Synergistic effect of alkali halide and Lewis base on the catalytic synthesis of cyclic carbonate from CO2 and epoxide

The synthesis of cyclic carbonates from CO2 and epoxides catalyzed by alkali metal halides (MX) in combination with a Lewis base (LB) is reported here. The unique synergistic effect between MX and LB has been observed at an optimum mole ratio of 1:1. High turnover frequency (TOF, h−1) indicates that an increase in the reaction efficiency of up to 40 times is obtained by comparison with the reaction carried out using only MX. The activity of MX primarily falls in the order of alkali metal ion’s Lewis acidity. The optimum conditions for this solventless reaction were 130 °C and 2 MPa of CO2 pressure.