Perfluoroalkyl sulfide

Hydrocarbon Gngnard reagents give the alkyl cyanides, whereas perfluo-rinated Grignard reagents produce the sulfides This reaction is useful for the preparation of alkyl perfluoroalkyl sulfides to the exclusion of di and polysulfides, which are produced by other methods... 

In the presence of zinc, bromotnfluoromethane and perfluoroalkyl iodides react with thiocyanates and isocyanates to give the corresponding perfluoroalkyl sulfides and substituted perfluoroalkylacetamides, respectively [48 (equation 39)... 

Acyclic alkyl perfluoroalkyl sulfides react with chlorine monofluoride to yield the tetrafluo-rinated products.99-100 Attempts to stop the reaction at the stage of the intermediate difluoridcs have been unsuccessful. 

Several alternative polymerization media have been proposed for reducing the amount of unstable end groups in poly(tetrafluoroethylene). These include chlorofluorocarbons, which are detrimental to the environment, perfluoro-carbons, hydrofluorocarbons, and perfluoroalkyl sulfide acids, which are all expensive. Supercritical carbon dioxide has been identified as a viable alternative to aqueous and fluorocarbon reaction media [31]. Further more, mixing... 

FITS reagents reacted very easily with thiols in the presence of pyridine to give the perfluoroalkyl sulfides in good to high yields. S-perfluoroalkylation was selective in the case of polyfiinctional substrates. In the presence of groups such as hydroxy, carboxy, alkoxycarbonyl or dialkylamino, the sulfur atom was always selectively substituted.216 (Table 5.10)... 

Oxidation. The range of oxidation potential of HOF-MeCN has been extended to the direct preparation of epoxy carboxylic acids from alkenoic acids, oxidative cleavage of methyl ethers to ketones, and conversion of aryl perfluoroalkyl sulfides to the sulfones. ... 

Xenon difluoride has been used to initiate oxidative decarboxylation of perfluorocarboxylic acids for Rp generation and with aromatic and heterocyclic compounds the perfluoroalkyl groups can also become incorporated into the aromatic ring [59]. On the other hand, Sipyagin et al. [60] have employed this method for the perfluoroalkylation of thiols such as polychloropyridine thiols. Two different methods were used the action of preformed xenon carboxylates or treatment of a pyridinethiol solution in RpCOOH directly with xenon difluoride. A range of isomeric perfluoroalkyl sulfides was obtained (Scheme 27). 

A simple method for the generation of metal derivatives of perfluoroalkyl carbanions by the decarboxylation of alkali salts of perfluorocarboxylic acids, has also been used. For example, heating potassium perfluoroalkyl carboxylates in the presence of dipyridine disulfides in DMF or sulfolane leads to the formation of the corresponding pyridine perfluoroalkyl sulfides [61] (Scheme 28). 

Another way to prepare fluorinated sulfides is the photochemical alkylation of sulfides or disulfides by perfluoroalkyl iodides [69, 70, 71] (equations 62-64). Reaction of trifluoromethyl bromide with alkyl or aryl disulfides in the presence of a sulfur dioxide radical anion precursor, such as sodium hydroxymethanesulfi-nate, affords trifluoromethyl sulfides [72] (equation 65). 

It is well known that palladium on carbon catalysts are poisoned by hydrogen cyanide and thiol products or hydrogen sulfide (6). Therefore, it was of interest to investigate the reduction of perfluoroalkyl thiocyanates as a function of tin concentration, keeping the concentration of palladium and reaction conditions constant. Figure 15.1 delineates the % conversion vs. Sn/Pd ratio, under the same reaction conditions of 175°C, 700 psig H2 for 2 hours with 5% Pd on carbon catalysts in ethyl acetate solvent at a 1000 1 substrate catalyst molar ratio. The increase in... 

A linear correlation of the oxidation potentials Bp of sulfides with Taft s a values of fluoromethy] groups is obtained as shown in Fig. 1 [42]. This dearly indicates that the polar effect of the fluoroalkyl group plays a significant role in the electron-transfer step from the sulfides to anode. Namely, the oxidation potential increases linearly as the number of fluorine atoms of the fluoroalkyl group increases. However, interestingly the oxidation potential was not appreciably affected by the length of the perfluoroalkyl group (Table 4). 

