Insecticidal agent 21 (Compound 6) is an insecticide targeting Culex pipiens larvae with an LC50 of 0.4 μg/mL. It achieves multi-target neurotoxicity by inhibiting acetylcholinesterase (AChE) and simultaneously targeting other neural receptors, including nicotinic acetylcholine receptors (nAChR), voltage-gated sodium channels (VGSC), and γ-aminobutyric acid receptors (GABAAR). Insecticidal agent 21 shows potent insecticidal activity and can be utilized in the development of new insecticides to combat mosquito resistance to conventional agents.