Synthesis and Antioxidant Activity of Novel Biginelli Adducts with Phenolic Fragments

In this work, eco-friendly ceric ammonium nitrate (CAN) and ferric chloride hexahydrate catalysts in ethanol/acetonitrile systems were used to efficiently synthesize novel dihydropyrimidinone (-thione) derivatives via the Biginelli reaction. The obtained compounds with phenolic fragments at the C4 position demonstrated enhanced antioxidant properties. Significant structure–activity relationships were indicated by three complementary assays (PFRAP, ABTS, and AAPH-induced DNA oxidation): oxo-derivatives demonstrated superior ferric ion reduction (PFRAP), while thio-substituted analogs consistently outperformed their carbonyl counterparts in radical scavenging. Remarkably, all compounds surpassed the reference antioxidant BHT, demonstrating the potential of synthesized dihydropyrimidine structures as multifunctional antioxidants for therapeutic applications. The study also shows the relationship between the catalyst–solvent system and its effect on product yields, using ceric ammonium nitrate and ferric chloride hexahydrate.