SYNTHESIS OF 2-ACETYL-3-METHYL-4H-1,4-BENZOTHIAZINE AND ITS DERIVATIVES

2-Aminothiophenol (1) reacts with 3-chloro-2,4-pentanedione (2) in the presence of pyridine to form 2-acetyl-3-methyl-4H-1,4-benzothiazine ( 3) in high yields. Reaction of 3 with hydrazine gives 4-(2'-aminopheny lthio)-3,5-dimethylpyrazole (5). Condensation of 3 with 4-nitrobenzald ehyde yields the corresponding Schiff base 7. Hydroxylamine with benzo thiazine 3 affords 3,9a-dimethyl-3a, 9a-dihydro-9H-isoxazolo[4,5-b][1, 4]benzothiazine (8).