Hydroxy-Functionalized Imidazolium Bromides as Catalysts for the Cycloaddition of CO2 and Epoxides to Cyclic Carbonates

Hydroxy-functionalized mono- and bisimidazolium bromides were synthesized and applied as catalysts for the cycloaddition of CO2 and epoxides to cyclic carbonates. A catalyst screening showed the influence of the number of protic hydrogen atoms at the cation for the activation of epoxides. The most active catalyst operates at very mild reaction conditions (70 degrees C, 0.4 MPa CO2) and can be easily recycled ten times without loss of activity.