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.
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.
Huang
Ming-Zhi
MZ
College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, China. huang-mz@l63.com
Huang
Ke-Long
KL
Ren
Ye-Guo
YG
Lei
Man-Xiang
MX
Huang
Lu
L
Hou
Zhong-Ke
ZK
Liu
Ai-Ping
AP
Ou
Xiao-Ming
XM
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
D048588:Benzoxazines; D006540:Herbicides; D010078:Oxazines; D010797:Phthalimides; C106487:flumioxazin