Multiphase homogeneous catalysis aqueous reactions

Fluorous catalysis is now a weU-established area and provides a complementary approach to aqueous- or ionic-biphase catalysis and the other possibilities of multiphase homogeneous catalysis (not to mention combinations of the different processes). Since each catalytic chemical reaction could have its own perfectly designed catalyst (e.g., a chemzyme), the possibility of selecting from biphase systems ranging from fluorous to aqueous systems provides a powerful portfolio for catalyst designers. 

Aqueous processes will become more important in the future because of the immense advantages of this version of homogeneous catalysis in the multiphase version. In addition to the syntheses already utilized now, an enormous laboratory study has been done to convert conventional syntheses to the aqueous-multiphasic mode (see Section 2.5.2). A selection of recent work covering a multitude of reactions and and catalysts based on various transition metals is presented in Table 3. 

One of the key factors controlling the reaction rate in multiphasic processes (for reactions talcing place in the bulk catalyst phase) is the reactant solubility in the catalyst phase. Thanks to their tunable solubility characteristics, the use of ionic liquids as catalyst solvents can be a solution to the extension of aqueous two-phase catalysis to organic substrates presenting a lack of solubility in water, and also to moisture-sensitive reactants and catalysts. With the different examples presented below, we show how ionic liquids can have advantageous effects on reaction rate and on the selectivity of homogeneous catalyzed reactions. 

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