Aryl-Decarboxylation Reactions Catalyzed by Palladium: Scope and Mechanism

Palladium-catalyzed cross-couplings and related reactions have enabled many transformations essential to the synthesis of pharmaceuticals, agrochemicals, and organic materials. A related family of reactions that have received less attention are decarboxylative functionalization reactions. These reactions replace the preformed organometallic precursor (e.g., boronic acid or organostannane) with inexpensive and readily available carboxylic acids for many palladium-catalyzed reactions. This review focuses on catalyzed reactions where the elementary decarboxylation step is thought to occur at a palladium center. This review does not include decarboxylative reactions where decarboxylation is thought to be facilitated by a second metal (copper or silver) and is specifically limited to (hetero)arenecarboxylic acids. This review includes a discussion of oxidative Heck reactions, protodecarboxylation reactions, and cross-coupling reactions among others. 1 Introduction 2 Oxidative Heck Reactions 3 Protodecarboxylation Reactions 4 Cross-Coupling Reactions 5 Other Reactions 6 Conclusion.