Semicarbazone and Thiosemicarbazone of 5-acetyl-3-(methylsulfanyl)-1,2,4-triazine

Semicarbazone as well as thiosemicarbazone of 5-acetyl-3-(methylsulfanyl)-1,2,4-triazine were synthesised as reactive intermediates for the synthesis of 1H-pyrazolo[4,3-e][1,2,4]triazine derivatives via acid promoted ring closure [1,2,3].

Starting ketone 1 was prepared according to a reported procedure [4]. To a solution of ketone 1 (169 mg, 1 mmol) and semicarbazone or thiosemicarbazone (1.2 mmol) in ethanol (20 ml) 10% HCl (0.5 ml) was added. The resulting reaction mixture was heated at reflux for 5 min and then stirred at room temperature for additional 30 min. The precipitated solid was filtered off, recrystallized from dioxane and dried under vacuum.