Photocatalyzed (3+2) Cycloaddition for the Dearomatization of Electron‐Poor Arenes under Flow Conditions.

The photocatalyzed dearomative reaction between various electron‐deficient aromatic compounds and a non‐stabilized azomethine ylide is successfully performed in a flow system. Whereas the use of supported eosin as organic photocatalyst exhibits limited efficiency, turning to the soluble Rose Bengal allows to transform a broad range of substrates from hetarenes (indole, benzofuran, quinoline, pyridine) to naphthalenes and benzenes. This photocatalyzed (3+2) dearomative cycloaddition under green light irradiation provides a simple and efficient access to tridimensional pyrrolidino scaffolds with a tetrasubstituted carbon center at ring junction and can be performed in the friendly ethyl acetate. Computational studies support the mechanism involving azomethine ylide as reactive species toward the electron‐poor arene. [ABSTRACT FROM AUTHOR]