Synthesis and reactions of 3-amino-2-methyl-3H-[1,2,4]triazolo[5,1-b]-quinazolin-9-one and 2-hydrazino-3-phenylamino-3H-quinazolin-4-one

The reaction of 3‐N‐(2‐mercapto‐4‐oxo‐4H‐quinazolin‐3‐yl)acetamide (1) with hydrazine hydrate yielded 3‐amino‐2‐methyl‐3H‐[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‐3H‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one (5), which on subsequent reduction by SnCl2 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‐3H‐quinazolin‐4‐one (11) with hydrazine hydrate afforded 2‐hydrazino‐3‐phenylamino‐3H‐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‐3H‐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, 1H nmr, 13C nmr and mass spectra.