REACTION OF 4-HYDROXY-5-OXIMINO-3-THIOPHENECARBOXYLATES WITH HYDRAZINES - FORMATION OF PYRAZOLYLTHIOHYDROXAMIC ACIDS

The reactions of 4-hydroxy-5-oximino-3-thiophenecarboxylates with hydr azine 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 S ilberstrom. Two alternate mechanisms are proposed which account for th e regiochemical outcome. The structures of the pyrazole3- and 5-thiohy droxamic acids and corresponding nitriles have been proven by independ ent synthesis, comparison to known compounds, and by proton and carbon magnetic resonance and long range HETCOR experiments.