Lewis-Acid-Catalyzed Decarboxylative Annulation of 2-Aminoindole-3-Carboxylate with Ynals Involving [3+2] Spirocycloaddition and 2,3-Aza Migration

摘要

2-Aminoindole-3-carboxylates undergo a Lewis-acid-catalyzed decarboxylative annulation with ynals to afford dihydro-chromeno-fused delta-carbolines through a 2,3-aza migration, via a spirocyclic intermediate generated from an initial [3 + 2] spirocycloaddition. Bronsted acid interference changes the path from a [3 + 2] to a [4 + 2] addition. 2-Aminoindoles without an ester functional group at C3 underwent a different condensation, followed by hetero-Diels Alder reaction to generate chromeno-fused alpha-carbolines.