Utility of α-Oxoketene and α-Cyanoketene Thioacetals in Heterocyclic Syntheses: Synthesis of Some New Benzothiazepine Derivatives

Abstract

Benzo[b][1,5]thiazepines 1a or 1b were prepared via reaction of o-aminothiophenol with 3-(bis(methylthio)methylene)-pentane-2,4-dione or 2-(bis(methylthio)methylene)-3-carbonitrile, respectively. Reaction of compound 1a with malononitrile afforded pyrano[4,3-b]benzothiazepine 2a, which underwent cyclization into pyrido[4,3-b][1,5]benzothiazepine 2b. Also, reaction of compound 1a with ethyl cyanoacetate afforded pyrano[4,3-b][1,5]benzothiazepin-3-one 3. Reaction of compound 1a with hydrazine, phenylhydrazine, or hydroxylamine afforded the corresponding azolobenzothiazepines, 4–6, respectively. Reaction of compound 1a with ethylenediamine afforded 1,5-benzothiazepin-ethanone 7, which underwent cyclization to [1,4]diazepino[5,6-b][1,5]benzothiazepine 8. Also, compound 1b was reacted with acetylacetone or ethyl acetoacetate to afford pyrano[4,3-b][1,5]benzothiazepines 9a or 9b, which reacted with ammonium acetate to give pyrano[4,3-b][1,5]-benzothiazepine 10a or pyrido[4,3-b][1,5]-benzothiazepine 10b, respectively. Compound 1b was allowed to react with hydrazine, phenylhydrazine, or hydroxyl amine to afford pyrazolo or isoxazolo[3,4-b][1,5]benzothiazepines 11, 12, or 13, respectively.

Keywords:

• Active methylene
• benzothiazepines
• α-oxoketene dithioacetals
• piperidine