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.