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

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]PF6 as reaction medium, gave excellent catalytic activity and enantioselectivity with 80%-91% ee values and 84%-92% yields for the asymmetric epoxidation of alpha-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.