Chasing C,C-Palladacycles

Abstract

The different approaches for the synthesis of C,C-palladacycles are reviewed in this manuscript. These species hold a bidentate ligand that chelates the Pd atom through two C-donor moieties. Their relevance is closely related to the fact that they are intermediates in many palladium-catalyzed transformations. Furthermore, some of them have been used as efficient catalyst in cross coupling reactions. The review is structured according to the different strategies that have been employed to achieve the synthesis of the C,C-palladacycle derivatives, starting with those involving one elemental step (such as the oxidative addition of strained C−C bonds to Pd(0) or the transmetalation reactions between organometallic reagents and Pd(II) precursors), and continuing with more complex processes, where at least two elementary steps of Pd chemistry are involved (for example, carbometalation of alkenes followed by a C−H activation process). A final section highlights some aspects of synthetic methodologies based on Pd catalysis in which one or several C,C-palladacyclic intermediates are involved.