Design, Synthesis, and Herbicidal Activities of N-(5-(3,5-Methoxyphenyl)-(thiazole-2-yl))phenoxyacetamide Derivatives

Thiazole and phenoxyacetic acid are key moieties in many natural and synthetic biologically active agents. A series of N-(5-(3,5-methoxyphenyl)-(thiazole-2-yl))phenoxyacetamide derivatives 6an-6bd were designed and synthesized, and their structures were confirmed by NMR and HRMS. Most of derivatives exhibited superior inhibition of Echinochloa crusgalli (E.c.) and Lactuca sativa (L.s.) seed germination by the Petri dish bioassay. Indeed, herbicidal bioassays indicated that 6an (2-(2,4-dichlorophenoxy)-N-(5-(3,5-dimethoxyphenyl)-1,3,4-thiadiazol-2-yl)acetamide) had the best inhibition against L.s. (IC₅₀ = 42.7 g/ha, 375 g/ha at field experiments). 6an also had no harmful effect on Zea mays at 2- to 4-fold field usage. Moreover, transcriptomics and metabolomics analysis showed that 6an significantly influenced cell metabolism, including galactose metabolism and ascorbate and aldarate metabolism. These discoveries highlight that 6an shows promise to be developed as a potential herbicide.