Design and synthesis of N‐(2,4=difluorophenyl)‐2‐(3‐trifluoromethylphenoxy)‐3‐pyridinecarboxamide (diflufenican), a novel pre‐ and early post‐emergence herbicide for use in winter cereals

Abstract

AbstractThe pre‐ and early post‐emergence herbicidal activity of diflufenican, a novel herbicide, is reported and attention is drawn to its ability to control important weeds in winter cereals, including Galium aparine, Veronica hederifolia, Veronica persica and Viola arvensis, which are resistant to substituted‐urea herbicides. The synthesis of a series of related compounds is described and the relationship between structure and activities against a range of plant species is examined in respect of changes in the phenyl, phenoxy and pyridine rings. The design and synthesis of a small number of compounds combining the best patterns of substitution in each of the rings is described. The resulting optimisation of herbicidal activity in the series is reported, together with field trial results comparing the herbicidal efficacy, crop selectivity and soil persistence of the most active structures.