Solvents for Fluorous Synthesis

ChemFiles Volume 4 Article 9

Following the definition offered by Gladysz and Curran[1] a “Fluorous Medium” is “any phase of a perfluoroalkane, perfluorodialkylether, perfluorotrialkylamine, or similar non-polar species, or any similarly-composed micro-environment within a non-fluorous medium that shares key physical properties with these species.” Fluorous solvents are used in liquid-liquid extractions to quickly separate fluorous compounds from organic compounds in a two phase liquid-liquid extraction, or from organic and inorganic (or water soluble organic) compounds in a three-phase liquid-liquid extraction. Such extractions are readily automated, and can be used to quickly partition reaction mixtures into organic, inorganic and fluorous fractions. In many cases, the crude organic products are pure enough to be taken on to the next reaction, and the fluorous products can usually be recycled, if desired. In the best cases, only a single separation is needed. With lower partition coefficients, the organic fraction is washed several times with the fluorous solvent. Thanks to the exceedingly low solubilities of organic compounds in fluorous solvents, the washing process can be conducted repeatedly without extractive loss of the organic product. Liquid-liquid extractive methods are typically used when the desired product is organic and some other reaction component (reactant, reagent, catalyst, scavenged product) is fluorous. Please note that perfluoroarenes are significantly more polar than perfluoroalkanes and preferentially partition into organic media. Therefore they are not fluorous under the definition above. Partially fluorinated solvents like (trifluoromethyl)-benzene (# 12811 ) provide a homogenous liquid medium for the reaction of fluorous and non-fluorous reactants.[2]

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