Synthesis and bioactivities of novel 2-(thioether/sulfone)-5-pyrazolyl-1,3,4-oxadiazole derivatives

By introducing the pyrazole moiety into the 5-position of 1,3,4-oxadiazole, a series of novel 2-(thioether/sulfone)-5-pyrazolyl-1,3,4-oxadiazole derivatives were synthesized. Preliminary bioassays suggested that target compounds exhibited appreciable activity against pathogenic bacteria Xanthomonas oryzae pv. oryzae ( Xoo ) and five phytopathogenic fungi in vitro . Among them, the half-maximal effective concentration (EC 50 ) values of 6c , 7a , 7b and 7c against Xoo were within 16.6   μg/mL and 65.7   μg/mL, which were better than those of commercial agricultural antibacterial bismerthiazol (92.6   μg/mL) and thiodiazole copper (121.8   μg/mL). While compounds 7a , 7b , and 7c exerted comprehensive antifungal activity toward five plant fungi, which were comparable with that of hymexazol. The results demonstrated that this kind of compounds can be further studied and developed as promising antifungal and antibacterial agents.