Magnetic nanostructure-anchored mixed-donor ligand system based on carboxamide and N-heterocyclic thiones: An efficient support of CuI catalyst for synthesis of imidazo[1,2-a]pyridines in eutectic medium

Abstract

A Cu-incorporated nanocatalyst has been developed by immobilizing copper iodide on a magnetically retrievable mixed-donor ligand system, containing carboxamide, imidazolidine-2-thione and imidazole-2-thione donor groups and characterized by various analysis techniques such as FT-IR, XRD, FE-SEM, EDX elemental mapping, TEM, ICP-OES, TGA, and VSM. The versatility of the synthesized nanocatalyst has been demonstrated for the one-pot synthesis of imidazo[1,2-a]pyridine derivatives via three-component reaction of 2-aminopyridines, aldehydes and alkynes using tetrabutyl ammonium bromide/glycerol (TBAB/glycerol) deep eutectic mixture as a sustainable medium. The nanocatalyst has exhibited high activity and stability under the reaction conditions with a negligible copper leaching, which can be due to the effective coordination interaction between the oxygen atom of carbonyl group as well as the sulfur atoms of thiocarbonyl groups in the supported ligand with copper iodide. The catalyst system can be readily recovered and successfully reused at least five times. Eco-friendly conditions, solvent recoverability, higher TON, wide functional group tolerance and lower E factor (0.2) are some other merits of the present work.