Abstract
The reaction of 3‐N‐(2‐mercapto‐4‐oxo‐4__H__‐quinazolin‐3‐yl)acetamide (1) with hydrazine hydrate yielded 3‐amino‐2‐methyl‐3__H__‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one (2). The reaction of 2 with o‐chlorobenzaldehyde and 2‐hydroxy‐naphthaldehyde gave the corresponding 3‐arylidene amino derivatives 3 and 4, respectively. Condensation of 2 with 1‐nitroso‐2‐naphthol afforded the corresponding 3‐(2‐hydroxy‐naphthalen‐1‐yl‐diazenyl)‐2‐methyl‐3__H__‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one (5), which on subsequent reduction by SnCl~2~ and HCl gave the hydrazino derivative 6. Reaction of 2 with phenyl isothiocyanate in refluxing ethanol yielded thiourea derivative 7. Ring closure of 7 subsequently cyclized on refluxing with phencyl bromide, oxalyl dichloride and chloroacetic acid afforded the corresponding thiazolidine derivatives 8, 9 and 10, respectively. Reaction of 2‐mercapto‐3‐phenylamino‐3__H__‐quinazolin‐4‐one (11) with hydrazine hydrate afforded 2‐hydrazino‐3‐phenylamino‐3__H__‐quinazolin‐4‐one (12). The reactivity 12 towards carbon disulphide, acetyl acetone and ethyl acetoacetate gave 13, 14 and 15, respectively. Condensation of 12 with isatin afforded 2‐[N‐(2‐oxo‐1,2‐dihydroindol‐3‐ylidene)hydrazino]‐3‐phenylamino‐3__H__‐quinazolin‐4‐one (16). 2‐(4‐Oxo‐3‐phenylamino‐3,4‐dihydroquinazolin‐2‐ylamino)isoindole‐1,3‐dione (17) was synthesized by the reaction of 12 with phthalic anhydride. All isolated products were confirmed by their ir, ^1^H nmr, ^13^C nmr and mass spectra.