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

Abstract

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.