title: Two unusual, competitive mechanisms for (2-ethynylphenyl)triazene cyclization: pseudocoarctate versus pericyclic reactivity.
abstract: The cyclization of (2-ethynylphenyl)triazenes in ODCB at 200 degrees C gives exclusively cinnolines, whereas addition of CuCl to 1,2-dichloroethane solutions of the triazenes at 50 degrees C results in the sole formation of isoindazoles. DFT calculations and deuterium labeling studies suggest the intermediacy of a 3-dehydrocinnolinium ion, produced through a pericyclic transition state. Calculations and trapping studies strongly implicate a carbene intermediate in isoindazole formation, which proceeds through a pseudocoarctate transition state.
authors.affiliation: Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Kimball
authors.forename: Rainer
authors.initials: R
authors.lastname: Herges
authors.forename: Michael M
authors.initials: MM
authors.lastname: Haley
mesh_terms: D006571:Heterocyclic Compounds / Q000138:chemical synthesis*; D007191:Indazoles / Q000737:chemistry; D013816:Thermodynamics; D014226:Triazenes / Q000737:chemistry*
chemical_list: C453559:(2-ethynylphenyl)triazene; D006571:Heterocyclic Compounds; D007191:Indazoles; D014226:Triazenes