Reaction of 4-Hydroxy-5-oximino-3-thiophenecarboxylates with Hydrazines. Formation of Pyrazolylthiohydroxamic Acids

Article abstract of DOI:10.1002/jhet.5570340210

The reactions of 4-hydroxy-5-oximino-3-thiophenecarboxylates with hydrazine and substituted hydrazines have been investigated. The products of the reactions have been shown to be pyrazole-3- or 5-thiohydroxamic acids rather than the hydrazones previously described by Benary and Silberstrom. Two alternate mechanisms are proposed which account for the regiochemical outcome. The structures of the pyrazole-3- and 5-thiohydroxamic acids and corresponding nitriles have been proven by independent synthesis, comparison to known compounds, and by proton and carbon magnetic resonance and long range HETCOR experiments.