Piperazine-Grafted Magnetic Reduced Graphene Oxide (Fe₃O₄@rGO-NH) as a Reusable Heterogeneous Catalyst for Gewald Three-Component Reaction

In recent years, interesting physical and chemical properties of graphene oxide (GO) have led to a great deal of excitement in the chemistry. One of the most promising results is the use of GO and the functionalized GOs as heterogeneous catalysts in organic synthesis. In this work, GO was functionalized with piperazine (GO-NH), converted to magnetic GO-NH by incorporating Fe₃O₄ particles into GO-NH (Fe₃O₄@rGO-NH), and then reduced with hydrazine hydrate to yield piperazine-grafted magnetic reduced graphene oxide (Fe₃O₄@rGO-NH). The obtained Fe₃O₄@rGO-NH was used as a heterogeneous catalyst in the Gewald three-component reaction between some aldehydes or ketones, sulfur, and malononitrile or ethyl cyanoacetate. The catalyst showed good activity for various starting materials, easy separation from the reaction mixture using an ordinary magnet and reusability. Also, the catalyst was used six times without significant loss of activity.