Process for alkenes cyclopropanation into high-energy fuels by ionic liquid catalysis

High-energy fuels are widely used in the aerospace industry, and cyclopropane-based high-energy fuels have attracted to their high intramolecular energy and density. However, the precise synthesis of these compounds remains a significant challenge due to the low reactivity of carbene intermediates. Herein, ionic liquids (ILs) are proposed to catalyze alkene cyclopropanation. Among the catalytic performance of 14 ILs, N-butylmethylbenzimidazole trifluoroacetate ([BMBIm][TFA]) achieves excellent conversion (99.9%) and selectivity (97.5%). This catalyst also exhibits good substrate versatility (11 alkenes). Experimental and theoretical results confirm the synergistic catalysis of IL cations and anions: (1) The cation interacts with dicyclopentadiene through π-π interactions, effectively enhancing alkene adsorption. (2) The anion forms a highly reactive carbene intermediate, enhancing the electrophilicity of the Zn carbene to facilitate cyclopropanation. This work enables highly selective, efficient, and safe alkene cyclopropanation, offering a promising route for the industrial production of cyclopropane-based high-energy fuels.