An Eco-Friendly and Highly Efficient Synthesis of Pyrimidinones Using a TiO2-CNTs Nanocomposite Catalyst

Background: The recent development of using heterogeneous catalysts in organic synthesis has increased the need for fine metal oxide nanoparticles. Nanosized titanium dioxide nanoparticles (TiO2 NPs) can be used in several organic and inorganic transformations because of their superior properties such as high catalytic activity, non-toxicity, easily availability, moisture stability and reusability. Pyrimidinones are privileged heterocycles in the field of drugs and pharmaceutical industry. Method: The current methodology deals with the direct assembly of Meldrum's acid, aromatic aldehydes, and guanidine nitrate in the presence of a catalytic amount of the synthesized TiO2-CNTs nanocomposite could be utilized to afford 2-amino-6-aryl-5,6-dihydro-4(3H)-pyrimidinones under solventfree conditions within 2-3 h. Results: A series of 2-amino-6-aryl-5,6-dihydro-4(3H)-pyrimidinones were synthesized in high yields (90-98%) via a simple one-pot three-component coupling reaction using the synthesized TiO2-CNTs nanocomposite with the weight ratio of 50: 50 as an efficient and recyclable catalyst. All synthesized compounds were well characterized by their satisfactory elemental analyses, IR, H-1 and C-13 NMR spectroscopy. The synthesized catalyst was fully characterized by XRD, SEM, and elemental analysis. Conclusion: We have developed a general and highly efficient TiO2-CNTs nanocomposite catalyzed procedure for the synthesis of 2-amino-6-aryl-5,6-dihydro-4(3H)-pyrimidinones from a one-pot threecomponent coupling reaction of Meldrum's acid, aromatic aldehydes, and guanidine nitrate with high yields under solvent-free conditions. This new protocol has revealed several advantages such as recyclability of catalyst, short reaction times, high to excellent yields of products and solvent-free conditions.