Gold‐Catalyzed Cyclization of Indole‐Tethered Alkynes Enabling Synthesis of Exocyclic Alkenyl Tetrahydrocarbazoles

A gold‐catalyzed intramolecular cyclization of indole‐tethered alkynes using Hantzsch ester (HE) and AgNTf 2 as additives has been developed, providing diverse functionalized exocyclic alkenyl tetrahydrocarbazoles in good to excellent yields. Control experiments and DFT studies indicate that the reaction proceeds via a 6‐ exo ‐dig cyclization pathway, with gold acetylide complexes as key intermediates and HE serving as a base. The reaction proceeds under mild conditions, shows broad functional‐group tolerance, and is amenable to scale‐up. Selected tetrahydrocarbazole products also exhibited moderate antifungal activity against two forest pathogenic fungi.