Asymmetric Hydrogenation of Ketones with Ruthenium Complexes of rac- and Enantiopure (S,S)-1,2-Bis((diphenylphosphino)methyl)cyclohexane: A Comparative Study with rac- and
文摘
Ruthenium(II) complexes of the type trans-[RuCl2{1,2-bis((diphenylphosphino)methyl)cyclohexane}(diamine)] basedon the inexpensive and easy-to-prepare rac- and (S,S)-1,2-bis((diphenylphosphino)methyl)cyclohexane form highly active andenantioselective catalysts for the asymmetric hydrogenation ofa wide range of aryl and heteroaryl ketones, in most cases givingee's that exceed those obtained with their BINAP counterparts.Although precatalysts based on 1,2-bis((diphenylphosphino)methyl)cyclohexane slowly isomerize in solution to afford thethermodynamically favored isomer with a cis arrangement ofchlorides, catalysts generated from both isomers afford similarenantioselectivities.