Preparation of 1, 3, 7, 9-Tetrabromophenothiazine

Abstract

The bromination of Phenothiazine [1] with bromine in several solvents at 30°C was carried out.1, 3, 7, 9-Tetrabromophenothiazine [2] was obtained in the yields of 92, 87 and 54% by. use of excess bromine in chloroform, nitromethane and acetic acid, respectively. In carbon tetrachloride, however, excess bromine gave unidentified dark purple crystals, seemingly a Br₂-adduct of 3, 7-dibromophenothiazine [3]. This gave [3]in 90% yield on treatment with dioxane at room temperature or with boiling carbon tetrachloride.