Diverse radical C-F functionalizations of hexa- to difluoroarenes using boryl radicals as link-and-lose mediators.

Selective fluorine substitution(s) in polyfluoroarenes with other functionalities can effectively tune their properties. However, diverse C-F functionalizations of polyfluoroarenes with varying fluorine numbers and substitution patterns remain a formidable challenge. Here we describe a distinct radical approach employing reactivity-tunable pyridine-boryl radicals as link-and-lose mediators for C-F transformations of various hexa- to difluoroarenes. The reaction starts with pyridine-boryl radical attack to a polyfluoroarene ('link'), which facilitates a distinct heterolytic cleavage of the ipso C-F bond to generate a unique polyfluoroaryl radical cation intermediate under non-reductive conditions. Capturing this intermediate by diverse coupling partners with concurrent departure of boron moiety ('lose') enables hydro- and deuterodefluorination, as well as defluorinative arylation with arenes and alkylation with alkenes/alkanes. This process is applicable to functionalize the second, third and even fourth C-F bond, enabling vast structural diversity. Time-resolved electron paramagnetic resonance spectroscopy provides direct evidence of key intermediates involved, validating the distinct radical cascade.