Hexafluorothioacetone dimer

Hexafluoropropene and sulfur react at 425 °C in the vapor phase to give hexafluorothioacetone and its dimer [/]. In dimethylformamide, it reacts with potassium fluoride and sulfur to give hexafluorothioacetone dimer, which further reacts with hexafluoropropene to give the E and Z isomers of perfluoro-2,4,6-tris(trifluoromethyl)-5-thia-3-heptene [2] (equation 1). 

Earlier methods of preparing 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dlthletane (hexafluorothioacetone dimer, HFTA dimer) include the reaction of hexafluoropropene (HEP) and sulfur over a carbon bed at 425< C,3 and the reaction of HFP and sulfur in tetramethylene sulfone at 120°C 1n the presence of potassium fluoride (autoclave). Dimethylformamide appears to be a far superior solvent for this reaction, permitting the use of atmospheric pressure and modest temperatures, as well as affording a cleaner product. 

Treatment of hexafluorothioacetone dimer, (CF8)2C S C(CF8)2 S, withKF-HgF2 in DMF also provides a solution containing bis(perfluoroisopropyIthio)mercury.i ... 

CF2 CFa CF2 CF SAg (not isolated) -- (with EtI at 75 °C) CF2 CF2 CF2 CF SEt (21%). Raman and photoelectron spectral data are available for some CFs S-compounds, and so are e.s.r. parameters for the radical CFs S CHs-CBu a [generated via photolysis of a solution of the appropriate olefin in (CFs-S)2]. Unsuccessful attempts have been made to generate a radical anion via electrochemical or chemical (NaK alloy) reduction of 3,4-bis(tri luoromethyl)-l,2-dithieten. i Reactions between trifluoromethanesulphenyl chloride and JV-chloro-amines are portrayed in Scheme 26 (p. 216) and some involving hexafluorothioacetone dimer in Scheme 27 (p. 217) many unsuccessful attempts are claimed to have been made to isolate bis(trifluoromethyl)methanethiol from the products of the reactions of the dimer with amines, the conversion into hexafluoroisopropylidenimines being... 

Thietans substituted with two trifluoromethyl groups (143) are obtained by treatment of hexafluorothioacetone dimer (142) and olefins (e.g. cyclohexene, dimethyl maleate) with potassium fluoride-DMF. ... 

Many cycloaddition reactions have been carried out with ketenes and thioketones. The products are thiolactones (52). Hexafluorothioacetone and diphenylketene, however, do not undergo cycloaddition even after prolonged heating at 100°C. Good results can be obtained when the more stable dimer of this fluorinated thioketone (53) is used. Anionic monomer 54 could be released by the action of potassium fluoride in an aprotic solvent. Two-step cycloaddition to diphenylketene yields ketone 55. 

With slight modification, the methods used to prepare fluorothioacyl fluorides can also be used for synthesis of fluorothioketones. Hexafluorothioacetone, the member of this class that has been studied most extensively, is readily obtained by high-temperature reaction of hexafluoropropylene and sulfur (53). The thio-ketone is a deep-blue liquid, bp 8° C, that dimerizes on standing to 2,2,4,4-tetrakis-(trifluoromethyl)-l,3-dithietane. 

The hexafluorothioacetone is isolated as its dimer, 2,2,4,4-tetrakis(trifluoro-methyl)-f,3-dithietane, which forms immediately. In the case of the tri- and tetrasulfides, excess triphenylphosphine is used to remove the extra sulfur atoms by formation of triphenylphosphine sulfide. 

Fluorothioketones are more difficult to polymerize. There are two reasons. First, agents that promote polymerization also catalyze dimerization to dithi-etanes, which is a very fast reaction. Second, ceiling temperature of polymerization is low with the result that polymer decomposes back to monomer as it is being isolated. However, poly(hexafluorothioacetone) can be formed at very low temperatures by initiation with dimethylformamide or BF3 etherate, even though at — 78° C the only product isolated is 2,2,4,4-tetrakis(trifluoromethyl)-l,3-di-thietane. 

The dimer of hexafluorothioacetone may also be obtained from hexafluoropropene [259] and the former has now been used in a route to a sulphene [260] (Figure 8.98). 

In a paper dealing with the reactions of methylenediphosphines with hexa-fluoroacetone (HFA) and hexafluorothioacetone (HFTA) dimer, Roschenthaler... 

The most easily accessible compounds of this class are 1,3-dithietanes. They are formed by a spontaneous dimerization of fluorinated thioketones or acyl halides. Thus, hexafluorothioacetone 34, generated in the reaction of bis(perfluoroisopropyl) mercury with molten sulfur at about 450°C (Scheme 2.18), undergoes at ambient temperature slow dimerization to form dithietane 35. This dimerization is significantly accelerated by catalytic amount of base, such as pyridine. At elevated temperature, the dimer 35 can be converted back into 34. 

Bicychc 2,2-bistrifluoromethyl thiepine 123 is synthesized in moderate yield by CsF-catalyzed reaction of cycloheptadiene-1,3 with the cyclic dimer of hexafluorothioacetone (Fig. 10.47). ... 

When they react with diazomethane, aromatic thiones are dimerized with incorporation of a methylene group (108). Benzophenone is recalcitrant to this treatment. Hexafluorothioacetone participates in a similar process, but the... 

The dimer of hexafluorothioacetone (217) reacts, as shown in Scheme 8, with mercuric fluoride-potassium fluoride to give the mercuric mercaptide of perfluoropropane-2-thiol in DMF, potassium flucnide promotes the reaction of (217) with alcohols, thiols, thiophenols, and olefins to give products derived from the thioacetone monomer. Reaction with styrene gave the bis-Diels-Alder adducts (218) and (219) thietan (220) is obtained with cyclohexene. Amino-alcohols, o-aminophenol, o-aminothiophenol, and o-phenylenediamine yield 2,2-bis(trifluoromethyl)-l,3-het ocyclic derivatives, e.g. (221). 1,3-Dithietans did not react with Fe2(CO) and were discarded as possible intermediates in the ortho-metallation reactions of thiobenzophenones. The hydrolysis reactions of a 1,3-cyclodisiladithietan and its reaction with o-hydroxymercuribenzoic acid have been investigated. ... 

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