Polyfunctionalized Thieno[2,3- <i>b</i> ]pyridine Compounds: Preparation, DFT Calculations, Molecular Docking Studies, and Agricultural Potency Evaluation against <i>Aphis gossypii</i>

This study evaluated the insecticidal efficacy of various thieno[2,3-b]pyridine compounds (1, 3, 4a–4c, and 5a–5c) against adults of Aphis gossypii on eggplant. The insecticidal activity was assessed using the leaf-dip technique after 24 h. Several compounds exhibited remarkable potency at very low concentrations, as indicated by their low LC50 values. Notably, compound 4c demonstrated the highest efficacy with a very low LC50 value of 0.005 ppm (0.003–0.008). Regression analysis showed good fits, with slopes ranging from approximately 0.46 to 0.86 and confidence intervals supporting the reliability of the results. Using density functional theory, we calculated the highest occupied molecular orbital and lowest unoccupied molecular orbital electronic distributions for all of the compounds. To further pinpoint reactive regions, we generated electrostatic potential maps, which highlighted the most electrophilic and nucleophilic areas in every compound. Molecular docking was additionally employed to predict the binding interactions and affinities between the synthesized compounds and acetylcholinesterase. Molecular docking showed the strength and type of interactions of these compounds with acetylcholinesterase. All compounds illustrated excellent binding affinities with a high correlation between their docking scores and insecticidal efficacy. These findings suggest that the synthesized thieno[2,3-b]pyridine derivatives are promising candidates for developing effective insecticidal agents.