title: Oxidant-free direct coupling of internal alkynes and 2-alkylpyridine via double C-H activations by alkylhafnium complexes.
abstract: We have developed a novel oxidant-free direct cross-coupling reaction of 2,6-lutidine and internal alkynes leading to five-membered carbocyclic compounds mediated by nonmetallocene cationic hafnium alkyl complexes. Mechanistic studies of the coupling reaction showed that the reaction begins with C(sp(3))-H bond activation via σ-bond metathesis, after which the coordinatively unsaturated hafnium center mediates further insertion, migration, and β-H elimination reactions to give five-membered carbocycles from readily available substrates.
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Tsurugi
authors.forename: Koji
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Kazushi
authors.initials: K
authors.lastname: Mashima
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D055772:Green Chemistry Technology; D006195:Hafnium / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
chemical_list: D000480:Alkynes; D009942:Organometallic Compounds; D011725:Pyridines; C023666:pyridine; D006195:Hafnium