The Traditional Biphasic Approach

There are several problems with this type of system. The first is that vigorous mixing is usually required in order to get high reaction rates, by increasing both the amount of substrate dissolved in the catalyst phase and the area of the interface between the two solvents. It should be noted that rapid mixing does not result in the formation of a homogeneous phase, but rather an emulsion in which the surface area between the two phases is maximized. 

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Palladium-catalyzed amidocarbonylation of aldehyde amide mixtures was performed in ionic liquids to obtain N-acyl-a-amino acids [36]. It was found that strongly acidic ionic liquids such as [Rmim]HS04 (R= —(CH2)3S03H) act as powerful cocatalysts giving higher yields compared to traditionally added sulfuric acid. A subsequent biphasic approach was applied to the workup of catalytic batches and the catalyst-containing IL phase reused without further addition of palladium, phosphine, or cocatalyst. 

ILs were briefly introduced in section Attachment to the Support via SILC or SILP Catalysis where they were employed for the generation of immobilized catalyst complexes via the SILP procedure. ILs can also be used in a more traditional sense, serving as recyclable reaction media. Typically, this approach uses a biphasic mixture of IL along with an organic solvent, where the IL acts as the catalyst carrier, and the organic solvent solubilizes the reaction substrates. The products, free of catalyst contamination, can be easily isolated by phase separation, and the catalyst containing IL can be recycled. 

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