Ionic Liquids Catalyzed Friedel–Crafts Alkylation of Substituted Benzenes with CCl4 Toward Trichloromethylarenes

Abstract

An ionic liquid catalyzed Friedel–Crafts alkylation reaction of substituted benzenes with CCl4 was developed. The reaction proceeded efficiently under mild conditions, gave corresponding trichloromethylarenes with diversity functional groups in moderate to good yields. The influence of Lewis acidity of ionic liquids on the conversion of the alkylation reaction has been investigated. Notably, the probable mechanism of this reaction has been proposed with the assistance of 27Al NMR spectroscopy. It was noteworthy that the predominance of [Al2Cl7]− species in EmimCl–AlCl3, N = 0.67 could be detected by 27Al NMR spectral analysis, and [AlCl4]− was generated at the beginning of reaction. Additionally, it was found that [AlCl4]− could be transformed into [Al2Cl7]− when the reaction finished. Some control experiments confirmed that the interaction between Lewis acidic species [Al2Cl7]− of the ionic liquid and CCl4 led to the change in speciation of aluminum during the alkylation reactions.