Synthesis of Energetic Material 4-Nitro-3,5-bis(trinitromethyl)-1H-pyrazole via [4 + 1] Cycloaddition

The synthesis of highly nitrated pyrazole derivatives, such as 4-nitro-3,5-bis(trinitromethyl)-1H-pyrazole, is challenging due to thermal instability and limited available ring sites. In this work, a novel, efficient synthetic route combining nucleophilic substitution and [4 + 1] cycloaddition skeletal editing was developed, achieving compound 1 in five steps with a 44.1% yield and its ammonium salt in four steps with a 56.5% yield. This strategy offers a promising approach for the efficient synthesis of poly-nitrated pyrazoles, marking the first use of skeletal editing of [4 + 1] cycloaddition in energetic material synthesis.