Synthesis of some stable 4H-3,1-Benzoaxazin-4-ones and their behaviour toward nucleophiles

4H-3,I-Benzoxazin-4-ones 2a,b were synthesised from the corresponding anthranils la, b using acetic anhydride as a dehydrating agent. The effect of some nucleophiles, namely, primary aromatic amines, hydrazine hydrate, Grignard's reagents and sulpha drugs on the title compounds was investigated. 1 H- and 13C-NMR, mass spectra as well as infrared spectra and microanalyses were used to elucidate the structures of new compounds.