Activation of carbon dioxide by electrogenerated superoxide anion: a new carboxylating reagent

A new mild, safe carboxylating reagent is available from the electrochemical reduction of O2 in the presence of CO2. When applied to NH-protic carboxamides bearing a leaving group at the carbon atom adjacent to the carbonyl, the procedure affords oxazolidine-2,4-diones in high to excellent yields. The substrate can be added to the solution at the beginning of the electrolysis or, taking advantage of the stability of the reagent, after the current is switched off, thus making the carboxylation process independent of the presence of electrophores in the substrate, which are even more easily reducible than O2.