Copper-Based Metal-Organic Frameworks as Reusable Heterogeneous Catalysts for the One-Pot Syntheses of Imidazo[1,2-a]pyridines

A copper terephthalate metal-organic framework (Cu(BDC) MOF, BDC=1,4-benzenedicarboxylate) is used as a highly efficient heterogeneous catalyst for the one-pot, atom-economical synthesis of imidazo[1,2-a]pyridines that proceeds through the three-component coupling of aldehydes, aminopyridines, and nitromethane. This heterocyclic synthesis, which uses MOFs for the first time, involves an intermolecular aza-Michael addition with a subsequent intramolecular cyclization and uses air as an environmentally benign oxidant. This heterogeneous Cu(BDC) MOF can be reused without the loss of its activity. Its catalytic efficiency was also highlighted by comparing it with other catalytic systems that have been used for the syntheses of imidazo[1,2-a]pyridines. This procedure not only eliminates the use of environmentally hazardous reagents but also involves mild reaction conditions.