Water Oxidation Catalyst Enables Highly Selective Electrochemical Baeyer-Villiger Oxidation

The Baeyer–Villiger oxidation of ketones is crucial for producing esters but traditionally requires difficult-to-handle peroxides. Electrochemical methods can use water as the oxygen source but often suffer from low selectivity due to poor control over oxidation processes and reactions occurring away from the catalytic site. We proposed improving its selectivity by utilizing surface-anchored species for the reaction. We report in this work the application of a known water oxidation catalyst, iron oxide (Fe2O3), for the synthesis of ε-caprolactone with ca. 99% selectivity as a benchmark example of Baeyer–Villiger oxidation through electrochemical OAT with H2O as the oxygen donor. Mechanistic studies revealed that surface hydroperoxo intermediates (M-OOH) are key for promoting nucleophilic attacks on ketone substrates. By confining reactions to the catalyst surface, we limited competing processes such as dehydrogenation and hydroxylation, leading to high selectivity. Kinetic studies and spectroelectrochemical characterizations confirmed the surface-initiated nature of the reaction. This discovery adds nucleophilic oxidation to the tools available for electrochemical organic synthesis.