Search

A series of 3-phenyl benzo[d][1,2,3]triazin-4(3H)-one derivatives were synthesized through the condensation of phenol E and alkyl (alkenyl, alkynyl) chlorides (bromides, iodide) or alkyl chloroacetates or N-alkyl chloroacetamides using K2CO3 as the acid acceptor in N,N-dimethylformamide. Phenol E was prepared from starting material, 5-amino-2-chloro-4-fluorophenyl ethyl carbonate, in four steps involving in amidation, reduction, diazotization, and deprotecting-group reaction. The herbicidal activities of the title compounds were tested against two dicotyledonous plants and two monocotyledonous plants, in which some of them exhibited high herbicidal activities against two dicotyledonous plants in preemergence and postemergence treatments. Moreover, when the dosage was decreased to 180 and 90 g/ha, compounds F1, F8, and F9 showed highly selective inhibitory activities against amaranth pigweed, alfalfa, asteraceae, field sowthistle, morning glory, purslane, and velvetleaf in postemergence treatment but had no herbicidal efficacy on rape except F1, suggesting that it be possible to find a kind of herbicides to inhibit dicotyledonous weeds in the field of dicotyledonous crops with the same genus as aforementioned weeds.

A variety of 3-N-substituted amino-6-benzyloxypyridazine derivatives were designed and synthesized in satisfactory yields. Their structures were confirmed by IR, 1H-NMR, and elemental analysis; compound 5j was further determined by X-ray diffraction crystallography. Their herbicidal activities were evaluated through barnyard grass and rape cup tests in laboratory bioassays. Most of the title compounds 5 displayed moderate herbicidal activities against the dicotyledonous plant Brassica campestris L. The most active compounds in the laboratory were also evaluated in the greenhouse.

A computer-assisted retention prediction system (RPS) of fifteen O-ethyl O-aryl N-isopropyl phosphoramidothioates (1) in reversed-phase HPLC was investigated. The system is based on the use of four physicochemical parameters (hydrophobicity II, electric effect σ, field effect F and steric effect Es) which is closely related to the retention mechanism in reversed-phase HPLC. The system was evaluated by comparing the measured retention data with the predicted ones. The predicted values were consistent with the measured values within a relative error of 11.5%.

In order to obtain new lead compounds with high herbicidal activity, a series of 5-amino pyrazole derivatives were designed and synthesized using a series of relational synthons. Their structures were determined by IR, 1H NMR, and elemental analyses. These compounds were screened for herbicidal activities against rape and barnyard grass. Their structure-activity relationships are discussed.

A series of novel 6,7,8,9-tetrahydro-2-(2-aryloxypyrimidin-4-yl)-2H-[1,2,4]triazolo[4,3-a]azepin-3(5H)-ones were designed and efficiently synthesized. Their structures were determined by IR, 13C and 1H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a-5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1-(azepan-2-ylidene)-2-(2-chloropyrimidin-4-yl)-hydrazine (3) was studied and the reason for the low yield in the initial procedure is discussed as well.

A series of 2-cyano-3-methylthio-3-substituted methylaminoacrylates were synthesized as herbicidal inhibitors of photosystem II (PSII) electron transport, in order to estimate the effect of fluorine atom, pyridyl group, chirality and ester chain on activity. The important intermediate 2-fluoro-5-aminomethylpyridine was synthesized with high yield. The bioassay results showed that most of title compounds had high herbicidal activity in postemergence treatment. The introduction of an α-methyl into the 3-substituted methylamino could improve the activity notably. The replacement of hydrogen by chlorine or fluorine group and phenyl by pyridyl group showed different effects, and at the same time, the ester chain affected the activity too.

A series of novel alpha,alpha,alpha-trifluoro-m-tolyl pyridazinone derivatives was synthesised. Herbicidal activities of the two intermediate compounds and 15 pyridazinone derivatives were evaluated through barnyardgrass and rape cup tests and Spirodela polyrrhiza (L.) Schleiden tests. Selected compounds were also evaluated under greenhouse conditions. Bleaching activities were observed at 10 microg ml(-1) and some compounds exhibited herbicidal activities at a rate of 300 g ha(-1). The relationship between crystal structures and herbicidal activities is discussed through a comparison of two compounds (5a and 5f).

Two series, totaling twelve, of new compounds, ethyl 1-aroyl/(aroylmethyl)-5-methyl-3-methylthiopyrazole-4-carboxylates (5/6), have been synthesized via highly regioselectively acylation and alkylation reactions of ethyl 3-methyl-5-methylthio-1 H-pyrazole-4-carboxylate (2a) with aroyl chloride (3) and eco-friendly reagents alpha-tosyloxysubstituted acetophenones (4), respectively, and a green protocol has been developed. The acylation reactions were carried out under ultrasound irradiation, and the alkylation reactions were under microwave irradiation and ultrasound irradiation, respectively. Conventional reaction conditions, as well as the use of alpha-bromosubstituted acetophenone (4′) have also been applied in the synthesis of some randomly selected compounds in both series and have generated identical compounds correspondingly. Unexpected structures of compounds were unambiguously determined by X-ray crystallographic analysis.

