Ir-Catalyzed Asymmetric Hydrogenation of N-Fused Heteroarenes with High Nitrogen Density: An Access to Chiral 2,5-Disubstituted 5,6-Dihydropyrrolo[1,2-a][1,2,4]triazolo[5,1-c]pyrazines

Abstract

A highly enantioselective Ir-catalyzed asymmetric hydrogenation of 2,5-disubstituted pyrrolo[1,2-a][1,2,4]triazolo-[5,1-c]pyrazines containing four nitrogen atoms has been first realized. Under additive-free conditions, a variety of chiral 2,5disubstituted 5,6-dihydropyrrolo[1,2-a][1,2,4]triazolo[5,1-c]pyrazines can be afforded in high yields (86−98%) with excellent enantioselectivities of up to 99% ee. This method provides a straightforward strategy for the efficient synthesis of chiral multinitrogen polyheterocyclic compounds.