Studies on Herbicidal Activities of Phenoxypyridines

Fujikawa, K.; Kondo, Katsuhide; Yokomichi, Isao; Kimura, Fumio; Haga, Takahiro; Nishiyama, Ryuzo

doi:10.1080/00021369.1970.10859585

Cited by 8 publications

(3 citation statements)

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“…In the literature, rare examples utilizing C−H bond activation/functionalization were investigated toward 2-aryloxypyridine compounds . On the other hand, herbicidal and antimycobacterial activities of aryloxypyridine derivatives have been systematically investigated, whereas the structure−activity relationship of phenoxypyridine and its analogues in the investigation of thyroid hormone was also studied . We herein present palladium(II)-catalyzed direct ortho arylation of 2-phenoxypyridine and its derivatives with potassium aryltrifluoroborates via C−H bond activation and demonstrated that the pyridines can be further removed to produce ortho -arylated phenols.…”

Section: Introductionmentioning

confidence: 99%

Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization

Chu

Lin

2010

Organometallics

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An efficient synthesis of ortho-arylated 2-phenoxypyridines catalyzed by palladium acetate is described. Treatment of 2-phenoxypyridines with two and a half equivalents of potassium aryltrifluoroborate and 10 mol % of Pd(OAc) 2 in the presence of two equivalents of Ag 2 CO 3 , one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H 2 O at 130-140 °C for 48 h in dried CH 2 Cl 2 gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. p-Benzoquinone is found to be an important ligand and co-oxidant for the transmetalation reductive elimination step in the catalytic reaction. The investigation of kinetic isotope effect (k H /k D ) is determined to be 5.25, which indicates that C-H bond cleavage occurs in the rate-determining step. One of the arylated compounds, 2-(4 0 -nitrobiphenyl-2-yloxy)pyridine, was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-(4nitrophenyl)phenol in 79% yield, demonstrating that pyridine is a removable directing group.

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Section: Introductionmentioning

confidence: 99%

Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization

Chu

Lin

2010

Organometallics

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“…Following the general procedure 2-bromopyridine (0.155 mL, 1.6 mmol) and 2,4-dichlorophenol (0.39 g, 2.4 mmol) yielded 0.157 g of DCP-O-pyr as a clear oil (41%): 1 H NMR (300 MHz, CD 2 Cl 2 ) δ 8.15 (dd, J = 4.9, 1.2 Hz, 1H), 7.74 (td, J = 7.2, 2.0 Hz, 1H), 7.49 (d, J = 2.5 Hz, 1H), 7.30 (dd, J = 8.6, 2.5 Hz 1H), 7.17 (d, J = 8.7 Hz, 1H), 7.05–7.00 (m, 2H); 13 C NMR (151 MHz, CDCl 3 ) δ 162.6, 148.5, 147.4, 139.6, 130.7, 130.3, 128.2, 128.0, 124.7, 118.8, 111.1.…”

Section: Methodsmentioning

confidence: 99%

Influence of Chlorine Substitution on the Hydrolytic Stability of Biaryl Ether Nucleoside Adducts Produced by Phenolic Toxins

et al. 2013

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A kinetic study is reported for the acid-catalyzed hydrolysis of oxygen (O)-linked biaryl ether 8-2'-deoxyguanosine (dG) adducts produced by phenolic toxins following metabolism into phenoxyl radical intermediates. Strikingly, the reaction rate of hydrolysis at pH 1 decreases as electron-withdrawing chlorine (Cl) substituents are added to the phenoxyl ring. The Hammett plot for hydrolysis at pH 1 shows a linear negative slope with ρX = -0.65, implying that increased Cl-substitution diminishes the rate of hydrolysis by lowering N(7) basicity. Spectrophotometric titration provided an N(7)H(+) pKa value of 1.1 for the unsubstituted adduct 8-phenoxy-dG (Ph-O-dG). Model pyridine compounds suggest N(7)H(+) pKa values of 0.92 and 0.37 for 4-Cl-Ph-O-dG and 2,6-dichloro-Ph-O-dG (DCP-O-dG), respectively. Density functional theory (DFT) calculations also highlight the ability of the 8-phenoxy substituent to lower N(7) basicity and predict a preference for N(3)-protonation for highly chlorinated O-linked 8-dG adducts in water. The calculations also provide a rationale for the hydrolytic reactivity of O-linked 8-dG adducts in the gas-phase, as determined using electrospray mass spectrometry (ESI-MS). The inclusion of our data now establishes that the order of hydrolytic reactivity at neutral pH for bulky 8-dG adducts is N-linked> C-linked > O-linked, which correlates with their relative ease of N(7)-protonation.

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“…To obtain a safener for fomesafen, the active structure of fomesafen was studied. The structure of the diphenyl ether group in fomesafen, shared by all diphenyl ether herbicides, was removed and replaced by phenoxypyridine via a bioisosteric strategy [23,24,25,26]. As a mature safener, furilazole exhibited good biological activity and had an oxazolidine reactive group in common with other safeners [27,28].…”

Section: Introductionmentioning

confidence: 99%

Novel Thiazole Phenoxypyridine Derivatives Protect Maize from Residual Pesticide Injury Caused by PPO-Inhibitor Fomesafen

et al. 2019

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The herbicide fomesafen has the advantages of low toxicity and high selectivity, and the target of this compound is protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4). However, this herbicide has a long residual period and can have phytotoxic effects on succeeding crops. To protect maize from fomesafen, a series of thiazole phenoxypyridines were designed based on structure–activity relationships, active substructure combinations, and bioisosterism. Bioassays showed that thiazole phenoxypyridines could improve maize tolerance under fomesafen toxicity stress to varying degrees at a dose of 10 mg·kg−1. Compound 4i exhibited the best effects. After being treated by compound 4i, average recovery rates of growth index exceeded 72%, glutathione content markedly increased by 167% and glutathione S-transferase activity was almost 163% of fomesafen-treated group. More importantly, after being treated by compound 4i, the activity of PPO, the main target enzyme of fomesafen, recovered to 93% of the control level. The molecular docking result exhibited that the compound 4i could compete with fomesafen to bind with the herbicide target enzyme, which consequently attained the herbicide detoxification. The present work suggests that compound 4i could be developed as a potential safener to protect maize from fomesafen.

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Studies on Herbicidal Activities of Phenoxypyridines

Cited by 8 publications

References 0 publications

Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization

Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization

Influence of Chlorine Substitution on the Hydrolytic Stability of Biaryl Ether Nucleoside Adducts Produced by Phenolic Toxins

Novel Thiazole Phenoxypyridine Derivatives Protect Maize from Residual Pesticide Injury Caused by PPO-Inhibitor Fomesafen

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