Mild and eco‐friendly chemoselective acylation of amines in aqueous medium using superparamagnetic nanoparticles as a highly efficient and recyclable catalyst

Acylation of amines is a basic and important reaction in organic chemistry. Many pharmacological molecules possess at least one amide bond [1]. Several methods for acylation have been developed, among them N‐acylation reaction is commonly carried out with acetic anhydride or acetyl chloride in the presence of either acidic or basic catalysts under various conditions [2]. Guanidine acetic acid (GAA) is the essential precursor of creatine, and belongs to the class of guanidino compounds that are characterized by the presence of a basic guanidine group. GAA has a carboxylic acid group that facilitates the linkage of the compound to a magnetite support and the guanidino group renders it suitable to serve as a complexing agent for most transition metal ions. Herein, we report the rapid and highly selective N‐acylation of amines using thioacids in water at room temperature mediated by copper‐grafted GAA‐modified magnetite nanoparticles (Fe3O4@GAA‐Cu(II)).Robust and effective Fe3O4@GAA‐Cu(II) as a green, superparamagnetic and recoverable nanocatalyst for N‐acylation of a variety of amines was synthesized and studied. When thioacetic acid is used as the acylation agent in water, N‐acylation can be carried out to afford corresponding products in excellent yields and short time. This method is found to be highly selective for amines and not sensitive to other functional groups such as thiol, phenol and amino acids. Mild reaction conditions, high selectivity, efficiency, simple workup and excellent yields are some of the major advantages of the procedure