Access to Polycyclic Indol(en)ines via Base-Catalyzed Intramolecular Dearomatizing 3-Alkenylation of Alkynyl Indoles

摘要

Main observation and conclusion Polycyclic 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.

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