Synthesis of 2-acetyl-3-methyl-4H-1,4-benzothiazine and its derivatives

摘要

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 of3with hydrazine gives 4-(2′-aminophenylthio)-3,5-dimethylpyrazole (5). Condensation of3with 4-nitrobenzaldehyde yields the corresponding Schiff base7. Hydroxylamine with benzothiazine3affords 3,9a-dimethyl-3a, 9a-dihydro-9H-isoxazolo4,5-b1,4benzothiazine (8