Oxygen-Radical Capture Enabled Nickel-Catalyzed Carbon(sp2)-Heteroatom Coupling of Two Nucleophiles.

Hypervalent transition-metal complexes serve as pivotal intermediates enabling reductive elimination for carbon-heteroatom bond formation. Significant efforts have focused on nickel-catalyzed couplings of aryl (pseudo)halides with nucleophiles, utilizing, for example, photo- or electrochemical strategies to access high-valent Ni(III) species. Nevertheless, the analogous Ni(III)-mediated oxidative cross-coupling of two nucleophilic partners for carbon-heteroatom bond construction remains elusive, despite the central role of such nucleophiles, for example, boronic acids, in cross-coupling chemistry. Herein, we report a general oxygen-radical capture strategy that accelerates the single-electron oxidation of Ni(II) and subsequent reductive elimination, enabling diverse carbon-heteroatom bond formations with aryl boronic acids. We demonstrate the oxidative coupling of aryl boronic acids with alcohols, a transformation that has never been realized by nickel catalysis, likely due to the facile β-hydride elimination of the corresponding metal alkoxides. Mechanistic investigations and DFT calculations suggest the crucial role of the tert-butoxyl radical in the transformation of Ni(II) to Ni(III), enabling facile reductive elimination that bypass other possible side pathways. Furthermore, we show that a broad range of nucleophiles can be employed for the construction of C-O, C-S, C-N, and C-P bonds using this method.