Dual Activation of Carboxylic Acid Functionality by Protic Ionic Liquid: Solvent and Metal Free Strategy for Selective Esterification of Alcohols and Acylation of Aromatic Amines

Highly efficient and chemoselective esterification of alcohols and acylation of aromatic amines with carboxylic acids using imidazolium based protic ionic liquid, 1-butyl-imidazolium trifluoroacetate ([HBIm]TFA) as activator has been realized under organic volatile solvent free condition. The protic ionic liquid played dual role for activation of carboxylic acid which was proved by NMR study. A very interesting aspect of the present protocol is the acylation of less basic aromatic amines than the more reactive aliphatic amines as the later one forms salt with carboxylic acid. Our methodology offers several advantages like high yield, fast, efficient, chemo-selectivity, metal and other coupling agent free procedure, recyclability of ionic liquid used and formation of water as the only by-product.