A mild and efficient method for Synthesis of novel fused thiopyrano[2,3-b] indole derivatives

Thiopyran and fused-thiopyran derivatives are main classes of sulfur-containing heterocycles due to the frequency of occurrence in the molecular structure of natural products [1]. and have been found to exhibit of bioactivities, such as anti-bacterial and anti-cancer activities On the other hand, the indole scaffold is a structural motif common to a large and varied group of natural products with a remarkable array of biological activities [2]. Over recent decades, synthesis of anti-cancer thioflavone derivatives as a thiopyran analogues have also been developed [3]. In this research, a facile and efficient protocol for the regioselective synthesis of thiopyrano[2,3-b]indole-2-carboxylates using AlCl3 is developed. The reaction of various acetylenecarboxylates and indoline-2(3H)-thiones using of Eaton s reagent affords indole-fused heterocyclic compounds in good to excellent yields. This procedure has advantages of mild reaction conditions, short reaction times, and ease of product isolation.