Design,Synthesis And Biological Activity Of Imidazo[4,5-b]pyridines

The creation of new types of pesticides is an important step to promote the progress of pesticides.As an important nitrogen-containing fused heterocycles,imidazo[4,5-b]pyridine derivatives can occupy an important position in the field of drug synthesis due to the particularity of the structure and the diversity of biological activities.However,the application of these compounds is not extensive in the field of pesticide,and the reports are extremely rare.At present,imidazo[4,5-b]pyridine pesticides have not been put into production,so it is of great significance to explore its applaction in the pesticide.Based on our previous work and literature,30 imidazo[4,5-b]pyridines were designed and synthesized by the principle of active sub-structure combination and their structure（A1-A30）were confirmed by ¹H NMR and LC-MS.Besides,the biological activities were also tested.The biological activity shows that the imidazo[4,5-b]pyridines have no significant activity against Mythimna separata,but have a significant insecticidal activity against Aphis fabae.Compound A3,A10,A15,A20,A21,A22,A24,A25 and A27 exhibited a 100%mortality rate against Aphis fabae at the concentration of 500 mg/L.Specially,A20 displayed the best insecticidal activity with a LC₅₀ value of 4.72 mg/L.Compared with Tolfenpyrad(LC₅₀=0.58 mg/L),the activity was not at the same level,but it plays a vital role in the development of subsequent insecticides.Some compounds also showed good acaricidal activity:A10,A20,A21,A23,A24 have more than 90%effects against Tetranychus urticae.In terms of fungicidal activity,A2 has a broad-spectrum fungicidal activity:it exhibited 95%fungicidal activity against Erisiphe griminis and Puccinia Polysora at the concentration of 500 mg/L,and more than 60%fungicidal activity against Botrytis cinerea and Sclerotonia sclerotiorum at 25 mg/L.The herbicidal activity of targets compound was very unsatisfactory.Only A22 showed 80%herbicidal activity,the others was very low or no activity.The relationship between structure and biological activity was also summarized.It indicated that the introduction of trifluoromethyl on the imidazopyridine ring was beneficial for the insecticidal activity,which may be related to the improvement of liposolubility of the compound.