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

A series of neonicotinoids analogues of hexahydroimidazo[1,2-alpha]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-NO(2)-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.