Memoli, Sofia, Pietro Tundo, David Herault, Karlheinz Hill. METHYLETHERS FROM METHYL CARBONATES VIA DIMETHYLCARBONATE
Interuniversity Consortium "Chemistry for the Environment" Via della Libertá 5/12, Marghera Venice 30175, Italy (smemoli@unive.it)
While a number of nucleophilic substrates (phenols, anilines, methylene-active compounds) are efficiently methylated by dimethylcarbonate (DMC), only methylcarbonates are formed in the reaction of alcohols with DMC. We report now that, in the presence of alumina or hydrotalcite, methylcarbonates immediately undergo decarboxylation to the corresponding methylethers. The synthesis can be performed by a two-step procedure (transesterification followed by decarboxylation, both steps being carried out under atmospheric pressure) or a one-step procedure (straightforward reaction of alcohols with DMC, performed in autoclave). While the latter affords good yields and selectivity (up to 99%), side reactions occur in the two-step procedure where the decarboxylation of methylcarbonates is performed in the absence of DMC. The reactivity of primary, secondary and tertiary alcohols with DMC, and the influence of reaction parameters - such as nature of the catalyst, catalyst/substrate ratio, temperature, solvent - on the decarboxylation of methylcarbonates are discussed.