Enantioselective Brønsted acid catalyzed transfer hydrogenation: organocatalytic reduction of imines.

The first enantioselective Brønsted acid catalyzed reduction of imines has been developed. This new organocatalytic transfer hydrogenation of ketimines with Hantzsch dihydropyridine as the hydrogen source offers a mild method to various chiral amines with high enantioselectivity. The stereochemistry of the chiral amines can be rationalized by a stereochemical model derived from an X-ray crystal structure of a chiral BINOL phosphate catalyst. [reaction: see text]