title: Synthesis and herbicidal activity of 2-(7-fluoro-3-oxo- 3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)isoindoline-1,3-diones.
abstract: The mode of action of 2-(7-fluoro-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)-4,5,6,7-tetrahydro-2H-isoindoline-1,3-diones, including the commercial herbicide flumioxazin, had been identified as inhibition of protoporphyrinogen oxidase (protox). As part of continuous efforts to search for new herbicides with high efficacy, broad-spectrum activity, and safety to crops, flumioxazin and its iodo analogue (B2055) were used as lead compounds for further optimization. Series of novel compounds were prepared by multistep synthetic procedures starting from 5-fluoro-2-nitrophenol. All of the test compounds were structurally confirmed by 1H NMR, IR, mass spectroscopy, and elemental analysis. Preliminary bioassay data showed that some of them possess commercial levels of herbicidal activity comparable to those of other protox-inhibiting herbicides. One of the best compounds, 5-fluoro-2-(7-fluoro-3-oxo-4-(prop-2-ynyl)-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)isoindoline-1,3-dione (8e), has IC50 values for velvetleaf (Abutilon theophrasti Medic) and crabgrass (Digitaria sanguinalis) comparable to thos of B2055. With respect to crop selectivity, compound 8e is similar to flumioxazin. Compound 8e is safe to cotton and maize at a rate of 150 g of active ingredient (ai)/ha or less when applied at pre-emergent stage, and it has the best safety to wheat among the tested crops, showing no injury after post-emergent application at 7.5-30 g of ai/ha.
authors.affiliation: College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, China. huang-mz@l63.com
authors.forename: Ming-Zhi
authors.initials: MZ
authors.lastname: Huang
authors.forename: Ke-Long
authors.initials: KL
authors.lastname: Huang
authors.forename: Ye-Guo
authors.initials: YG
authors.lastname: Ren
authors.forename: Man-Xiang
authors.initials: MX
authors.lastname: Lei
authors.forename: Lu
authors.initials: L
authors.lastname: Huang
authors.forename: Zhong-Ke
authors.initials: ZK
authors.lastname: Hou
authors.forename: Ai-Ping
authors.initials: AP
authors.lastname: Liu
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Ou
mesh_terms: D048588:Benzoxazines; D006540:Herbicides / Q000138:chemical synthesis* / Q000494:pharmacology*; D010078:Oxazines / Q000138:chemical synthesis* / Q000494:pharmacology*; D010797:Phthalimides / Q000138:chemical synthesis / Q000494:pharmacology; D010944:Plants / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D048588:Benzoxazines; D006540:Herbicides; D010078:Oxazines; D010797:Phthalimides; C106487:flumioxazin