Ligand-free catalytic system for the synthesis of diarylethers over Cu2O/Cu-CNTs as heterogeneous reusable catalyst

Various substituted diarylether derivatives were prepared by using heterogeneous reusable Cu₂O- and Cu-coated carbon nanotubes (Cu₂O/Cu-CNTs) as catalyst under ligand-free conditions, which provided good to excellent yields. The catalyst was characterized by TEM, XRD, and AAS analysis. The effects of solvent, base, and amount of catalyst for the O-arylation were investigated. The catalyst could be recovered by simple filtration from the reaction mixture without further treatment and reused several times with consistent catalytic activity. In addition, CNTs could also be recovered from the used Cu₂O/Cu-CNTs by a simple acid treatment.