Direct Access to Polyannulated Azacyclics Through a Cascade Double Annulation of Allenamines Triggered by Friedel–Crafts Alkylation and Nucleophilic Substitution

Abstract

Here, we report a direct synthesis of polyfused azacyclics bearing an all‐carbon quaternary center from propargyl alcohols (PAs) and 2‐pyrrolyl anilines, catalyzed by Sc(OTf) 3 under solvent‐free conditions. This approach involves the cascade double annulation of in situ‐formed allenamines via an intramolecular Friedel–Crafts reaction, followed by 6‐exo‐tet cyclization. We demonstrated the substrate scope, gram‐scale synthesis, and mechanistic studies of the protocol.