Synthesis of substituted 3-phenyl-6H-pyrazolo[4,3-d]isoxazoles from corresponding 4-benzoyl-5-hydroxypyrazoles

Treatment of 1,(3)-(di) substituted 4-benzoyl-5-hydroxypyrazoles with phosphorus oxychloride affords the corresponding 4-benzoyl-5-chloropyrazoles. Reaction of the latter with hydroxylamine leads to oximes, which can be cyclized to novel 3-phenyl-6H-pyrazolo[4,3-d]isoxazoles by treatment with sodium hydride in dimethyl formamide. Detailed nmr spectroscopic studies (H-1, C-13) with all obtained compounds are presented.