Cycloaddition of CO2 to Epoxides Catalyzed by N-Heterocyclic Carbene (NHC)-ZnBr2 System under Mild Conditions

A very simple and convenient method toward coupling of CO₂ with epoxides catalyzed by NHC/ZnBr₂ has been developed. This catalytic system exhibits excellent activity and selectivity in the cycloaddition reactions of CO₂ to terminal epoxides. The reactions can even be carried out under CO₂ pressure as low as 0.05 MPa and give carbonates in high yields.