Synthesis of Diverse Indole-Containing Scaffolds by Gold(I)-Catalyzed Tandem Reactions of 3-Propargylindoles Initiated by 1,2-Indole Migrations: Scope and Computational Studies

Similar to propargylic carboxylates and sulphides, 3‐propargylindoles undergo 1,2‐indole migrations under cationic gold(I) catalysis. The intermediate Au–carbenoid complex may evolve through different pathways depending on the substituents at the propargylic and terminal positions of the alkyne moiety. Thus, 3‐indenylindole derivatives were easily obtained through formal iso‐Nazarov or Nazarov cyclizations. DFT computations support the formation of an alkylidenecyclopropane intermediate that undergoes gold‐iso‐Nazarov or gold‐Nazarov cyclizations upon torquoselective ring opening. In addition, 3‐dienylindoles could be accessed when none of the referred pathways were accessible and so the intermediate Au–carbenoid complex evolved via a 1,2‐CH insertion reaction. We have also demonstrated that the final products can be obtained in a one‐pot protocol from easily available propargylic alcohols and indoles. Precious‐metal catalysis: 3‐Propargylindoles are able to participate in 1,2‐migrations under gold‐catalysis. 3‐(Inden‐2‐yl)indoles could be accessed through gold‐iso‐Nazarov or gold‐Nazarov cyclizations, whereas 3‐(1,3‐dien‐2‐yl)indoles are generated when none of these pathways are accessible.