Organic aqueous tunable solvents OATS

Figure 3.12 Biocatalysis using organic-aqueous tunable solvents (OATS).

A recent proposal concerns mixed organic-aqueous tunable solvents (OATS) such as dimethyl ether-water, the solubility of which for substrates can be influenced by a third component such as carbon dioxide. CO2 acts as a antisolvent and as a switch to cause a phase separation and to decant the phases from each other (preferably under pressure). This behavior makes the operation of bi- or multiphase homogeneous catalytic processes easier and more economic the preferential dissolution at modest pressure of carbon dioxide causes phase separation which results in large distribution coefEcients of target molecules in biphasic organic-aqueous systems. This extraordinary behavior lead to a sophisticated flow scheme (Figure 6) [7]. 

P. Pollet, R. J. Hart, C. A. Eckert, C. L. Liotta, Organic Aqueous Tunable Solvents (OATS) A Vehicle for Coupling Reactions and Separations. Acc. Chem. Res., 43, 1237-1245 (2010). 

Another way to omit the fluorous solvent would be to utilize a catalyst immobilization solvent that is not fluorinated, such as water. We demonstrated the application of a phase change after reaction permits facile recycle of hydrophilic catalysts. This method is called OATS (Organic-Aqueous Tunable Solvent) (15). 

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