title: A General Nickel-Catalyzed Method for C-H Bond Alkynylation of Heteroarenes Through Chelation Assistance.
abstract: 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)3Ni]NiBr4(PheN=1,10-phenanthroline), was isolated and structurally characterized.
authors.affiliation: Organometallic Synthesis and Catalysis Group, Chemical Engineering Division, CSIR-National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune, 411 008, Maharastra, India.
authors.forename: Shrikant M
authors.initials: SM
authors.lastname: Khake
authors.affiliation: Organometallic Synthesis and Catalysis Group, Chemical Engineering Division, CSIR-National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune, 411 008, Maharastra, India.
authors.forename: Vineeta
authors.initials: V
authors.lastname: Soni
authors.affiliation: Centre for Material Characterization, CSIR-National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune, 411 008, Maharastra, India.
authors.forename: Rajesh G
authors.initials: RG
authors.lastname: Gonnade
authors.affiliation: Organometallic Synthesis and Catalysis Group, Chemical Engineering Division, CSIR-National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune, 411 008, Maharastra, India.
authors.forename: Benudhar
authors.identifier: http://orcid.org/0000-0002-9257-5236
authors.initials: B
authors.lastname: Punji
keywords: C−H activation; alkynylation; homogeneous catalysis; nickel; nitrogen heterocycles