Green Routes to Dimethyl Carbonate: A Green and Versatile Methylating Reactant

Abstract: This mini-review reports the current routes used for the production of dimethyl carbonate (DMC), a green and versatile methylating reactant widely used in organic synthesis. The use of DMC in methylation processes is also discussed. The main routes of DMC production, encompassing the reaction between phosgene and methanol and the oxidative carbonylation of methanol with CO and urea methanolysis, are summarised. However, none of them can be considered entirely green, and the drawbacks in terms of green chemistry principles are addressed. The present commercial route to DMC, which involves the initial reaction of CO2 with ethylene oxide to produce ethylene carbonate that further reacts with excess methanol, is also explored regarding the green chemistry principles. Moreover, this review focuses on the direct DMC production from the reaction of methanol and CO2, discussing catalysts and strategies to shift equilibrium. An emphasis is given to heterogeneous catalysts, especially those based on CeO2. A final remark on the production of DMC through the capture of CO2 using chitosan-derived adsorbents and renewable methanol is addressed.