Trifluoromethyl iodide, reaction

Trifluoromethylation is the most important perfluoroalkylation reaction. The initial work was earned out with trifluoromethyl iodide and copper metal in the... 

Other alkylgold(III) compounds are [Au2(/r-X)2(CF3)4] (X = Br, I) synthesized by co-condensation of gold with CF3Br and CF3I, respectively, and may be sublimed at room temperature.1654 Trifluoromethylated compounds are potentially useful precursors for CVD studies as they are expected to show enhanced volatility.1655 m-[Au(CF3)2I(PMc3)] is formed in quantitative yield by oxidative addition of trifluoromethyl iodide to [Au(CF3)(PMe3)], the reaction is proposed to proceed via radical intermediates.1524,1656... 

An analogous reaction occurs between trifluoromethyl iodide and elementary phosphorus, arsenic, antimony, sulphur or selenium (5). The experimental procedure was the same in each case, the fluoroalkyl iodide being heated in a sealed tube or autoclave with the clement in question at temperatures ranging from 170 to 280°. Table 4 shows the products of these reactions which have been isolated. 

In the reaction between trifluoromethyl iodide and selenium at 265—290° bistrifluoromethyl selenide, (CF3)2Se, and bistrifluoromethyl diselenide, (CF3)2Sea, are produced in yields of 40 and 20% respectively (Table 4). These two compounds show a number of interesting reactions. The compound (CF3)2Se is converted quantitatively to CF3CI and, SeCl4 when irradiated in a quartz vessel with ultraviolet light. If the irradiation is done in Pyrex, however, a new solid compound CFjSeClg is formed, which hydrolyses to the crystalline acid CF3SeO(OH) (m.p. 118°). The... 

Trifluoromethyl iodide is a poor substrate for SN2 reactions [28], The increased donativity of the methylene carbon as rendered by the fluorine atoms is reflected in its reluctance to enter a bonding relationship with a nucleophile. Similar reactivity patterns are known for chloromethyl phenyl sulfone [28] and chloromethyltrimethyl-silane. In these latter compounds the reactive center is directly linked to an acceptor group. 

Trifluoromethylation is the most important perfluoroalkylation reaction. Kobayashi and co-workers reported the trifluoromethylation of aryl, vinyl, alkyl halides with trifluoromethyl iodide in the presence of copper powder in aprotic solvents such as HMPA at 120-150 °C [83,84], and this methodology has been applied to the preparation of fluorinated pyrimidine and purine nucleosides [85,86] (Scheme 27). 

Due to the cost of trifluoromethyl iodide, other cheaper sources have been investigated for trifluoromethylation. Sodium trifluoroacetate reacted with aryl iodide in the presence of copper (I) iodide in NMP at 140 -160 °C to afford the corresponding coupling product [87]. No trifluoromethylation was observed without Cul. Under similar reaction conditions, sodium pentafluoropro-pionate worked well to give the pentafluoroethylated compounds [88, 89] (Scheme 28). 

The reactions of trifluoromethyl iodide with the main group elements and elemental mercury were extensively investigated by Eme-leus and his students almost as soon as the reagent became available in quantity. Trifluoromethyl iodide was shown to readily oxidize a number of elements, most notably those below nitrogen in Group VA, and the trifluoromethyl ligand was observed to possess a considerable amount of pseudohalogen character (5). 

The reaction of CF3I with low valent metals is remarkable for the very mild conditions that are required. Typically, trifluoromethyl iodide and the transition metal species are maintained at ambient temperatures for periods of time which range from a few minutes to a few days. When employed at all, solvents are noninteractive and, at most, only gentle heating is required. The utility of oxidative addition reactions with trifluoromethyl iodide has been demonstrated in numerous systems and representative examples are presented in Table II. 

Trifluoromethyl is a wonderful group with numerous substituent effect surprises84. Within the context of discussions of positive halogen , it is well-established85 that solution-phase nucleophilic reactions of trifluoromethyl iodide are consistent with the presence of formally positive iodine, e.g. equation 53. ]... 

Corrosion inhibitors, [1.2,4]triazino[4,3-ojbenzimidazoles, 59, 155 Coulson-Rushbrook theorem, 55, 273 Coumarins, see l-Benzopyran-2-ones Coupling reactions, trifluoromethyl iodide with aryl halides, 60, 12 Covalent hydration in 6-nitro-l 1,2,4]triazolo[ 1,5-a)-pyrimidines, 57, 107 of coordinated ligands, 58, 138 Creutz-Taube ion, 58, 124 Criss-cross cycloadditions, of... 

