Discovery of Novel Neonicotinoids with Conjugated Diene Enabled by Cascade Allylation/Isomerization Synthetic Methodology

As one of the most significant insecticides, neonicotinoids have played a pivotal role in crop protection and public sanitation. However, the high resistance and bee toxicity of neonicotinoid insecticides have attracted considerable attention. Herein, a series of neonicotinoid compounds with conjugated diene moieties were synthesized through the cascade allylation/isomerization reaction. Most of the target compounds exhibited excellent insecticidal activities against Aphis craccivora, and some compounds exhibited good insecticidal activities against Mythimna separata. In particular, compound A15 showed outstanding insecticidal activity against A. craccivora (LC₅₀ = 0.15 mg/L), which was superior to that of imidacloprid (LC₅₀ = 0.36 mg/L). In addition, this candidate exhibited minimal cross-resistance to imidacloprid. The acute contact toxicity tests on Apis mellifera suggested that compound A15 was 10 times less toxic than imidacloprid. Electrophysiological experiments and molecular docking studies indicated that compound A15 exerted its insecticidal effects by interfering with nicotinic acetylcholine receptors. This work identifies a novel conjugated diene neonicotinoid candidate with significant potential for further development.