Construction of the Cyclohepta[b]indole Scaffold via Gold-Catalyzed Cyclization of 3-(5-Hexynyl)indoles

Abstract The cyclohepta[b]indole scaffold is a privileged motif embedded in structures of many biologically active natural products. Herein, we report for the first time the assembly of this tricyclic system via a gold-catalyzed 7-exo-dig cyclization of acyclic 3-(5-hexynyl)indoles. This efficient transformation proceeds under very mild, neutral conditions and may serve as a key step in the synthesis of cyclohepta[b]indole alkaloids. Further redox manipulations demonstrate the potential of this approach for application in the total synthesis of various indole alkaloids.