Lithium perchlorate-catalyzed Boc protection of amines and amine derivatives

A new mild and chemoselective method for mono-N-protection of amines and amine derivatives as tert-butoxycarbonyl derivatives is reported. The reaction proceeds with lithium perchlorate (20 mol %) and pyrocarbonates, and shows general applicability. The catalytic action of LiClO4 is specific for the activation of Boc(2)O, thus acid-sensitive functionalities of the starting materials remain unchanged in the protection process. This procedure works well for sterically hindered primary arnine as well as electron-deficient primary arylamines, primary and secondary amino alcohols, alpha-amino acid esters, hydroxylamines, hydrazines and sulfonamides.