[Cu(bpdo) 2·2H2O]2+ /montmorillonite: a highly effective and recyclable catalyst for the synthesis of 2‑amino‑4H‑chromenes, 2‑amino‑4H‑benzopyrans and spiroacenaphthylene derivatives via MCR in aqueous media

Abstract

[Cu(bpdo)2·2H2O]2+/Montmorillonite was successfully prepared by impregnation method and characterized by XRD, FESEM, EDS, ICP, FT-IR, and TGA. The XRD patterns show swelling of montmorillonite layers, leading more absorption of the Cu (II) complexes. The catalytic activity of this novel nanocomposite was investigated in the efficient synthesis of 2-amino-4H-chromene and 2-amino-4H-benzopyran derivatives via Multicomponent Reactions (MCRs). A wide range of substituted benzaldehyde, malononitrile (or ethyl cyanoacetate), and diverse enolizable C–H activated acidic compounds were reacted in the presence of [Cu(bpdo)2·2H2O]2+/Mont, in EtOH/H2O under reflux conditions to afford the corresponding 2-amino-4H-chromene and 2-amino-4H-benzopyran derivatives. In addition, spirochromene and spiroacenaphthylene derivatives were synthesized successfully in the presence of [Cu(bpdo)2·2H2O]2+/Mont under reflux conditions in EtOH/H2O. Some advantages of this method involved efficiency and rapidness leading to short reaction times, easy workup procedure, high yields, and recyclable green catalyst and being performed under eco-friendly conditions. This novel nanocatalyst was easily separated, recovered, and reused at least for five times without noteworthy loss in its catalytic activity and performance.