Methionine-ethylenediaminetetraacetic acid-chitosan magnetic nanocomposite: A multifunctional organocatalyst for green heteroannulation of imidazoles

Abstract

Straightforward procedure for the preparation of a novel magnetic decorated DL-methionine amino acid grafted onto the chitosan backbone using EDTA linker (CS−EDTA−MET@Fe₃O₄) is described. The supramolecular CS−EDTA−MET@Fe₃O₄ nanocomposite was properly characterized using FTIR, EDX, XRD, FESEM, TGA, DTA and VSM methods. The obtained CS−EDTA−MET@Fe₃O₄ nanomaterial was then investigated, as a multifunctional heterogeneous organocatalyst, to promote the heteroannulation of a wide range of imidazoles through multicomponent reactions strategy. The three- and four-substituted imidazole derivatives, as an important pharmaceutical scaffold, were smoothly synthesized from benzoin or benzil, different aldehyde derivatives, and NH₄OAc as well as aromatic or aliphatic amine derivatives in EtOH. The CS−EDTA−MET@Fe₃O₄ nanocatalyst exhibited high catalytic activity, selectivity, and stability to promote the multi-component condensations. The key advantages of the present protocol are high to excellent yields, the use of a low loading renewable, bio-based and biodegradable chitosan- as well as amino acid-based nanomaterial, and simple procedure for the preparation of CS−EDTA−MET@Fe₃O₄ nanomaterial. In addition, the catalyst's properties including its magnetic properties and appropriate surface area characteristics contribute to its excellent catalytic performance. Furthermore, the CS−EDTA−MET@Fe₃O₄ nanocatalyst can be used for up to six cycles in the synthesis of imidazole derivatives with only a slight decrease in its catalytic activity.