1‐Aminopyrazolin‐5‐ones. Synthesis and reactivity

Abstract

Abstract A synthesis of 1‐aminopyrazolin‐5‐ones (I) by chloramine attack on the 2‐benzylpyrazolones (IVd‐e) has been accomplished. Nucleophilic substitution reactions of aminopyrazolones (I) are investigated; with 1,4‐diketones, N , N' ‐pyrrolylpyrazolones (XVIIa‐c) are obtained. Chlorination of acetylaminopyrazolones (VII) led to the corresponding 1‐amino‐5‐chloropyrazoles (XXI) via the isolable pyrazolo[3,2‐ b ]oxadiazoles (XIX).