Phosphorus trifluoromethyl compounds

Neutral phosphorus(V) compound containing divalent tridentate azo ligands were studied by Cavell and coworkers.83 The 31P and, 9F chemical shifts and /(31P, 19F) coupling constants are collected in Tables 9 and 10 for (2,2 -azophenoxy)trifluorophosphorus (22), /rans-(2,2 -azophenoxy)(trifluoro-methyl)difluorophosphorus (23) and cis-(2,2 -azophenoxy)(trifluoromethyl) difluorophosphorus (24). 

Reaction of Heteroatom Nucleophiles. Reaction of A -tetraethylthiourea with nitrated -(trifluoromethyl)-diarylsulfonium salt proceeds smoothly without a base to provide a 5 -trifluoromethylated compound (eq 13). Sodium sulfinate readily converts into the corresponding aryl triflone in 81% yield (eq 14). Trivalent phosphorus compounds are also viable electrophiles in the electrophihc trifluoromethylation reaction, providing diethoxytrifluoromethylphosphonate with 70% yield (eq 15). 

Recently developed trifluoromethylatmg agents capable of transferring the trifluoromethyl group as a cation to strongly nucleophilic compounds such as carbanions and sulfur and phosphorus nucleophiles are prepared from o-biphenyl trifluoromethyl sulfoxide [164] and are shown in equation 141... 

Fluoroolefins may he prepared by the reaction of Wittig reagents and other pho sphorus-containtng y tides with fluorinated carbonyl compounds. (A discussion of the fluorinated Wittig reagents or other fluonnated phosphorus reagents with nonfluorinated carbonyl compounds is on page 581.) Tnphenylphosphoranes, derived from alkyltriphenyl phosphonium salts, react with 1,1,1-trifluoroacetone [3/] or other trifluoromethyl ketones [32, iJ] (equation 26) (Table 10). 

Previously, trifluorosilyl groups have been bound to phosphorus (40) and silicon via the SiF (g), fluorine-bond insertion-mechanism (41). The new compound HgCSiFs) is readily hydrolyzed, but it can be stored for long periods of time in an inert atmosphere. It is a volatile, white solid that is stable up to at least 80°C. The preparation of bis(trifluoro-silyDmercury, of course, raises the possibility of (a) synthesis of the complete series of trifluorosilyl, "silametallic compounds, as had previously been done for bis(trifluoromethyl)mercury by using conventional syntheses, and (b) transfer reactions similar to those in Section II, as well as (c) further exploration of the metal-vapor approach. The compound Hg(SiF.,)j appears also to be a convenient source of difluoro-silane upon thermal decomposition, analogous to bis(trifluoromethyl)-mercury ... 

To date, however, only few reactions between phosphine and a non-metal halide, in which a chemical bond is formed between phosphorus and a non-metal by HCl condensation, are known. To these, apart from the above-mentioned reactions, belongs also the reaction with CF3SCI which, depending upon the chosen proportions of the reactants, in a sealed tube at -95 °C leads to the formation of (CF3S)2PH or (CF3S)3P Both compounds are not very stable thermally and decompose at 40-50 °C. Tris(trifluoromethylthio)-phosphine forms an unstable adduct with chlorine, which decomposes at 0 °C to give a mixture of PCI3, bis(trifluoromethyl)-disulphide and trifluoromethyl-sulphenyl chloride. 

Both compounds crystallize with the cadmium diiodide structure (space group P3ml) as previously reported on polycrystalline samples.3 For platinum disulfide, ao = 3.542(1) A and c0 = 5.043(1) A, and for platinum ditelluride, a0 = 4.023(1) A and c0 = 5.220(3) A. Direct chemical analysis for the component elements was not carried out. Instead, precision density and unit-cell determinations were performed to characterize the samples. The densities of both compounds as determined by a hydrostatic technique with heptadecafluorodeca-hydro-l-(trifluoromethyl)naphthalene as the density fluid4 indicated that they are slightly deficient in platinum. For platinum disulfide, = 7.86 g/cm3 and Pmeas = 7.7(1) gm/cm3, and for platinum ditelluride, p = 10.2 gm/cm3 and Pmeas = 9.8(1) gm/cm3. In a typical experiment an emission spectrum of the platinum disulfide showed that phosphorus was present in less than 5 ppm. A mass spectroscopic examination of the platinum ditelluride revealed a small doping by sulfur (less than 0.4%) and traces of chlorine and phosphorus (less than 100 ppm). 

