Sustainable Synthesis of Amides from Carboxylic Acids and Equivalent Amounts of Amines Using a Reusable Brønsted Acidic Ionic Liquid as a Catalyst and a Solvent

The simple and easily prepared Brønsted acidic ionic liquid (BAIL) could act as both the solvent and catalyst and could be easily recovered and reused at least six times without considerable loss in catalytic activity. Moreover, the direct amidation of carboxylic acids and amines in a stoichiometric proportion could be catalyzed efficiently by BAIL with a broad substrate scope, a multigram scale, and a significant sustainability improvement [scalable up to 100 mmol, (process mass intensity) PMI (reaction and purification) < 3]. Notably, the water formed during condensation did not inhibit the direct amidation. This protocol could be used to efficiently, greenly, and sustainably prepare amides and has broad applications in organic chemistry.