Abstract A novel Brönsted acidic room temperature ionic liquid (1-H-3-methyl-imidazolium bisulfate) is found to catalyze efficiently the acetylation of a wide rang of alcohols as well as phenols with acetic anhydride in good to excellent yields at 50 C under solvent-free conditions. Products are easily isolated by extraction with ether and the protocol is mild and green, compared to the existing method based on toxic solvents.
