Fluorous Solvents

　Solvents containing fluorine with a relatively large component in molecules are called fluorous solvents. Most fluorous solvents have high thermostability and chemostability and are low in toxicity.

　The characteristic feature of fluorous solvents is that they mix with neither common organic solvents nor water at room temperature thus forming biphasic systems, and they dissolve fluorine-rich compounds well. To utilize these features, a method of separation and purification called a fluorous biphase system (FBS) has been developed. In this synthetic manner, after the reaction of substrates having a perfluoroalkyl group with some reactants in a mixture of fluorous/organic solvents, the fluorous compounds can be selectively recovered from phase-separated fluorous layer. On the other hand, organic compounds without fluorine containing functional groups are recovered from the phase-separated organic layer, so that the FBS allows some purification processes such as column chromatography to be omitted. For example, Curran et al. applied FBS to the Stille coupling reaction of organotin compounds having a fluoroalkyl group with aryl bromides. Generally, organotin byproducts are hard to remove but fluorinated organotin byproducts in FBS are easily dissolved in the phase-separated fluorous layer, and can be simply removed by extraction.