Application of functional metal anionic Lewis acid ionic liquids in the alkylation of chlorobenzene/SOCl2

4,4'-Dichlorodiphenyl sulfoxide is the main raw material for the manufacture of polysulfone, polyether sulfone and other engineering plastics. It is also an intermediate for medicines, dyes and pesticides, which has been widely utilized in engineering plastics, fine chemicals and other fields. The alkylation of chlorobenzene with thionyl chloride can give 4,4'-dichlorodiphenyl sulfoxide as a product using Lewis acidic ionic liquids. In this work, metal-based methylimidazolium ionic liquids were synthesized, which were found to be efficient catalysts for alkylation reactions. The molar ratio of different metal chlorides to 1-butyl-3-methyl imidazole chloride and the influence of different metal chlorine additives on the catalytic Lewis acid center were investigated. The fissionable species of AlCl₃ in ionic liquids will enhance the acidity of ionic liquids and, thus, promote the catalytic performance of ionic liquids. Under the optimized reaction conditions, the conversion rate of excess chlorobenzene was 45.3% and the selectivity of 4,4'-dichlorodiphenyl sulfoxide was 31.9%.