Palladium in Organic Synthesis: Fundamental Transformations and Domino Processes

Transition metals have been invaluable reagents for the organic chemist since the beginning of this century. In particular, palladium, formerly used only for redox reactions, has recently achieved a prominent role in synthesis due to the manifold and unique transformations that it is capable of mediating, often in a catalytic mode.1 In recent years, the pioneering work of a couple of scientists has demonstrated that, using a single catalytic starter, many reactions in cascade could be devised from suitable precursor substrates. Multiple consecutive one-pot reactions, thereafter named domino reactions, are not, of course, confined to organometallic chemistry. The large number of organic transformations mediated, the wide functional group tolerance, and the catalytic nature of most of these processes, however, make palladium an ideal basis for devising unbeatable domino processes. In order to understand satisfactorily the palladium catalysed domino processes it is essential to survey brie¯y the basic organometallic chemistry associated with this metal.