Base-Promoted Tandem Synthesis of 2‑Substituted Indoles and N‑Fused Polycyclic Indoles

Herein is developed a base-promoted approach for the synthesis of C2-substituted indoles and N-fused polycyclic indoles via 5-endo-dig cyclization of 2-alkynyl anilines, followed by a 1,3′-acyl migration or a dearomatizing Michael addition process. A range of N–H free indoles and 8,9-dihydropyrido­[1,2-a]­indol-6­(7H)-one scaffolds were synthesized in good to excellent yields with broad scope.