Nucleophilic Aryl Fluorination and Aryl Halide Exchange Mediated by a CuI/CuIII Catalytic Cycle

Copper-catalyzed halide exchange reactions under very mild reaction conditions are described for the first time using a family of model aryl halide substrates. All combinations of halide exchange (I, Br, Cl, F) are observed using catalytic amounts of CuI. Strikingly, quantitative fluorination of aryl–X substrates is also achieved catalytically at room temperature, using common F– sources, via the intermediacy of aryl–CuIII–X species. Experimental and computational data support a redox CuI/CuIII catalytic cycle involving aryl–X oxidative addition at the CuI center, followed by halide exchange and reductive elimination steps. Additionally, defluorination of the aryl–F model system can be also achieved with CuI at room temperature operating under a CuI/CuIII redox pair.