Ni-Catalyzed Deoxygenative Borylation of Phenols Via O‑Phenyl-uronium Activation

Herein, we report an efficient method for the Ni-catalyzed deoxygenative borylation of unprotected phenols and also demonstrate that this Ni-catalyzed phenolic C­(sp2)-O transformation is applicable to the Suzuki–Miyaura-type and Heck-type cross-couplings of phenols. Investigations on the reaction intermediate have revealed that the achievement of general, mild deoxygenative cross-coupling reactions of phenols is ascribed to the conversion of phenols into the unusual O-phenyl-uroniums that feature active phenolic C­(sp2)-O bonds. The Ni-complex intermediate resulting from an oxidative addition of a phenolic C­(sp2)-O bond to monophosphine-supported Ni(0) catalyst was characterized and confirmed to be (PCy3)2Ni­(Ar)­(F) complex, offering experimental evidence for the generally proposed C­(sp2)-O oxidative addition step.