Synthesis and reactivity of 1,2,4-triazolo[1,5-c]quinazolines

The preparation of 1,2,4-triazolo[1,5-c]quinazolines 4a-d, 5, 8a-d by cyclo condensation of la-e with carboxylic acids and carboxylic anhydrides, respe ctively, is described. By different pathways, the 5-thioxo-5,6-dihydro-1,2, 4-triazolo[1,5-c]quinazolines 4a-d react with hydrazine hydrate or amines w ith the formation of 5-substituted 1,2,4-triazolo[1,5-c]quinazolines 9 and 10a-d. Cyclocondensation of 9 with carboxylic acids, carboxylic anhydrides, and nitrous acid, respectively, leads to the new anellated heterocycles bi s-1,2,4-triazolo[4,3-a:1,5-c]quinazoline 13 and tetrazolo[1,5-a]-1,2,4-tria zolo[1,5-c]quinazoline (14).