Anion Dependent Imidazolium Protic Ionic Liquid Catalyzed Solvent-Free General Strategy for Chemoselective Fmoc and Cbz Protection of Amines and Their Chiral Analogues

摘要

An efficient solvent-free rapid transformation of amines to 9-fluorenylmethyloxycarbonyl protected amines derivatives (NHFmoc) is demonstrated using inexpensive and readily available Fmoc-Cl and moist imidazolium trifluoroacetateprotic ionic liquid as a powerful catalyst at ambient temperature. The scope of the chemo-selective protection strategy was successfully explored for the selective Fmoc protection of amino esters, amino alcohols, amino acids and amino phenol. The optically pure amino acids, amino acid esters and amino alcohols were efficiently converted into the corresponding N-Fmoc protected derivatives without racimization. Our study reveals that anionic part of the ionic liquid played vital role in the success of the protection of amines using Fmoc-Cl. The scope of the present method is extended for efficient benzyloxycarbonyl (Cbz,Z) protection of amines.