Phosphine-Catalyzed [3 + 2] Annulations of Indole N-Alkynamides with Ynones: Direct Synthesis of Arylidene Spiro-Cyclopentanone Pyrroloquinolinediones.
We report a phosphine-catalyzed [3 + 2] annulation of indole N-alkynamides with ynones, providing efficient access to arylidene spiro-cyclopentanone pyrroloquinolinediones. The reaction proceeds through the in situ generation of a reactive enedione intermediate and exhibits broad substrate scope, high regioselectivity,...