A New Synthesis of 2-Aryloxy propionic Acids Derivatives via Selective Mono-C-Methylation of Methyl Aryloxy acetates and Aryloxyacetonitriles with Dimethyl Carbonate

A one-pot procedure for the monoC-methylation of methyl aryloxyacetates and aryloxyacetonitriles by dimethyl carbonate (DMC) is reported. The reaction is carried out in an autoclave at high temperatures (180-200 °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 monomethylated products (methyl 2-aryloxypropionates and Z-aryloxypropionitriles, 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.