Perfluoroalkanesulfonyl fluoride

Perfluoroalkanesulfonyl fluorides are oxidized with nitrogen oxides in the vapor phase at high temperatures.9 Nitrogen dioxide gives, in several cases, good yields of perfluoroalkanecar-boxylie acid fluorides (Table 19).9 The products are usually isolated in the form of free acids. 

Simple ct-fluorosulfides are reduced to the fluoroalkanes by sodium-ethanol [93] (equation 75). Clean conversion of bis(trifluoromethyl) disulfide to trifluoromethyl mercaptan is accomplished with hydrogen sulfide and ultraviolet irradiation [94] (equation 76). Perfluoroalkanesulfonyl fluorides are converted to the sulfinate salts by hydrazine [95] (equation 77)... 

Fluorination with perfluoroalkanesulfonyl fluorides. Since triflate formation is an expensive procedure, we examined the use of an inexpensive perfluoroalkanesulfonyl fluoride such as perfluoro-1-butanesulfonyl fluoride (nonafluoro-l-butanesulfonyl fluoride, C4F9S02F, NfF) or perfluoro-1-octanesulfonyl fluoride (C8Fi7S02F, OctF) for fluorination,... 

Takamatsu, S., Katayama, S., Hirose, N., et al. (2002) Convenient synthesis of fluorinated nucleosides with perfluoroalkanesulfonyl fluorides. Nucleosides, Nucleotides, Nucleic Acids, 21, 849-861. 

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. 

The yields of the perfluoroalkanesulfonyl fluorides fall off rapidly with increasing chain length of the starting material. 

The 19F NMR spectra of perfluoroalkanesulfonyl fluorides, chloride and bromide CF3(CF2)3S02C1, C1(CF2)6S02X, X = Cl, Br were recorded by using their corresponding pure samples at room temperature. However, the 19F NMR spectrum of C1(CF2)6S02I was only recorded by using its freshly prepared solution in dichloromethane at low temperature (e.g. — 50 °C)18,64. The chemical shifts are given below ... 

As a result of easy access to perfluoroalkanesulfonyl fluorides in recent years, variety of esters have been synthesized by their reactions with fluorinated alcohols and phenols. The first example is the preparation of polyfluoroalkyl triflates, reported by Burdon and McLaughlin, who carried out the reaction in the presence of one equivalent of triethylamine in dichloromethane at — 30 °C91 (equation 60). Excessive base had to be avoided in the reaction, otherwise the nonvolatile quaternary ammonium salt, instead of the desired triflate, was obtained. 

Perfluoroalkanesulfonic acid salts (e.g., potassium, lithium, ammonium, and diethanol ammonium salts) are useful surfactants and are prepared by the hydrolysis of the fluoride as shown in Scheme 18.1. Long-chain perfluoroalkanesulfonyl fluorides are only slowly hydrolyzed by water. For example, perfluorooctanesulfonyl fluoride is minimally hydrolyzed by water at 180°C, even... 

As outlined in Figures 18.1 and 18.2, perfluoroalkanesulfonyl fluorides, especially perfluorooctanesulfonyl fluoride, are industrial intermediates that are converted into the corresponding sul-fonamides. These sulfonamide intermediates are ultimately converted into a whole host of fluorinated surfactants, but have also been used in large quantities for the preparation of surface treatments or paper protectants. The following sections discuss important aspects of the synthesis of perfluoroalkanesulfonamides followed by an overview over the synthesis of selected perfluoroalkanesulfonyl surfactants (Section 18.2.4). 

Perfluoroalkanesulfonamides have been claimed as intermediates for the synthesis of fluorinated surfactants. Their synthesis by reaction of the corresponding perfluoroalkanesulfonyl fluoride (or chloride) with liquid ammonia is prototypical for the synthesis of alkylated perfluoroalkane-sulfonamide surfactants. This reaction initially forms a complex ammonium salt as shown in Scheme 18.2. The desired amide is obtained by dissolving the crude product in dioxane and... 

Perfluorooctanesulfonamidoethanol derivatives, which are important intermediates for the synthesis of surfactants, cannot be synthesized by the reaction of ethanolamine derivatives with perfluoroalkanesulfonyl fluorides because of the formation of several products that cannot be separated. An important side reaction is the intermediate formation of sulfonyl esters by reaction of the fluoride with the OH group. The sulfonyl esters are excellent alkylating agents that participate in various side reactions, for example, the alkylation of ethanolamine derivative under formation of a sulfonate anion. ... 

Analogous to perfluoroalkanesulfonyl fluorides, PFCA fluorides are useful starting materials for the synthesis of PFCAs, flnorinated esters, amides, or other intermediates. These PFCA intermediates can subsequently be converted into numerous fluorinated surfactants. The industrial production pathways for these important intermediates are outlined in Figure As outlined in... 

Okazoe T, Murotani E, Watanabe K, Itoh M, Shirakawa D, Kawahara K, Kaneko I, Tatematsu S (2004) An entirely new methodology for synthesizing perfluorinated compounds synthesis of perfluoroalkanesulfonyl fluorides from non-fluorinated compounds. J Fluorine Chem 125 1695-1701... 

Perfluoroalkanesulfonyl fluorides, prepared by the electrochemical fluori-nation process, yield fluorinated carboxylic acids via the sulfonamide as the intermediate. The N-substituted perfluorohexanesulfonamide is condensed with sodium monochloroacetate in aqueous isopropyl alcohol [106] ... 

Perfluoroalkanesulfonyl fluorides or chlorides obtained by electrochemical fluorination are hydrolyzed to give the corresponding sulfonic acid or its salt [51-53] ... 

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