Electrochemical Annulation of Indole-Tethered Alkynes Enabling Synthesis of Exocyclic Alkenyl Tetrahydrocarbazoles.

An electrochemical sulfonylation-triggered cyclization reaction of indole-tethered terminal alkynes with sulfinates as sulfonyl sources has been developed, which affords exocyclic alkenyl tetrahydrocarbazoles in good chemical yields. This reaction features convenient operation and tolerates a wide scope of substrates with a variety of electronically and sterically diverse substituents. Furthermore, high E -stereoselectivity is observed for this reaction, which provides an efficient method for the preparation of functionalized tetrahydrocarbazole derivatives.