Catalytic asymmetric hydrogenation of quinoline carbocycles: unusual chemoselectivity in the hydrogenation of quinolines

The reduction of quinolines selectively took place on their carbocyclic rings to give 5,6,7,8-tetrahydroquinolines, when the hydrogenation was conducted in the presence of a Ru(η3-methallyl)2(cod)–PhTRAP catalyst. The chiral ruthenium catalyst converted 8-substituted quinolines into chiral 5,6,7,8-tetrahydroquinolines with up to 91 : 9 er.