Some reactions of 2-phenyl-4(3H)-quinazolinones

Reaction of 2-phenyl-3,l-benzoxazin-4H-one 1 with thiocarbohydrazide in refluxing ethanol affords 2-phenyl-3-thiosemicarbazido-4(3H)-quinazolinone 2. However, thioxotetrazinoquinazoline 3 is obtained in 79% isolated yield when the reaction mixture is fused in an oil bath at 160 °C. Compound 3 is also obtained when compound 2 is heated in an oil bath at 170 °C. On the other hand, compound 3 reacts with paraformaldehydc and secondary amines to afford the corresponding quinazoline derivatives 4 and 5. The diazonium salt of 3-amino-2-phenyl-4(3H)-quinazolinone 6 reacts with some active methylene compounds (diethyl malonate, ethyl acetoacetate, malononitrile and acetylacetone) to affords the quinazolinone derivatives 8-11 in good yields. Reactions of 8 with hydrazine hydrate and phenylhydrazine afford the corresponding pyrazolonoquinazolinones 12 and 13, respectively. Reaction of 8 with urea furnishes pyrimidinoquinazolmone 14 in 79% isolated yield. However, reaction of 11 with hydrazine hydrate gives pyrazoloquinazolinone 15 in 83% isolated yield