Enantioselective Parallel Kinetic Resolution of Aziridine-Containing Quinoxalines via Chiral Phosphoric Acid-Catalyzed Transfer Hydrogenation

This article describes the asymmetric synthesis of chiral aziridinoquinoxalines using (R)-TRIP-catalyzed parallel kinetic resolution under transfer hydrogenation conditions. This resolution was successfully accomplished for 16 different substrates and led to highly enantioenriched diastereomers with the (R)-configuration of the newly formed stereocenter (32-61% yield and 64-99% ee for the (R,R,R)-diastereomers and 7-46% yield and 97-99% ee for the (S,S,R)-diastereomers). This process could be coupled to ring-opening of the (S,S,R)-diastereomer with thiophenol to produce chiral tetrahydroquinoxalines with three contiguous stereocenters.