Synthesis and Herbicidal Activity of Novel Pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine Derivatives

To discover N-containing fused heterocyclic compounds with novel structure and excellent herbicidal activity, forty-two pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives (I-1 similar to I-42) were synthesied using 2-(alkylthio)-5carbonitrile-6-(methylthio)pyrimidine-4-aminos as starting materials. Their structures were clearly confirmed by melting point, H-1 NMR, C-13 NMR, infrared absorption spectroscopy (IR), and high-resolution mass spectra (HRMS). The preliminary bioassay indicated that many target compounds exhibited remarkable herbicidal activities against the monocotyledons (Triticum aestivum L., Echinochloa crusgalli, and Sorghum bicolor) and dicotyledons (Raphanus sativus, Brassica campestris, and Cucumis sativus) at the concentration of 100 mg/L. Especially, compounds I-13, I-14, I-23, I-25 and I-30 similar to I-42 showed excellent herbicidal activities against the roots and stalks of the six test plant at 100 mg/L with 100% inhibition rates.