Synthesis And Antifungi Activity Of Phenol-azo-benzimidazole Derivatives

Many crop diseases which were caused by microorganisms especially fungus leaded to the significant losses in agricultural production.So it was very important to find a new fungicide with high efficiency and low toxicity.It was well-known that heterocyclic compounds with nitrogen atom such as triazolylazo,indole,morpholine,pyridine and imidazole played an important role in the medicinal,insecticidal and fungicidal fields.In the meantime many phenol derivatives exhibited great antifungal activity.So we decided to combine the phenol derivatives with substituted benzimidazoles through coupled reactionr to get the new compounds which had great antifungal activity.The experiment results were obtained as follows:1.By using o-phenylenediamine or 4-nitro-o-phenylenediamine as starting materials,we got three 5-amino substituted benzimidazole compounds through the cyclization,nitrification,and reduction reactions;2.In the presence of concentrated hydrochloric acid and sodium nitrite at 0℃,the corresponding 5-amino substituted benzimidazole compounds were tranferred to diazonium salts,followed by coupling with the substituted phenols to get 28 phenol-azo-benzimidazole derivatives;3.The structures of the target compounds were identified by m.p.,1H NMR,MS and IR.Among them,9a,10a,11b and 11e were known compounds,and another 24 compounds were new ones;4.The antifungal activity of 28 target compounds,by using the inhibition of mycelial growth rate method,were determined against the following five phytopathogenic fungus,such as Fusarium graminearum,Alternaria solani,Valsa mali,Botrytis cinerea,and Curvularia lunata.Among them,10b,10c,10h,11j and 11k showed the promising antifungal activity against A.solani,V mali and C.lunata.Especially 10b showed a significant broad-spectrum antifungal activity against F.graminearum,V mali,B.cinerea,and C.lunata;5.Finally,the EC50 values of 10b,10c,10h,11j and 11k were calculated.Compound 10b had a significant inhibitory effect on V mali(EC50=18.2μg/mL),which is more potent than hymexazol(EC50=131.7μg/mL).Compound 11k showed the greatest inhibitory effect on C.lunata with the value of EC50 was 15.4μg/mL,whereas the value of EC50 of hymexazol was 42.7μg/mL.