Abstract
A series of novel strobilurin analogues (1a-1f, 2a-2e, 3a-3e) containing arylpyrazole rings were synthesized and characterized by NMR spectroscopy. The structures of 1f, 2b and 3b were also determined by single crystal X-ray diffraction analysis. These analogues were collected together with other twenty-eight similar compounds 4a-4f, 5a-5h, 6a-6h and 7a-7f from our previous studies, for in vitro bioassays and thorough structure-activity relationships (SARs) studies. Most compounds exhibited excellent-to-good fungicidal activity against Rhizoctonia solani, especially 5c, 7a, 6c, and 3b with 98.94%, 83.40%, 71.40% and 65.87% inhibition rates at 0.1 μg mL−1, respectively, better than commercial pyraclostrobin. Comparative molecular field analysis (CoMFA) was employed to study three-dimensional quantitative structure-activity relationships (3D-QSARs). Density functional theory (DFT) calculation was also carried out to provide more information regarding SARs. The present work provided some hints for developing novel strobilurin fungicides.
Highlights
The resistance of pathogens has become one of the puzzling problems to crop protection, and the main solution is to develop novel fungicides with unique structures and mechanisms of action
Readily accessible 2-(o-tolyl)acetic acid was used as starting material, and intermediate III-c could be obtained through three steps including esterification, condensation and methylation
The present work indicated that 5c (98.94% at 0.1 μg mL−1, methoxyiminoacetate pharmacophore, R = 4-Cl, X = H), 7a (83.40% at 0.1 μg mL−1, methoxyiminoacetate pharmacophore, R = H, X = Cl), 6c (71.40% at 0.1 μg mL−1, methoxyiminoacetamide pharmacophore, R = 4-Cl, X = H) and 3b (65.87% at 0.1 μg mL−1, methoxyacrylate pharmacophore, R = 4-Cl, X = H) could be used as potential lead compounds for further studies of novel fungicides
Summary
A previous report by Kim et al.[18] described that intermediate (E)-methyl 3-methoxy-2-(o-tolyl)acrylate III-c could be synthesized from 1-bromo-2-methylbenzene and (E)-methyl 3-methoxyacrylate via Suzuki-Miyaura coupling reaction (Fig. 3). This approach required Grignard reagent and costly catalyst Pd(PPh3)[4], which faced harsh reaction conditions and complicated processes. Several strobilurin analogues (4a-4f, 5a-5h, 6a-6h, Fig. 1) have been prepared by the substitution of N-arylpyrazoles with benzyl bromide in acetone, using potassium carbonate (K2CO3) as acid-binding agent[7,8] Motivated by this reaction, in our procedure, N-arylpyrazoles IV and I were allowed to react with benzyl bromide II and III, respectively, in a molar 1:1.1 equiv. Empirical formula CCDC number Formula weight Temperature [K] Wavelength [Å] Crystal system Space group Unit cell dimensions a [Å] b [Å] c [Å] α [°] β [°] γ [°] Volume [Å3] Z ρcalcd [g cm−3] μ [mm−1] F(000) Crystal size [mm3] θ range [°] for data collection Index ranges
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
