A Catalytic Intramolecular Aldehyde–Alkyne Metathesis Approach to Azepino[1,2‐a]indoles

Reported herein is a method for the construction of azepino[1,2‐a]indoles via an intramolecular aldehyde–alkyne metathesis of 1‐(5‐aryl‐4‐pentynyl)indole‐2‐carbaldehydes. This Sc(OTf)3‐catalyzed reaction has several remarkable features, such as ready accessibility of the starting materials, broad substrate scope, operational simplicity, and high yields. The practicality of the process and the synthetic potential of the products were demonstrated with an upscaling experiment and downstream synthetic derivatizations of the obtained products. We have also extended this methodology to synthesize a 6,7‐dihydropyrido[1,2‐a]indole derivative.