Nickel-Catalyzed Inter- and Intramolecular Reductive Cross-Coupling Reactions of Arylbenzylammonium Salts through Highly Site-Selective C–N Bond Cleavage

Abstract

The site selectivity has been investigated for the C−N bond cleavage of arylbenzylammonium salts in reductive crosscoupling reactions with carbon electrophiles. A wide variety of arylbenzylammonium triflates participated in nickel-catalyzed zincmediated benzyl−aryl cross-electrophile coupling with aryl bromides to afford diarylmethanes with extremely high site selectivity. The same reaction conditions were successfully extended to the intramolecular reductive cross-coupling of benzyl(bromoaryl)ammonium triflates. Moreover, arylbenzylammonium triflates underwent nickel-catalyzed manganese-mediated benzyl−acyl crosselectrophile coupling with aromatic carboxylic acids in the presence of di-tert-butyl pyrocarbonate. These reactions employ readily available feedstocks and reagents, exhibit extremely high site selectivity for the cleavage of benzylic C−N bonds rather than aromatic C−N bonds, and tolerate a variety of functional groups.