title: Structural and rate studies of the formation of substituted benzynes.
abstract: The key elimination step for the formation of 3-substituted and 3,6-disubstituted benzynes from 2-haloaryllithiums displays a pronounced solvent-dependent regioselectivity. All 2-haloaryllithiums with electron withdrawing groups in the 6 position are shown by 6Li and 13C NMR spectroscopic studies to be monomers in THF. DFT computational studies implicate trisolvates. Rate studies reveal that LiF eliminates via monomer-based pathways requiring THF dissociation whereas LiCl eliminates via nondissociative pathways. Elimination to form 3-chloro- and 3-fluorobenzyne from 2-chloro-6-fluorophenyllithium displays a pronounced solvent-dependent regioselectivity that is traced to competing solvent-dissociative and nondissociative dissociative pathways for the elimination of LiCl and LiF, respectively.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Riggs
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramirez
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Cremeens
authors.forename: Crystal G
authors.initials: CG
authors.lastname: Bashore
authors.forename: John
authors.initials: J
authors.lastname: Candler
authors.forename: Michael C
authors.initials: MC
authors.lastname: Wirtz
authors.forename: Jotham W
authors.initials: JW
authors.lastname: Coe
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D003198:Computer Simulation; D006846:Hydrocarbons, Halogenated / Q000737:chemistry; D007700:Kinetics; D008094:Lithium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D012997:Solvents / Q000737:chemistry
chemical_list: D001555:Benzene Derivatives; D006846:Hydrocarbons, Halogenated; D009942:Organometallic Compounds; D012997:Solvents; D008094:Lithium