Palladium(0)/Copper(I)‐Catalyzed Tandem Cyclization of Aryl 1‐Cyanoalk‐5‐ynyl Ketone System: Rapid Assembly of Cyclopenta[b]naphthalene and Benzo[b]fluorene Derivatives

We have developed a new and general approach to construct a variety of benzo[b]fluorene and cyclopenta-[b]naphthalene derivatives via the palladium(0)/copper(I)-catalyzed tandem cyclization of aryl 1-cyanoalk-5-ynyl ketone systems in an extremely efficient manner. The key operation lies in the copper(I)-catalyzed aerobic oxidation, which allows for activation of two successive intramolecular cycloadditions immediately after the Sonogashira coupling reaction has occurred.