SYNTHESIS OF 5-ß-KETO-1,2,4-OXADIAZOLES AND CONVERSION OF 5-ß-KETO-1,2,4-OXADIAZOLES TO N-PYRAZOLYL AMIDOXIMES

摘要

The disclosed invention relates to a process for preparing 5-β-keto-1,2,4-oxadiazoles of formula (I), and conversion of 5-β-keto-1,2,4-oxadiazoles (I) into N-pyrazolyl amidoximes of the formula (II) through reaction with hydrazine. The process is defined by two steps. An amidoxime, which may be prepared in situ, is condensed with a β-keto ester to form a 5-β-keto-1,2,4-oxadiazole. The 5-β-keto-1,2,4-oxadiazole is subsequently reacted with hydrazine to furnish the desired N-pyrazolyl amidoxime. The disclosed invention provides several advantages over the current state of the art for the synthesis of N-pyrazolyl amidoximes, which require the condensation of a pyrzolylamine with an actived substrate and subsequent reaction with hydroxyl amine. N-pyrazolyl amidoximes are useful synthetic intermediates, especially for the preparation of photographic developing chemicals.