Visible Light-Driven Metal-free and Photocatalyst-free Intramolecular Cyclization of Chalcones to Access Phenanthrenes

We report a visible-light-driven metal-free and photocatalyst-free protocol for the synthesis of phenanthrenes through the intramolecular cyclization of chalcones. The transformation proceeds through light irradiation and base- and oxygen-based promotion, and enables the generation of a series of phenanthrenes. The further functionalization of an as-synthesized phenanthrene to afford a fluorescent molecule was explored.