One-step ring-closure procedure for 4,5-dihydro-1,3-thiazino[5,4-b]indole derivatives with Lawesson's reagent. The fifth dihydro-1,3-thiazino[b]indole isomer

✍ Scribed by Péter Csomós; Lajos Fodor; Gábor Bernáth; Antal Csámpai; Pál Sohár

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2011
• Tongue: English
• Weight: 126 KB
• Volume: 48
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.607

✦ Synopsis

Abstract

We report a convenient approach for the synthesis of a new ring system: 4,5‐dihydro‐1,3‐thiazino[5,4‐b]indoles. The procedure involves the use of Lawesson's reagent in the presence of silica to achieve the one‐step ring‐closure reactions of 2‐benzoylamino‐3‐hydroxymethylindole intermediates to furnish 4,5‐dihydro‐2‐aryl‐1,3‐thiazino[5,4‐b]indoles. 2‐Phenylimino‐1,3‐thiazino[5,4‐b]indoles were obtained via the corresponding 3‐phenylthiourea‐2‐carboxylic acid ester derivatives by chemoselective reduction of the ester group, followed by ring closure under acidic conditions. The structures of the novel products were elucidated by IR, ^1^H‐NMR, and ^13^C‐NMR spectroscopy, including 2D‐HMQC, 2D‐HMBC, and DEPT measurements. J. Heterocyclic Chem., (2011).