An emerging strategy towards the iodine-catalyzed synthesis of Streptindole and its derivatives in water medium

In this study, we propose an alternative metal-free methodology for the synthesis of Streptindole and its derivatives. This approach employs economically viable and easily handled molecular iodine (I2) as the catalyst in an aqueous medium. The method demonstrates remarkable tolerance towards a diverse array of functional groups. The versatility of the developed protocol is highlighted by its application in the efficient total syntheses of the alkaloid natural products, Streptindole and Arsindoline B accomplished in a single step from indole. Furthermore, the methodology is also useful for the synthesis of pharmaceutically significant compounds, specifically anti-TMV agents (5 c, 5 d, and 5 e) and an anticancer agent (5 f). Control experiments have been carried out to study the plausible catalytic cycle by finding the key intermediates. The experimental findings support the mechanistic pathway involving halogen bond activation in molecular iodine catalysis. This study introduces a new metal-free method using iodine (I2) as a catalyst in aqueous conditions for synthesizing Streptindole and its derivatives. The approach is economically viable, easily handled, and exhibits remarkable tolerance to various functional groups. The protocol's versatility is showcased through the one-step total syntheses of alkaloid natural products Streptindole and Arsindoline B from indole. image