A Poly(hydroxyethyl methacrylate)-Immobilized Chiral Manganese(III)salen Catalyst for Asymmetric Epoxidation of α-Methylstyrene

Abstract

Phenylalaninol was introduced in the C5 and C5′ position of a chiral Mn(III)salenCl compound, and the catalyst was then immobilized on poly(hydroxyethyl methacrylate) (pHEMA) by axial coordination. The catalytic system, with ( R,R )( R,R )pHEMA-immobilized Mn(III)salenCl as catalyst and [bmim]PF 6 as reaction medium, gave excellent catalytic activity and enantioselectivity with 80%–91% ee values and 84%–92% yields for the asymmetric epoxidation of α-methylstyrene. The catalyst can be reused several times without significant loss of catalytic activity. This was due to a chiral synergy between the chiral carbons of the amino alcohol and the chiral carbons of ( R,R )-diaminocyclohexane. 在手性 Mn(III)salenCl 配合物的 5 和 5′位上引入氨基醇, 将其通过轴配位作用负载于聚甲基丙烯酸羟乙酯 (pHEMA) 上, 并用于离子液体[bmim]PF 6 中, 催化 α-甲基苯乙烯的不对称环氧化反应. 结果表明, 该催化剂表现出良好的催化活性和区域选择性, 对映体过量值 (ee) 和产率可分别达 80%-91% 和 84%-92%, 循环使用 5 次后催化活性没有明显降低. 这可归结为氨基醇和环己二胺中手性碳原子间相互协同作用. A catalyst synthesized by the introduction of phenylalaninol into the C5 and C5′ position of a Mn(III)salenCl compound and its subsequent immobilization on p(HEMA) by axial coordination was highly selective in the asymmetric epoxidation of α-methylstyrene.