Chiral Brønsted Acid Catalyzed Dynamic Kinetic Asymmetric Hydroamination of Racemic Allenes and Asymmetric Hydroamination of Dienes

Abstract

The first highly efficient and practical chiral Brønsted acid catalyzed dynamic kinetic asymmetric hydroamination (DyKAH) of racemic allenes and asymmetric hydroamination of unactivated dienes with both high E/Z selectivity and enantioselectivity are described herein. The transformation proceeds through a new catalytic asymmetric model involving a highly reactive π-allylic carbocationic intermediate, generated from racemic allenes or dienes through a proton transfer mediated by an activating/directing thiourea group. This method affords expedient access to structurally diverse enantioenriched, potentially bioactive alkenyl-containing aza-heterocycles and bicyclic aza-heterocycles.

Keywords: Brønsted acids; allenes; dienes; heterocycles; hydroamination.