Ruthenium-Catalyzed Enantioselective Hydrogenation of 1,8-Naphthyridine Derivatives.

The first asymmetric hydrogenation of 2,7-disubstituted 1,8-naphthyridines catalyzed by chiral cationic ruthenium diamine complexes has been developed. A wide range of 1,8-naphthyridine derivatives were effectively hydrogenated to give 1,2,3,4-tetrahydro-1,8-naphthyridines with up to 99% ee and full conversions. The method provides a practical and facile approach to the preparation of valuable chiral heterocyclic building blocks and useful motifs for a new kind of P,N-ligand.