A General Nickel-Catalyzed Method for C-H Bond Alkynylation of Heteroarenes Through Chelation Assistance.

A general nickel-catalyzed method for the alkynylation of heteroarenes through monodentate chelation assistance is described. Many heterocycles, including indoles, pyrroles, imidazoles, and pyrazole, efficiently coupled with (triisopropylsilyl)alkynyl bromide, and synthetically important functional groups, such as halides, ether, nitrile, and nitro, are tolerated. Synthetic applicability of this Ni-catalyzed method is demonstrated by the removal of the triisopropylsilyl group and further functionalization to triazolyl, benzofuranyl, and alkynyl arene derivatives. Preliminary mechanistic investigations of the alkynylation of indole suggest that the reaction proceeds through kinetically relevant C-H activation and follows a two-electron redox pathway. A catalytically relevant Ni species, namely, [(Phen) Ni]NiBr (PheN=1,10-phenanthroline), was isolated and structurally characterized.