A Short Review on the Synthetic Efforts Toward Hexaazaisowurtzitane Based Energetic Derivatives

As a multi-nitrogen caged skeleton, hexaazaisowurtzitane endows its energetic derivative CL-20 with outstanding energetic properties, making it a classic compound in energetic material synthesis. In this review, we focus on summarizing and comparing the different synthetic routes of CL-20, as well as CL-20 analogues containing other energetic groups, starting from the construction of multi substituted hexaazaisowurtzitanes. The synthesis of multi-substituted hexaazaisowurtzitane is directly related to the chosen substituents, and the electronic effects of the substituents is crucial for the successful formation of the hexaazaisowurtzitane skeleton. Substituents with conjugation effects similar to benzyl group are the most promising substituent structures. The different heat and gas release characteristics of nitration and nitrolysis bring significant differences in the subsequent processes, which deserve significant attention. In addition, modifications to N-NO₂ have brought about a series of new energetic analogues, but so far, these compounds still have a long way to go before large-scale applications.