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With the increase of herbicide-resistant weeds, novel, more selective and even more potent herbicides to control weeds are needed. In this paper, a series of N-fluorinated phenyl-N′-pyrimidyl urea derivatives were synthesized and screened for their herbicidal activities against Amaranthus retroflexus (AR) and Setaria viridis (SV). Compound 25 (N-(3-trifluoromethylphenyl)-N′-(2-amino-4-chloro-6-methylpyrimidyl) urea) exhibited marked herbicidal activity against SV (IC50 = 11.67 mg/L) and is more potent than bensulfuron (IC50 = 27.45 mg/L), a commercially available herbicide. A statistically significant CoMFA model with high prediction abilities (q2 = 0.869, r2 = 0.989) was obtained.

To study the growth effects of differing concentrations of bensulfuron-methyl on Chlorella pyrenoidosa and to evaluate the ecological risk, the effects of bensulfuron-methyl on the growth and the content change of chlorophyll and protein in Chlorella pyrenoidosa were studied through 96 h acute toxicity tests. Bensulfuron-methyl accelerated the growth of algae at lower concentrations (＜1 mg L^(-1)) with content increase of chlorophyll or protein, and it inhibited the growth of algae at higher concentrations (＞5 mg L^(-1)). The content of chlorophyll or protein in algae cells reduced with the increasing concentration of bensulfuron-methyl, exhibiting the good concentration-effect relationship. The 96h-EC50 of bensulfuron-methyl upon the algae was 15.7 mg L^(-1). Bensulfuron-methyl has inhibiting effect on the growth of Chlorella pyrenoidosa and is low in toxicity.

With the objective of finding valuable herbicidal candidates, a series of new 5-heterocycloxy-3-methyl-1-substituted-1H-pyrazoles were synthesized and their herbicidal activities were evaluated. The bioassay results showed that some compounds exhibited excellent herbicidal activities at the concentration of 100 mg/L, and compound 5-chloro-2-((3-methyl-1-(2,2,2-trifluoroethyl)-1H-pyrazol-5-yl)oxy)pyrimidine showed bleaching activity to green weeds. In greenhouse conditions, this compound also showed excellent post-emergence herbicidal effect against Digitaria sanguinalis L. at the dosage of 750 g a. i. ha(-1).