A somewhat different approach is used for the preparation of the analogue that contains a trifluoromethyl group. The scheme involves first the conversion of ort/zo-trifluoromethyl aniline (27-1) to a quinolol. The compound is thus condensed with EMME and cyclized thermally (27-2). That intermediate is then saponified the resulting acid is decarboxylated and finally converted to the 4-chloroquinoline (27-3) by reaction with phosphorus oxychloride. The displacement of chlorine with methyl anthranilate (27-4) then affords the coupled intermediate (27-5). An ester interchange of that product with glycerol leads to the glyceryl ester. There is thus obtained the NSAID flocatfenine (27-6) [31]. 

Treatment of difluoroallylic alcohols with sulfur(II) or phosphorus(III) halides resulted in [2,3]-rearrangement (Eq. 135) under mild conditions [349]. This method constitutes a potential alternative route to difluorophosphonates, and to difluorosulfoxides and sulfones. The Jussieu group showed that thionyl chloride or bromide converted difluoroallylic alcohols to the corresponding halodi-fluoromethyl allylic compounds (Eq. 136) [350]. Exposure to DAST afforded the trifluoromethyl congeners [351, 352] and Kumadaki showed that /i-chloro-y,y-difluoroallylic alcohols afforded the trifluoromethyl alkene products upon treatment with HF. 

Trifluoromethyl hypofluorite reacts with various sulfides in trichlorofluoromethane at — 78 C forming difluoro- 624 and tctrafluorosulfancs 7,25 while fluorodesulfuration is observed in the reaction of amino acids, e.g. formation of 8.26 In a similar manner, trivalent phosphorus compounds react with trifluoromethyl hypofluorite to give difluoro-substituted derivatives 9.27... 

B) Preparation of 5-Trifluoromethyl-2,4-Disulfamylaniline - The 5-trifluoromethylaniline-2,4-disulfonyl chloride obtained in step (A) is taken up in ether and the ether solution dried with magnesium sulfate. The ether is removed from the solution by distillation, the residue is cooled to 0°, and 60 ml of ice-cooled, concentrated ammonia water is added while stirring. The solution is then heated for one hour on a steam bath and evaporated in vacuo to crystallization. The crystallized product is 5-trifluoromethyl-2,4-disulfamylaniline, which is filtered off, washed with water and dried in a vacuum-desiccator over phosphorus pentoxide. After recrystallization from a mixture of 30% ethanol and 70% water, the compound has a MP of 247°-248°C. 

The solution was then heated for one hour on a steam bath and evaporated in vacuo to crystallization. The crystallized product was 5-trifluoromethyl-2,4-disulfamylaniline, which was filtered off, washed with water and dried in a vacuum exsiccator over phosphorus pentoxide. After recrystallization from a mixture of 30% ethanol and 70% water the compound had a MP of 247° to 248°C. 

On the other hand, in the reaction of trifluoroiodomethane and tris(diethylamino)phos-phane other products are formed, namely bis(diethylamino)(trifluoromethyl)phosphanc [(EtjNlaPCFj] and the salt (Et2N)4P l The salt 16 is stable up to its melting point. The high positive charge on the phosphorus atom in this compound promotes the reaction with the fluoride ion (arising from CsF, TASF, etc.). The fluoro-A -phosphane 17 is formed as an intermediate in this reaction. It reacts, for example, with benzaldehyde to form the alcohol 18. ... 

It was shown by us that the reaction of P with CF3I is not limited to the condensed or liquid phase. Red phosphorus is also alkylated by trifluoro-iodomethane vapor over a copper catalyst The products are the same as in the liquid reaction but in reduced yield and different composition. The mono-and dialkylated compounds are the major products wliich is the reverse of the liquid system where the tris (trifluoromethyl)phosphine is usually the dominant product. This indicates that the phosphorus dihalide is a primary product of the reaction and not a decomposition or disproportionation product. 

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