Abstract:

Asymmetric epoxidation of unfunctional olefin（styrene，α-methyl styrene，indene）was performed  with Jacobsen’s catalyst and silica gel supported (Salen)-Mn(Ⅲ) complex as catalysts（1,2），ionic liquids tetrafluoroborate（1-methyl-3-butyl imidazole）onium salt（BMIMBF₄）and hexafluorophosphate（1-methyl-3-butyl imidazole）onium salt（BMIMPF₆）as reaction medium，sodium，hypochlorite as oxidant，ammonium acetate as axial ligand. The results indicated that the ionic liquids were more effective for enhancing the conversion and enantiomeric excess than dichloromethane，and（BMIMPF₆）was better than（BMIMBF₄）. At the same time，the silica gel supported (Salen)-Mn(Ⅲ) complex demonstrated satisfactory enantioselectivity and activity even higher than homogeneous Jacobsen’s catalyst. Especially，in the epoxidation of a-methylstyrene，the enantiomeric excess in the BMIMPF₆ reached 100%，and could be recycled five times without obvious loss of activity.