Facile synthesis of α-hydroxy-α-methyl carboxylic acids by electrochemical carboxylation of methyl aryl ketones

Electrochemical carboxylation of methyl aryl ketones in the presence of atmospheric pressure of carbon dioxide using platinum cathode and dissolved magnesium anode at constant current density of 10 mA/cm(2) gave the corresponding alpha-hydroxy-alpha-methyl carboxylic acids in 79-84% isolated yields. The precursor of cicloprofen, alpha-hydroxy-alpha-methylfluorene-2-acetic acid (1a) and biprofen, alpha-hydroxy-alpha-methybiphenyl-4-acetic acid (2a) were readily obtained in good yield by a similar electrochemical carboxylation of 2-acetylfluorene (1) and 4-acetylbiphenyl (2). Cyclic voltammetric studies showed that the reaction is reversible indicating the preferential generation of stable anion radicals from methyl aryl ketones and that further addition of carbon dioxide does not take place in these electrochemical carboxylations.