Synthesis Of Salen Mn(Ⅲ)Heterogeneous Catalysts Immobilized Onto A Novel Layered Crystalline Zirconium Oligostyrenylphosphonate-phosphate By Axially Coordination And Their Application For Asymmetric Epoxidation Of Olefins

Based on our previous work, a new type of inorganic-organic layered crystalline hybrid material-zirconium oligostyrenylphosphonate-phosphate (LCZSPP) with high thermal stability was designed and synthesized. After chloromethed, the chiral salen Mn (â…¢) was axially immobilized onto a novel diamine or diphenoxyl linker modified layered crystalline hybrid material-zirconium oligostyrenylphosphonate-phosphate (LCZSPP) which was synthesized for the first time by our group. The prepared heterogeneous catalysts show comparable ee values for asymmetric epoxidation of unfunctionalized olefins with the homogeneous chiral salen Mn (â…¢) catalyst. The influence of the two types of axial linker on the catalytic performance of the heterogeneous salen Mn (â…¢) was investigated in detail. The results demonstrated that the conversions and ee values increase in the presence of axial additive such as NMO for the salen Mn (â…¢) immobilized onto LCZSPP via diamine linkers, which is in agreement with the literatures reported earlier for both homogeneous and heterogeneous systems, but which is the exact opposite for the immobilized salen Mn (â…¢) via diphenoxyl. The results of two diametrically opposed Illustrated that the axial linker have a important influence.on immobilized chiral Salen Mn (â…¢) Catalysts and catalytic mechanism. Moreover, the prepared catalysts could be conveniently separated from the reaction system by simple precipitation in hexane, and could be reused at least twelfth times without significant loss of activity and enantioselectivity.