A facile and efficient synthesis of novel 1,2,4-triazolo[5,1-b]quinazolin-9-one derivatives

A facile and efficient synthesis of a series of novel 1,2,4-triazolo[5,1-b] quinazolines is described. 2,3-Diaryl-2,3-dihydro-1H-1,2,4-triazolo[5,1-b]q uinazolin-9-ones were obtained by reaction of 3-amino-2-arylamino-3H-quinaz olin-4-ones with aromatic aldehydes as well as by ring closure of the corre sponding anils. Treatment of 3-amino-2-arylamino-3H-quinazolin-4-ones with aromatic carboxylic acids afforded 2,3-diaryl-3H-1,2,4-triazolo[5,1-b]quina zolin-9-ones which could also be synthesized by dehydrogenation of the corr esponding dihydro derivatives. Reaction of 3-amino-2-arylamino-3H-quinazoli n-4-ones with diethyl malonate and acetylacetone gave 3-aryl-3,9-dihydro-9- oxo-1,2,4-triazolo[5,1-b]quinazolin-2-yl-acetic acid ethyl ester and 3-aryl -2-methyl-3H-1,2,4-triazolo[5,1-b]quinazolin-9-ones, respectively. The latt er compounds were also prepared via reaction with acetic anhydride, whereas acetylation with acetic anhydride in the presence of pyridine afforded the acetyl derivatives.