Ion For The Preparation Of Mesoporous Chiral Rhodium Catalysts And Asymmetric Hydrogen Transfer Reaction

Inorganic mesoporous materials have a wide range ofapplications in the field of separation, adsorption, catalytic because ofits larger adsorption capacity and specific surface area. Therefore,inorganic mesoporous materials provide a good carrier for theimmobilization of homogeneous catalysts. Mesoporous silica SBA-15material is idea support due to its high surface area and orderedtwo-dimensional hexagonal pore structure (p6mm). Mesoporous silicamaterial SBA-16has a large cage-like structure, larger surface area andhigh thermal stability. Thus, the mesoporous silica SBA-16material has apotential application in asymmetric catalysis. In addition,ion-pair-based mesoporous catalysts do not only possess good stability,but also disperse uniformly active centers to improve greatly thecatalytic efficiency. In this thesis, we have developed two kinds ofion-pair-based mesoporous catalysts and their catalytic properties werestudied and discussed.(1) Preparation of the SBA-15-type chiral rhodium catalyst andcatalytic reactionBy employing a surface-bound triflate (CF3SO3-) counterion asa means of immobilization, we entrapped successfully thehomogeneous ion-pair Rh catalyst into Me-SBA-15to prepareheterogeneous ion-pair-based chiral Rh catalyst. The asymmetrictransfer hydrogenation of aromatic ketones was studied systematically.The result showed that the catalyst presented a highly efficient catalyticactivity and enantioselectivity. Meanwhile, the heterogeneous catalystcan be recovered easily, and the reused catalyst after seven times stillkeep high catalytic activity without affecting significantly itsenantioselectivity.(2)Preparation of the SBA-16-type chiral rhodium catalyst and catalytic reactionWe use the strategy of "ship in bottle" and the ion-pair typeSBA-16chiral rhodium catalyst was synthesized by filling thehomogeneous catalyst wrapped in the mesoporous silica materialSBA-16. The homogeneous catalyst can be wrapped in cage-likestructure because the mesoporous silica material SBA-16has a specialpore structure to achieve the effect of phase separation ofhomogeneous catalysis。 The catalyst for the asymmetric transferhydrogenation of aromatic ketones did show good activity andenantioselectivity and it is easy to achieve catalyst separation andrecycling.