Thiatriazoles Substituted with C-Radicals

The 5-arylthiatriazoles, on the other hand, are as a rule quite stable, although they decompose on melting with the formation of nitrogen, 

Whereas a number of 5-aryl thiatriazoles have been reported, the only previously known true aliphatic and alicyclic representatives were 5-tert-butyl31 and cyclohexyl thiatriazole.32 These are unstable oils that decompose at 0° with nitrogen evolution and formation of sulfur. They are prepared from the corresponding thioacylhydrazides and nitrous acid, but the method is not generally applicable because of difficulties in obtaining the required aliphatic thioacylhydrazides.1 Wijers et o/.17 have found that aliphatic thiatriazoles can be prepared from 1-acetylthio-l-alkynes. Thus a substance believed to be 5-pentylthiatriazole was isolated from the reaction between 1-acetylthio-l-hexyne and ammonium azide. It is an oil that solidifies at about —16° and could not be analyzed because of its explosive character and poor stability at room temperature. Its formation is explained by the following scheme [Eq. 

The structure is in part inferred from the observation that in boiling tetrahydrofuran the substance loses nitrogen and sulfur and gives pentyl cyanide. The absence of absorption in the neighbourhood of 2150 cm-1 indicative of an azide group excludes the thioacyl azide structure.17 

It is remarkable that thermal decomposition in polar solvents (dimethyl formamide, tetrahydrofuran) gives pentyl cyanide whereas in a nonpolar solvent (decane, 150°) pentyl cyanide is formed together with pentyl isothiocyanate in a 4 1 molar ratio. The same ratio is obtained on injecting 5-pentylthiatriazole into glass wool heated at 350° in an evacuated flask. 

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. 

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