Synthesis and Fungicidal Activity Evaluation of Novel Triazole Thione/Thioether Derivatives Containing a Pyridylpyrazole Moiety

Compounds containing N-pyridylpyrazole motif have aroused interest and brought about research hotspots due to their highly-efficient insecticidal activity. The fungicidal potential of N-pyridylpyrazole derivatives has gradually been disclosed in recent years. To discover new agrochemicals with poly-heterocyclic features, a series of novel triazole thione/thioether derivatives containing pyridylpyrazole motif (8-11) was synthesized. The new compounds were identified by melting point, ¹H-NMR, ¹³C NMR, ¹⁹F NMR, HRMS, and elemental analysis. The bioassays showed that most of the pyridylpyrazole-containing triazole thione Mannich bases possessed favorable in vitro fungicidal activity toward pathogenic fungi, such as Magnaporthe oryzae, Sclerotinia sclerotiorum, Botrytis cinerea and Fusarium verticillioides, and were comparable with those of the contrast compounds A and triadimefon. Some of them exhibited moderate to good in vivo fungicidal activity against S. sclerotiorum at 0.2 mg/mL (e. g. 8f control efficacy: 60.9±3.2 %). The SEM observation displayed that 8f might cause disruption of cell membrane and wall of S. sclerotiorum. Compounds 8a, 8c, 8f-8h, 8p and 9b can serve as promising new fungicidal agents to make further structural optimization. The findings in this article provide useful clue and guidance for the design and development of new poly-heterocyclic agrochemicals.