VERFAHREN ZUR HERSTELLUNG VON 2,6-DICHLORCHINOXALIN

摘要

In a process for preparing 2,6-dicholoroquinoxaline, 6-chloro-2-hydroxyquinoxaline-N-oxide is hydrogenated in sodium hydroxide aqueous solution in the presence of approximately 0.001 to approximately 0.5 mol per cent, referred to the 6-chloro-2-hydroxyquinoxaline-N-oxide used, of a platinum shell catalyst at temperatures of approximately 20 DEG C to approximately 120 DEG C at a hydrogen pressure of approximately 1 to approximately 100 bars. Approximately 1 to approximately 3 equivalents of sodium hydroxide, referred to the 6-chloro-2-hydroxyquinoxaline-N-oxide used, are added. After removal of the catalyst from the hot solution, the dissolved 6-chloro-2-hydroxyquinoxaline-N-oxide is precipitated as the sodium salt in crystalline form by cooling the reaction solution to a temperature of approximately 0 to approximately 20 DEG C. It is then dried azeotropically with an inert solvent and chlorinated in the usual manner with a chlorinating agent to 2,6-dichloroquinoxaline.