Perfluorinated cyclic compounds

For larger saturated rings only perfluorinated derivatives have been studied in the gas phase. No data have been reported for perfluorocyclopentane, and five-membered rings containing S(II), S(IV) and S(VI) are considered instead (Table 15). Within their experimental error limits, the C—F bond distances in these perfluorinated cyclic compounds are... 

When subjected to ECF, heterocyclic bicyclic compounds with rings of varying composition lead to perfluorinated cyclic compounds, which are useful as components of blood substitutes and as liquids for conservation of organs (85USP4526969, 81/82JAP(K)59204192, 85USP4534978) (Scheme 73). 

The products of the electrochemical perfluorination of aromatic and heteroaromatic compounds are the corresponding perfluorinated cyclic and heterocyclic alkanes.28 and also per-fluorinated derivatives of the heteroaromatic compounds. Perfluorocyclohexane is the principal product from the electrochemical fluorination of benzene and fluorobenzene. Chloro derivatives of perfluorocyclohexane are produced from chlorobenzenes. Anisoles give fully saturated per-fluoro ethers, together with cleavage products. Extensive cleavage is observed in the fluorination of benzenethiols. Chloropyridines, fluorocarbons and sulfur hexafluoride or nitrogen trifluoride are characteristic byproducts from the above scries of reactions. 

Dioxathiolan-4-one 2-oxides (50) were converted by aniline into a-hydroxycarb-oxylic acid anilides (123) and sulfur dioxide, while phenylhydrazine liberated the parent acids (124) without release of sulfur dioxide (66HC(21-1)1). Analogous to the methanolysis of the perfluorinated cyclic sulfate (96) (cf. Section 4.33.3.3.1), the aminolysis of this compound gave the anilide (125) (73IZV2725). 

Review papers on cyclic compounds with a phosphazene moiety have covered several areas, viz. metal complexes derived from organo-substituted, polymers with cyclotriphosphazene entities and chemistry of perfluorinated cyclo-phosphazenes. Azaphosphinines have been reviewed in the scope of the phosphorus-carbon heterocyclic chemistry. ... 

Other examples of electrophilic reactions of perfluorinated heterocyclic compounds include mentioned earlier hydrolysis of cyclic chlorinated ethers 20 (Fig. 9.5), unsaturated ether 27 (Fig. 9.8), and cyclic amines leading to fluorinated lactams (Fig. 9.10). 

Several methods are available for the preparation of perfluorinated cyclic imidoyl fluorides. For example, reductive defluorination of cyclic A-fluoro compounds... 

Available data on chemical transformations of perfluorinated cyclic dienes are hmited. Dienes 129 and 130 were reported to undergo interconversion under the action of CsF (Fig. 9.39) " and compound 119—an interesting isomerization into 147 under the action of CsF (Fig. 9.44). 

Beside these compounds which combine alkyl chains and perfluorinated chains at opposite ends of a cyclic unit, there are several examples of liquid crystalline materials combining a single aromatic ring with a single semiperfluorinated alkyl chain or with two or three Rp-chains in close proximity. 

With < 1 mol% MTO cyclobutanones are fully converted within one hour. Another approach consists of the use of a fluorous Sn-catalyst under biphasic conditions [245]. A perfluorinated tin(IV) compound, Sn[NS02C8F17]4, was recently shown to be a highly effective catalyst for BV oxidations of cyclic ketones with 35% hydrogen peroxide in a fluorous biphasic system (Fig. 4.83). The catalyst, which resides in the fluorous phase, could be easily recycled without loss of activity. 

A wide range of fluids with similar physical and chemical properties, including linear and cyclic perfluoroalkanes, linear and cyclic perfluoroethers and polyethers, perfluorotertiary amines and, in a few instances, perfluoroalkylhalides, may be considered to be perfluorinated or fluorous . Solvents within these categories are marketed around the world under a series of brandnames (Table 1). In certain instances, the commercial fluids represent mixtures of similar compounds with... 

To study these systems, we used a model compound 1 that has been shown previously to be very efficiently fluorinated by both C0F3 and the Simons cell process. We have now established that this cyclic ether (which like many oxygen containing species is moderately soluble in aHF) is efficiently fluorinated by RNip3 at or below, room temperature, to give the perfluorinated compound la. Interaction of MeCOF with RNip3... 

Perfluoroalkanesulfonyl fluorides and of related materials are manufactured by the electrochemical fluorination of the corresponding alkanesulfonyl fluorides or cyclic sulfonesP This electrochemical synthesis results in replacement of all C-H bonds in the feedstock. The perfluorinated alkanesulfonyl fluoride products are neutralized to make the anhydrous salt, then acidified and distilled to afford the anhydrous sulfonic acid. Alkyl chain degradation in the electrochemical cell becomes more pronounced at longer chain lengths. Addition of short-chain divalent sulfur compounds (e.g., thiols, sulfides) to the cell inhibits buildup of tarry materials and loss of efficiency. 

If pushed to an extreme the perfluorinated bridge concept can be used to obtain liquid crystals with no cyclic moieties in their mesogenic core structure [4-8]. Since the beginning of the 1980s it has been known that semi-fluorinated n-alkanes, so-called diblock compounds, F(CF2) (CH2) H, form smectic phases [49], because of microphase separation as a result of separate, layer-like aggregation of the hydrocarbon and fluorocarbon moieties. Nevertheless, if introduced into a nematic host mixture, even small quantities of these diblocks cause gelation of the mixture. Their solubility is also limited to a few percent by weight. 

The presence of highly electrophilic C=N bond defines the reactivity of this class of compounds. Similar to other perfluorinated imidoyl fluorides, cyclic analogues are sensitive to the action of nucleophiles. For example, compounds 81 and 124 react with metal fluoride anion in polar solvents with the formation of the salt 125, which can react with a strong electrophiles (Fig. 9.38). 

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