Mechanism and Substrate-Dependent Rate-Determining Step in Palladium-Catalyzed Intramolecular Decarboxylative Coupling of Arenecarboxylic Acids with Aryl Bromides: A DFT Study

The mechanism of palladium-catalyzed intramolecular decarboxylative coupling of arenecarboxylic acids with aryl bromides has been studied computationally with the aid of density functional theory. Full free-energy profiles have been computed for all ether- and amine-containing substituted substrates. The calculations indicate that the rate-determining step is indeed substrate dependent, as reflected in free energy profiles; the oxidative addition, decarboxylation, or reductive elimination step can become the rate-determining step for the full catalytic cycle due to the different substituents on the substrates. In addition, we also demonstrate the preference of NCH3- over NH-containing amine substrates for the decarboxylation process. The calculations are in good agreement with the experimental observations.