CdO Nanoparticles: A Highly Effective Catalyst in Cyclocondensation Reaction of 3,4-Methylenedioxyphenol, Aromatic Aldehydes, and Active Methylene Compounds under Ultrasonic Irradiation

In the last decades, metal oxide nanoparticles (NPs) have been used as inexpensive efficient heterogeneous catalysts in different chemical reactions, due to their favorable properties such as high available surface area, small loading of catalyst, convenient catalyst recycling, and degradation of environmental pollutants. An efficient synthesis of xanthenones and [1]benzopyrano[d]pyrimidinediones are achieved by cyclocondensation reaction of 3,4-methylenedioxyphenol, aromatic aldehydes, and active methylene compound including dimedone or 1,3-dimethylbarbituric acid using CdO NPs as a robust catalyst under ultrasonic irradiation in water at room temperature. The described catalyst was prepared successfully by a simple precipitation method and characterized by the Fourier transformed infrared absorption (FT-IR) spectroscopy, X-Ray diffraction (XRD) analytical technique, and scanning electron microscopy (SEM). All synthesized compounds were well characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. The remarkable advantages of this protocol are high yields of products, short reaction times, use of simple and readily available starting materials, experimental simplicity, and applying the sonochemical method as an efficient method and innocuous tool for the synthesis of heterocycles.