Benzoxazoles as novel herbicidal agents

Abstract

Despite the need to develop new herbicides with different modes of action, due to weed resistance, many important classes of compounds have been studied poorly for this purpose. Benzoxazoles are considered privileged structures because of their biological activities, but their phytotoxic activities have not received a lot of attention until now.Double vinylic substitution reactions were carried out to furnish four 2‐nitromethylbenzoxazoles and one oxazolidine. Benzoxazol‐2‐ylmethanamine was obtained by reduction of compound 3a. These compounds were evaluated for their phytotoxicity in Allium cepa (onion), Solanum lycopersicum (tomato), Cucumis sativus (cucumber) and Sorghum bicolor (sorghum). Comparison with oxazolidine analogue allowed us to understand that the benzoxazolic structure is very important for the herbicidal activity. All the synthesized compounds exhibited biological activity on seed germination. The four 2‐nitromethylbenzoxazoles showed phytotoxic activity and the 5‐chloro‐2‐(nitromethyl)benzo[d]oxazole (3b) exhibited higher inhibition than the commercial herbicide against all four plant species tested. © 2018 Society of Chemical Industry.