Copper-catalyzed electrochemical C–H fluorination

We report the systematic development of an electrooxidative methodology that translates stoichiometric C–H fluorination reactivity of an isolable CuIII fluoride complex into a catalytic process. The critical challenges of electrocatalysis with a highly reactive CuIII species are addressed by the judicious selection of electrolyte, F− source, and sacrificial electron acceptor. Catalyst-controlled C–H fluorination occurs with a preference for hydridic C–H bonds with high bond-dissociation energies over weaker but less hydridic C–H bonds. The selectivity is driven by an oxidative asynchronous proton-coupled electron transfer (PCET) at an electrophilic CuIII–F complex. We further demonstrate that the asynchronicity factor of hydrogen-atom transfer, η, can be used as a guideline to rationalize the selectivity of C–H fluorination.