Efficient Synthesis of Mandel Acetates by Electrochemical Carboxylation of Benzal Diacetates

Efficient synthesis of mandel acetate, 2-acetoxy-2-phenylacetic acid, from benzaldehyde was successfully performed in two steps using electrochemical carboxylation of benzal diacetate as a key step. When benzal diacetate, readily prepared from benzaldehyde and acetic anhydride in one step, in DMF containing 0.1 M Bu4NBF4 was electrolyzed in the presence of carbon dioxide using an undivided cell equipped with a platinum plate cathode and a magnesium rod anode under constant current conditions, reductive cleavage of the C-OAc bond followed by capture of carbon dioxide took place efficiently at the benzylic position to give mandel acetate in good to high yields. Wide scope, high yields and the use of carbon dioxide as a carbon source of the carboxyl group would provide novel environmentally-benign synthesis of mandelic acid derivatives.