Design, synthesis, and insecticidal activity of novel neonicotinoid derivatives containing N-oxalyl groups
Yu Zhao, Yongqiang Li, Suhua Wang, and Zhengming Li*
State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, People’s Republic of China
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Abstract
Two series of novel neonicotinoid derivatives containing N-oxalyl groups were designed and synthesized, and their structures were characterized by 1H NMR spectroscopy, high-resolution mass spectroscopy, elemental analysis and single crystal X-ray diffraction analysis. The insecticidal activities of the new compounds were evaluated. The results of bioassays indicated that some of these title compounds exhibited excellent insecticidal activities. The insecticidal activities of compounds 13c, 13d, 13g, 13h, and 13i against bean aphids at 12.5 mg kg-1 were 100%; the insecticidal activities against bean aphids of the derivative 13 c, 13d, 13g, 13h, and 14h were comparable to imidacloprid at 6.25 mg kg-1. Surprisingly, the results indicated that the activity of ethyl 2-(3-((6-chloropyridin-3-yl)methyl)-2-(nitroimino)imidazolidin-1-yl)- 2-oxoacetate (13b) against bean aphids at 6.25 mg kg-1 was 96%, which was higher than the commercialized imidacloprid.
Keywords: Neonicotinoid, N-oxalyl derivatives, synthesis, insecticidal activity, bean aphid, imidacloprid
Introduction
Since the introduction of imidacloprid (1) in the 1980s as an insecticide for crop protection,1 neonicotinoid insecticides have been rapidly developed worldwide for controlling insects because of their high potency, low mammalian toxicity, broad insecticidal spectra, and good systemic properties. Neonicotinoids, which interact with nicotinic acetylcholine receptors (nAChR), have a higher affinity for the insect receptor than for the mammalian receptor and are relatively safe toward mammals and aquatic life.2-5 Imidacloprid (1), the first neonicotinoid insecticide acting on a nAChR, has been widely used to control not only various plant pests, but also fleas on cats and
