Synthesis of Phenantridinones and Benzochromenes by C-H Activation Reactions Catalised by Palladium Nanoparticles

In recent years, Palladium (Pd) catalysis has expanded to the use of metallic nanoparticles (NPs), due to their physicochemical properties that are related to catalytic activity. In particular, C-H bond activation reactions catalyzed by Pd attract interest because they can generate new C-C bonds without the need for prior functionalization, shortening synthesis steps and reducing waste generation. An example is phenanthridin-6(5H)-ones and benzo[c]chromenes, which are heterocycles present in various natural products and with important biological activities. Several synthetic routes for these structures have been reported. However, these systems require high catalyst loading, the use of additives, oxidants and solvents that are not very friendly to the environment. This work presents the synthesis of phenanthridin-6(5H)-ones and benzo[c]chromenes by intramolecular C-H bond activation reactions catalyzed by Pd NPs. The NPs were synthesized by photoinduced reactions and used without further purification. An efficient and selective Pd nanocatalysis system has been developed for the synthesis of these molecules, without generating large amounts of waste. The reaction conditions used involve aqueous reaction media, without the use of additives, oxidants or inert atmospheres and uses economic bases. This system can be improved with a Pd nanocatalyst that is reusable for several reaction cycles. It would also be appropriate to change the solvent used for a fully aqueous system or another reaction medium.