Expanding the Diversity of Azepino [3,2,1‐hi] Indoles via Transition Metal‐based Strategies such as Cross‐coupling Reaction and Ring Closing Metathesis

Abstract

AbstractHere we report several useful synthetic strategies to azepino hi‐indoles, that are structural units in natural products by using commercially available indole derivatives such as 7‐bromo indole and 7‐formylindole via palladium catalyzed cross‐coupling reaction, ring closing olefin metathesis (RCM) as key steps. Later, we extended this strategy to seven‐membered fused indoles containing dioxano and dioxocano derivatives via allylation, double bond isomerization and RCM sequence as key step. Additionally, azepino indole having diene moiety was obtained by enyne metathesis and shown to be useful for Diels−Alder strategy. Along similar lines, we also report eight‐membered fused azocino indole using Grignard reaction and RCM as key steps and we demonstrated that the product obtained is useful for Fischer indolization to obtain bis‐indole derivative. Here several synthetically useful transformations were performed to generate diversity in the fused indole derivatives. All the compounds synthesized here are well characterized by NMR and HRMS data.Introduction