Magnetic guanidinylated chitosan nanobiocomposite: A green catalyst for the synthesis of 1,4-dihydropyridines.

In this study, a novel magnetic guanidinylated chitosan nanobiocomposite was synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (CHN), thermogravimetric analysis (TGA), X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) analysis, vibrating sample magnetometer (VSM) curves, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. SEM and TEM images of the nanobiocomposite showed its nearly spherical shape and uniform size distribution with an average size of about 42 nm. In the current protocol, the amino functional groups on the surface of chitosan were increased due to successfully modification of chitosan via simply conversion of amino groups to guanidine. Therefore, due to the highly amount of amino functional groups and magnetic properties of the synthesized nanobiocomposite, it was successfully utilized as a heterogeneous catalyst for the one-pot multicomponent synthesis of 1,4-dihydropyridines. These products are important class of N-heterocyclic and biologically-active compounds. Many of these reported synthesis methods for these nucleuses require expensive reagents, organic solvents, long reaction time and tedious work-up methods. Noteworthy, the advantages of this method are easy separation and reusability of catalyst, high-to-excellent yields of products, use of a green solvent, mild reaction conditions and simple and chromatography free work-up procedure.