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 cyclocondensation of 1a‐c with carboxylic acids and carboxylic anhydrides, respectively, 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 with 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 bis‐1,2,4‐triazolo[4,3‐ a :1,5‐ c ]quinazoline 13 and tetrazolo [1,5‐ a ]‐1,2,4‐triazolo[1,5‐ c ]quinazoline ( 14 ).