Operando study of the coupling reactions using ligand-free palladium catalysts

The combined application of UV-spectroscopy and GC-MS has been used to control the amount of oxidized palladium in situ under the Heck reaction with benzoic anhydride as well as indole direct arylation using the catalytic systems based on PdX2 salt (II). It has been established that under the Heck reaction the majority of loaded Pd (up to 90%) are in [PdBr4]2- form possessing no catalytic activity. In the direct arylation of indole the amount of oxidized Pd in the inactive [PdI4]2- form does not exceed 25% of Pd loaded.