A new strategy to efficiently cleave and form C–H bonds using proton-coupled electron transfer

Oxidative activation and reductive formation of C–H bonds are crucial in many chemical, industrial, and biological processes. Reported here is a new strategy for these transformations, using a form of proton-coupled electron transfer (PCET): intermolecular electron transfer coupled to intramolecular proton transfer with an appropriately placed cofactor. In a fluorenyl-benzoate, the positioned carboxylate facilitates rapid cleavage of a benzylic C–H bond upon reaction with even weak 1e(−) oxidants, for example, decamethylferrocenium. Mechanistic studies establish that the proton and electron transfer to disparate sites in a single concerted kinetic step, via multi-site concerted proton-electron transfer. This work represents a new elementary reaction step available to C–H bonds. This strategy is extended to reductive formation of C–H bonds in two systems. Molecular design considerations and possible utility in synthetic and enzymatic systems are discussed.