Acylation of salicylamide to 5-acetylsalicylamide using ionic liquids as dual catalyst and solvent

The Lewis acidic ionic liquids, 1-butyl-3-methylimidazolium chloroaluminate ([BMIM]Cl-nAlCl3) and N-butylpyridinium chloroaluminate ([BPy]Cl-nAlCl3), were used as both catalyst and solvent in Friedel–Crafts acylation of salicylamide with acetyl chloride to 5-acetylsalicylamide. The Lewis acidic ionic liquids, substituting for the conventional carcinogenic nitrobenzene solvent and anhydrous AlCl3 catalyst, showed excellent catalytic activity in the acylation of salicylamide to 5-acetylsalicylamide. When [BMIM]Cl-2AlCl3 was used as the catalyst, the yield of 5-acetylsalicylamide reached 81.3%. When [BPy]-2AlCl3 was used as the catalyst, the maximum yield of 5-acetylsalicylamide was 89.2%. The content of AlCl3 and the structure of the cations in the ionic liquids had synergistic effect on the acylation reaction.