A bi-alkyl-bridge strategy for highly thermally stable tetrazoles via enhanced conjugation

In this study, we introduced the “bi-alkyl-bridge” strategy to synthesize a bi-alkyl-bridged cyclotetrazole energetic material. This method improves the stability by introducing an alkyl bridge at the C and N positions of the tetrazole to form a bi-alkyl-bridged structure. The formed parallel ring structure effectively improves the degree of conjugation of the compound and improves the stability. The target compound ( 3 ) exhibits a high decomposition temperature ( T d = 289 °C), which is significantly superior to its mono-alkyl-bridged analogues, the C-bridged ( 1 , T d = 223 °C) and N-bridged ( 2 , T d = 200 °C) tetrazoles. This strategy realized the successful synthesis of bi-alkyl-bridged cyclotetrazole compounds, and further clarified the advantages of the bi-alkyl-bridged structure by comparing with two alkyl-bridged tetrazole compounds. The bi-alkyl-bridge strategy of this work provides new insights into the synthesis of new heat-resistant energetic materials in the future. ● A bi-alkyl-bridge strategy is realized to construct highly stable tetrazoles. ● Target 3 achieves enhanced thermal stability (Td = 289°C) and low sensitivity ● Enhanced conjugation and aromaticity drive the superior stability of compound 3.