title: Mechanistic Investigation on the Formation of 2-Halo-3-aryl-4(3H)-quinazoliniminium Halides from Heteroenyne-allenes: A Computational Study.
abstract: Intramolecular cyclization of the heteroenyne-allene, 2-((phenylimino)methyleneamino)-benzonitrile (1) in the presence of HCl to produce 2-chloro-3-phenyl-4(3H)-quinazoliniminium chloride (Qz) involves the formation of two new bonds: a C-Cl bond and a C-N bond. We propose five pathways for this reaction. Four of these pathways involve chloride capture to form the C-Cl bond prior to the intramolecular nucleophilic attack to form the C-N bond, while one pathway involves ring closure to form the C-N bond prior to C-Cl bond formation. All calculations were carried out at B3LYP and MP2 levels of theory and employed the 6-311G* basis set. The solvent effects were considered using a Polarized Continuum Model with dichloromethane as the solvent. The calculations at both levels show that the mechanism involves initial protonation of 1, preferentially at Nα to give 2 which rapidly captures the chloride ion to form 5. This intermediate is protonated at the -CN group to form 8ROT, which then tautomerizes to its more stable isomer 9ROT. The latter undergoes intramolecular nucleophilic attack from Nβ to the protonated -CN group to form the cyclized intermediate 12, which tautomerizes to its most stable isomer 13. The coordination of Cl(-) ion present in the solution with 13 gives the final product Qz.
authors: Department of Chemistry, Ball State University, Cooper Physical Science Building, Muncie, Indiana 47304-0445, United States.
authors: Pamela S
authors: PS
authors: Filby
authors: Department of Chemistry, Ball State University, Cooper Physical Science Building, Muncie, Indiana 47304-0445, United States.
authors: Sundeep
authors: S
authors: Rayat
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D011799:Quinazolines / Q000737:chemistry*
chemical_list: D000475:Alkenes; D000480:Alkynes; D006846:Hydrocarbons, Halogenated; D011799:Quinazolines