Asymmetric Hydrogenations of Acetophenone and Its Derivatives over RuRh/γ-Al2O3 Modified by (1S,2S)-DPEN and PPh3

The asymmetric hydrogenations of acetophenone and its derivatives over the bimetallic catalyst RuRh/γ-Al2O3 modified by PPh3 and (1S, 2S)-DPEN [(1S, 2S)-1,2-diphenylethylene-1,2-diamine] were studied. The effects of the concentration of KOH, temperature, ratio of ruthenium to rhodium, and the concentration of diamine on the asymmetric hydrogenation of acetophenone were investigated in detail. The results showed that this catalyst system had high activity and moderate enantioselectivity for the asymmetric hydrogenations of acetophenone and its derivatives. Under the optimum conditions, the conversions of acetophenone, ethylphenylketone, and isopropylphenylketone were up to 92.5%, 95.9%, and 100%, and the enantioselectivities for the formation of (R)-aromatic alcohols were 79.6%, 81.2%, and 81.4%, respectively.