Metal‐Free Dearomatization: Direct Access to Spiroindol(en)ines in Batch and Continuous‐Flow

A metal‐free, phosphine‐catalyzed intramolecular “umpolung Michael addition” on alkynes to form spiroindol(en)ines is reported. This nucleophilic catalysis enables the formation of a wide scope of five‐ and six‐membered spiroindol(en)ines in moderate to excellent yields in batch as well as under continuous‐flow conditions. Triphenylphosphine‐catalyzed nucleophilic activation of alkynes allows the exclusive formation of exo‐product under mild reaction conditions. A metal‐free, phosphine‐catalyzed intramolecular “umpolung Michael addition” on alkynes to form spiroindol(en)ines is reported. This nucleophilic catalysis enables the formation of a wide scope of five‐ and six‐membered spiroindol(en)ines in moderate to excellent yields in batch as well as under continuous‐flow conditions.