Synthesis and herbicidal activity of phenylpyridines - A new lead

Novel phenylpyridines were synthesized based on molecular modeling oriented design by superposition of herbicidal phenyl-uracils, -indazoles, and diphenylethers. Their preparation follows Suzuki-type coupling conditions of reactive 2-chloro-pyridines with appropriate 2,5-substituted 4-chloro-phenyl boronic acids. Depending on the nature of substituents in the pyridine, and in particular the phenyl group, a large number of derivatives are readily accessible. Besides open-chain phenylpyridines also anellated compounds, such as pyridine-substituted 2H-1,4-benzothiazin-3(4H)-one or 3,4-dihydro-1H-quinolin-2-one, were prepared. Phenylpyridines act by inhibition of protoporphyrinogen-IX-oxidase. Their synthesis will be, described in conjunction with structure-activity relationships. Phenylpyridines are highly active against many important broadleaf and grass weed species under pre- and - in particular - post-emergent conditions.