Synthesis, Crystal Structure, and Herbicidal Activities of 2‐Cyanoacrylates Containing 1,3,4‐Thiadiazole Moieties.

Three series of novel 2-cyanoacrylates 7a–7f, 9a–9f, 10a–10f containing 1,3,4-thiadiazole ring moieties were synthesized as herbicidal inhibitors of photosystem II (PS II) electron transportation. Their structures were clearly verified by 1H NMR, 13C NMR, elemental analysis (or HRMS analysis) and single-crystal X-ray diffraction analysis. Bioassay showed that a suitable group at the 3-position of acrylates was essential for high herbicidal activity. In particular, compound 7e showed the best herbicidal activities and gave 100% inhibitory activity against rape and amaranth pigweed at a dose of 1.5 kg/ha. Introduction of substituent with higher polarity such as sulfinyl or sulfonyl to the 5-position of 1,3,4-thiadiazole decreased herbicidal activities.