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 (¹H, ¹³C) with all obtained compounds are presented.