A NEW SYNTHESIS OF 2-ARYLOXYPROPIONIC ACIDS DERIVATIVES VIA SELECTIVE MONO-C-METHYLATION OF METHYL ARYLOXYACETATES AND ARYLOXYACETONITRILES WITH DIMETHYL CARBONATE

A one-pot procedure for the mono-C-methylation of methyl aryloxyacetates and aryloxyaceto nitriles by dimethyl carbonate (DMC) is reported The reaction is carried out in an autoclave at high temperatures (180-200 degrees C) and in the presence of a base (K2CO3 or t-BuOK). Although DMC is used either as the alkylating agent or as the solvent (30 molar excess with respect to the substrates), The selectivity towards the mono-methylated products (methyl 2-aryloxypropionates and 2-aryloxypropio nitriles, respectively) is typically up to 99%, at complete conversion; no dialkylated by-products form. The reasons of such an unusual behaviour is explained by a mechanism involving an initial carboxymethylation followed by a methylation reaction.