What about Fluorous Reagents, Reactants and Catalysts ?
Fluorous Technology Primer - Part V
Introduction
For many types of organic reactions, it is desirable to use fluorous reaction components (reagents, reactants, catalysts) with fewer fluorines. Such molecules have advantages of lower molecular weight and increased solubility in organic solvents. With these types of molecules, fluorous reaction solvents are not used, and the fluorous phase (either solid or liquid) is used only in the separation stage.
Example
The reductive radical cyclizations with the family of fluorous tin hydrides shown below illustrate many of the features of this branch of fluorous chemistry. In general, the substrate and the product are organic molecules and one of the other reaction components (in this case, the tin hydride) is fluorous. The fluorous component can be used either catalytically or stoichiometrically and the reaction and separation stages are decoupled. After standard reactions, members of the tin hydride family with more fluorines can be separated either by liquid-liquid extraction or by solid-liquid extraction, while the solid-liquid extraction is preferred for members with fewer fluorines. For the most highly fluorinated member of the series, a fluorinated reaction co-solvent like benzotrifluoride (C6H5CF3) is needed. Benzotrifluoride is not a "fluorous" solvent since it is miscible in all organic solvents (and indeed dissolves many types of organic compounds as well), but it still aids in the solubilization of fluorous compounds in the reaction medium.
Features
These methods are broadly useful for all types of organic synthesis from process chemistry (fluorous catalysts preferred) through traditional synthesis to solution phase parallel synthesis and combinatorial chemistry. Tuning of preferred reaction solvents and separation methods is accomplished by selecting a reagent with an appropriate fluorine content. The reagents with fewer fluorines are especially attractive since they often have excellent solubility in organic solvents, yet can still be separated from standard organic compounds by solid-liquid extraction. Fluorous compounds are also soluble in supercritical CO2, and can be used in green chemical reactions in that solvent. The general solubility of the fluorous reaction components is an attractive feature in comparison to reagents, quenchers, and catalysts that are immobilized on insoluble polymers.
Our Technology Primer - Table of Contents
1. Introduction: What are Fluorous Molecules ?2. Fluorous Separation Methods
3. Fluorous Biphasic Catalysis
4. Fluorous Triphasic Reactions
5. Fluorous Reagents, Reactants and Catalysts
6. Fluorous Substrates and Products (Fluorous Synthesis)
7. Fluorous Mixture Synthesis
8. Summary