Semi-empirical treatment of intramolecular nitrogen heterocyclic triazenesring closure

The semi-empirical MNDO, AMI and PM3 methods are used to study nitrogen het erocyclic ring-closure reactions. Geometries, energies and reactivities inv olved in the ring closure of azidopyridine to tetrazolazine are examined. T he ring-closure mechanisms of o-diazoaniline to benzotriazole, and of o-dia zobenzamide to benzo-1,2,3-triazin-4-one through protonated intermediates a re determined. The effect of aryl ring substituents on ring closure is inve stigated for all structures. Transition states for the o-diazoaniline, and the enol mechanism of o-diazobenzamide ring closures an investigated. (C) 2 001 Elsevier Science B.V. All rights reserved.