Chiral Ru complex immobilized on mesoporous materials by ionic liquids as heterogeneous catalysts for hydrogenation of aromatic ketones

Four kinds of mesoporous material-supported ionic liquid phase catalysts containing chiral Ru complex were synthesized using mesoporous MCM-41, MCM-48, SBA-15 and amorphous SiO2, respectively. The results of N2 sorption and XRD indicated the successful immobilization of chiral Ru complex inside the channels of the mesoporous materials. These immobilized catalysts were evaluated in the asymmetric hydrogenation of aromatic ketones and the reaction conditions were optimized. Comparable catalytic activities and enantioselectivities to those of nonimmobilized counterpart were obtained. Moreover, all the four catalysts were stable and could be easily recovered for reuse for at least four times without obvious decrease in conversions and ee values. Especially, the SiO2-based catalyst still preserved high activity and enantioselectivity in the fifth run. The comparison experiments indicated that the two kinds of ionic liquids in the heterogeneous catalyst were beneficial to the enhancement of the stability of active species.

. The chiral Ru catalysts immobilized in the mesoporous material-supported ionic liquid phase were highly active, enantioselective and stable for the asymmetric hydrogenation of aromatic ketones.Figure optionsDownload high-quality image (46 K)Download as PowerPoint slideResearch highlights▶ Chiral Ru complex was immobilized on mesoporous materials by ionic liquids. ▶ Immobilized catalysts showed as high catalytic performance as homogeneous one. ▶ Immobilized catalysts were stable and could be easily recovered for reuse. ▶ Both the two ionic liquids contributed to the high stability of immobilized catalyst.