Synthesis and Herbicidal Activity of 2-Alkyl(aryl)-4-amino-3-[alkyl(alkoxy)carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-pyridines

To find novel bleaching herbicide lead compounds, a series of novel 2-alkyl(aryl)-4-amino-3-[alkyl(alkoxy)carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-pyridines was designed and synthesized by the multistep reactions. N,S-acetal 1 reacted with 2 to obtain multisubstituted pyridines 3 in the presence of zinc nitrate as the catalyst. The target compounds 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, 5l were formed by the oxidation of 3, followed by the substitution with 3-(trifluoromethyl)phenol in the presence of potassium carbonate. Their structures were confirmed by IR, 1H NMR, EI-MS, and elemental analyses. The preliminary bioassays indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L at the concentration of 100mg/L.