Enantioselective epoxidation of unfunctionalized olefins catalyzed by chiral salen Mn(III) catalyst immobilized on zirconium oligostyrenylphosphonate-phosphate

A general method for the covalent attachment of chiral salen Mn(III) complex to zirconium oligostyrenylphosphonate-phosphate has been used. The immobilized chiral salen Mn(III) catalyst shows higher chiral induction (ee, 60-70%) compared with the corresponding homogeneous catalyst (ee, 54%) for asymmetric epoxidation of alpha-methylstyrene with NaCIO as oxidant, while the heterogeneous catalyst exhibits relatively low ee values for asymmetric epoxidation of indene. Interestingly, the ee values for the immobilized catalyst with NaCIO as oxidant are higher than those for the same catalyst with m-chloroperbenzoic acid as oxidant. This stands in contrast to the literatures reported. The heterogeneous catalyst can be recycled nine times, while the activity will decrease after use in reactions. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.