Design, synthesis, and fungicidal evaluation of a series of novel 5-methyl-1H-1,2,3-trizole-4-carboxyl amide and ester analogues.

Succinate dehydrogenase inhibitors (SDHIs) are efficient fungicides that are widely used to control plant diseases caused by phytopathogenic fungi, although their effectiveness is undermined by the development of resistance across a range of different fungi. One of the most common structural features of SDHIs is their amide bond. The introduction of greater structural diversity to SDHIs is a promising strategy to delay the onset of resistance. A series of novel SDHIs containing a bioactive 1,2,3-triazole moiety have been designed and synthesized and their fungicidal and insecticidal activities evaluated. The results of these analyses show that most of the newly synthesized 1,2,3-trizole-4-carboxyl amide (ester) analogues exhibit good fungicidal activities, especially towards Sclerotinia sclerotiorum, and a structure-activity relationship study confirmed that the replacement of the amide group with an ester group had little effect on fungicidal activity, which could be provideous in terms of issues and metabolism. 1,6-Dimethyl phenyl was confirmed as the most efficient substituent of the current study when it was placed on both the amide and ester compounds. Interestingly, some of the newly synthesized compounds displayed good insecticidal activities against Culex pipiens pallens. The results of the current study show that these 1,2,3-triazole-4-carboxyl amide and ester analogues represent a new type of SDHI that could be used for the development of novel pesticides.