| Abstract: | The synthesis and biological activity of twenty-six halophenazines is described. the Wohl-Aue reaction and the new method for cyclisation of 2-nitrodiphenylamines by oleum were found to be the most convenient methods of synthesis. Phytotoxicity of a characteristic type was higher in foliar spray than in pre-emergence tests. Chlorine substitution appeared to confer higher activity than other halogen substituents, and in the chlorophenazines activity decreased with increasing substitution. Both 1-and 2-chlorophenazine were highly effective herbicides. Acaricidal and fungicidal activity showed similar responses to structural changes, and optimum activity, together with a low level of phytotoxicity, was reached with 1, 4-dichlorophenazine. |
