Synthesis of the 1,2,4-Triazolo[4,3-<i>a</i>]quinazolin-5-ones and Related Compounds

Abstract

Abstract 2-Hydrazino-3-phenyl-4(3H)-quinazolinone (1) underwent ring closure with aliphatic acid, aldehydes, and carbon disulfide to 1-alkyl-, 1-aryl-, and 1-mercapto-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones (7) for instance. The 1-alkylthio-3-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones were readily obtained from 7 and alkyl halides. Reaction of 1 with ethyl acetoacetate gave the corresponding hydrazone which was readily converted into 2-(3-methyl-5-oxo-2-pyrazolin-1-yl)-3-phenyl-4(3H)-quinazolinone.