Characterization and Reactivity of Copper(II) and Copper(III) σ-Aryl Intermediates in Aminoquinoline-Directed C-H Functionalization

Over the past decade, numerous reports have focused onthe developmentand applications of Cu-mediated C-H functionalization reactions;however, to date, little is known about the Cu intermediates involvedin these transformations. This paper details the observation and characterizationof Cu-II and Cu-III intermediates in aminoquinoline-directedC(sp(2))-H functionalization of a fluoroarene substrate.An initial C(sp(2))-H activation at Cu-II occurs at room temperature to afford an isolable anionic cyclometalatedCu(II) complex. This complex undergoes single-electron oxidationwith ferrocenium or Ag-I salts under mild conditions (5min at room temperature) to afford C(sp(2))-C(sp(2)) or C(sp(2))-NO2 coupling products.Spectroscopic studies implicate the formation of a transient diamagneticCu(III)-& sigma;-aryl intermediate that undergoes either (i)a second C(sp(2))-H activation at Cu-III followed by C-C bond-forming reductive elimination or (ii)reaction with a NO2 (-) nucleophile andC(sp(2))-NO2 coupling.