Preparation of microgel-supported chiral catalysts and their application in the asymmetric hydrogenation of aromatic ketones

An enantiomerically pure chiral monomer (S,S)-2 was prepared and copolymerized with styrene and four different cross-linkers to produce four distinct microgel-supported chiral TsDPEN derivatives. These chiral copolymers were allowed to form complexes with [RuCl2(cymene)]2 and the resulting homogeneous catalysts were applied in asymmetric hydrogenation reactions of aromatic ketones to give enantioenriched secondary alcohols in quantitative yield. These polymeric catalysts can be easily separated from the reaction mixture and recycled several times without a significant loss in catalytic activity.