Chapter 1 An introduction to palladium catalysis

Organopalladium chemistry has found widespread use in organic synthesis. Palladium catalysts facilitate unique transformations that cannot be readily achieved using classical techniques, and in many cases palladium-catalyzed reactions proceed under mild reaction conditions and tolerate a broad array of functional groups. As such, the use of palladium catalysts for the synthesis of important, biologically active heterocyclic compounds has been the focus of a considerable amount of research. This chapter describes the fundamentals of palladium catalysis in the context of heterocyclic chemistry, including the basic mechanisms of many useful transformations along with a number of new synthetic and mechanistic developments. The majority of the Pd-catalyzed reactions proceed via catalytic cycles that are comprised of eight fundamental organopalladium transformations presented in the chapter. Most of these transformations can occur via more than one mechanistic pathway. Palladium chemistry involving heterocycles has many unique characteristics stemming from the inherently different structural and electronic properties of heterocyclic molecules in comparison to the corresponding aromatic carbocycles.