Chiral Salen Mn(â…¢)Immobilized On Diphenol Modified ZnPS-PVPA And Aminopyridine Modified ZnPS-PVPA And ZPS-PVPA As Effective Catalysts For Asymmetric Epoxidation Of Unfunctionalized Olefins

The importance of chiral building blocks, such as optically active epoxides, for drugs and vitamins synthesis has been published largely on homogeneous Jacobsen-type complexes in recent years. However, such catalysts are not easily recovered for reuse or recycle. The last decades have witnessed an intense research effort to heterogenize chiral Jacobsen-type salen Mn(Ⅲ) complexes on supports in an attempt to make them recyclable.A series of novel layered of zinc poly(styrene-phenylvinylphosphonate)-phosphate Zn(NaPO4)l-x(O3PG)x·mH2O (x=0.35-1.0, G is poly(styrene-phenylvinyl)) have been synthesized under mild conditions in the absence of template agent in this paper. The phenylvinylphosphonate and sodium dihydrogen phosphate have been used as phosphorus resource. These compounds were well characterized by FT-IR,DR UV-Vis,N2 volumetric adsorption,TG,XRD,SEM,TEM. The results showed that the new hybrid materials are crystalline with regular layered structure, and the ideal structure model is proposed. In addition, which was used to compare with the support ZPS-PVPA synthesized by our group.Based on our previous work, the chiral salen Mn(III) complex axially immobilized onto diphenol modified ZnPS-PVPA or aminopyridine modified ZnPS-PVPA and ZPS-PVPA. The supported catalysts were used to catalyze the asymmetric epoxidation of styrene,α-methylstyrene and indene. To gain a better catalytic effect, we investigate the effects of various reaction parameters such as catalyst amount, solvent, oxidant and axial additive on the asymmetric epoxidation of olefins. The catalytic results show that the heterogeneous catalysts effectively catalyze the epoxidation of the various olefins in comparable or even higher conversion and enantioselectivity than those of homogeneous catalyst. It is interesting to find out that remarkably increases of conversions and ee values were obtained in the absence of axial additives for the asymmetric epoxidation with the heterogeneous catalyst. Moreover, these diphenol modified catalysts could be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which offer a great possibility for application in industry.