Perfluoroalkyls compounds, perfluoroalkyl

Synthetic oils have been classified by ASTM into synthetic hydrocarbons, organic esters, others, and blends. Synthetic oils may contain the following compounds diaLkylben2enes, poly(a-olefins) polyisobutylene, cycloaUphatics, dibasic acid esters, polyol esters, phosphate esters, siUcate esters, polyglycols, polyphenyl ethers, siUcones, chlorofluorocarbon polymers, and perfluoroalkyl polyethers. 

Other well-known reactions are those offluorinated olefins with fluoride ion and negatively substituted aromatic compounds leading to the formation of per-fiuoroalkylated aromatic compounds The reaction may be considered an amonic version of a Fnedel Crafts process and can result in introduction of one or several perfluoroalkyl substituents [/ /] Aromatic substrates include substituted and unsuhstiluled perfiuorobenzenes [J3l, 212, 213, 214], fiuorinated heterocycles [131, 203, 215, 216, 217, 218, 219, 220, 221, 222, 223],perchlorinated heterocycles [224] (equation 44), and other activated aromatic compounds [225] (equation 45) The fluonnated olefins can be linear or cyclic [208] (equation 46)... 

A more efficient agent than peroxy compounds for the epoxidation of fluoro-olefins with nonfluonnated double bond is the hypofluorous acid-acetomtrile complex [22] Perfluoroalkylethenes react with this agent at room temperature within 2-3 h with moderate yields (equation 13), whereas olefins with strongly electron-deficient double bond or electron-poor, sterically hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-alkylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 C IS finished after 10 mm in 80% yield [22] The trifluorovinyl group in partially fluorinated dienes is not affected by this agent [22] (equation 13)... 

Although nitrosation of (l-dicarbonyl compounds becomes increasingly more facile upon successive replacement of the a alkyl groups with perfluoroalkyl groups because of the increased ionization of the perfluorinated enolate (equation 7), the stability of the nitrosodiketone tautomers decreases Thus, 1,1,1-trifluoro pentane-2,4-dione and 1,1,1,5,5,5-hexafluoropentane 2,4 dione mtrosate much faster than penta-2,4 dione but yield ketoximes, which decompose upon workup... 

Perfluoroalkylation of substituted benzenes and heterocyclic substrates has been accomplished through thermolysis of perfluoroalkyl iodides in the presence of the appropriate aromatic compound Isomeric mixtures are often obtained W-Methylpyrrole [143] and furan [148] yield only the a-substituted products (equation 128) Imidazoles are perfluoroalkylated under LTV irradiation [149] (equation 129). 4-Perfluoroalkylimidazoles are obtained regioselectively by SET reactions of an imidazole anion with fluoroalkyl iodides or bromides under mild conditions [150] (equation 130) (for the SET mechanism, see equation 57)... 

The cyanohydrin of methyl perfluoroheptyl ketone was synthesized by a two-step process addition of sodium bisulfite and subsequent treatment with sodium cyanide. When the ketone was reacted with sodium cyanide, cyclic addition products were obtained, instead of the product of cyanohydrin formation. This result was attributed to the solubility characteristic of a long perfluoroalkyl group, which makes the compound less soluble in water and polar organic solvents [54] (equation 40) (Table 14). 

Table 1. Perfluoroalkylation of Carbonyl Compounds by Perfluoroalkyltin(rV) Halides [/2]...

Solvent plays a significant role in these reactions In contrast to the formation of organocadmium compounds in the duect reaction of perfluoroalkyl iodides and cadmium powder in DMF [729], dimerization of the perfluoroalkyl halide was observed in acetonitrile [777] (equation 100)... 

Table 6, Perfluoroalkyl Aromatic Compounds Prepared via the Reaction of Perfluoroalkylcopper Reagents with lodo-or Bromoaromatic Compounds...

Copper-promoted coupling of RflCH=CIRf2 compounds gives the 1,2,3,4-tetrakis(perfluoroalkyl)-l,3-butadienes m 62-77% yields [250 ... 

