Ketonization of carboxylic acids by decarboxylation: Mechanism and scope

In the ketonic decarboxylation process, a ketone is formed from two moles of carboxylic acid; water and carbon dioxide are produced as side-products. At present, the mechanism of this reaction remains under debate; it has been proposed as a radical mechanism, a mechanism involving a P-keto acid as intermediate, or a concerted mechanism. This paper demonstrates that the latter mechanism is the most likely one and that weak bases may play the role of promoters. Different processes are reviewed for the syntheses of the following ketones: symmetrical ketones, such as acetone or 3-pentanone, cyclic ketones, such as cyclopentanone (parent compound and substituted derivatives), fatty ketones, and some unsymmetrical ketones. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).