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.

Development of a novel herbicide, metazosulfuron.

Metazosulfuron is a novel sulfonylurea herbicide discovered and developed by Nissan Chemical Industries, Ltd., which exhibits excellent herbicidal activity against Echinochloa spp., annual and perennial weeds including sulfonylurea resistant biotypes in paddy fields at 60-120 g a.i./ha with good crop safety to rice. In addition, it has favorable toxicological, ecotoxicological and environmental profile. Metazosulfuron (trade name; Altair®) was registered and launched in Japan in 2013, and has been also introduced in Korea and China as of 2016. This paper describes a history of discovery, syntheses, herbicidal characteristics and crop safety of metazosulfuron.

Iridium complex-catalyzed [2+2+2] cycloaddition of alpha,omega-diynes with monoynes and monoenes.

[reaction: see text] [Ir(cod)Cl]2/DPPE was found to be a new catalyst for the cycloaddition of alpha,omega-diynes with monoynes to give polysubstituted benzene derivatives in high yields. Internal monoynes as well as terminal monoynes could be used. The reaction tolerates a broad range of functional groups such as alcohol, amine, alkene, ether, halogen, and nitrile. The reaction of 1,6-octadiyne derivatives with 1-alkynes gives ortho products and meta products. The regioselectivity could be controlled by the choice of ligand. The reaction with DPPE was meta selective, with meta selectivity of up to 82%. The reaction with DPPF was ortho selective, with ortho selectivity of up to 88%. We propose a mechanism to account for this regioselective cycloaddition. [Ir(cod)Cl](2)/DPPE also catalyzed the cycloaddition of alpha,omega-diynes with 2,5-dihydrofuran to give bicyclic cyclohexadiene derivatives. The reaction with 2,3-dihydrofuran and n-butyl vinyl ether gave benzene derivatives instead of cyclohexadiene derivatives. We also propose a mechanism to account for this novel aromatization that includes cleavage of the C-O bond.

Iridium complex-catalyzed highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes: 2:1 coupling versus 1:2 coupling.

[reaction: see text] Highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes is achieved by using a catalytic amount of [Ir(cod)Cl](2) and ligand. The ligand had a considerable effect on the reaction. When 1,2-bis(diphenylphosphino)ethane was used, two molecules of dimethyl acetylenedicarboxylate (DMAD) reacted with one molecule of a monoyne to give the 2:1 coupling product. When 1,2-bis(dipentafluorophenylphosphino)ethane was used instead of dppe, one molecule of DMAD reacted with two molecules of a monoyne to give the 1:2 coupling product.