The S- and Se-(perfluoroalkyl)dibenzothiophenium salts 17-27 were synthesized according to three methods (Eq. 4) (1) fluorination of the corresponding sulfide 1-6 or 8 or selenide 11 or 12 with F2 in the presence of an acid or a Lewis acid (2) fluorination with F2, followed by treatment with an acid or a Lewis acid and (3) treatment of sulfoxide 13, 14, or 15 or selenoxide 16 with triflic anhydride (Tf20). Sulfoxides 13-15 and selenoxide 16 were prepared by oxidation of the corresponding sulfides or selenide with m-chloroperbenzoic acid. 

Sulfur is oxidatively fluorinated up to its highest valence state, six. For instance, alkyl thiols give perfluoroalkyl-sulfurpentafluorides (Fig. 40) [104] and sulfides give perfluorodialkyl-sulfurtetrafluorides (Fig. 41) [105,106]. Similarly, phosphorous is oxidatively fluorinated up to the pentavalent state (Fig. 42) [107]. 

Perfluoroalkyl halides can be converted into phenyl sulfides by treatment with aromatic or aliphatic disulfides under reductive conditions involving the presence of various precursors of the SO/ radical anion. ... 

Much of the research on the SbCls-catalyzed halogenation of arenes has focused on the chlorination and bromination of perfluoroalkyl-substituted aromatics [14]. The reaction of organic disulfides with electron-rich aromatic compounds under catalysis with SbCls and AgSbFg affords unsymmetrical aryl sulfides in modest yields [15a]. Electrophilic sulfinylation and sulfonation can be similarly effected by SbCls [15a-c]. Alkyl- and halobenzenes give thiocyano derivatives when treated with a mixture of SbCls and Pb(SCN)2 in CCI4 [16],... 

Related to these reacations is the anodic methoxylation of sulfides carrying an electron-withdrawing substituent, such as cyano [105], fluoromethyl [106], difluoromethyl [106], or trifluoromethyl [106-109] in the a-position [Eq. (41)]. Yields are typically between 50 and 90%. An analogous reaction has been reported for selenides carrying electron-withdrawing perfluoroalkyl or cyano substituents [110]. 

The reaction of trifluoromethyl iodide with arene thiolates provides trifluoromethyl aryl sulfides via a single electron transfer (SET) reaction rather than the SN2 reaction, which is the only formal mechanism (Scheme 2.31). In general, perfluoroalkyl (Rf—X), ferf-alkyl, and vinyl and aromatic halides are strongly deactivated for the replacement of halogens with... 

Fluoroalkyl(aryl)iodonium salts are the most stable and practically important class of alkyl(aryl)iodonium derivatives. The application of such salts as electrophilic fiuoroalkylating reagents was reviewed in 1996 by Umemoto [1017]. Perfluoroalkyl(phenyl)iodonium trifiates (FITS reagents) 764 are efficient perfluoroalky-lating reagents toward various nucleophiUe substrates, sueh as arenes, carbanions, alkynes, alkenes, carbonyl compounds, amines, phosphines and sulfides [1017]. Scheme 3.300 shows several representative examples of electrophilic perfluoroalkylations using FITS reagents. 

For the gasket, instead of PP, poly(phenylene sulfide), poly(ethyl-ene terephthalate), poly(amide), liquid crystal polymer, tetrafluoroethyl-ene/perfluoroalkyl vinyl ether copolymer resin, PEEK, and poly(ether nitrile) have been found to be free of explosions and other drawbacks at the reflow temperature." ... 

Terminal alkenes, primary aUylic alcohols, esters, aUyl boronate esters, aUyl halides, styrenes (without large orf/ro-substituents), aUyl phosphonates, aUyl sUanes, aUyl phosphane oxides, aUyl sulfides, protected aUyl amines Styrenes (with large ert/jo-substituents), acrylates, acrylamides, acrylic acid, acrolein, vinyl ketones, unprotected tertiary aUyfic alcohols, vinyl epoxides, secondary aUyhc alcohols, perfluoroalkyl alkenes... 

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