Enantioselective Epoxidation Of Unfunctionalized Olefins Catalyzed By Chiral Salen-mn (Ⅲ) Catalyst By Axially Coordination Grafted On Novel Types Of Layer Crystalline ZnPS-PVPA

Chiral epoxides are versatile intermediates that can be readily converted into a wide variety of enantiomerically pure compounds by means of region-and stereo-selective ring opening reactions. The asymmetric epoxidation of unfunctionalized olefins is an important approach for synthesizing optically active epoxides, and thus is widely used in the synthesis of fine chemicals, such as Pharmaceuticals, agrochemicals and perfumes. Chiral salen Mn (Ⅲ) complexes have demonstrated activities and selectivities for the enantioselective epoxidation of unfunctional olefins under homogeneous conditions. Compared with the homogeneous asymmetric catalysts, the heterogeneous ones have the advantages of easy catalyst/product separation and simple catalyst recycling. And more and more interests have been focused on the studies of heterogenization of chiral complexes.A novel type of organic polymer-inorganic hybrid material layered crystalline zinc poly (styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPA) was prepared in mild conditions, completely different to the traditional methods. As support, ZnPS-PVPA was modified by multi-steps and then chiral salen Mn (Ⅲ) was grafted on it coordinatedly to obtain the heterogenous catalysts. The catalysts were investigated in asymmetric epoxidation of unfunctional olefins.An array of zinc poly (styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPA) Zn(NaPO4)1-x[O3P-(CH(C6H5)CH2)n]x·mH2O (x=0-1.0) synthesized with different ratios of organic phosphonate to inorganic phosphate were applied as supports and characterized by FT-IR, diffusion reflection UV-vis, AAS, N2volumetric adsorption, SEM, TEM. XPS, XRD and TG. The structures of the supports were explored attentively and the hypothesized structures of the supports were also proposed. The optimized ZnPS-PVPA (x=0.33) was chosen as support and then the new heterogeneous catalysts were gained by grafting chiral salen Mn (Ⅲ) on ZnPS-PVPA modified by aryldiamines and characterized by the same means. Meanwhile, the catalytic activities of immobilized catalysts were also tested. The supported catalysts indicated superior catalytic activities in the asymmetric epoxidation of a-methylstyrene and indene with m-CPBA and NalO4as oxidative systems, compared with the corresponding homogeneous catalyst (ee,>99%vs54%and>99%vs65%). Surprisedly. the catalytic activities did not increase but decrease with the addition of NMO in w-CPBA oxidative system or slightly increased in the presence of imidazole with NalO4as oxidative system. In addition, the influences of x values, linkages and the additives on the catalytic activities of the heterogeneous Mn (Ⅲ) salen catalysts were explored at length. And the heterogeneous catalysts were relatively stable and could be recycled nine times in the asymmetric epoxidation of a-methylstyrene. Furthermore, the immobilized catalyst could also be validly used in large-scale reactions with superior catalytic dispositions being maintained at the same level.Zn(NaPO4)0.65[03P-(CH(C6H5)CH2)n]0.35·mH2O as support was undergoing chloro-methylation and alkyldiamination in turn and then axially coordinated with chiral salen Mn (Ⅲ). The synthesized heterogenerous catalysts were characterized by FT-IR, diffusion reflection UV-vis, AAS, N2volumetric adsorption, SEM, TEM, XPS, XRD and TG. Simultaneously, the catalytic activities of catalysts were also investigated in the asymmetric epoxidation of a-methylstyrene and indene with m-CPBA as oxidative system. The catalytic results displayed superior catalytic activities (conv%,>99%; ee%,>99%) and reusabilities (recycling for ten times).After chloromethylation, the support Zn(NaP04)0.65[O3P-(CH(C6H5)CH2)n]0.35·mH2O was then modified by imidazolium or triazolium and subsequently axially coordinated with chiral salen Mn (Ⅲ). The prepared catalysts were characted by FT-IR, diffusion reflection UV-vis, AAS, N2volumetric adsorption, SEM, TEM, XPS, XRD and TG. And their catalytic abilities were also tested in the asymmetric epoxidation of a-methylstyrene and indene with m-CPBA and NalO4as oxidative systems at the same time. The catalytic results showed that this type of supported catalysts manifested superior catalytic activities (conv%,>99%; ee%,>99)and reusabilities (recycling for ten times) as well as the additives played different roles in different oxidative systems.The heterogenous catalysts were obtained through chloromethylation of the support Zn(NaPO4)0.65[O3P-(CH(C6H5)CH2)n]0.35mmH2O and then the modification of1,2,3-triazole by means of click chemistry as well as axial coordination with chiral salen Mn (Ⅲ). The immobilized catalysts were charactered by FT-IR, diffusion reflection UV-vis, AAS, N2volumetric adsorption, SEM, TEM, XPS, XRD and TG. Meanwhile, the catalytic abilities of the supported catalysts were tested in the asymmetric epoxidation of styrene, a-methylstyrene and indene with m-CPBA, NalO4and NaClO as oxidative systems. The results made clear that the immobilized catalysts indicated superior catalytic activities and reusabilities (recycling for twelve times) as well as the different effects of the additives in different oxidative systems.