Metal-mediated and Catalysed Reactions

After polymerization processes, one of the most important aqueous phase reactions to be performed on an industrial scale is the Rhone-Poulenc hydro-formylation process that utilizes a water soluble rhodium phosphine catalyst. This process will be discussed in more detail in Chapter 10. The success of this process has led to many exciting results in metal catalysed aqueous phase chemistry. Additionally, amazing advances have been made where reactions that are typically considered unsuited to the presence of moisture, e.g. Grignard-type chemistry, can be performed in water. 

Extracted with ethyl acetate flash chromatography, heptane/ethyl acetate 

Some of the most widely studied organic reactions at this time are palladium catalysed carbon-carbon cross coupling reactions, which have been extensively investigated in water. For example, palladium catalysed Suzuki reactions can be performed in water in the presence of poly (ethylene glycol) (PEG). It should be noted that the PEG may be playing the role of a surfactant (PTC) and/or a support for the metal catalyst in water. Interestingly, in this example, no phosphine is needed and the products are easily separated and the catalyst phase reused. Unfortunately, diethyl ether was used to extract the product and as this solvent is hazardous (low flash point and potential peroxide formation), the overall process would be greener if an alternative solvent could be used. 

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