Minggui Chen

Research on controllable degradation of sulfonylurea herbicides

In order to seek ecologically safer and environmentally benign sulfonylurea herbicides (SU), insight into the structure/bioassay/soil degradation tri-factor relationship was first established. With the introduction of various groups (alkyl, nitro, halogen, cyano etc.) at the 5th position of its benzene ring, structural derivatives of chlorsulfuron were designed, synthesized, and evaluated for their herbicidal activity. The structures of the title compounds were confirmed by infrared spectroscopy, ultraviolet spectroscopy, 1H and 13C NMR, mass spectrometry, elemental analysis and X-ray diffraction. Bioassay results confirmed that most derivatives retained their superior herbicidal activities in comparison with chlorsulfuron. After investigating the soil degradation behavior of each molecule under set conditions, it was found that structures with electron-withdrawing substituents at the 5th position of the benzene ring retained their long degradation half-lives, yet the introduction of electron-donating substituents accelerated the degradation rate. These results will provide a valuable clue to further explore the potential controllable degradation of SU and other herbicides, and to discover novel herbicides that are favorable for environmentally and ecologically sustainable development.

Design, Synthesis and Herbicidal Activity of Novel Sulfonylureas Containing Tetrahydrophthalimide Substructure

To develop novel sulfonylurea herbicides, a series of chlorsulfuron derivatives was designed and synthesized through introducing tetrahydrophthalimide substructure taken from protoporphyrinogen IX oxidase(PPO) inhibitors onto the critical 5-position of the classical benzene ring. The structures of title compounds were confirmed by infrared spectroscopy, ultraviolet spectroscopy, 1H and 13C NMR spectrometry, mass spectrometry and elemental analysis. In addition, the crystal structure of compound II-5 was further determined by X-ray diffraction analysis. Bioassay results showed that individual compounds exhibited good herbicidal activities, especially compound II-8, which displayed 100% inhibition rate against Echinochloa crusgalli at 150 g/ha(1 ha=104 m2) with the method of foliage spray in the pot experiment.

Research on Controllable Degradation of Novel Sulfonylurea Herbicides in Acidic and Alkaline Soils

The degradation issue of sulfonylurea (SU) has become one of the biggest challenges that hamper the development and application of this class of herbicides, especially in the alkaline soils of northern China. On the basis of the previous discovery that some substituents on the fifth position of the benzene ring in Chlorsulfuron could hasten its degradation rate, apparently in acidic soil, this work on Metsulfuron-methyl showed more convincing results. Two novel compounds (I-1 and I-2) were designed and synthesized, and they still retained potent herbicidal activity in tests against both dicotyledons and monocotyledons. The half-lives of degradation (DT50) assay revealed that I-1 showed an accelerated degradation rate in acidic soil (pH 5.59). Moreover, we delighted to find that the degradation rate of I-1 was 9-10-fold faster than that of Metsulfuron-methyl and Chlorsulfuron when in alkaline soil (pH 8.46), which has more practical value. This research suggests that a modified structure that has potent herbicidal activity as well as accelerated degradation rate could be realized and this approach may provide a way to improve the residue problem of SUs in farmlands with alkaline soil.

Design, synthesis and insecticidal evaluation of novel N-pyridylpyrazolecarboxamide derivatives containing isoxazole, isoxazoline and 1,3,4-thiadiazole rings

With the introduction of various heterocyclic rings at the benzene part of anthranilic diamides, a series of N-pyridylpyrazolecarboxamide derivatives containing isoxazole, isoxazoline and 1,3,4-thiadiazole rings was designed, synthesized and evaluated for their insecticidal activities. The structures of the obtained novel target compounds were confirmed by means of 1H NMR, 13C NMR and HRMS. The bioassay results indicated that most of the target compounds displayed moderate or good insecticidal activities against oriental armyworm and diamondback moth at the adopted concentrations compared with chlorantraniliprole, especially compounds Ii and Il, of which the LC50 and LC95 values against oriental armyworm were further measured. The structure-activity relationship demonstrated that the introduction of chlorine in benzene ring, bromomethyl and acetoxyl substituents in 4,5-dihydroisoxazole part was more advantageous to improve the corresponding insecticidal activities than the introduction of other substituents and heterocycles.

Design, Synthesis and Herbicidal Activity of Novel Sulfonylureas Containing Triazole and Oxadiazole Moieties

Three novel series of 5-substituted sulfonylurea derivatives were designed and synthesized via introducing a triazole or oxadiazole ring at the 5th position of the benzene ring in classical sulfonylurea herbicides. All the target compounds were confirmed by means of 1H nuclear magnetic resonance(NMR), 13C NMR and elemental analysis. The bioassay results show that the target compounds containing an oxadiazole ring at the 5th position display moderate to excellent herbicidal activities against Brassica campestris and Amaranthus retroflexus under soil treatment. Especially, compounds zdk20, zdk21 and zdk22 possess 98.6%, 96.5% and 94.5% inhibition rates, respectively, against Amaranthus retroflexus at a concentration of 75 g/ha(1 ha=1×104 m2) under soil treatment, which approach to those of the commercial herbicide chlorsulfuron.