolecular interaction terms dominate the preference for 1,5- over 1,4-cycloadducts. In addition, the major regioisomer also has more favorable electrostatic and dispersion terms. Additionally, while static DFT calculations suggest a concerted but highly asynchronous Ei-type HNO2 elimination mechanism, quasiclassical direct-dynamics calculations reveal the existence of a dynamic intermediate. (AU)

• Processo FAPESP: 17/01754-0 - Estudos experimentais e teóricos em reações de cicloadição (3+2) de azidas a nitro-olefinas
• Beneficiário: Meire Yasuko Kawamura
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 20/10246-0 - Ressonância magnética nuclear: das sequências de pulso a determinação estrutural
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 20/01255-6 - Aplicação de ferramentas estatísticas em catálise para entendimento e predição de reações orgânicas
• Beneficiário: Marco Antonio Barbosa Ferreira
• Modalidade de apoio: Auxílio à Pesquisa - Regular