| Heterogeneous asymmetric catalysis has received considerable attention in the field of catalysis.The suitable type of catalyst support for chiral immobilized catalysts is the key importance for obtaining high catalytic properties in the heterogeneous asymmetric catalysis.The reported supports such as organic polymers,silica or aluminosilicates and dendrimers are available for the immobilization of homogeneous chiral catalysts.In this thesis,linear styrene-phenylvinyl phosphonic acid copolymer was newly synthesized by free radical reaction in solution with PVPA and styrene. Ulteriorly,a new kind of catalyst support material,Zirconium poly(styrene-phenylvinylphosphonate) -phosphate,was synthesized by reaction of PS-PVPA with zirconyl chloride and hydrated sodium orthophosphate.Thus,a series of new heterogeneous chiral Salen Mn(Ⅲ) catalysts were obtained by immobilizing the homogeneous ones onto diamine or polyamine modified ZPS- PVPA by axially coordination.All the supported heterogeneous chiral Salen Mn(Ⅲ) catalysts prepared were characterized by FT-IR,diffusion reflection UV-Vis,AAS,N2 volumetric adsorption,SEM,TEM and TG.The catalytic performances of these catalysts were studied in the asymmetric epoxidation of unfunctionalized olefins.The effect of factors such as co-catalyst,the reaction temperature and the reaction solvents for the asymmetric epoxidation were investigated.All the synthesized heterogeneous catalysts exhibited good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins.Especially, in the epoxidation ofα-methylstyrene,both the conversion and enantiometric excess(ee) could exceed 99%.Furthermore,the catalysts were conveniently separated from the reaction system by simple precipitation in hexane and could be reused at least ten times without significant loss of activity and enantioselectivity. |
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