Structural and rate studies of the formation of substituted benzynes.
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.
Riggs
Jason C
JC
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Ramirez
Antonio
A
Cremeens
Matthew E
ME
Bashore
Crystal G
CG
Candler
John
J
Wirtz
Michael C
MC
Coe
Jotham W
JW
Collum
David B
DB
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
D001555:Benzene Derivatives; D006846:Hydrocarbons, Halogenated; D009942:Organometallic Compounds; D012997:Solvents; D008094:Lithium