Synthesis and insecticidal bioactivities of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one derivatives

A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one 4 and its derivatives were described. Preliminary bioassays showed that some of the target compounds exhibited excellent insecticidal activities against brown planthopper (Nilaparvata lugens), cowpea aphids (Aphis craccivora) (4, 5a, 5c, 5g, 5h, 5j, 5r, 6b, 6e) and carmine spider mite (Tetranychus cinnabarinus (5f, 5s, 6a) at 500 mg/L. Among them, compound 4 was still active against brown planthopper and cowpea aphids at 4 mg/L. The insecticidal activities were influenced by the types and position of the substituents, which provided guidance for the structure modifications.