Dehydroabietic acid chloride was prepared by the reaction of dehydroabietic acid with thionyl chloride, followed by the reaction of the dehydroabietic acid chloride with hydrazine hydrate to provide dehydroabietacyl hydrazine. A series of target compounds 2-substituted amino-5-dehydroabietyl-1,3,4-oxadiazoles 5 were synthesized by the cyclization of 1-dehydroabietacyl-4-substituted thiosemicarbazides (4) under catalysis of Hg(OAc)₂/EtOH. And the intermediates 4 were prepared by the reaction of dehy-droabietacyl hydrazine with aryl isothiocyanates. The intermediates 4 and target compounds 5 were analyzed and characterized by means of IR, MS, ¹H NMR, ¹³C NMR techniques and elemental analysis. The preliminary herbicidal assay showed that all the compounds 4 and 5 exhibited a certain growth inhibition on rape root (Brassica campestris) and barnyard grass (Echinochloa crusgalli (L.)). Among the tested compounds, 4d dis-played 88.2% inhibition on rape root (Brassica campestris) at 100 mg/L concentration in herbicidal tests.

Key words: dehydroabietic acid, 1-dehydroabietacyl-4-substituted thiosemicarbazide, 2-substituted amino-5-dehydroabietyl-1,3,4-oxadiazole, herbicidal activity