Synthesis and Herbicidal Activity of N-(4-Chloro-2-fluoro-5-substituted phenyl)isoindole-1,3-dione Derivatives

In order to find new herbicidal leading compounds, a series of N-(4-chloro-2-fluoro-5-substituted phenyl)-isoindole-1,3-dione derivatives (6a similar to 6f, 7a similar to 7k) were designed and synthesized via the strategy of linking active sub-structures which are chlorophthalim and phenoxy carboxylic ester. The target compounds were synthesized from starting material 2-chloro-4-fluoro-5-nitrophenol in four steps, and their structures were confirmed by H-1 NMR, C-13 NMR and HRMS. The preliminary bioassay results indicated that most compounds exhibited excellent herbicidal activities at 1500 g/ha in both pre- and post-emergence treatments against Abutilon theophrasti and Amaranthus retrollexus. On the basis of advanced screening tests, compound 6d exhibited 100% inhibitory effect against Abutilon theophrasti and Amaranthus retrollexus at 750 g/ha, compounds 7a and 7i were much more effective against Abutilon theophrasti than commercial acifluorfen with 80% similar to 86% inhibitory activity at 22.5 g/ha.