Synthesis, Bioactivities and Structure Activity Relationship of N ‐4‐Methyl‐1,2,3‐thiadiazole‐5‐carbonyl‐ N ′‐phenyl Ureas

Twenty nine novel N ‐4‐methyl‐1,2,3‐thiadiazole‐5‐carbonyl‐ N ′‐phenyl ureas were designed and synthesized, and their structures were confirmed by proton nuclear magnetic resonance ( 1 H NMR), infra red spectroscopy (IR) and high‐resolution mass spectroscopy (HRMS). Compounds V‐9 , V‐11 , V‐12 , V‐15 , V‐19 , V‐21 , V‐22 and V‐24 exhibit excellent activity against Culex pipiens pallens . Compounds V‐12 and V‐22 present good insecticidal activity against Plutella xylostella L. Their median lethal concentrations (LC 50 ) are 164.15 and 89.69 mg·L −1 , respectively. Compound V‐11 also has potential wide spectrum of fungicide activity. Its median effective concentrations (EC 50 ) detected from 3.82 µg·mL −1 against Physalospora piricola to 31.60 µg·mL −1 against Cercospora arachidicola . Compounds V‐15 and V‐24 show outstanding induction activities as same as positive controls TDL and ningnanmycin, furthermore V‐24 has the highest induction activity of 41.85%±4.43%. To elucidate the structure activity relationship in these compounds, a 3D‐QSAR model has been built. The established model showed a reliable predicting ability with q 2 values of 0.643 and r 2 values of 0.982.