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(7 H )-one scaffolds were synthesized in good to excellent yields with broad scope.