The perfluoroacetylenic copper compounds undergo coupling reactions with aryl iodides and provide a useful synthetic route to the perfluoroalkyl aryl alkynes [147, 255] (equation 170) Coupling of these copper reagents with the 1-iodo-perfluoroalkynes gives the perfluorodiynes [747 255] (equation 171)... 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

Perfluoroalkyl- and perfluoroaryltitanium compounds were prepared m situ via reaction of the corresponding Gngnard reagents with chlorotris(diethyl-amido)titanium [28S] Reaction of the titanium compounds with aldehydes resulted in fluoroalkylative amination [288] (equation 192)... 

Perfluoroalkyl or -aryl halides undergo oxidative addition with metal vapors to form nonsolvated fluonnated organometallic halides and this topic has been die subject of a review [289] Pentafluorophenyl halides react with Rieke nickel, cobalt, and iron to give bispentafluorophenylmetal compounds, which can be isolated in good yields as liquid complexes [290] Rieke nickel can also be used to promote the reaction of pentafluorophenyl halides with acid halides [297] (equation 193)... 

The addition of halogenated aliphatics to carbon-carbon double bonds is the most useful type of carbon-carbon bond forming synthetic method for highly halogenated substrates Numerous synthetic procedures have been developed for these types of reactions, particularly for the addition of perfluoroalkyl iodides to alkenes using thermal or photolytic initiators of free radical reactions such as organic peroxides and azo compounds [/]... 

Fluorinated heterodienophiles and heterodienes Diels-Alder reactions in which the dienophiles have perfluoroalkyl-substituted multiple bonds between carbon and a heteroatom are quite common Reported earlier were reactions of perfluoroketones, thiones, ketimines, thioesters, nitroso compounds, and nitriles [9] Examples of a-fluoroimines [107], co-hydroperfluorothioaldehydes [108], perfluorosulfines [109, IIO], and selenocarbonyidifluoride [III] (equations 89-92) have been reported recently... 

Perfluoroalkyl groups adjacent to multiple bond systems lower the frontier molecular orbitals (FMOs) Therefore, cycloaddition reactions preferentially occur with electron-rich multiple-bond systems The preference of bis(trifluoromethyl)-substituted hetero-l,3-dienes for polar reacuons makes them excellent model compounds for developing new types of diene reactions deviating from the well documented Diels-Alder scheme (pathway 1) A systematic study of the reactions of diene (1 =2-3=4)-dienophile (5=6) combinations reveals new synthetic possibilities that have not yet been fully exploited as tools for preparative organic cherrustry (equation 25)... 

The dienophilic character of imines parallels that of carbonyl compounds Consequently, electron deficient imtnes are the most reactive dienophiles of this class, particularly those having C perfluoroalkyl [5, 146, 150, 228], /V-acyl [/2i5 127], or A/-sulfonyl groups [148, 229 230]... 

FITS reagents), has undergone considerable development recently [141,142,143, 144, 14S. These compounds, available fromperfluoroalkyhodides (equation 76), are very effective electrophilicperfluoroalkylating agents They react with carban-lons, aromatic compounds, alkenes, alkynes, silyl enol ethers, and other nucleophiles under mild conditions to introduce the perfluoroalkyl moiety mto organic substrates (equation 77) (see the section on alkylation, page 446). 

Selenium analogues RN=SeCl2 are unknown for R = aryl or alkyl and thermally unstable when R = CE3 or C2E5. The perfluoroalkyl derivatives are prepared by the reaction of dichloroamino compounds and Sc2Cl2 in CCI3E (Eq. 8.18), but they decompose at room temperature to the corresponding diazene and a mixture of selenium chlorides. 

These compounds present a new class of LC molecules having a perfluoroalkyl tail on one end and an ordinary alkyl tail on the other. Earlier studies of several groups indicated that terminal fluorination considerably extends the temperature range of the smectic phase [81]. Moreover, mesogens incorporating... 

Fig. 15. Tilt angles of the different molecular fragments as a function of temperature for polyphilic compound FsHnOCB aromatic core (circles), alkyl chain (crosses) and perfluoroalkyl chain (diamonds) (Ostrovskii et al. [45])...

There are two types of hypofluorite compounds that have been prepared the perfluoroalkyl hypofluorites, such as CF3OF, and the acyl hypofluorites, such as CH3C02F. The fluorines of such compounds are very deshielded and thus have significantly positive chemical shifts (Scheme 7.11). 

Many perfluoroalkyl SF5 compounds are known and are exemplified by the data given in Scheme 7.26 for CF3SF5. 

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