Bis-trifluoromethyl thioketene

Thioketenes (83) are generally unstable and very reactive, although bis (trifluoromethyl)thioketene (83 R1 = CF3) is stable enough for isolation. 

Raasch, and Schaumann and co-workers, have studied the reactions of bis (trifluoromethyl)thioketene (83 R1 = CF3) with alkenes, with thioketones, and with carbodiimides or Schiff-base imines. The products were, respectively, thietans, 1,3-dithietans (84 R1 = CF3), and 1,3-thiazetidines (85 R1 = CF3) (from the carbodiimide).114,115 With phenyl azide the 1,2,3,4-thiatriazoline (86 R = CF3) is formed subsequent pyrolysis yields2,l-benzisothiazole.114... 

As mentioned above (303) (Scheme 3.90, Eq. 1), bis-trifluoromethyl thioketene has the deoxygenating ability toward alkyl nitronates, which is also based on cycloaddition to the C=S bond. 

Bis(trifluoromethyl)thioketene (42) is sufficiently stable to handle. It readily adds to 2,3-dimethyl-1,3-butadiene to yield 43 (equation 28)28, l,2,4,7-(tetrakis)methylenecyclooc-tane gives 44 (equation 29)29 and cyclooctatetraene affords 46 via the valence isomer 45 (equation 30)30. 

The 1 1 adducts formed from bis(trifluoromethyl)thioketene and aryl azides are believed to be A -l,2,3,4-thiatriazolines based on NMR, IR spectroscopy and on thermolysis which leads to a product believed to be 2,1-benzisothiazole <78JOC2500>. 

Isothiocyanates (70LA(731)120) and bis(trifluoromethyl)thioketene (78JOC2500) have also been reported to add to benzalimines but these are undoubtedly special cases (Scheme 94). 

Bis(trifluoromethyl)thioketene reacts with some imines to form 1,3-thiazetidines (78JOC2500). One derivative has been used by Dupont in surface treatment of water-repellent textiles (71USP3592811). 

The dimer of bis(trifluoromethyl)thioketene is most useful as a precursor of its monomeric form, which is used to make a number of useful products (Scheme 133). The one illustrated is an antistatic agent for wool (67USP3337586). Others are also useful as textile treating agents (67USP3336334). 

Raasch33 has prepared 5-[2,2,2-trifluoro-l-(trifluoromethyl)ethyl]-thiatriazole from bis(trifluoromethyl)thioketene and hydrogen azide [Eq. (16)]. This highly volatile solid (m.p. 60.5-61°) is interesting in that it is thermally stable at 25°. At 100° it decomposes with formation of sulfur, but the other products were not determined. 

Thus, bis(trifluoromethyl)thioketene 156 reacts with hydrazoic acid to afford the 5-hexafluoropropyl-2-ene derivative that tautomerizes to hexafluoroisopropyl-l,2,3,4-thiatriazole 157. In contrast to other 5-alkylderivatives of 1,2,3,4-thiatriazole this compound was reported to be stable at room temperature (Scheme 37) <1970JOC3470>. 

It is known that aryl azides undergo 1,3-dipolar cycloaddition reaction with bis(trifluoromethyl)thioketene 156 to form the yellow A3-l,2,3,4-thiatriazolines 159 in very low to fair yield supporting the mechanism of reaction of this thioketene with hydrazoic acid (Equation 14) <1978JOC2500>. 

Adducts are formed from bis(trifluoromethyl)thioketene and aryl azides (78JOC2500). The yellow, crystalline products are believed to be the so far unknown A3-l,2,3,4-thiatriazo-lines (23 equation 50), as indicated by 19F and IR spectra and the formation of 2,1-benzisothiazole on thermolysis (Section 4.28.2.3.l(i)). 

Bis(trifluoromethyl)thioketene and aryl azides form orange 2 1 adducts, which can also be obtained from the thiatriazolines and one equivalent of bis(trifluoromethyl)thioketene. The structure of these adducts is unknown. 

Cycloadducts 249 are also obtained in the reaction of bis(trifluoromethyl)thioketene 248 with carbodiimides. ... 

Bis-(trifluoromethyl)thioketene undergoes cycloaddition to alkenes to give 2-methylenethietanes. ... 

Treatment of desaurin 572 with P4S10 leads to extensive rearrangement with incorporation of additional sulfur atoms in the products.The synthesis of the important dimer of bis(trifluoromethyl)thioketene 573 involves treating the tetra-ester 586 with Depending on conditions, two, three or... 

Acetyl groups in desaurins may be oxidized to carboxylic acid groups by sodium hypochlorite without affecting the basic bis(methylene)dithietane structure. Treatment of 575 with bromine in chloroform effects replacement of the two methine hydrogen atoms by bromine atoms.An unusual methylene-1,3-dithietane reacts with bis(trifluoromethyl)thioketene to give a complex structure embodying a new methylene-l,3-dithietane and a 2-methylenethietane. Bis-... 

Thioketenes are generally unstable and difficult to prepare. Therefore only few compounds have been studied. Bis(trifluoromethyl)thioketene reacts with a wide range of C=C and C=X bonds (equations 78-80). The products always result from addition across the 0=S bond of the cumulene. 

Figure 6.15 Absorption spectra of sulfur containing compounds. Top thiophenol (in heptane, ), thioxanthone (in hexane, ), thiourea (in water, ), bis(trifluoromethyl)thioketene (in isooctane, —).280 Bottom absorption ( ) and emission (—) spectra of adamantanethione in perfluoroalkane solvents.1257 The peak at the red edge of the S0—> Si transition coincides with the 0 0 band of phosphorescence and is attributed to S0—>T-i absorption...

Although monomeric thioketenes are generally highly unstable, Raasch has found that bis(trifluoromethyl) thioketene (20) is stable enough to handle and that it is excellent dienophile. Some examples of its reactions are compiled in Scheme 5-XIX.34 47... 

It should be pointed out that the oxidation of quadricyclane-bis(trifluoromethyl)-thioketene cycloadduct 46 by MCPBA (25°C, 2 days) was reported to proceed without oxidation of either hydrocarbon or fluorinated double bonds, leading to selective formation of the corresponding sulfone, isolated in 92% yield. ... 

Raasch, M.S. Bis(trifluoromethyl)thioketene. I. S3mthesis and cycloaddition reactions. 

Dimerization and analogous cycloadditions of thiocarbonyl compounds also lead to 1,3-dithietans. Adamantanethione on irradiation or on treatment with methanesulphonic acid gave the dimer, containing a 1,3-dithietan ring, and 2-isopropylidene-5,5-dimethyl-6-oxo-l,3-oxathian-4-thione also dimerized on irradiation. Bis(trifluoromethyl)thioketen reacted with a variety of thiocarbonyl compounds, including isothiocyanates, to give 2-(hexafluoroisopropylidene)-l, 3-dithietan derivatives. ... 

The formation of 2-alkylidene-l,3-diselenoles by the photolysis of 1,2,3-selenadiazoles suggested to the investigators the intermediacy of selenoketens. The tetramerization of bis(trifluoromethyl)thioketen (100), which was found to take place only in the presence of selenium, was considered by Raasch to depend on the transient existence of the seleno-carbonyl intermediate (338). The preparation of transition-metal complexes... 

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