A series of novel sulfone-containing pyrazolo[1,5-a]pyrimidines (2-3) and pyrazolo[5,1-d][1,2,3,5]tetra-zine-4(3H)-ones (5a-5k) were designed and efficiently synthesized, some of which have been identified as being potential rape inhibitors. These results widen the structural diversity of rape inhibitors and confirm the perspectives of further investigations in this area. Moreover, a plausible reaction mechanism is outlined.

A series of new 2-aryl-7-cyano/ethoxycarbonyl-6-methylthio-1H-imidazo[1,2-b]pyrazoles (5) have been synthesized in moderate to good yields, via a two-step cyclocondensation procedure of 5-amino-4-cyano/ethoxycarbonyl-3-methylthio-1H-pyrazole (1) and α-bromoacetophenones (3) or α-tosyloxyacetophenones (2), which were prepared by the reactions of acetophenones with [hydroxy(tosyloxy)iodo]benzene (HTIB). The intermediates, 5-amino-1-(aroylmethyl)-4- cyano/ethoxycarbonyl-3-methylthio-1H-pyrazoles (4), have been isolated, serving as evidence for the regioselectivity. When utilizing α-tosyloxy-acetophenones, the reactions were more eco-friendly, the reaction time was significantly reduced and the synthetic procedure was more convenient and easier to manipulate. Surprisingly, using potassium carbonate to displace sodium carbonate in the synthesis of 4, in the case of 1 (R CN), two novel cyclocondensation products have been isolated and fully characterized, followed by the proposal of a plausible mechanism.

The title compound, C16H23N5O3S, ethyl 5-amino-l-(5′-methyl-l'-t-butyl-4′-pyrazolyl)carbonyl-3-methylthio 1H-pyrazole-4-carboxylate (5) has been synthesized by the treatment of ethyl 2-cyano-3,3-dimethylthioacrylate with 1 -t-butyl-5-methyl-4-hydrazinocarbonylpyrazole (4) in refluxed ethanol. The possible mechanism of the above reaction was also discussed. The results of biological test show that the title compound has fungicidal and plant growth regulation activities.

For the purpose of better understanding the molecular mechanism of action of sulfonylurea and sulfonamide herbicides, the quantitative relationship between their structure and herbicidal activity against rape, Brassica campestris L, was analysed using physicochemical parameters and regression analysis and comparative molecular field analysis (CoMFA). The results showed that the structure–activity relationships of the two sets of compounds were identical, which suggested that the two different sets of compounds affect a common region of the receptor site. The CoMFA results were consistent with those derived from traditional QSAR analysis. Combining the traditional QSAR analysis with the CoMFA results, we can conclude that the variations in the herbicidal activity of the two sets of ALS inhibitors were governed dominantly by the three-dimensional steric and electrostatic field parameters of molecules participating in the interaction with the receptor site and there is apparently an optimum electronic property (Σσ or pKa) for the molecules to fit the receptor. © 1999 Society of Chemical Industry

A series of 2-(3-(trifluoromethyl)-5-(alkoxy)-1H-pyrazol-1-yl)-4-aryloxypyrimidine derivatives were designed and synthesized. The structures of all the title compounds were confirmed by 1H NMR and elementary analysis. These compounds were screened for herbicidal activity against rape and barnyard grass. Compound B13 exhibited moderate herbicidal activity.

A series of novel 6,7,8,9-tetrahydro-2-(2-aryloxypyrimidin-4-yl)-2H-[1,2,4]triazolo[4,3-a]azepin-3(5H)-ones were designed and efficiently synthesized. Their structures were determined by IR, 13C and 1H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a-5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1-(azepan-2-ylidene)-2-(2-chloropyrimidin-4-yl)-hydrazine (3) was studied and the reason for the low yield in the initial procedure is discussed as well.

Ethyl 5-amino-3-trifluoromethyl-1H-pyrazole-4-carboxylate (1) was efficiently synthesized via the condensation of ethyl cyanoacetate and trifluoroacetic anhydride, followed by chloridization and the condensation with aqueous hydrazine. Its unique reactivity was exploited for the synthesis of trifluoromethylated pyrazolo[1,5-a]pyrimidine (5) and pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones (8a–j). Among them, 5 was firstly found to be a novel fluorescent molecule that might be exploited as an attractive fluorophore for possessing many binding sites, and its fluorescence intensity was obviously stronger than its methyl analogue. 8 were found to be a new chemical class of potential monocotyledonous Echinochloa crus-galli L. Beauv inhibitors, and were more active than their methyl analogues.

A series of novel sulfone-containing pyrazolo[1,5-a]pyrimidines (2-3) and pyrazolo[5,1-d][1,2,3,5]tetra-zine-4(3H)-ones (5a-5k) were designed and efficiently synthesized, some of which have been identified as being potential rape inhibitors. These results widen the structural diversity of rape inhibitors and confirm the perspectives of further investigations in this area. Moreover, a plausible reaction mechanism is outlined.