One-pot synthesis of 2-amino-3-cyanopyridines and hexahydroquinolines using eggshell-based nano-magnetic solid acid catalyst via anomeric-based oxidation

In the present research, the eggshell as a hazardous waste by European Union regulations was converted to a valuable catalyst, namely nano-Fe3O4@(HSO4)(2). The as-prepared catalyst, first, was characterized using different techniques, including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Back-titration method confirmed the loading of a high surface density of acidic group, namely 8.8 mmol HSO4 per gram of the catalyst. The catalytic property of the as-prepared catalyst was examined in the synthesis of 2-amino-3-cyanopyridines via anomeric-based oxidation (ABO), and hexahydroquinolines derivatives. High yield, short reaction time, solvent-free condition, waste to wealth, and optimization with the design of experiment are the major advantages of the present work. Taken together, these results suggest the conversion of waste to wealth products around the world and usage in organic transformation. [GRAPHICS] .