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 Cu fluoride complex into a catalytic process. The critical challenges of electrocatalysis with a highly reactive Cu species were 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 elelctron transfer (PCET) at an electrophilic Cu-F complex. We further demonstrate that the asynchronicity factor of hydrogen atom transfer can be used as a guideline to rationalize the selectivity of C-H fluorination.