Chiral Salen Mn(Ⅲ) Immobilized On Sulfoalkyl Modified ZSP-IPPA/ZPS-PVPA As An Effective Catalyst For Asymmetric Epoxidation Of Unfunctionalized Olefins

Chiral Salen Mn(â…¢) complexes, excellent catalysts have emerged as extremely efficient systems for the asymmetric epoxidation of the unfunctionalized olefins. However, the separation of product and such homogeneous catalysts from the reaction systems remains troublesome. To overcome this problem, Heterogeneous asymmetric catalysis has received considerable attention in the field. The suitable catalyst support for heterogeneous catalysts is the key importance for get high catalytic properties ang ee in the asymmetric catalysis.Based on our previous work, a new type of inorganic-organic hybrid materials-zirconium poly (styrene-isopropenyl phosphonate)-phosphate and zirconium poly (styrene-phenylvinyl phosphonate)-phosphate (ZPS-IPPA and ZPS-PVPA) with high thermal stability was designed and synthesized. After chloromethed, serials of new type of chiral Salen Mn(â…¢) heterogeneous catalysts with different linkage lengths 3a-3c and 4a-4c were obtained by anchoring of chiral Salen Mn(â…¢) complexes axially coordinating onto sulfoalkyl modified (ZPS-IPPA) 1a-1c and (ZPS-PVPA) 2a-2c. The resulted heterogeneous catalysts were characterized by FT-IR, DR UV-vis, XPS, TG, AAS, N2 volumetric adsorption, SEM and TEM.The supported catalysts showed higher chiral induction for enantioselective epoxidation of styrene, a-methylstyrene and indene than its homogeneous chiral Salen Mn(â…¢). In addition, ZPS-PVPA-supported catalyst (4c), with a larger pore diameter, was found to be more active than ZPS-IPPA-based catalyst (3c). The influence of the oxidant, linkage lengths, action temperature and solution on the catalytic performance was investigated. What's more, we can easily separated the catalysts from the systems. Especially, the catalyst 4c could be reused for eight times without significant loss of catalytic activity.