Synthesis of Imidazole Adducts of BH3, BF3, and B3H7 and Comparison of Their Nucleophilic Substitution Reaction Activity

Abstract

N-Methylimidazole borane adducts were synthesized and their reactivities with different electrophiles after deprotonation were compared. Subsequently, we used the more stable and reactive imidazole adducts with B₃H₇, a multinuclear borane, to generate various C2, C2 benzyl, and C2,5-disubstituted imidazole adducts of B₃H₇ under mild reaction conditions. Some 2,5-disubstituted imidazole products are usually difficult to synthesize directly from imidazole molecules. Furthermore, the borane moiety of these adducts can be easily removed to obtain the corresponding imidazoles. The higher reactivity of the imidazole adducts of B₃H₇ compared to their corresponding imidazoles may be attributed to the σ-aromaticity of B₃H₇ or mediated by double hydrogen bonds.