Nickel(II) Chromite Nanoparticles: An Eco-Friendly and Reusable Catalyst for Synthesis of 2,4-Diamino-6-aryl-pyrimidine-5-yl Cyanides under Ultrasonic Radiation

Abstract

Background: One of the principal factors in the field of research in green chemistry is to drive chemical reactions using 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-arylpyrimidine- 5-yl cyanides under ultrasonic radiation.

Methods: A direct cyclocondensation reaction of guanidine nitrate, aromatic aldehydes, and malononitrile was 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, dispersive energy 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-arylpyrimidine- 5-yl cyanides was developed using NiCr₂O₄ NPs as a green nanocatalyst, and under ultrasound radiation as a green tool. The mild reaction conditions, avoiding the use of toxic solvents or reagents, high atom economy, high yields, and simple workup are the attractive features of this new protocol.

Keywords: Green synthesis; antimicrobial; nickel(II) chromite nanoparticles (NiCr2O4 NPs); pyrimidines; recyclability of catalyst; ultrasonic radiation.