Electrochemical synthesis of 3,5-disubstituted isoxazoles

The electrochemical oxidation of chalcone oximes has been explored using preparative scale electrolysis and cyclic voltammetry (CV). The results show that a constant current electrolysis of chalcone oximes in an undivided cell affords the corresponding isoxazoles in moderate to good yields, using graphite as the working electrode and NaClO4/CH3OH as the supporting electrolyte. The cyclic voltammograms for nearly all of the chalcone oximes investigated exhibit only one oxidation peak. On the basis of preparative electrolysis results and CV analysis, a reaction mechanism, involving a combination of electrochemically-generated base and an iminoxy radical intermediate, is proposed.