Palladium-mediated CO2 extrusion followed by insertion of isocyanates for the synthesis of benzamides: translating fundamental mechanistic studies to develop a catalytic protocol

Mechanistic studies of a stoichiometric palladium-mediated ExIn (ExIn = extrusion–insertion) decarboxylative amidation of aromatic carboxylic acids are presented, providing gas-phase and condensed-phase spectroscopic data, as well as theoretical computational evidence for intermediates in a proposed stepwise process. The understanding gained from these mechanistic studies directed the development of a palladium-catalyzed procedure in which benzamides are obtained in good to high yields in a one-pot 30 min microwave irradiation assisted protocol. A combination of experimental data and DFT calculations reveals that certain ligand additives favor the selective formation of benzamides rather than the undesired protodecarboxylation side product.