Reactions

First, the Lewis Acid coordinates to the halogen atom from the acyl chloride, increasing the electrophilicity of the carbonyl carbon and making the halide a better leaving group. This interaction facilitates the departure of the chloride ion, leading to the formation of an acylium ion. This highly electrophile intermediate undergoes a nucleophilic attack from the aromatic compound, forming a resonance arenium ion intermediate. Finally, the last step of deprotonation regenerates the aromaticity and the catalyst. An important feature is that the reaction does not occur when the aromatic reagent contains electron-withdrawing group. Indeed, these latter would decrease the electron density of the aromatic, which disfavours the nucleophilic attack.