Access to Polycyclic Indol(en)ines viaBase‐Catalyzed Intramolecular Dearomatizing 3‐Alkenylation of Alkynyl Indoles

Abstract

Main observation and conclusionPolycyclic indolines and indolenines were synthesized via base‐catalyzed intramolecular dearomatizing 3‐alkenylation reactions of alkynyl indoles 1 at room temperature. The base enhanced the nucleophilicity of the carbon at the 3‐position of the indole moiety, facilitating an exclusive 5‐exo‐dig cyclization reaction with the alkyne to form spiroindolenines 2. The imine functionality of 2 could undergo in situ nucleophilic addition to form spiroindolines 3 when R was a carbamoyl group or reduction to form spiroindolines 4 when R was H.