Abstract
In a search for novel agrochemicals with high activity and low toxicity, a series of diheterocyclic compounds containing 1,2,4βtriazolo[1,5βa]pyrimidine and 1,3,4βoxadiazole rings were designed and synthesized by a fourβstep synthetic route starting from 2βmercaptoβ5,7βdimethylβ1,2,4βtriazolo[1,5βa]pyrimidine. The structures of all the compounds synthesized were confirmed by ^1^H NMR, mass spectroscopy and elemental analysis. The preliminary bioassay against Brassica campestris L and Echinochloa crusgalli Beavu indicated that the title compounds displayed herbicidal activity at the concentration of 100βppm and that compounds 5a (Rβ=βCH~3~), 5d (Rβ=βC~2~H~5~) and 5f (Rβ=βiβBu) were found to have particularly high activities. In addition, the results of an in vivo test at a concentration of 50βppm showed that all the compounds prepared were highly active against Rhizoctonia slain, but not active against Fusarium oxysporum, Gibberella zeave and Phoma sparagi. A further in vivo test showed that compound 5j possessed better fungicidal activity against Rhizoctonia solani at a concentration of 200βppm than Carbendazim and Validamycin A, which are well known for their fungicidal activity against Rhizoctonia solani. To our knowledge, this is the first report that 1,2,4βtriazolo[1,5βa]pyrimidine derivatives display fungicidal activity against Rhizoctonia solani.
Β© 2001 Society of Chemical Industry