Discovery and structure-activity relationship of dimesulfazet: a novel rice paddy herbicide

Dimesulfazet, a novel herbicide for use in paddy rice, was discovered during studies on haloalkylsulfonanilide derivatives. Our research revealed that cyclic sulfonamide derivatives exhibited herbicidal efficacy against paddy weeds prevalent in Japan, such as Schoenoplectiella juncoides (Roxb.) Lye. Furthermore, these derivatives showed efficacy against hard-to-control perennial sedges such as Eleocharis kuroguwai Ohwi. Subsequently, we converted the cyclic sulfonamide derivatives into cyclic amide derivatives, which demonstrated enhanced herbicidal activity. Among these derivatives, dimesulfazet was selected because of its exceptional efficacy against both annual and perennial sedges, while being safe for use on transplanted rice. A simple method was developed for the condensation of benzyl alcohol and cyclic amide intermediates to synthesize trifluoromethanesulfonanilide derivatives. We found that the mode of action of dimesulfazet involved the inhibition of very long-chain fatty acid biosynthesis. Dimesulfazet represents a valuable new tool for controlling S. juncoides, including biotypes resistant to acetolactate synthase inhibitors, and other perennial sedges in rice paddies. © 2024 Society of Chemical Industry.