Studies on 1, 4-Benzothiazines. I. Synthesis of 2, 3-Dihydro-3-imino-4H-1, 4-benzothiazines and Acetylation of the N-Methyl Derivative

抄録

o-Amino-S-cyanomethylthiophenol (1) obtained by the reaction of o-aminothiophenol with monochloroacetonitrile was converted to 2, 3-dihydro-3-imino-4H-1, 4-benzothiazine (2). Furthermore, the N-methyl derivative (6) was prepared from o-(formyl-methylamino)-S-cyanomethylthiophenol (5) which was obtained by the reaction of benzothiazolium iodide (4) with monochloroacetonitrile under basic conditions. Acetylation of 6 was attempted. The compound 6 (base) was acetylated with acetic anhydride in pyridine at room temperature to give the acetylimino compound (9) by the usual reaction. Unexpectedly, heating under reflux of the hydrochloride of 6 in acetic anhydride afforded a new ring system compound, 8, 15-diazaphenothiazino [8, 7-h] phenothiazine derivative (10) in fair yield. The last reaction gave a small amount of two by-products, which proved to be o-(acetyl-methylamino)-S-acetylcarbamoylmethylthiophenol (11) and 2, 3-dihydro-4-methyl-4H-1, 4-benzothiazin-3-one (12), respectively.