Successful application of an ionic liquid carrying the fluoride counter-ion in biomacromolecular chemistry: microwave-assisted acylation of cellulose in the presence of 1-allyl-3-methylimidazolium fluoride/DMSO mixtures.

The use of ionic liquids with fluoride anion (IL-F) is challenging because of side reactions. Neat 1-allyl-3-methylimidazolium fluoride (AlMeImF) is used as a solvent in microwave-assisted acylation of cellulose. The results are disappointing due to side reactions in the IL proper, and F(-) -mediated hydrolysis of the produced ester. A dramatic improvement is observed, when AlMeImF/DMSO mixture is employed. The results are comparable to those obtained when pure 1-allyl-3-methylimidazolium chloride is employed. FTIR spectroscopy shows that dissolving a carboxylic acid anhydride in IL-F leads to the formation of acyl fluoride. Thus ILs are far from being "spectator" solvents. The new approach (use of IL-F/DMSO) is attractive because of its efficiency, low cost, and applicability to the derivatization of any polymer.