Synthetic Applications of Palladium Catalysed Carbonylation of Organic Halides
Abstract:Palladium catalysed reactions serve as versatile tools in synthetic organic chemistry. By using these methodologies carbon monoxide can be introduced directly into a number of different sites in an organic molecule leading to the synthesis of carbonyl compounds and carboxylic acid derivatives.
The substrate is reacted with a nucleophile such as an alcohol (alkoxycarbonylation), a primary or secondary amine (aminocarbonylation) or water (hydroxycarbonylation) or an organometallic reagent (formylation, crosscoupling reactions) in the presence of carbon monoxide and a palladium complex. Cyclocarbonylation, leading to a variety of heterocyclic compounds, can be regarded as a special type of the former reactions. Double carbonylation usually takes place at elevated CO pressures and produces α-ketoamides or -esters. Cascade reactions may be defined as multireaction ‘one-pot’ sequences in which the first reaction creates the functionality to trigger the second one. The use of two-phase processes makes catalyst recovery and recirculation, one of the greatest drawbacks of homogeneous catalytic processes, possible. As palladium-catalysed carbonylations usually tolerate a great variety of functional groups, they are attractive methods for the selective synthesis of intermediates of natural or biologically active products.
The reactions mentioned above can often be achieved in good yield and with high selectivity usually under very mild conditions. Because of the vast number of publications in this field, this review is dealing only with the conversion of organic halides and its contents is limited to the description of the most recent developments published until the end of 2001.