Synthesis of dimethyl carbonate from methanol and CO2 under low pressure

A mild and highly efficient approach has been developed for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2 under low initial pressure. The key to a successful transformation is the use of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), CH2Br2 and ionic liquid. Under the optimized reaction conditions, the yield of DMC was obtained up to 81% under 0.25 MPa. The direct synthesis of DMC can be carried out at balloon pressure using CH2Br2 and DBU. In this case, after the reaction, DBU was proved to be recyclable after having been treated with KOH in ethanol. In addition, a plausible mechanism for this synthetic reaction was proposed according to the experimental results.