Herbicidal Activity of New α-Chloroacetamide Derivatives

Abstract

In order to identify a new effective rice herbicide, α-chloroacetanilide derivatives were synthesized and their herbicidal activity and safety to rice were examined in a pot test carried out in a green house. The results are summarized as follows:
1. Pre-emergence treatment
The effects of the compound substituted on the amide nitrogen atom (Y) on the pre-emergence herbicidal activity against Echinochloa oryzicola VASING. and rice phytotoxicity were studied and the 2-thienylmethyl group was found to be most suitable (Table 2). The introduction of a methoxyl, methyl or chloro group at the 3 position on the thiophene ring further enhanced the activity (Table 3). The compounds used for substitution of the aniline moiety (X) greatly affected the activity and high activities were associated with the 2, 6-disubstituted compounds (Tables 4 and 5).
2. Post-emergence treatment
Post-emergence herbicidal activities against Echinochloa oryzicola VASING., Cyperus difformis L., Monochoria vaginaris L. and Rotala indica (WILLD.) KOEHNE for the selected compounds which had shown strong pre-emergence herbicidal activities were evaluated. Among them, α-chloro-N-(3-methoxy-2-thienyl) methyl-2′, 6′-dimethyl acetanilide (code number, NSK-850) which showed the highest activity, effectively controlled all the paddy weeds tested at a dose of 2.5g a. i./a and was active at lower doses than those of butachlor and pretilachlor against Echinochloa oryzicola VASING. (Table 6).