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

• A series of new chiral bifunctional ionic liquid catalysts incorporating the N,N′-bis(salicyclidene)cyclohexene diaminatocobalt and an imidazolium salt in one molecule were designed and synthesized.
• A kinetic resolution of racemic epoxides with carbon dioxide to generate chiral cyclic carbonates was achieved in high yield with reasonable enantioselectivity.
• The effects of anixal anion, counterions and the chain length of alkyl of catalysts in these asymmetric cycloadditions were discussed.

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−.

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