Perfluoroalkyl derivatives

Fluorocarbon organometallic chemistry began with the first syntheses of perfluoroalkyl iodides (see Chapter 7, Sections EC, Subsection 7, and HE, Subsection 2, for current methods). On the basis of classical methods, this might have been expected to lead logically to the corresponding lithio derivatives and these, in turn, to a considerable 

Fluorine in Organic Chemistry Richard D. Chambers 2004 Blackwell Publishing Ltd. ISBN 978-1 05-10787-7 

A warning has been given [24] about carrying out exchange reactions to form pentafluoroethyl-lithium at very low temperatures, where violent decomposition has been observed. The most likely explanation for these events is that solid perfluoroethyl-lithium is precipitated at the low temperature and, of course, this is extremely unstable with respect to formation of the metal fluoride. The same cautionary note may be made for all fluorinated alkyl- or aryl-lithium compounds (see Chapter 9, Section HE, Subsection 1) 

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Perfluoroalkyl derivatives have important technical uses, e.g. sulphonic acids as surfactants introduction of perfluoroalkyl groups confers useful properties on many drugs. 

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. 

Fig. 5. Suggested structures of perfluoroalkyl derivatives of SeF4. From Lau and Pass-more (108).

The development of new types of reagents for the formation of perfluoroalkyl derivatives of metals is of interest since, as discussed below (Section II), the types of trifluoromethyl complexes which could be prepared until quite recently have been severely limited by the synthetic methods that have been historically available. Virtually all of the trifluoromethyl-containing transition metal species prepared prior to the 1980s arose from only two types of reactions thermal decarbonylations of trifluoroacetyl complexes or oxidative additions of CF3I. 

The diphenylprolinol silyl ether 45a catalyst was developed by the Hayashfs group for the addition of a-unbranched aldehydes to aryl and alkyl substituted nitroolefins [35]. This catalyst, as well as the perfluoroalkyl derivative 45b [36],... 

Phenylenediamine and 2-aminophenol initially give N-arylimidoyl fluoride. Elimination of hydrogen fluoride from the product and further intramolecular nucleophilic cyclization lead to perfluoroalkyl derivatives of benzimidazole and benzoxazole, respectively. In the case of 2-aminothio-phenol, the reaction occurs at the sulfur atom and forms a carbanion. If RF is fluorine, then the carbanion is destabilized by the interaction of the lone electron pairs of fluorine with the center, and the stabilization reactions occur with participation of the proton. If, however, RF is the trifluoro-methyl group, the negative charge is stabilized by it. The fluoride ion is eliminated with further intramolecular nucleophilic cyclization. 

The formation of the perfluoroalkyl derivatives of 1,3-dioxolane in reactions of perfluoroolefins with ethyleneglycol is a general process. It was... 

In what is probably a radical-based substitution, thiocoumarins 391 react with perfluoroalkyl iodides in the presence of rongalite, H0CH2S02Na, to give 3-perfluoroalkyl derivatives 392 <1994J(P1)101>. 

Although fluorochemical surfactants containing perfluoroalkyl carbonyl fluorides currently exist in the art, it is difficult to obtain perfluoroalkyl derivatives containing six or more carbons. A method to address this problem using organosilicon compounds is described. 

Good yields of certain rhodium(III) perfluoroalkyl derivatives have been obtained in oxidative addition reactions of perfluoroalkyl iodides (R I) with rhodium (I) trifluorophosphine complexes (method C). 

Perfluoroalkyl derivatives are strong Lewis acids owing to the electron-withdrawing elfects of the fluorine substituents, and readily form stable adducts, for example, (CF3)2Cd(glyme), that have been characterized by F NMR spectroscopy. ... 

A recent exciting development [132, 133] of this chemistry involves conversion of perfluoro(4,5-di-isopropyl)phthalonitrile to corresponding metal perfluorophthalocyanine complexes for example, when perfluoro(4,5-di-isopropyl)phthalonitrile was melted with zinc acetate at 180°C, a blue-green solid was obtained which was established as the phthalocyanine derivative. These perfluoroalkyl derivatives are much more soluble than other halogenated phthalocyanines and, moreover, they appear to be excellent sensitisers for the production of singlet oxygen. 

Perfluoropropynyl [15, 26, 27] and perfluorovinyl [16, 28-30]-lithium and -magnesium are considerably more stable than perfluoroalkyl derivatives, whilst the corresponding perfluoroaryl derivatives may be used as effectively as in the hydrocarbon series, and direct syntheses involving iodo compounds are also possible (Figure 10.3). 

Outstandingly different in character from the perfluoroalkyl derivatives described above are the lithium and magnesium compounds derived from highly fluorinated bicyclo-[2.2.1]heptanes [37, 38]. Some reactions of the lithio derivative are shown in Figure 10.8, illustrating that it can be utilised in the normal synthetic procedures with much less competition from elimination. 

Perfluoroalkyl derivatives of mercury were the first fluorocarbon-organometallic compounds to be reported. Alkylmercurials are valuable in that they are able to alkylate other metals, but the toxicity of mercurials greatly inhibits the use of these systems. Perfluoroalkyl iodides react with mercury on heating or irradiation with ultraviolet light to give perfluoroalkylmercury(ll) iodides [58-60] (Figure 10.17). 

Factors analogous to those which limit the stability of perfluoroalkylboron compounds are even more dominant in the case of aluminium. Indeed, no perfluoroalkyl derivatives of tri-covalent aluminium have been obtained, although salts of the type Li[( -C3F7)2All2] are produced [83] in reactions of perfluoroalkyl iodides with LiAlH4. 

The Grignard or lithium route is of limited value for the preparation of perfluoroalkyl derivatives. Much of the early work was concerned with the addition of silanes to fluorinated alkenes [88, 89], leading to the preparation of important fluorinated poly-siloxanes, manufactured by Dow Coming Co. (Figure 10.39). 

H. C. Clark Advan. Fluorine Perfluoroalkyl derivatives of the 44 Transition metal compounds, p. 54... 

Incorporation of CO2 into organic perfluoroalkyl derivatives by electrochemical methods... 

We have been interested in tbe carbon dioxide fixation into organic substrates for tbe synthesis of speciality products of the carboxylic acid family. We focussed our attention on tbe formation of new carbon-carbon bonds between CO2 and perfluoroalkyl derivatives, particularly perfluoroalkyl olefins. The perfluorinated chain being highly hydrophobic, the expected perfluoroalkyl carboxylic acids are precursors of amphiphilic molecules, of interesting applicability in the field of surfactants and medicinal chemistry [1]. 

The electrochemical incorporation of CO2 into perfluoroalkyl derivatives has been explored in the case of (perfluoroalkyl)alkyl iodides and (perfluoroalkyl)alkenes, with an electrochemical system based on the use of consumable anodes combined with organometallic catalysis by nickel complexes. Iodide derivatives have been functionalized to the corresponding carboxylic acids by reductive carboxylation. Interesting and new results have been obtained from the fixation of CO2 into perfluoroalkyl olefins. Good yields of carboxylic acids could be reached by a carefull control of the reaction conditions and of the nature of the catalytic system. The main carboxylic acids are derived from the incorporation of carbon dioxide with a double bond migration and loss of one fluorine atom from the CF2 in a position of the double bond. 

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