Asymmetric hydrogenation of aromatic ketones using new chiral-bridged diphosphine/diamine–Ru(II) complexes

A series of chiral secondary alcohols were easily prepared by means of asymmetric hydrogenation of prochiral aromatic ketones using a new ((Rax)-BuP)/(R,R)-DPEN–Ru(II) complex catalyst system. The hydrogenation of 2-methylacetophenone in n-butanol (t-BuOK/Ru = 45.6/1, S/C = 500, 20 atm. of H2, 20 °C, 48 h) afforded (S)-1-(2′-methylphenyl)ethanol in 92% ee and >99% conversion.