Perfluoroalkyl derivatives iodides

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>. 

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 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 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. 

The trifluoromethylation of aryl iodides has been achieved using the reaction with (trifluoromethyl)-trimethoxyborate and a copper(I)/phenanthroline catalyst." A copper chloride/phenanthroline catalyst has also been used together with (TMP2Zn), zinc bis-tetramethylpiperidide, in the reaction of aryl iodides with perfluoroalkyl derivatives to yield arylperfluoroalkanes. The mechanism is thought to involve initial formation of bis(perfluoroalkyl)zinc species followed by rate-limiting transmetalation with copper halide and reaction with the aryl iodide to give the coupled product." ... 

No stable compounds of the type R2Fe(CO)4 with iron-carbon a bonds have been isolated by the reaction between [Fe(CO)4] and alkyl halides such as methyl iodide. However, the perfluoroalkyl derivatives (Rf)2Fe (CO)4 (Rf = C2F5 and C3F7) have been obtained as air-stable very pale yellow crystals by the reaction between Na2[Fe(CO)4] prepared in tetra-hydrofuran and the perfluoroacy/ chlorides RfCOCl. The intermediate perfluoroacyl derivatives (RfCO)2Fe(CO)4 were not isolated, but instead were decarbonylated spontaneously in the boiling tetrahydrofuran 50). For reasons which are not clear at the present time the yields of the perfluoroalkyl compounds (Rf)2Fe(CO)4 in this reaction were only about 15%. Attempts to prepare (CF3)2Fe(CO)4 by this technique have been unsuccessful. A related compound is the extremely stable perfluorotetramethylene derivative C4FgFe(CO)4 (XXIX) 182) obtained from tetrafluoroethylene and iron pentacarbonyl. This fluorocarbon derivative was first erroneously formulated as a tricarbonyl derivative 183). 

Hydroxy-4-methylthiazole failed to react when submitted to Friedel-Crafts benzoylation conditions (349) on the other hand, it reacted normally in Gattermann and in Reimer-Tiemann formylation reactions, affording the 5-formyl derivative (348). 4-Methylthiazole is insufficiently activated and fails to react under the same conditions. 2,4-Dimethylthiazole undergoes perfluoroalkylation when heated at 200° for 8 hr in a sealed tube with perfluoropropyl iodide and sodium acetate (116) (358). 

Aromatic perfluoroaLkylation can be effected by fluorinated aUphatics via different techniques. One category features copper-assisted coupling of aryl hahdes with perfluoroalkyl iodides (eg, CF I) (111,112) or difluoromethane derivatives such as CF2Br2 (Burton s reagent) (113,114), as well as electrochemical trifluoromethylation using CF Br with a sacrificial copper anode (115). Extmsion of spacer groups attached to the fluoroalkyl moiety, eg,... 

Silyl enol ethers have also been used as a trap for electrophilic radicals derived from a-haloesters [36] or perfluoroalkyl iodides [32]. They afford the a-alkylated ketones after acidic treatment of the intermediate silyl enol ethers (Scheme 19, Eq. 19a). Similarly, silyl ketene acetals are converted into o -pcriluoroalkyl esters upon treatment with per fluoro alkyl iodides [32, 47]. The Et3B/02-mediated diastereoselective trifluoromethylation [48,49] (Eq. 19b) and (ethoxycarbonyl)difluoromethylation [50,51] of lithium eno-lates derived from N-acyloxazolidinones have also been achieved. More recently, Mikami [52] succeeded in the trifluoromethylation of ketone enolates... 

The use of iodo derivatives CH2I2 or CHI3 in reaction 66 results only in polymeric products308. However, 1-iodosilatrane (51) can be obtained in almost quantitative yield from 1-hydrosilatrane (49) and perfluoroalkyl iodides under UV irradiation (equation 68)309. 

The benzene derivatives containing the fluorinated sulfone have been prepared either by nucleophilic substitution of the 4-fluorophenyl derivative (e.g. 1) or by starting with the appropriately substituted sodium thiophenoxide and reacting with perfluoroalkyl iodide follow by oxidation with either MCPBA or chromium oxide (12. li.) The biphenyl derivatives have been prepared by palladium catalyzed cross coupling chemistry of the 4-bromophenyl derivative (e.g. 2) with substituted phenyl boronic acid (yields 37-84%) (JLH, .). Compound 16 has been prepared by palladium catalyzed cross coupling of (4-bromophenyl)perfluorohexyl sulfone with vinyl anisole in 37 % yield (JJL). The vinyl sulfones, 7 and 9, have been prepared by condensation of CH3S02Rf (JJL) with the appropriate aldehyde (yields 70,and 73%) following a literature procedure (1 ). Yields were not optimized. 

Electrochemical oxidation of perfluoroalkanoic acids can lead to radical derived products, although the same problems apply to such oxidations as applied to the electrochemical reduction processes of perfluoroalkyl iodides. 

Whereas it has been demonstrated that both malonate ions and thiolate ions can catalyze the free radical chain addition reaction of perfluoroalkyl iodides to olefins [289,290], under appropriate conditions one can obtain products deriving from substitution in such processes. Following early work carried out photo-lytically in liquid ammonia, recent reports have indicated that good yields of substitution products can be obtained in polar solvents at room temperature, without irradiation [291-296]. 

The first successful syntheses utilizing trifluoromethyl iodide in transition metal chemistry were reported by Stone and his students. Stone reasoned that if CF3I would not react with transition metal anions to form trifluoromethyl derivatives [see Eq. (3)] then perhaps compounds containing perfluoroalkyl substituents could be generated by the oxidative addition of perfluoroalkyl halides to low valent transition metal substrates (9,10). The first reported trifluoromethyl-substi-tuted transition metal complex prepared by this route is shown in Eq. (4) (41). 

Perfluoroalkyl radicals were generated according to a procedure developed by this research group, involving iodine abstraction from perfluoroalkyl iodides by phenyl radical (Equation 14.13) this latter derives from thermal decomposition of benzoyl peroxide (Equation 14.14). 

Dyatkin and coworkers have reported the reaction of perfluoroalkylsilver derivatives with iodine to give perfluoroalkyl iodides, and with elemental sulfur to give the perfluoroalkylthiosilver, which was subsequently alkylated with ethyl iodide to give the thioether (Scheme 1.12).36... 

Also of interest are the chemical changes from derivatives of perfluoroalkyl iodides [17] ... 

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