title: Experimental and computational evidence for gold vinylidenes: generation from terminal alkynes via a bifurcation pathway and facile C-H insertions.
abstract: Facile cycloisomerization of (2-ethynylphenyl)alkynes is proposed to be promoted synergistically by two molecules of BrettPhosAuNTf(2), affording tricyclic indenes in mostly good yields. A gold vinylidene is most likely generated as one of the reaction intermediates on the basis of both mechanistic studies and theoretical calculations. Different from the well-known Rh, Ru, and W counterparts, this novel gold species is highly reactive and undergoes facile intramolecular C(sp(3))-H insertions as well as O-H and N-H insertions. The formation step for the gold vinylidene is predicted theoretically to be complex with a bifurcated reaction pathway. A pyridine N-oxide acts as a weak base to facilitate the formation of an alkynylgold intermediate, and the bulky BrettPhos ligand in the gold catalyst likely plays a role in sterically steering the reaction toward formation of the gold vinylidene.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
authors.forename: Longwu
authors.initials: L
authors.lastname: Ye
authors.forename: Yanzhao
authors.initials: Y
authors.lastname: Wang
authors.forename: Donald H
authors.initials: DH
authors.lastname: Aue
authors.forename: Liming
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007192:Indenes / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D050607:Organogold Compounds / Q000737:chemistry*; D013816:Thermodynamics; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D000480:Alkynes; D007192:Indenes; D050607:Organogold Compounds; D014753:Vinyl Compounds; C545570:vinylindene; D002244:Carbon; D006859:Hydrogen