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 paraformaldehyde 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.