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.