Ethanol-Drop Grinding Approach: Cadmium Oxide Nanoparticles Catalyzed the Synthesis of [1,3]Dioxolo[g][1]benzopyran-6-carboxylic Acids and Pyrido[d]pyrimidine-7-carboxylic Acids

Abstract

Aim and Objective: In the last decades, it has been extensively verified that nanostructured transition metal oxides emerge as inexpensive, available and extremely efficient heterogeneous catalysts in chemical transformations. The high electrical conductivity, high carrier concentration, and improved reactivity in cadmium oxide nanoparticles (CdO NPs) make it as a potential candidate for applications in the fields of nanocatalysis. [1]Benzopyran and pyridopyrimidine derivatives compose major classes of heterocyclic compounds, which have a wide spectrum of biologically activities. Materials and Methods: In the present work we report a facile and highly effective synthesis of 8-aryl-8H-[1,3]dioxolo[4,5- g][1]benzopyran-6-carboxylic acids and 1,3-dimethyl-2,4-dioxo-5-phenyl-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidine-7- carboxylic acids via CdO NPs catalyzed cyclocondensation reaction of 4-substituted phenylmethylidenepyruvic acids with 3,4- methylenedioxyphenol or 1,3-dimethylbarbituric acid which was accomplished under ethanol-drop grinding 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). Results: A number of [1,3]dioxolo[g][1]benzopyran-6-carboxylic acids and pyrido[d]pyrimidine-7-carboxylic acids were effectively synthesized in high yields (96-98%) within short reaction times (10-15 min). All synthesized compounds were well characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. Conclusion: In summary, we have developed a very simple and impressive procedure for the synthesis of 8-aryl-8H- [1,3]dioxolo[4,5-g][1]benzopyran-6-carboxylic acids and 1,3-dimethyl-2,4-dioxo-5-phenyl-1,2,3,4,5,8-hexahydropyrido[2,3- d]pyrimidine-7-carboxylic acids as biologically interesting structures in the presence of CdO NPs as an efficient recyclable heterogeneous catalyst. The remarkable advantages for the offered protocol compared with traditional methods are short reaction time, good yields of the products, and the ease of operation with simple work-up procedure.

Synthetic strategies of heterocycle-integrated pyridopyrimidine scaffolds supported by nano-catalysts

“…Recently, Dahi-Azar et al 78 reported an impressive procedure for the synthesis of 1,3-dimethyl-2,4-dioxo-5-phenyl-1,2,3,4,5,8-hexahydropyrido[2,3- d ]pyrimidine-7-carboxylic acids in 96–98% yields using a recyclable nanocatalyst. Thus, cyclocondensation reaction of 4-substituted phenylmethylidenepyruvic acids with 6-amino-1,3-dimethyluracil under ethanol drop grinding, and nano-catalytic conditions using cadmium oxide nanoparticles at room temperature.…”