Background: One of the principal factors in the field of research in green chemistry is to drive chemical reactions under ultrasonication as a versatile synthetic tool. Moreover, nanostructured metal salts occupy an important position as low cost, efficient, heterogeneous, and green catalysts in chemical reactions. Pyrimidine has also acquired significance because it is a core structure in a variety of natural and non-natural agents, many of which display versatile biological activities and medical applications. Objective: The aim of this study was to explore the role of nickel(II) chromite nanoparticles (NiCr2O4 NPs) as a green and recyclable catalyst for the synthesis of 2,4-diamino-6-aryl-pyrimidine-5-yl cyanides under ultrasonic radiation. Methods: A direct cyclocondensation reaction of guanidine nitrate, aromatic aldehydes, and malononitrile were performed using NiCr2O4 NPs as an effective heterogeneous catalyst under ultrasonic radiation at room temperature conditions to prepare 2,4-diamino-6-aryl-pyrimidine-5-yl cyanides in high yields. The described catalyst was prepared successfully according to a simple hydrothermal route and fully characterized by the X-Ray diffraction (XRD) technique, energy dispersive X-Ray (EDS) analysis, scanning electron microscopy (SEM), and dynamic light scattering (DLS). Results: A number of 2,4-diamino-6-aryl-pyrimidine-5-yl cyanides were effectively synthesized in high yields (94-98%) within short reaction times (15 min). All synthesized compounds were well characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. Conclusion: In conclusion, a simple, efficient, and green synthesis of 2,4-diamino-6-aryl-pyrimidine-5-yl cyanides was developed using NiCr2O4 NPs as green nanocatalyst, and under ultrasound radiation as green tool. The mild reaction conditions, avoiding the use of toxic solvents or reagents, high atom economy, high yields, and simple work-up are the attractive features of this new protocol.
Background: The importance of fused chromene motifs in bioactive compounds highlighted the current research to explore novel methods for the construction of these heterocyclic scaffolds. Regarding the attractive features of developing novel methodological approaches in the presence of heterogeneous nanocatalysts, we will try to synthesize 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones and 8-aryl-7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene-6-ones through this method. Objective: The aim of the present research was to prove the catalytic efficiency of the synthesized nickel(II) chromite nanoparticles (NiCr2O4 NPs) as bifunctional Lewis acid-Lewis base catalyst in the synthesis of pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones. Methods: Pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones were conveniently prepared from a three-component condensation reaction between aromatic aldehydes, meldrum’s acid, and active methylene compounds including 4-hydroxycoumarin or 3,4-methylenedioxyphenol using NiCr2O4 NPs as an efficient, easily obtained, and recyclable catalyst, under ethanol-drop grinding at room temperature. The synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. Results: A number of 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones and 8-aryl-7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene-6-ones were effectively synthesized as target compounds in high yields. Conclusion: This study provides a simple, inexpensive and NiCr2O4 NPs catalyzed route to synthesis pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones in high yields. The reaction offers several benefits including simple experimental procedures, higher yields, shorter reaction times and use of easily obtained and recyclable catalyst compared with previously reported methods and has a great foreground of development.
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