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

Abstract

A rhodium(II)-catalyzed denitrogenative coupling of N-sulfonyl-1,2,3-triazoles with ambiphilic β-enamino esters affords 2,5-dihydro-1H-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 α-imino rhodium-carbene, followed by enamine-imine tautomerization and conjugate addition. Moreover, the reaction proceeds with high diastereoselectivity for α-substituted β-enamino esters (R(3) = Me, Ph) to give a single diastereomer.