A series of N-(substituted pyridinyl)-1-methyl(phenyl)-3-trifluoromethyl-1H-pyrazole-4-carboxamide derivatives were synthesized. All target compounds were characterized by spectral data (1H-NMR, 13C-NMR, IR, MS) and elemental analysis and were bioassayed in vitro against three kinds of phytopathogenic fungi (Gibberella zeae, Fusarium oxysporum, Cytospora mandshurica). The results showed that some of the synthesized N-(substituted pyridinyl)-1-methyl-3-trifluoromethyl-1H-pyrazole-4-carboxamides exhibited moderate antifungal activities, among which compounds 6a, 6b and 6c displayed more than 50% inhibition activities against G. zeae at 100 µg/mL, which was better than that of the commercial fungicides carboxin and boscalid.

A series of novel 1‐(3‐chloropyridin‐2‐yl)‐5‐amino‐4‐pyrazole derivatives containing a 1,3,4‐thiadiazole thioether or sulfone moiety were designed and synthesized. All the title compounds were confirmed by 1H NMR, 13C NMR, and MS, and the intermediate 2 and title compound 5e were confirmed by single crystal X‐ray diffraction analysis. Bioassay evaluation revealed that compound 5a (54.2 ± 2.0%) and 5r (75.2 ± 3.9%) exhibited good curative and protection activity against TMV, respectively, which was slightly lower than that of ningnanmycin (57.1 ± 2.2% and 73.8 ± 3.4%). Compound 5b (64.7 ± 8.5% and 67.7 ± 2.1%) exhibited good curative and protective activity against CMV, which was better than that of ningnanmycin (55.8 ± 1.4% and 64.2 ± 5.8%). The lethality rates of 5a, 5c, 5d, 5h, 5j, 5n, 5o, 5p, 5q, 5r, 5t, 6a, and 6e against C. pipiens were 100% at a concentration of 10 μg/ml, as well as chlorantraniliprole (100%). These results may provide enough support to justify further molecular design and derivation.