Asymmetric hydrogenation of aromatic ketones in ionic-liquid media catalyzed by Ru-TPPTS–(1 S,2 S)-DPENDS complexes

Abstract

The catalytic performance of ruthenium phosphine complexes using (1 S,2 S)-DPENDS [(1 S,2 S)-1,2-diphenyl-1,2-ethylene diamine sulfonate disodium] as a chiral modifier in the asymmetric hydrogenation of aromatic ketones was examined in a series of hydrophilic ionic liquids [RMIM] +[ p-CH 3C 6H 4SO 3] − (R = ethyl, butyl, octyl, dodecyl). The synergistic effect between (1 S,2 S)-DPENDS and KOH significantly accelerated the reaction and enhanced the enantioselectivity. An ee value of 84.8% was obtained in the asymmetric hydrogenation of acetophenone under the optimized conditions. The products were conveniently separated with cyclohexane extraction, and both the ruthenium catalyst and (1 S,2 S)-DPENDS were kept in the ionic liquid and could be reused.