Modified magnetic chitosan with mono(6-amino-6-deoxy)-β-cyclodextrin as a novel catalyst toward the synthesis of pyrazolopyranopyrimidines and pyrano[2,3-c]pyrazole-3-carboxylates

In this study, we successfully fabricated a novel biocomposite composed of 6-amino β-cyclodextrin (CDNH₂) grafted onto magnetic chitosan (Fe₃O₄@Cs). This biocomposite was thoroughly characterized using FT-IR, NMR, PXRD, EDX mapping, SEM, TEM, TGA, and VSM techniques. Subsequently, the innovative biocomposite was harnessed to serve as a heterogeneous catalyst to facilitate two series of multicomponent reactions (MCRs) aimed at synthesizing pyrazole-fused heterocycle derivatives. The first reaction involved the combination of hydrazine hydrate, ethyl 3-oxobutanoate, barbituric acid, and various benzaldehyde derivatives. In a separate reaction, dimethyl acetylenedicarboxylate (DMAD), hydrazine hydrate, benzaldehyde derivatives, and malonitrile were used as starting materials. By optimizing the reaction conditions and employing the Fe₃O₄@Cs@CDNH₂ catalyst, we successfully synthesized valuable pyrazole structures with high yields in both reactions. The ability to optimize conditions and produce new pyrazole structures with impressive yields highlights the effectiveness of using Fe₃O₄@Cs@CDNH₂ to direct these reactions.