Abnormal-NHC-Supported Nickel Catalysts for Hydroheteroarylation of Vinylarenes

Herein we report the hydroheteroarylation of vinylarenes with benzoxazole in the presence of a free abnormal N-heterocyclic carbene and Ni­(COD)2, resulting in 1,1-diarylethane products exclusively. In an attempt to understand the mechanism of this catalytic reaction, two abnormal-NHC (aNHC)-coordinated Ni­(II) cyclooctenyl complexes were isolated and their solid-state structures were determined by X-ray crystallographic studies. These Ni­(II) cyclooctenyl complexes act as active catalyst precursors to generate in situ aNHC-Ni­(0) species, which undergo oxidative addition with heteroarene to form Ni­(II) hydride intermediates.