Enantioselective Epoxidation Of Unfunctionalized Olefins Catalyzed By Chiral Salen-Mn(Ⅲ) Catalyst Grafted On Zirconium Oligostyrenylphosphonate-phosphate

Herein,a general method for the covalent attachment of chiral salen-Mn(â…¢) complex to the supports has been devised.And their catalytic activities on epoxidation of alkenes were investigated.A class of Zirconium oligostyrenylphosphonate-phosphates with the different fraction of the organic group(x)(ZSPP) Zr(HPO₄)_2-x[O₃P-(CH(C₆H₅)CH₂)_n]_x·mH₂O and corresponding chloromethyl-zirconium-oligostyrenyl-phosphonate-phosphate(ZCMSPP) Zr(HPO₄)_2-x[O₃P-(CH (C₆H₄CH₂Cl)CH₂)_n]_x·mH₂O have been synthesized.All the materials were characterized by FT-IR, SEM,N₂ volumetric adsorption,and their structural models were proposed.(R,R)-N-(3,5-Di-tert-butylsalicylidene)-N'-(4-hydroxylsalicylidene)-1,2-cyclohexanediamine salen ligand and corresponding salen-Mn(â…¢) complex were synthesized.A general method for the covalent attachment of chiral salen-Mn(â…¢) complex to those materials have been devised.All the immobilized chiral salen-Mn(â…¢) catalysts were characterized by FT-IR,diffusion reflection UV-Vis, AAS,SEM,TEM and TG.According to the SEM,a possible model for the catalysts was deduced.The catalytic activity of immobilized catalysts for the epoxidation of styrene,α-methylstyrene and indene was studied.First,the catalytic activity of the immobilized catalyst 4b(x=0.65) for the epoxidation of unfunctionalized olefines was investigated in CH₂Cl₂ with NaClO or m-CPBA as oxidant.The immobilized chiral salen-Mn(â…¢) catalyst shows higher chiral induction(ee,60-70%) compared with the corresponding homogeneous catalyst(ee,54%) for asymmetric epoxidation ofα-methylstyrene with NaClO as oxidant.Interestingly,the ee values for the immobilized catalyst with NaClO as oxidant are higher than those with m-CPBA as oxidant.This stands in contrast to the literatures reported;the influence of solvent on the catalytic activity was also separately studied in NaClO oxidated system.Second,the catalytic activity of the other immobilized catalysts was also studied in CH₂Cl₂ with NaClO as oxidant.Meanwhile,the influence of x values of zirconium oligostyrenyl-phosphonate-phosphates on the catalytic performance of the heterogeneous salen-Mn(â…¢) catalysts was investigated in detail.The heterogeneous catalysts are relatively stable and can be recycled nine times.