Synthesis and fungicidal activity against Rhizoctonia solani of 2-alkyl (alkylthio)-5-pyrazolyl-1,3,4-oxadiazoles (thiadiazoles)

Some series of 2-alkyl (alkythio)-5-((4-chloro)-3-ethyl-1-methyl-1H-pyrazole-5-yl)-1,3,4-oxadiazoles (thiadiazoles) were prepared as potential fungicides. Their fungicidal activity was evaluated against rice sheath blight, which is a major disease of rice in China. Structure-activity relationships for the screened compounds were evaluated and discussed. It was found that 5-(4-chloro-3-ethyl-1-methyl-1H-pyrazole-5-yl)-1,3,4-thiadiazole-2-thione has the higher fungicidal activity.