cis-Nitromethylene neonicotinoids as new nicotinic family: Synthesis, structural diversity, and insecticidal evaluation of hexahydroimidazo[1,2-α]pyridine

A series of neonicotinoids analogues of hexahydroimidazo[1,2-α]pyridine were modified at 5-, 6-, and 7-positions, and their insecticidal activities were evaluated. Introducing a methyl or ethyl at 7-position increased the insecticidal activities, while other substituents decreased activities. When alkyl substituents were introduced to 7-position, the insecticidal activities against Pea aphids decreased in the order methyl (7a) > ethyl (7b) > n-butyl (7e) > phenyl (7f) > n-propyl (7c) > iso-propyl (7d), p-NO2-phenyl (7g). Modifications at 5-, 6- or both at 6- and 7-positions with methyl or ethyl were unfavorable to activities. Interestingly, introducing methyl to 7-position not only increased insecticidal activities against pea aphids, but also show higher insecticidal activities than imidacloprid against imidacloprid-resistant brown planthopper.