Functionalized pyrimidines: synthesis, characterization, structure-activity relationship, and insecticidal evaluation studies against Aphis fabae

Neonicotinoids are strong insecticides that work well against a variety of agricultural pests. For many years, they have been used to effectively control aphid pests, which cause significant financial harm to crops. The growing resistance to conventional chemical pesticides has become a key driver in the development of new insecticidal agents. Examining new classes of insecticidal compounds with distinct modes of action is one way to meet this problem. So that, neonicotinoide analogues (ethyl 2-(cyanoamino)-6-oxo-4-arylhexahydropyrimidine-5-carboxylates 1-8) were created via a one-pot, three-component reaction of cyanoguanidine with a mixture of diethyl malonate and various aromatic aldehydes. The chemical structures of the novel products were verified using elemental and spectral analysis. Under laboratory conditions, all produced analogues were evaluated as insecticidal agents against black bean aphid (Aphis fabae) nymphs and adults. Bioassay experiments indicate that novel pyrimidine derivatives have good insecticidal activities against A. fabae. Compounds 3 and 5 were the most active toxicological agents with LC50 values of 0.04 and 0.07 ppm against nymphs and 0.88 and 1.2 ppm against adults of black bean aphids. In conclusion, synthesized pyrimidine derivatives have been successful in controlling aphids under laboratory conditions and are considered potential insecticides.   KEY WORDS: Black bean aphides, Aphis fabae, Insecticidal agents, Pyrimidines, Cyanoguanidine Bull. Chem. Soc. Ethiop. 2026, 40(3), 613-625.                                                          DOI: https://dx.doi.org/10.4314/bcse.v40i3.9