Borane-catalyzed metal-free hydrogenation of 2,7-disubstituted 1,8-naphthyridines.

Metal-free hydrogenation of 2,7-disubstituted 1,8-naphthyridines was successfully realized for the first time using in situ generated borane catalysts under mild conditions to furnish 1,2,3,4-tetrahydro-1,8-naphthyridine derivatives in 83-98% yields. Significantly, up to 74% ee was achieved for the corresponding asymmetric hydrogenation reactions.