Synthesis of derivatives of 1,2,4-triazin-3-thione and 5-amino-2-acyl-2,3-dihydro-1,3,4-thiadiazolium salts from 1,2-dicarbonyl compounds and 4-substituted thiosemicarbazides

The reactions of methyl- and phenylglyoxal with 2,4-disubstituted thiosemicarbazides and of diacetyl with 4-monosubstituted thiosemicarbazides gave monothiosemicarbazones which were converted in trifluoroacetic acid into previously unknown 5-amino-2-acyl-2,3-dihydro-1,3,4-thiadiazolium salts. Diacetyl monosemithiocarbazones are cyclized to 5-methylene-1,2,4-triazin-3-thiones which are also obtained in the reaction ofdiacetyl with 2,4-disubstituted thiosemicarbazides. In particular cases the monothiosemicarbazones are converted into the corresponding 5-alkoxy-1,2,4-triazin-3-thiones in the presence of alcohols. The 3-thio-1,2,4-triazinium cations are formed from the 5-methylene- and 5-alkoxy derivatives in trifluoroacetic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1418–1425, October, 1992.