Synthesis and Insecticidal Activity of 1,2,4-Oxadiazoles Derivates against (Plutella xylostella L.) Diamondback Moth

The diamondback moth (Plutella xylostella) is a cosmopolitan pest known for its destruction of cruciferous plants. Commercial insecticides, such as Decis 25 EC and Azamax, are the main forms of controlling this pest in irrigated systems in the agricultural communities of the city of Garanhuns (northeastern Brazil). However, the difficulty in controlling this pest resides in its high fecundity and short lifecycle, which serve as resistance mechanisms to insecticides. Considering the immediate need to find alternative products to insecticides employed in these agricultural communities, nine 1,2,4-oxadiazoles were synthesized using an easy, mild method with high to moderate yields. The effect of 4-(3-phenyl-1,2,4-oxadiazole-5-yl)-butan-2-one (6a), 4-(3-p-tolyl-1,2,4-oxadiazol-5-yl)-butan-2-one (6c) and (R, S)-3-p-benzylphenyl-1,2,4-oxadiazole-5-yl)-ethanol (7e) and its precursors was assessed against third instar larvae of Plutella xylostella and the results were compared to commercial insecticides available in the communities. Compounds 6a and 6c exhibited the same level of toxicity but were more toxic than compound 7e. All 1,2,4-oxadiazoles exhibited high toxicity. P. xylostella was less susceptible to the commercial insecticides used as the positive controls than the 1,2,4-oxadiazole derivatives. The results demonstrate that the larvae of P. xylostella are highly sensitive to the ring of 1,2,4-oxadiazole, which can be used as a potential insect-control agent. The present study aimed to describe the synthesis and evaluate the insecticidal activity of 4-(3-aryl-1,2,4-oxadiazole-5-yl)-butan-2-one and (R,S)-3-aryl-5-(1-hydroxy-ethyl)-1,2,4-oxadiazole against P. xylostella.