Ionic liquids as exceedingly convenient solvents for the Friedel-Crafts monoalkylation of electron-rich arenes with paraformaldehyde using HCl as catalyst

Friedel-Crafts hydroxyalkylation of 2-methoxynaphthalene, anisole and 2-methylfuran with parafermaldehyde has been carried out in N-ethyl-N'-methylimidazolium chloride (1(+)Cl(-)) or N-butyl-N'-methylimidazolium hexafluorophosphate (2(+)PF(6)(-)) or ethanol using concentrated aqueous HCl as catalyst. The results have shown an extraordinary activity and selectivity towards the formation of the corresponding hydroxymethyl derivative using 2(+)PF(6)(-) as solvent. This sharply contrasts with the case of the ethanol as solvent wherein the reaction is much slower and diarylation products are largely formed.