Reaction Products of Thiosemicarbazide with 1, 5-Diarylpent-1-Yne-3, 5-Diones

Acetylenic ß-diketones reacted with thiosemicarbazide to give either 6H or 3H, 6Hpyrazolo [1, 5-c] pyrimidinethiones depending on the nature of the substituents as well as the reaction conditions. The reaction of 2-aryl-5-phenyl-6H-pyrazolo [1, 5-c] pyrimidine-7-thiones with nitrous acid and benzenediazonium chloride gave the corresponding disulfide and phenylazo disulfide derivatives, respectively. With certain electrophiles, 3-substituted-7-thiones are formed. Moreover, oxidation with alkaline hydrogen peroxide afforded the respective pyrazolopyrimidinones.