Design, synthesis and bioactivity of 2-(tralopyril-1-yl)ethyl carboxylic acid derivatives

In order to find novel pesticide-active compounds, a series of new 2-(tralopyril-1-yl) ethyl carboxylic acid derivatives ( 5a-5m , 6a-6o ) were synthesized by nucleophilic substitution with tralopyril as the lead compound. Their structures were confirmed by ¹H NMR, ¹³C NMR and HRMS. The results of fungicidal bioassay showed that compounds 2 , 3 and 5m exhibited good fungicidal activity against Magnaporthe oryzae with EC₅₀ values of 0.0532, 0.0470 and 0.0174 mmol/L, respectively, which were better than the control agent fludioxonil (0.0914 mmol/L), but inferior to the control agent azoxystrobin (0.0001 mmol/L). Compound 5m showed a broad spectrum of fungicidal activity, and its EC₅₀ values for the control of Rhizoctonia solani and Bipolaris sorokiniana were 0.0218 and 0.0420 mmol/L, respectively, but inferior to the control agent fludioxonil (EC₅₀ values were 0.0002 and 0.0010 mmol/L, respectively). The bioassay results of insecticidal and acaricidal showed that at the concentration of 0.2 mmol/L, the target compounds had certain insecticidal and acaricidal activity, but they were not as effective as the control agent chlorfenapyr (corrected mortality 100%). The results of nematicidal bioassay showed good nematicidal activity of the target compounds. The LC₅₀ values of compound 2 and 5b against Caenorhabditis elegans were 0.0136 and 0.0109 mmol/L, respectively, which were better than the control agent fosthiazate (0.2798 mmol/L). The preliminary safety test showed that the highly active target compound was safer to Oryza sativa L. and Brassica campestris L. than the parent tralopyril. The target compounds synthesized in this study have certain fungicidal, insecticidal, acaricidal and nematicidal activities, which provide a guideline for the design and transformation of tralopyril derivatives and are of reference significance for exploring the biological activities diversity of tralopyril derivatives.