1,2,4-Triazole-Fused Heterocycles; Part 1: Preparation of 5,10-Dihydro-[1,2,4]-triazolo[5,1-b]quinazolines

Abstract

The reaction of benzophenone 1-ureidoethylidenehydrazones 9 with a mixture of triphenylphosphine, carbon tetrachloride, and triethylamine in dichloromethane provides a general route to 5,10-dihydro-[1,2,4]triazolo [5,1-b]quinazolines 7 via the electrocyclization of the expected azino carbodiimide intermediates 10. When one of the substituents on the ureas 9 was an aryl group, unusual guanidine compounds 13 were also produced, and their structures were confirmed by X-ray crystallographic analysis.