Synthesis and fungitoxicity of fluorinated-1,2,4-triazolo-and thiadiazolo[3,2-b]-1,3,4-oxadiazoles

2-Amino-5-aryl-1,3,4-oxadiazole 1 undergoes regioselective condensation wit h KSCN to give (5-aryl-1,3,4-oxadiazolyl)-thioureas 2a-c and with aryl isot hiocyanates to give N-phenyI-N'-(5-aryl-1,3,4-oxadiazol-2-yl)-thioureas 2d- i, in methanol. The ureas 2 on treatment with ethanol and iodine (till the decolourisation of iodine) yield 4. The compounds have been tested irt vitr o for their fungicidal activity against Cephalosporium saccharii, Aspergill us niger and Fusarium oxysporum and the results are compared with their par ent thioureas. The structural features of the tested compounds have been co rrelated with their fungicidal activity.