Nucleophilic Aryl Fluorination and Aryl Halide Exchange Mediated by a CuI/CuIII Catalytic Cycle
摘要:
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 Cu-I. Strikingly, quantitative fluorination of aryl X substrates is also achieved catalytically at room temperature, using common F- sources, via the intermediacy of aryl-Cu-III-X species. Experimental and computational data support a redox Cu-I/Cu-III catalytic cycle involving aryl X oxidative addition at the Cu-I center, followed by halide exchange and reductive elimination steps. Additionally, defluorination of the aryl-F model system can be also achieved with Cu-I at room temperature operating under a Cu-I/Cu-III redox pair.
Copper-Catalyzed Aerobic Oxidative Functionalization of an Arene C−H Bond: Evidence for an Aryl-Copper(III) Intermediate
摘要:
Recent studies have highlighted the ability of Cu-II to catalyze the aerobic oxidative functionalization of C-H bonds; however, very little is known about the mechanisms of these reactions. Here, we describe the Cu-II-catalyzed C-H methoxylation and amidation of a macrocylic arene substrate with O-2 as the stoichiometric oxidant. Kinetic and in situ spectroscopic studies demonstrate the involvement of three different oxidation states of Cu in the catalytic mechanism, including an aryl-Cu-III intermediate. These observations establish a novel mechanistic pathway that has implications for numerous other Cu-catalyzed aerobic oxidation reactions.