Microwave Assisted Sol-Gel Synthesis of MgO Nanoparticles and Their Catalytic Activity in the Synthesis of Hantzsch 1,4-Dihydropyridines

A microwave-assisted sol-gel method was employed for the preparetion of nano-sized MgO particles using Mg(NO3)(2)center dot 6H(2)O as precursor and deionized water as solvent. The sample calcined at 500 degrees C had a high specific surface area of 243.2 m(2)/g and particles sizes from 9.5 to 10.5 nm. For comparison, MgO nanoparticles were also synthesized without microwave irradiation. X-ray diffraction (XRD) characterization showed the formation of smaller particles after microwave irradiation. The structure and morphology of the MgO particles were analyzed by N-2 adsorption-desorption, XRD, scanning electron microscopy, and transmission electron microscopy. Their catalytic behavior was studied with the one-pot synthesis of Hantzsch 1,4-dihydropyridines from the reaction of aromatic aldehydes, ethyl acetoacetate, and ammonium acetate. The MgO nanoparticles have high catalytic activity and gave the desired products in good to high yields. The catalyst can be easily recovered by filtration and was used at least three times with only a slight reduction in its catalytic activity.