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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.

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 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.