An efficient and chemoselective Brّnsted acidic ionic liquid-catalyzed N-Boc protection of amines

The first report of a Brّnsted acidic ionic liquid, 1-methylimidazolium tetrafluoroborate [(HMIm)BF4], catalyzed efficient and chemoselective N-Boc protection of various amines using (Boc)2O is presented. Optically pure amino alcohols and amino acid esters were converted efficiently to their corresponding optically pure N-Boc derivatives. The reported method is mild, solvent-free and has the advantages of both homogeneous and heterogeneous catalysis with high product yields, selectivity and ease of product separation.