From Triazoles to Imidazolines through the Sequential N–H Insertion of α-Imino Rhodium–Carbenes into β-Enamino Esters/Enamine–Imine Tautomerization/Conjugate Addition Cascade
作者:Hyun Ji Jeon、Da Jung Jung、Ju Hyun Kim、Youngmee Kim、Jean Bouffard、Sang-gi Lee
DOI:10.1021/jo501785d
日期:2014.10.17
A rhodium(II)-catalyzed denitrogenative coupling of N-sulfonyl-1,2,3-triazoles with ambiphilic beta-enamino esters affords 2,5-dihydro-H-1-imidazoles (3-imidazolines) with broad functional group tolerance. Mechanistic studies using a deuterium-labeled triazole suggest that the reaction proceeds in a cascade through the N-H insertion of an alpha-imino rhodium-carbene, followed by enamine-imine tautomerization and conjugate addition. Moreover, the reaction proceeds with high diastereoselectivity for alpha-substituted beta-enamino esters (R-3 = Me, Ph) to give a single diastereomer.