Dendritic [RuCl2(BINAP)(DPEN)] catalysts with ‘Sandwich’ multi-layer structure for asymmetric hydrogenation of simple aryl ketones

A new kind of chiral dendritic [RuCl2(BINAP)(DPEN)] catalysts with a ‘Sandwich’ multi-layer structure have been synthesized via metal coordination reactions with dendritic chiral diphosphines and dendritic chiral diamine ligands. The formation of the dendritic catalysts was confirmed by 31P NMR. The catalyst performance was then investigated in the asymmetric hydrogenation of simple aryl ketones, and comparable enantioselectivities were achieved with comparison to that of the corresponding small-molecular catalyst. In addition, the recyclable property of these homogeneous catalysts was studied with the third-generation catalyst, which was reused nine times by simple solvent precipitation without any loss of enantioselectivity.