Synthesis of dimethyl carbonate from methanol and CO 2 under low pressure.

A mild and highly efficient approach has been developed for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO 2 under low initial pressure. The key to a successful transformation is the use of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), CH 2 Br 2 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 CH 2 Br 2 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.