Palladium-Catalyzed CarbonylationA Reaction Come of Age

The palladium-catalyzed carbonylation of aryl and vinyl halides was first described more than 30 years ago by Richard Heck. However, limitations in the conditions originally described have meant that this reaction has achieved less prominence than the coupling reaction that also bears his name. Nevertheless, the attractiveness of this chemistry for forming carbonyl derivatives has led many researchers over the intervening years to attempt to increase the scope of the reaction beyond the originally described bromide, iodide, and triflate substrates, with conditions suited to large-scale application (particularly low pressure). To a large degree, this has now been achieved. This review describes the progress made regarding the selection of catalysts and conditions for this set of reactions, including illustrations from our own research. Reactions can now be carried out with aryl chlorides and tosylates bearing a range of substituents affecting both the electronic and steric properties of the substrate. The complexities of the reaction, represented by the interplay of catalyst, CO pressure, temperature, base, and solvent, make parallel screening desirable for optimization studies.