Fused quinoline heterocycles VI: Synthesis of 5H-1-thia-3,5,6-triazaaceanthrylenes and 5H-1-thia-3,4,5,6-tetraazaaceanthrylenes

✍ Scribed by Ramadan Ahmed Mekheimer; Kamal Usef Sadek; Hisham Ahmed Abd El-Nabi; Afaf Abd El-Hameid Mohamed; Ehab Anwer Ebraheem; Michael B. Smith

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2005
• Tongue: English
• Weight: 129 KB
• Volume: 42
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570420415

✦ Synopsis

Ethyl 3-amino-4-chlorothieno[3,2-c]quinoline-2-carboxylate (4) is a versatile synthon, prepared by reacting an equimolar amount of 2,4-dichloroquinoline-3-carbonitrile (1) with ethyl mercaptoacetate (2). Ethyl 5-alkyl-5H-1-thia-3,5,6-triazaaceanthrylene-2-carboxylates 9a-c, novel perianellated tetracyclic heteroaromatics, were prepared by refluxing 4 with excess of primary amines 7a-c to yield the corresponding aminothieno [3,2-c]quinolines 8a-c. Subsequent reaction with an excess of triethyl orthoformate (TEO) furnished 9a-c. Reaction of 4 with TEO in Ac 2 O, at reflux, gave the simple acetylated compounds, thieno[3,2-c]quinolines 12 and 13. Refluxing 4 with benzylamine (7d) gave 10, and subsequent treatment with TEO gave the tetracyclic compound 11. Refluxing 13 with an excess of alkylamines 7a-d gave the thieno[3,2-c]quinolines 15. Refluxing the aminothienoquinolines 8b with an excess of triethyl orthoacetate gave thieno[3,2c]quinoline 17, while heating with Ac 2 O gave 18 and 19, with small amounts of 16. Reaction of 8a,b with ethyl chloroformate and phenylisothiocyanate generated the new 1-thia-3,5,6-triazaaceanthrylenes 20a,b and 21a,b, respectively. Diazotization of 8a-c afforded the novel tetracyclic ethyl 5-alkyl-5H-1-thia-3,4,5,6tetraazaaceanthrylene-2-carboxylates 22a-c in good yields.