Facile Access to 3-Acylindoles through Palladium-Catalyzed Addition of Indoles to Nitriles: The One-Pot Synthesis of Indenoindolones

A palladium-catalyzed addition of indoles to nitriles, leading to 3-acylindoles, was reported, and the scope of nitriles was investigated. The strategy described provides a more efficient and atom-economical alternative to indenoindolones. It was found that alkenyl, carbonyl, halogen, methoxy, and nitro groups on aryl nitriles, which could offer opportunities for further synthetic transformations, are all compatible with the conditions. N-unprotected indoles with electron-rich groups show excellent reactivity towards this addition reaction. Under the optimized conditions, an array of indenoindolones are obtained in synthetic useful yields from readily available indoles and nitriles in one pot. The results also show that both the electron-poor and electron-rich substituents could be introduced to indoles and nitriles and that the halogen atoms were compatible under the current conditions.