The NMR Study of the Mechanism of Alkene Arylation with Anhydrides of Aromatic Acids

The main steps of the catalytic cycle of the alkene arylation reaction with the participation of anhydrides of aromatic acids as arylation agents were studied by ³¹P NMR spectroscopy. In contrast to the mechanism proposed earlier, palladium complexes containing benzoate anions as acidoligands were not found in the reaction mixture. It was found that the catalytic cycle of the reaction includes the steps of oxidative addition of Pd(0) formed in situ to the anhydride of acid, the substitution of acidoligand, and the elimination of the CO molecule. Further transformations probably take place according to the usual steps of the Heck reaction. It was shown that CO elimination is a limiting step.