Fe3O4-supported N-pyridin-4-amine-grafted graphene oxide as efficient and magnetically separable novel nanocatalyst for green synthesis of 4H-chromenes and dihydropyrano[2,3-c]pyrazole derivatives in water

Fe3O4-magnetized N-pyridin-4-amine-functionalized graphene oxide [Fe3O4@GO-N-(pyridin-4-amine)] was readily prepared via a three-step procedure. The synthesized nanofilms were characterized by scanning electron microscopy, powder X-ray diffraction analysis, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, vibrating-sample magnetometry, and elemental analysis. The prepared magnetic amine-functionalized graphene oxide exhibited high catalytic activity for one-pot three-component synthesis of dihydropyrano[2,3-c]pyrazole and tetrahydrobenzo[b]pyran (4H-chromene) derivatives. Excellent product yield, short reaction time, use of water as green solvent, and easy workup procedure are the main advantages of the present protocol. In addition, the catalyst could be easily separated by magnetic decantation and reused for six cycles without significant loss of catalytic activity. [GRAPHICS] .