Design, Synthesis, and Biological Activity of New 8-Decylthio-10-methylthio-pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine Derivatives

A series of new 8-decylthio-10-methylthio-pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives was prepared and characterized by FTIR, H-1 NMR, C-13 NMR, and HRMS. The bioassay results revealed that the title compounds had moderate to excellent insecticidal activities against Aphis fabae at a concentration of 500 mg/L. Among them, 8-(decylthio)-2-((4-chlorophenoxy)methyl)-5-propyl-10-(methylthio)-5,6-dihydropyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine (4l) exhibited the highest insecticidal activity, with 95% mortality. Moreover, 8-(decylthio)-2-((2,4-dichlorophenoxy)methyl)-5-propyl-10-(methylthio)-5,6-dihydropyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine (4i) showed broad-spectrum postemergence herbicidal activities against Abutilon theophrasti, Amaranthus spinosus, Chenopodium album, Digitaria sanguinalis, Echinochloa crusgalli, and Setaria viridis, which were equivalent to the positive control flumetsulam. However, all new synthesized compounds displayed weak fungicidal activity against four kinds of phytopathogenic fungi including Botrytis cinerea, phytophythora capsici, Elsinoe fewcetti, and Diaporthe medusaea. Compound 4l with remarkable insecticidal activity, and compound 4i with excellent herbicidal activity could be promising lead compounds for further investigation.