1.2.4- Triazoline-3-thione

The synthesis of imidazo[2,Tc][l,2,4]triazolo-3-thiones has been investigated. For instance, the reaction of 1,2,4-triazoline-3-thione 361 <1995JHC275> with methyl trifluoromethanesulfonate affords the stable 3-methylmercapto-1,2,4-triazolium trifluoromethanesulfonate 362 in quantitative yield, which after treatment with sodium bicarbonate and bromine provides 6-bromomethyl-2,6-dimethyl-7-ethoxycarbonyl-2,3,5,6-tetrahydro-7//-imidazo[2,T4-[l,2,4]triazolo-3-thione 10 in 47% yield, via intermediate 363 (Scheme 36) <1996T791>. 

AT-Benzylhydrazino)-l,3,4-thiadiazole (14) rearranges quantitatively in the presence of HC1 to 4-amino-2-benzyl-l,2,4-triazoline-3-thione (15). In HCl-HOAc, (14) gives a mixture of (15) and (16). MO calculations indicate that the rr-electron stabilization is -0.61j8 units greater for the 4-amino-1,2,4-triazoline-3-thione system than for the 2-hydrazino-1,3,4-thiadiazole system (70ZC406). 

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