A straightforward approach for the synthesis of novel fused thiopyrano [2, 3-b] indole derivatives from the Intramolecular Friedel-Crafts acylation

• Published in: Journal of molecular structure Vol. 1208; p. 127854
• Main Authors: Taheri, Salman, Mohammadi, Ali Asghar, Ahdenov, Reza, Azarlak, Robab, Amini, Saeed K., Halvagar, Mohammad Reza
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2020
• Subjects: Acetylene carboxylates; Eaton’s reagent; Friedel-Crafts acylation; Fused thiopyran; Indoline-2(3H)-Thiones; Regioselective; Regioselective; Eaton’s reagent; Friedel-Crafts acylation; Indoline-2(3H)-Thiones; Fused thiopyran; Acetylene carboxylates
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.127854

In this research, a facile and efficient protocol for the regioselective synthesis of fused thiopyrano [2,3-b]indole-2-carboxylates using Eaton’s reagent (P2O5/MeSO3H) as an inexpensive, and easily available catalyst is developed under solvent-free condition at 80C. The reaction of various acetylenecarboxylates and indoline-2-(3H)-thiones using Eaton’s reagent affords fused indole heterocyclic compounds in good to excellent yields. This new method Compared to the Intramolecular Friedel-Crafts acylation has advantages of short reaction times, regioselectivity and ease of product isolation. [Display omitted] •Eaton’s reagent provided efficient media for synthesis of fused thiopyrano[2,3-b]indole-2-carboxylates.•This report mentioned environmentally friendly methodologies that afford fused polycyclic indole.•Good functional group tolerance is observed.•In all cases, good to excellent yields were obtained for the regioselective reaction.