Synthesis of the Energetic Material 4-Nitro-3,5-bis(trinitromethyl)-1 H -pyrazole through Two Synthetic Strategies

4‑Nitro‑3,5‑bis(trinitromethyl)‑1H‑pyrazole (1) is an intriguing and highly substituted polynitro pyrazole featuring two symmetric trinitromethyl groups and a 4‑nitro‑functionalized pyrazole core, which poses a formidable challenge for its concise synthesis. Herein, we describe the development of two complementary synthetic strategies toward compound 1. The symmetric trinitromethyl moieties are efficiently installed via nucleophilic substitution followed by a two‑step nitration sequence, starting from commercially available 3,6‑dichloro‑1,2,4,5‑tetrazine (13). Initially, a Knorr pyrazole approach was developed starting from commercially available ethyl acetoacetate; although the pyrazole ring could be efficiently constructed using hydrazine acetate, this route suffers from a relatively long synthetic sequence and low overall yield. Alternatively, a [4 + 1] cycloaddition strategy was investigated, which delivered the 4‑aminopyrazole intermediate in a single step. Subsequent oxidation of the amino group, followed by a high‑yielding nitration, successfully generated the 4‑nitropyrazole scaffold and enabled the highly efficient synthesis of 1 in only 5 steps.