CuO/Fe3O4/graphene oxide and NiO/Fe3O4/graphene oxide magnetic composites as efficient and reusable catalysts for Biginelli synthesis of dihydropyrimidinone

Dihydropyrimidinones (DHPMs) are heterocyclic compounds with various biological activities. These biological activities are important for pharmacological applications. DHPMs are commonly synthesized via the Biginelli reaction, which requires an efficient and recyclable catalyst to achieve high yields under optimized reaction conditions. Homogeneous catalysts have been widely used in the Biginelli reaction because of their high catalytic activity. However, their difficult separation from the reaction mixture and limited reusability have driven the development of heterogeneous catalysts with improved recovery and recycling performance. Previous studies on heterogeneous catalysts have reported several limitations, such as high catalyst loading, prolonged reaction times, reduced activity upon reuse, and complicated recovery procedures. As a result, this study aims to prepare CuO/Fe 3 O 4 /GO and NiO/Fe 3 O 4 /GO magnetic heterogeneous catalysts for the synthesis of a target DHPM compound. The catalysts were prepared through stepwise surface modification of Fe 3 O 4 , followed by the addition of graphene oxide, CuO, and NiO. Structural characterization confirmed the successful formation of the composites. Catalytic evaluation showed that CuO/Fe 3 O 4 /GO produced the highest yield of the target DHPM compound (85%) under optimized reaction conditions (10 wt% catalyst, 80 °C), whereas NiO/Fe 3 O 4 /GO produced a 50% yield under the same conditions. Raman analysis indicated a small difference in the degree of structural disorder between CuO/Fe 3 O 4 /GO and NiO/Fe 3 O 4 /GO. In addition, CuO/Fe 3 O 4 /GO exhibited a smaller average particle size, which may contribute to its higher catalytic performance. Furthermore, the CuO/Fe 3 O 4 /GO catalyst remained active after five reaction cycles, with a yield of 81%. These findings indicate that CuO/Fe 3 O 4 /GO is a promising reusable magnetic heterogeneous catalyst for DHPM synthesis.