Pulsed electrolysis enables unexpected lactonization of bicyclobutane carboxylic acids.

Anodic oxidation of bicyclobutane carboxylic acids leads to unexpected lactonization and provides access to substituted benzene bioisosteres from highly strained precursors. High selectivity was achieved under pulsed electrolysis. Mechanistic experiments, supported by computational analysis, indicate that the transformation is initiated by single-electron oxidation of the substrate to form a bicyclobutyl radical cation, a key intermediate in redox-mediated transformations. These results demonstrate the utility of electrochemical methods for controlling the reactivity of bicyclobutane derivatives and provide a foundation for further development of sustainable oxidative transformations of strained molecules.