Asymmetric Synthesis of Indolines by Catalytic Enantioselective Reduction of 3H-Indoles

A highly enantioselective metal-free reduction of 3H-indoles has been developed. This Bronsted acid catalyzed transfer hydrogenation of indole derivatives with Hantzsch dihydropyridine as the hydrogen source constitutes an efficient method for the synthesis of various optically active indolines with high enantioselectivities