Synthesis of 4-diazo-3,5-dinitropyrazole and characteristic features of its behaviour towards nucleophiles

Diazopyrazole containing two nitro groups in the ring – 4-diazo-3,5-dinitropyrazole – has been synthesised for the first time by diazotisation of the corresponding aminodinitropyrazole. 4-Diazo-3,5-dinitropyrazole reacts with salts of methylene-active compounds, CH₂(CN)NO₂ and CH₂(COCH₃)₂, to give azo coupling products, whereas its interaction with nucleophiles such as Br^–, N₃ or H₂O(H⁺) involves replacement of one of the nitro groups yielding 4-diazo-3-R-5-nitropyrazoles.