A series of novel diphenyl ether derivatives containing unsaturated carboxylates were designed and synthesized. Their structures were identified by (1)H nuclear magnetic resonance and elemental analyses. The bioassays indicated that the compounds 5b and 5c exhibited good herbicidal activities against velvetleaf at a concentration of 30-40 g/hm(2). The relationship between structure and herbicidal activity was also discussed. Among unsaturated carboxylates group, butenoate is the most promising one. Amonst them, 4-ethoxy-4-oxobutenyl 5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoate 5b was identified as the most promising candidate due to its high protoporphyrinogen IX oxidase inhibition effect (pI(50) = 6.64) and good herbicidal activity against broadleaf weeds with selectivity to soybean and low toxicity to mammals.
A series of novel substituted 3-(pyridin-2-yl)benzenesulfonamide derivatives were designed and synthesized using 2-phenylpridines as the lead compound by intermediate derivatization methods in an attempt to obtain novel compound candidates for weed control. The herbicidal activity assay in glasshouse tests showed several compounds (II6, II7, II8, II9, II10, II11, III2, III3, III4, and III5) could efficiently control velvet leaf, youth-and-old age, barnyard grass, and foxtail at the 37.5 g/ha active substance. Especially, the activities of II6, II7, III2, and III4 were proved roughly equivalent to the saflufenacil and better than 95% sulcotrione at the same concentration. The result of the herbicidal activity assay in field tests demonstrated that II7 at 60 g/ha active substance could give the same effect as bentazon at 1440 g/ha active substance to control dayflower and nightshade, meanwhile II7 showed better activity than oxyfluorfen to control arrowhead and security to rice. The present work indicates that II7 may be a novel compound candidate for potential herbicide.
BACKGROUND
Glyphosate is the most widely used and successful herbicide discovered to date, but its utility is now threatened by the occurrence of several glyphosate‐resistant weed species. Saflufenacil is a relatively new herbicide developed by BASF in 2010. It is a highly effective selective herbicide showing excellent control on broadleaf weeds (more than 90 species), significantly superior to other protoporphyrinogen oxidase (PPO) inhibitor herbicides at the level of weeds controlled. It is also effective against glyphosate‐resistant Conyza canadensis if used in combination with glyphosate. A series of novel uracil‐based PPO inhibitors containing an isoxazoline moiety were designed via the intermediate derivatization method, synthesized using a key saflufenacil raw material as starting material and evaluated for herbicidal activity.
RESULTS
The target compounds were characterized by 1H NMR and high‐resolution electrospray mass spectra. Bioassays indicated that some title compounds can control efficiently and effectively both broadleaf weeds and grassy weeds at low doses, especially the glyphosate‐resistant weeds C. canadensis and Eleusine indica.
CONCLUSION
This work provides a basis for further studies of 9b for control of a wider range of weeds, particularly for glyphosate‐resistant weeds.
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