Enantioselective Metal-Free Hydrogenations of Disubstituted Quinolines

A metal-free hydrogenation of 2,4-disubstituted quinolines was realized for the first time using chiral diene derived borane catalysts to furnish the corresponding tetrahydroquinolines in 75-98% yields with 95/5-99/1 dr's and: 86-98% ee's. This catalytic system was also effective for 2,3-disubstituted quinolines to give moderate to good ee's.