Potentially chemotherapeutic purine analogues. Part V. Some hydrazone derivatives of pyrazole-4,5-diones and their cyclisation to pyrazolo-[3,4-e][1,2,4]triazines
Abstract
4-Thiosemicarbazones of pyrazole-4,5-diones are prepared by the reaction of thiosemicarbazide with the diones themselves or with 4-p-diethylaminophenylimino-, 4-hydroxyimino-, or 4,4-dibromo-pyrazol-5-one. Cyclisation of 4-thiosemicarbazonopyrazol-5-ones under alkaline conditions leads to pyrazolo [3,4-e][1,2,4]triazine-3-thiols. The latter and their derivatives are of interest as potentially chemotherapeutic purine analogues.