Design, Synthesis, and SAR Studies of Some Novel Chalcone Derivatives for Potential Insecticidal Bioefficacy Screening on Spodoptera frugiperda (Lepidoptera: Noctuidae)

[Image: see text] Spodoptera frugiperda is a species of the order Lepidoptera. It is one of the species of fall armyworm moths distinguished by its larval life stage, is found in different regions of Africa, and can cause incredible damage. This is the first report produced by the preparation of an indexed combinatorial library of novel chalcone derivatives 3a–kvia treatment of 4-formylphenyl4-methylbenzenesulfonate (1) with some acetyl compounds 2a–k in the presence of NaOH. The structures of the synthesized compounds were proven by different spectroscopic techniques such as infrared, (1)H NMR, (13)C NMR, and elemental analyses. In this work, we studied their toxicity effect against S. frugiperda, followed by a structure–reaction relationship. Moreover, newly prepared chalcone derivatives were tested as insecticides using S. frugiperda. It has been found that most compounds have good to excellent potential effectiveness. Among all of the compounds, 3b, 3g, and 3j exhibited excellent effectiveness. Furthermore, compound 3c showed the most activity, with LC(50) = 9.453 ppm of the second instar larva and LC(50) = 66.930 of the fourth instar larva .