Fluorophilicities

Filippov DV, van Zoelen DJ, Oldfield SP, van der Marel GA, Overkleeft HS, Drijfhout JW, van Boom JH (2002) Use of Benzyloxycarbonyl (Z)-Based Fluorophilic Tagging Reagents in the Purification of Synthetic Peptides. Tetrahedron Lett 43 7809-7812... 

We may expect that the future will see many additional uses of cationic zirconocenes in organic synthesis, in which their Lewis acidic character, coupled with the special properties of zirconium (oxophilic, fluorophilic) and its d°-electron configuration (leading, for example, to weak back-bonding) will come into play. 

J.A. Olsen, D.W. Banner, P. Seiler, U.O. Sander, A. d Arcy, M. Stihle, K. Muller, F. Diederich, A fluorine scan of thrombin inhibitors to map the fluorophilicity fluoropho-bicity of an enzyme active site Evidence for C-F- C = O interactions, Angew. Chem. Int. Ed. 42 (2003) 2507-2511. 

C4F9C2H4), are highly fluorophilic and exhibit large partition coefficients in favor of fluorocarbon solvents over common organic solvents due to a double-layered structure where the stannoxane core is covered by fluoroalkyl groups. Fluorous technology allows transesterification and esterification in which 100% yield of the desired esters is achievable with reactants in a strict 1 1 ratio. The tin catalysts are recovered from the fluorous phase quantitatively (Equation (95)).260... 

In order to perform fluorous biphasic catalysis the (organometallic) catalyst needs to be solubilized in the fluorous phase by deploying fluorophilic ligands, analogous to the hydrophilic ligands used in aqueous biphasic catalysis. This is accomplished by incorporating so-called fluorous ponytails . 

Fluorophilic CD derivatives have been obtained as a result of combinations of CDs and a linear perlluorocarbon [73]. 2,3-Di-O-decafluorooctanoyl-y-CD was obtained with a protection-deprotection synthetic method and characterized further by thin-layer chromatography (TLC), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), elemental analysis, and time-of-flight mass spectrometry (OF-MS). 

Skiba, M., Skiba-Lahiani, M., and Arnaud, P. (2002), Design of nanocapsules based on novel fluorophilic cyclodextrin derivatives and their potential role in oxygen delivery, J. Indus. Phenom. Macroc. Chem., 44,151-154. 

The primary standard betaine dye (44) is only sparingly soluble in water and less polar solvents it is insoluble in nonpolar solvents such as aliphatic hydrocarbons. In order to overcome the solubility problems in nonpolar solvents, the more lipophilic penta-t-butyl-substituted betaine dye (45) has additionally been used as a secondary reference probe [174]. The excellent Hnear correlation between the Ej values of the two dyes allows the calculation of t(30) values for solvents in which the solvatochromic indicator dye (44) is not soluble. Introduction of electron-withdrawing substituents e.g. Cl [323], F, CF3, C6F13 [324]) in the betaine molecule reduces the basicity of its phenolate moiety, which allows the direct determination of x(30) values for somewhat more acidic solvents. Moreover, the Hpophilic and fluorophilic penta(trifluoromethyl)-substituted betaine dye (46) is more soluble in nonpolar solvents e.g. hexafluoro-benzene) than the standard dye (44) [324]. Conversely, the solubility in aqueous media can be improved through replacement of some of the peripheral hydrophobic phenyl groups in (44) by more hydrophilic pyridyl groups, to yield the more water-soluble betaine dye (47) [325]. The Ej values of these new secondary standard betaine dyes correlate linearly with the x(30) values of (44), which allows the calculation of x(30) values for solvents in which only betaine dyes (45)-(47) are sufficiently stable and soluble for the UV/Vis spectroscopic measurements [324, 325]. 

Fluorous reverse-phase silica gel (separation by solid phase extraction). The hydroxyl residues on silica gel are modified with perfluoroalkyl chains. This causes a fluorophilic effect between the fluorous reagent/ catalyst/product and allows facile separation independent of temperature. 

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