Immobilization of Zn(II) on Chitosan from Callinectes Sapidus Shells as an Efficient Heterogeneous Catalyst for the Synthesis of 4H-Pyran Derivatives.

A new sustainable heterogeneous catalyst for the effective synthesis of 4H-pyran derivatives under mild reaction conditions was investigated. This heterogeneous catalyst was prepared through the complexation reaction between the naturally obtained chitosan from Callinectes sapidus shells and zinc(II) ions (Zn(II)/Chitosan), and characterized using a variety of techniques, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (IR). The corresponding 4H-pyran derivatives were obtained in good to excellent yields (58–96%) in the presence of Zn(II)/chitosan catalyst using water as solvent at 60°C for only 20 min. The catalyst was easily separated from the reaction mixture by simple filtration, resulting in the desired products with excellent purity. In comparison to numerous other catalyst systems for the synthesis of 4H-pyran derivatives, Zn(II)/chitosan, a new sustainable heterogeneous catalyst, demonstrated remarkable efficacy in an environmentally benign solvent, allowing the desired products to be produced under more environmentally friendly reaction conditions. [ABSTRACT FROM AUTHOR]