Similarly, adenosine, inosine and 2 -deoxyinosine have been converted into their 8-trifluoromethyl derivatives by reaction with the copper complex formed from trifluoromethyl iodide and copper in hexamethylphosphorotriamide (80JCS(P1)2755). iV -Trifluoromethyl-purine riboside was also produced from 6-chloropurine riboside. Recently, guanosine has been shown to give the C (8)-substituted derivative (148) by reaction with a benz[a]anthracene 5,6-dioxide at pH 9.5 over 4 days at 37 °C (80CC82). 

Albeit with less overall success, trifluoromethyl iodide has also been employed to effect oxidative trifluoromethylations of elemental copper and a few chromium and cobalt coordination complexes and to oxidatively cleave metal—metal bonds in complexes like Ni2(CO)2(Cp)2, Co2(CO)g, and GeMe3Fe(CO)2Cp. One of the first examples of this type of reaction is (22)... 

The first characterization of simple halophosphines as the primary products of the direct reaction of white or red phosphorus with trifluoromethyl iodide at 200-220 °C under pressure was reported in 1953 by Bennett, Emeleus and Haszeldine ... 

A recent report describes the reaction of trifluoromethyl iodide with tetraethyl pyrophosphite under UV irradiation at room temperatme. The resulting diethyl trifluoromethylphosphonite is oxidized with t-BuOOH to give the corresponding phosphonate in 63% yield (see also Section 3.1.2.51.- ... 

Bis(trifluoromethyl)(trimethylsilyl)phosphine (22) has been prepared by an exchange reaction using bis(trifluoromethyl)phosphine. Fluoroalkylphos-phines (23) may also be obtained by treatment of (fluoroalkyl)iodophosphines with trifluoromethyl iodide in the presence of antimony powder. ... 

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... 

However, since the mid 1970s, some reactions of trifluoromethyl iodide with soft nucleophilic reagents, enamines (ref. 9), or thiolates (ref. 10), have been interpreted as single electron transfer (SET) processes (Fig 4, X = I) (refs. 9, 10, 11). 

Although the products differ considerably in these two reactions, presumably the mechanisms are not drastically different. The negative hydroxide ion attacks the most positive atom in the organic iodide. In methyl iodide this is the carbon atom Or, > c) and the iodide ion is displaced. In the trifluoromethyl iodide the fluorine atoms induce a positive charge on the carbon which increases its electronegativity until it is greater than that of iodine and thus induces a positive charge on the iodine. The latter is thus attacked by the hydroxide ion with the formation of hypoiodous acid, which then loses an H+ in the alkaline medium to form IO. ... 

The large volume of data on H-abstraction reactions of CF3 radicals is shown in Table 25. Most of the results have been obtained by generating the radicals from the photolysis of hexafluoroacetone, which is particularly convenient since the reaction scheme involves no attack of the CF3 radicals on the parent ketone (C—F bonds are too strong to be broken in ordinary atom or radical transfer reactions). More recently, the photolyses of trifluoromethyl iodide [301, 302] and perfluoroacetic anhydride [290] have also been utilized with equal success. 

The prorlucts can equilibrate under the reaction conditions so that the individual yields depend on the ratio of tlie starting materials and the reaction time. Moreover, the individual product yields can be varied by the addition of one of the reaction products. Thus, addition of tris(trifluoromethyl)phosphine or iodine increases the yields of the mono- and diiodophosphines. With excess phosphorus at temperatures above 250°, the major products are phosphorus fluorides and hexa-fluoroethane (14). Results obtained under various reaction condi-tions are summarized in Table II. Since the trifluoromethyl iodide is prepared by the reaction of silver trifluoromethyl acetate with iodine, the trifluoromethylphosphines may be prepared directly from silver trifluoromethylacetate, phosphorus, and iodine (15). 

The process of telomerisation of tetrafluoroethylene with trifluoromethyl iodide or pentafluoroethyl iodide is initiated by UV irradiation or by a catalyst. In the latter case the reaction is carried out under pressure and at / = 80-220 °C ... 

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