Preparation of Perfluoroalkyl Iodides

Preparation of Perfluoroalkyl Iodides.—C2F4 + IF5-2I2 + MoFe (cat.) at 75 C - CsFsI CFal-CFal + HF + SbCU + SOzClz at 165—168 °CC2F5I CsFa + I2 + KF doped with K2CO3 in MeCN at 110 °C (CFs)2CFI 2 8 CaFa + 

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This study relates to a continuous process for the preparation of perfluoroalkyl iodides over nanosized metal catalysts in gas phase. The water-alcohol method provided more dispersed catalysts than the impregnation method. The Cu particles of about 20 nm showed enhanced stability and higher activity than the particles larger than 40 nm. This was correlated with the distribution of copper particle sizes shown by XRD and TEM. Compared with silver and zinc, copper is better active and stable metal. 

Industrially, the perfluoroalkyl iodides by telomerization are mostly made by a batch system using peroxide initiators. However, the difficulty of mass production, and the production of hydrogen-containing byproducts in the process are disadvantageous [4]. In this study, a continuous process for the preparation of perfluoroalkyl iodides over nanosized metal catalysts in gas phase and the effects of the particle size on the catalytic activities of different the preparation methods and active metals were considered. 

Perfluoroalkanoic acids also undergo Hunsdiecker reactions, with the greatest utility for such methodology being the preparation of perfluoroalkyl iodides, bromides and chlorides [64]. 

Following the disclosures in the patent literature in 1968, a detailed paper has been published dealing with the preparation of perfluoroalkyl iodide di- and tetra-fluorides (RrlFa and RpIFa) via treatment of perfluoroalkyl iodides with fluorine, bromine tri- or penta-fluoride, or, preferentially,... 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

The reaction of perfluoroalkyl iodides with calcium amalgam at -20 to 40 °C has been used to prepare perfluoroalkyl carbinols in 30-70% yields [/, 2] Aromatic aldehydes (equation 1) and ketones (equation 2) undergo this reaction, aliphatic aldehydes give high boiling mixtures The results are interpreted in terms of the intermediate formation of an organocalcium species... 

The importance of solvent effects in the preparation of perfluoroalkyzinc reagents is further illustrated in the reaction of perfluoroalkyl iodides with zinc-copper couple. In DMSO, DMF, and HMPA, the main products are the fluo-roolefins The formation of the fluoroolefin is facilitated when the reaction is carried out in the presence of potassium thiocyanate [30] (equation 21)... 

The scope of haloaliphatic additions to alkenes has been extended to the preparation of 1,2-bis(perfluoroalkyl)iodoethanes by the addition of perfluoroalkyl iodides tofluoroalkyl alkenes [73] (equation 12) or to alkadienes [14] (equation 13)... 

Solvated perfluoroalkyl zinc reagents have been prepared by reaction of perfluoroalkyl iodides with zinc in ethereal solvents such as dioxane [36,37]. Self-coupled and cross-coupled products can be formed when a mixture of acetic anhydride and methylene chloride was used [38-40] (Scheme 11). 

Perfluoroalkyl iodides reacted with trialkylsilyl chloride in DMF in the presence of zinc followed by hydrolysis with acid to give perfluoroaldehydes in good yields [55]. Recently, Hu reported a new preparation of perfluoroalkyl aldehydes via reaction of perfluoroalkyl halides and DMF, initiated by redox... 

The first preparation of perfluoroalkyl copper reagents was reported by McLoughlin and Thrower in 1969 [68]. Perfluoroalkyl iodides react with copper... 

Finally perfluorinated alkenes, prepared according to various routes (decarboxylation of perfluorinated acids or anhydrides, action of organolithium, magnesium reagents or metallic zinc-copper couple to perfluoroalkyl iodides, oligomerisation of TFE and of HFP, addition of perfluoroalkyl iodides to per-fluoroallyl chloride [304], addition of KF to perhalogenated esters or alkanes... 

Controlled potential preparative electrolysis at glassy carbon cathodes results in the reduction of perfluoroalkyl iodides and bromides (equation 74). The reaction in the presence of phenolate ions in aprotic media gives products of perfluoroalkylation of phenol, and also the corresponding monohydroperfluoroalkanes11. ... 

Trifluoromethylpyrazoles were conveniently prepared in two steps via the radical addition of fluoroalkyl iodides to alkynes followed by condensation with hydrazines <1997S1489>. Photochemical reactions of perfluoroalkyl iodide 655 and a-chlorostyrenes 656 in the presence of hydrazine and acetic acid afforded 5-aryl-3-perfluoroalkylpyrazoles 657 (Scheme 83) <2001TL33>. 

Whereas haloalkanes are widely used for the electrophilic alkylation of a broad variety of nucleophiles, perfluoroalkyl bromides or iodides do not act analogously as electrophilic perfluoroalkylation reagents (Figure 2.7). For example, the reaction of perfluoroalkyl iodides with aliphatic alcoholates does not yield the expected alkyl perfluoroalkyl ether (analogous to the Williamson ether synthesis) but mostly the hydrofluorocarbon resulting from the reduction of the iodide [1]. In contrast, perfluoroalkyl iodides and bromides have been used as preparatively useful electrophilic iodination or bromination reagents [2]. 

Due to the availability of perfluoroalkyl iodides, this method quickly became the method of choice for the regioselective synthesis of perfluoroalkylated heterocycles. Chen and Tamborski used this reaction for the preparation of variety perfluoroalkyl-pyridines," azines," and triazines." For example, pyridines 72-73 and pyrimidine 74 were synthesized by addition of perfluorohexyl iodide to the agitated mixture of the corresponding heteroaryl bromide, cooper bronze powder in DMSO solvent under nitrogen at elevated temperature (Fig. 7.26)." ... 

Alkenes with perfluoroalkyl substituents have been prepared by the reaction of perfluoroalkyl iodides with terminal alkynes in the presence of ultrasonically dispersed zinc and Cul. A general procedure for the formation of organocopper reagents from alkyl and aryl halides and lithium metal in the presence of Cul or l-pentynylcopper(I) under ultrasonic irradiation has also been described. ... 

The fluorocarbon chlorosulfonates, e.g. 514, represent a new class of compounds and their formation by treatment of perfluoroalkyl iodides with chlorosulfonic acid appears to be a useful general preparative procedure. 

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