Dimethyl Carbonate: Green Solvent and Ambident Reagent

Abstract

DMC is a versatile compound which represents an attractive eco- friendly alternative to both methyl halides (or dimethyl sulfate) and phosgene for methylation and carbonylation processes, respectively. DMC, produced nowadays by a clean process, possesses properties of no toxicity and biodegradability which makes it a true green reagent to be used in syntheses that prevent pollution at the source. The reactivity of DMC is tunable: at T ≤ 90°C, methoxycarbonylations take place, while at higher reaction temperatures, methylation reactions are observed with a variety of nucleo- philes. Besides, DMC-mediated methylations are catalytic reactions which use safe solids (alkaline carbonates) avoiding the formation of undesirable inorganic salts as by-products. The high selectivity in methylation reactions is due to the ambident electrophilic character of DMC which reacts on its hard centre (the carbonyl group) with harder nucleophiles and on its soft one (the methyl group) with softer nucleophiles, according to the Hard-Soft Acid and Base (HSAB) theory.