Synthesis, Crystal Structures, and Fungicidal Activity of Novel 1,5-Diaryl-3-(glucopyranosyloxy)-1H-pyrazoles

Synthesis, Fungicidal Activity, Structure–Activity Relationship and Density Functional Theory Studies of Novel Oxime Ether Derivatives Containing 1-Aryl-3-Oxypyrazoles

A series of 16 oxime ether derivatives containing 1-aryl-3-oxypyrazoles were synthesised, and the structure of one of them, (E)-methyl 2-(2-({(1-(4-chlorophenyl)-1H-pyrazol-3-yl)-oxy}methyl)phenyl)-2-(methoxyimino)acetate was determined by X-ray diffraction crystallography. Preliminary bioassays indicated that some of these compounds exhibited very good fungicidal activities against Rhizoctonia solani, especially the ester 2-(2-({(1-(4-chlorophenyl)-1H-pyrazol-3-yl)-oxy}methyl)phenyl)-2-(methoxyimino)acetate, which displayed greater activity than control compound pyraclostrobin at a dosage of 0.1 μg mL-1. The relationship between structure and fungicidal activity was discussed. Density functional theory studies of the 3-methyl heterocyclic ester and the 4-chorophenyl heterocyclic N-methylamide were carried out and the results discussed in terms of the wide difference in fungicidal activity shown by each compound.

Synthesis, Crystal Structure, and Fungicidal activity of Novel 1-Aryl-3-Oxypyrazoles Containing a Z-Configuration Methyl 2-(Methoxyimino) Acetate Moiety

Six novel methyl( Z)-2-(4-{[(1-aryl-1 H-pyrazol-3-yl)oxy]methyl}phenyl) 2-(methoxyimino)acetate were synthesised by the reaction of 1-aryl-1 H-pyrazol-3-ols with methyl ( Z)-2-[4-(bromomethyl)phenyl]-2-(methoxyimino)acetate. The structure of methyl ( Z)-2-[4-({[1-(4-chlorophenyl)-1 H-pyrazol-3-yl]oxy}methyl)phenyl]-2-(methoxyimino)acetate was also determined by single-crystal X-ray diffraction analysis. A preliminary in vitro bioassay indicated that compounds 3-chlorophenyl, 4-chlorophenyl and 4-fluoro-3-(trifluoromethyl) derivatives exhibited moderate fungicidal activity against Rhizoctonia solani at a dosage of 10 μg mL-1.

Synthesis and fungicidal activity of novel chloro-containing 1-aryl-3-oxypyrazoles with an oximino ester or oximino amide moiety

Six novel chloro-containing 1-aryl-3-oxypyrazoles TMa–TMf with an oximino ester or an oximino amide moiety were prepared by the reaction of 1-aryl-1H-pyrazol-3-ols with benzyl bromide. Their structures were characterized by ¹H-NMR, ¹³C-NMR, IR, MS, and elemental analysis. A preliminary in vitro bioassay indicated that compounds TMa, TMe and TMf displayed excellent fungicidal activity against Rhizoctonia solani and could be used as potential lead compounds for further development of novel fungicides.

Crystal structures, vibrational spectra, and fungicidal activity of 1,5-diaryl-3-oxypyrazoles

The aryloxypyrazole structure is present in a number of bioactive molecules. Four 1,5-diaryl-3-oxypyrazoles containing benzoyl (I), thiazolidinethione (II and III) or per-O-acetylated glucopyranosyl (IV) moieties were characterized by single-crystal X-ray diffraction. Compounds I and II crystallize in a triclinic P-1 system, whereas III and IV crystallize in an orthorhombic Pbca and a monoclinic P21 space groups, respectively. The dihedral angles between the two benzene rings of the pyrazole are 61.33° (I), 62.87° (II), 57.09° (III) and 70.25° (IV). The structures were stabilized by classical intra- (C-H···S for II and III, C-H···O for IV) and intermolecular (C-H···O for I and IV) H-bonds, as well as intermolecular C-H···π stacking interactions. The theoretical FTIR results showed good agreement with the experimental data. Compounds IV, II and III showed moderate fungicidal activity against Sclerotinia sclerotiorum and Gibberella zeae. The structure-activity relationships were discussed.