Synthesis, Crystal Structure, Herbicidal Activity, and SAR Study of Novel <i>N</i>-(Arylmethoxy)-2-chloronicotinamides Derived from Nicotinic Acid

Abstract

Nicotinic acid, also known as niacin, is a natural product, which is widely found in plants and animals. To discover novel natural-product-based herbicides, a series of <i>N</i>-(arylmethoxy)-2-chloronicotinamides were designed and synthesized. Some of the new <i>N</i>-(arylmethoxy)-2-chloronicotinamides exhibited excellent herbicidal activity against <i>Agrostis stolonifera</i> (bentgrass) at 100 μM. Compound <b>5f</b> (2-chloro-<i>N</i>-((3,4-dichlorobenzyl)oxy)nicotinamide) possessed excellent herbicidal activity against <i>Lemna paucicostata</i> (duckweed), with an IC₅₀ value of 7.8 μM, whereas the commercial herbicides clomazone and propanil had values of 125 and 2 μM, respectively. The structure-activity relationships reported in this paper could be used for the development of new herbicides against monocotyledonous weeds.