Guanidine-annelated Heterocycles XV. Synthesis of 2-Substituted 4-Phenylamino[1,2,4]triazolo-[2,3-a]quinazolin-5(4H)-ones as Potential Antihypertensive Agents^1

Starting from isatoic anhydride (1) and via one-pot process to 2-methylthio-3-phenylamino-quinazolin-4(3H)-one (4) was isolated in excellent yield. Hydrazinolysis of 4 converted it into the hydrazino derivative 5. Cyclocondensation of 5 with appropriate carboxylic acid orthoesters 6a-c, N,N’-carbonyl-, N,N’-thiocarbonyldiimidazole (6d,e), ethyl chloroformate, carbon disulfide, trifluoro- and trichloroacetic anhydride (6h,i) under elevated temperature gave 4-phenylamino-1「1,2,4」triazolo「2,3-a」 quinazolin-5(4H)-one (8a) and its 2-substituted derivatives 8b-g in different yields. These compounds activated satisfactory antihypertensive activity after the pharmacological evaluation on anesthetized rats.