Design, synthesis, and bioassay of novel 1‐(3‐chloropyridin‐2‐yl)‐5‐amino‐4‐pyrazole derivatives containing a 1,3,4‐thiadiazole thioether or sulfone moiety

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. 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. Bioassay evaluation revealed that most title compounds exhibited good antiviral activities against TMV and CMV, and some of them showed a 100% lethality rate against C. pipiens at a concentration of 10 μg/ml.