A Stepwise Electrochemical Baeyer-Villiger Oxidation with Water as the Oxygen Source.

Baeyer-Villiger oxidation is a method with a 125-year history that produces lactones through a synergistic mechanism by reaction with stoichiometric peracids. Therefore, substituted lactones can be obtained from only substituted cyclic ketones. In this context, an electrochemical Baeyer-Villiger oxidation was developed using a CeO2@PbO2@Ti electrode, which produces substituted lactones through a stepwise mechanism. PbO2, in combination with a benzoic acid molecular catalyst, can generate and utilize reactive oxygen species from electrochemical water splitting to serve as the oxidant. CeO2 is designed to promote the stepwise mechanism while suppressing the synergistic mechanism. Therefore, substituted lactone can be produced from unsubstituted cyclic ketone with high selectivity (77%) and yield (20 mM) through a carbocation rearrangement process. The developed stepwise electrochemical Baeyer-Villiger oxidation, using water as the oxygen source, offers a new green approach to organic synthesis.