In order to find new lead compounds with high pesticidal activity, a series of 1,3,4-oxadiazole thioether compounds (
5
series) were designed by using penthiopyrad as a synthon. They were synthesized easily via five steps by using ethyl 4,4,4-trifluoro-3-oxobutanoate and triethyl orthoformate as starting materials. The synthesized compounds were characterized by
1
H NMR,
13
C NMR and HRMS. The compound 2-(benzylthio)-5-(1-methyl-3-(trifluoromethyl)-1
H
-pyrazol-4-yl)-1,3,4-oxadiazole (
5a
) was further determined by X-ray single-crystal diffraction. It crystallized in the monoclinic system, space group
P2
1
/c
,
Z
= 4. All the 1,3,4-oxadiazole thioether derivatives were screened for fungicidal activity against ten fungi and herbicidal activity against two weeds. The bioassay results indicated that some of the synthesized 1,3,4-oxadiazole compounds exhibited good fungicidal activity (> 50% inhibition) against the plant pathogens
Sclerotinia sclerotiorum
and
Rhizoctonia solani
at 50 μg/mL. Some of them exhibited certain herbicidal activity, and compounds 2-((3-chlorobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1
H
-pyrazol-4-yl)-1,3,4-oxadiazole (
5e)
and 2-((4-bromobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1
H
-pyrazol-4-yl)-1,3,4-oxadiazole
(5 g)
had bleach effect. Molecular docking is to find the best fit orientation of the 2-((4-bromobenzyl)thio)-5-(1-methyl-3-(trifluoromethyl)-1
H
-pyrazol-4-yl)-1,3,4-oxadiazole
(5 g)
molecule with the SDH protein (PDB: 2FBW). The docking results indicate that the compound
5 g
and the lead compound penthiopyrad have similar binding interactions with SDH and carbonyl is a key group for these compounds.
Supplementary Information
The online version contains supplementary material available at 10.1007/s11164-022-04839-x.