Palladium-Mediated CO<sub>2</sub> Extrusion Followed by Insertion of Isocyanates for the Synthesis of Benzamides: Translating Fundamental Mechanistic Studies To Develop a Catalytic Protocol
Yang Yang, Allan J. Canty, Alasdair I. McKay, Paul S. Donnelly, Richard A. J. O’Hair
Abstract
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.