Catalytic asymmetric cycloaddition of CO2 to epoxides via chiral bifunctional ionic liquids

Abstract

A series of new chiral ionic liquid catalysts composed of the N,N'-bis(salicyclidene) cyclohexene diaminatocobalt and an imidazolium salt were designed, prepared and applied for the chiral cyclic carbonate synthesis from racemic epoxides and carbon dioxide. All reactions exhibit good enantioselectivity for the chiral cyclic carbonate without polycarbonate and other by-products. The order of The order of catalytic activity toward the axial anions is OAc−>CF3CO2−>CCl3CO2−>OTs− and the order of enantioselectivity is OTs−>OAc−>CCl3CO2−>CF3CO2−.