Palladium(II)-Catalysed Rearrangement Reactions

The synthesis of new carbon-carbon and carbon-heteroatom bonds in a stereochemically well defined manner still presents a challenge in modern synthetic methodology. An important class of reactions, which can carry out the aforementioned transformations, are the [3,3]-sigmatropic rearrangements. These rearrangements have traditionally been carried out thermally at high temperatures. However, the discovery that these transformations can be accelerated by Pd(II) at ambient temperature has led to more widespread use of these reactions for the synthesis of biologically active and pharmaceutically important molecules. This review presents an overview of the use of palladium(II) catalysis for the acceleration of three of the most commonly used rearrangements in organic chemistry, namely, the Cope, Claisen and aza-Claisen rearrangements. In particular, the mechanism of catalysis, stereochemical outcome and synthetic application of these reactions will be discussed.