Nickel-Catalyzed Intermolecular Carbobromination of Alkynes

Organohalogen
compounds such as alkenyl bromides are versatile
and essential building blocks in organic synthesis. Herein, we describe
the nickel-catalyzed intermolecular carbobrominations of alkynes with
aryl bromides to form highly substituted and functionalized alkenyl
bromides. The reductive elimination of the carbon–bromine bond
from a Ni­(II) species, which is usually a disfavored process, is achieved
from a high-valent Ni­(III) species in this reaction. This transformation
not only expands the scope of transition-metal-complex-promoted bond-forming
reactions but also, more particularly, accomplishes the formation
of labile bonds, which is as challenging to achieve as the cleavage
of inert bonds, such as C–O or C–H bonds.