Electrocarboxylation of aromatic ketones: Influence of operative parameters on the competition between ketyl and ring carboxylation

The purpose of this work is to investigate the effect of operational parameters on the competition between the formation of the target 2-hydroxy-2-arylpropanoic acid and ring carboxylation in the electrocarboxylation of aromatic ketones. For the investigated ketones, this competition has been found to be dramatically influenced by different parameters such as the water content and the ratio between the carbon dioxide and the ketone concentrations (q = [CO2]/[ketone]). In particular, the target carboxylic acid formation can be favoured with respect to ring carboxylation by operating at high q ratios or by addition of small amounts of H2O to the reaction medium. An increase of the water content leads, otherwise, also to an increase of the selectivity of other by-products such as alcohol and pinacol. The selectivity of the process was not appreciably influenced by other operative parameters such as the cathodic material or the presence of sacrificial anodes.