A Concise One‐Pot Synthesis of 3,4‐Diaryl‐1 H ‐pyrazoles from Natural Isoflavones and Hydrazine Hydrate

An efficient protocol has been developed for the preparation of a series of new 3,4‐diaryl‐1 H ‐pyrazoles, potential pharmacological and agricultural targets, by the reaction of hydrazine hydrate with different natural isoflavones or their derivatives. The target compounds were obtained in good‐to‐excellent yields (80–95%; Table 2 ) under fairly mild reaction conditions (80°) tolerating various functional groups. The new compounds were fully characterized, and the single‐crystal X‐ray structures of 3,5‐diethoxy‐2‐[4‐(4‐ethoxyphenyl)‐1 H ‐pyrazol‐3‐yl]phenol ( 26 ) and of the peracetylated compound 2‐{1‐acetyl‐4‐[4‐acetoxy‐3‐(diacetylamino)phenyl]‐1 H ‐pyrazol‐3‐yl}‐5‐acetoxyphenyl acetate ( 35 ) were solved ( Figure ).