Design, Synthesis, and Herbicidal Evaluation of Novel Uracil Derivatives Containing 1,3,4‐Thiadiazolyl Moiety

Abstract

Uracil derivatives, such as commercial herbicides butafenacil and benzfendizone, have been identified as inhibitors of protoporphyrinogen oxidase (Protox, EC 1.3.3.4), one of the most important action targets of herbicides. In order to search for novel Protox inhibitors with high efficacy, broad‐spectrum activity, and safety to crops, commercially herbicide butafenacil was used as lead compound for further optimization; a series of title compounds 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h, 8i, 8j, 8k, 8l, 8m, 8n were designed and synthesized by introducing 1,3,4‐thiadiazole moiety into the uracil skeleton. The preliminary bioassays (in vitro) indicated that most of the target compounds displayed better inhibition against Echinochloa crus‐galli than Brassica campestris. The greenhouse bioassay results indicated that most of the compounds tested exhibited good‐to‐excellent herbicidal activities against B. campestris, A. retroflexus, E. crusgalli, and D. sanguinalis in pre‐emergence treatment at a dose of 1500 g/ha, for example, compound 8d showed 100% inhibition against the four plants tested in pre‐emergence treatment at a dose of 1500 g/ha. So, these types of skeletons can be used as valuable lead compounds for the development of a pre‐emergent herbicide.