The mechanistic and synthetic chemistry of imidazole-based superelectrophiles has been studied. The protonated imidazole ring, or imidazolium group, is shown to enhance the electrophilic reactivity of an adjacent carboxonium group (compared to a related monocationic species). This leads to efficient condensation reactions between imidazole aldehydes and ketone with arenes in the Brønsted superacid CF3SO3H. The imidazole-based superelectrophiles are shown to be useful in other reactions leading to functionalized heterocycles. The imidazolium group may also trigger charge migration reactions in dicationic species.