Abstract
A class of zirconium oligostyrenyl-phosphonate-phosphates in a number of stoichiometric pendant group ratios has been synthesized (Zr (HPO 4) 2− x [O 3P–(CH(C 6H 5CH 2)CH 2) n ] x · mH 2O). A general method for the covalent attachment of chiral Mn (III) salen complex to those materials has been devised. The heterogeneous catalysts showed higher chiral induction for enantioselective epoxidation of α-methylstyrene (ee, 57–71%) in the presence of pyridine N-oxide as axial base using aqueous NaOCl as oxidant than that observed in homogeneous catalyst system (ee, 54%). Meanwhile, styrene and indene were efficiently epoxidized with these supported catalysts, and the results were comparable to that for the homogeneous system. In addition, the influence of x values of zirconium oligostyrenyl-phosphonate-phosphates on the catalytic performance of the heterogeneous Mn (III) salen catalysts was investigated in detail. Intermediate x values result in intermediate steric constraints, resulting in spacing values between the two organic groups. The heterogeneous catalysts are relatively stable and can be recycled nine times.
Published Version
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