Ionic liquid-water-tert-butanol solvent

The catalyst system can be reused if an ionic liquid-water or ionic liquid-water-tert-butanol solvent system is used [155-157]. Some care has to be taken with the choice of ligand under these conditions, as the presence of an alkene within the ligand itself results in dihydroxylation during the reaction and, as a result, the modified ligand is not extracted from the ionic liquid into the organic layer [158]. Supercritical C02 can be used in place of the organic solvent to extract the product [159, 160]. 

The enzyme may be dissolved in a mixed aqueous-ionic liquid medium, which may be mono- or biphasic or it could be suspended or dissolved in an ionic liquid, with little or no water present. Alternatively, whole cells could be suspended in an ionic liquid, in the presence or absence of a water phase. Mixed aqueous-organic media are often used in biotransformations to increase the solubility of hydrophobic reactants and products. Similarly, mixed aqueous-ionic liquid media have been used for a variety of biotransformations, but in most cases there is no clear advantage over water-miscible organic solvents such as tert-butanol. 

Recently, Yao showed that osmium tetroxide could be immobilized in an ionic liquid. The recyclability of osmium tetroxide was improved by the addition of DMAP. Both the catalyst and the ionic liquid were reused in six consecutive runs without significant reduction in yield [47]. Dihydroxylations in a solvent mixture of l-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), tert-butanol, and water with 0s04 (2 mol%), DMAP (2.4 mol%), and NMO (1.1 equivalents) as cooxidant afforded diols in good yield (73-99% depending... 

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