Synthesis of new bicyclo[4.1.0]heptane-2,4-dione derivatives and their herbicidal activity

Various triketone type 4-HPPD inhibitors were synthesized and their herbicidal activity and corn safety were evaluated. In the course of synthetic studies, we invented convenient methods to synthesize novel benzoyl-substituted bicyclo[4.1.0]heptanediones, and it was found that some showed excellent herbicidal activity against weeds in a corn field. Among these compounds, 3-(4-chloro-2-nitrobenzoyl)bicyclo[4.1.0]heptane-2,4-dione was found to be not only highly active against broadleaf weeds but also grass weeds, whereas it caused severe damage to corn. As a result of further efforts to modify benzoyl substituents, we found a compound, (1R*,6R*)-3-(2-chloro-4-methylsulfonylbenzoyl)bicyclo[4.1.0]heptane-2,4-dione, which provided a good combination of herbicidal activity and corn safety.