A Fully Palladium‐Mediated Construction of Phenanthrenes and Naphthoxindoles

A fully palladium‐catalyzed synthesis of unusual naphthoxindole alkaloids through a key intramolecular direct C–H arylation step leading to the formation of the phenanthrene core is described. The three‐step process involves a highly efficient Heck coupling of aryl diazonium salts with phenylacrylates, giving the corresponding cis‐stilbenes. Cyclization of stilbenes into phenanthrenes through a direct intramolecular C–H arylation, followed by a palladium‐mediated cyclization of an amino ester, led to the formation of novel naphthoxindoles.