反应详情

24.6 g (170 mmol) of 4-chloro-1,2-benzenediol are added while stirring, under nitrogen, to a solution of 28.8 g (163 mmol) of 2-chlorobenzenesulphinic acid (obtained by the reduction of 2-chlorobenzenesulphonyl chloride with sodium sulphite) in 163 ml of 1N sodium hydroxide solution. In the course of 40 minutes there is added dropwise thereto, at room temperature, a solution of 82 g (240 mmol) of potassium hexacyanoferrate (II) and 150 g of sodium acetate trihydrate in 300 ml of water. The solution becomes turbid and an oil forms which, after stirring for 2 hours, crystallises. The reaction mixture is extracted three times with ethyl acetate. The organic phases are washed with water and saturated sodium chloride solution, dried and concentrated by evaporation. The crude brown crystals are dissolved in warm isopropanol and treated with activated carbon. The solution is filtered, concentrated to 200 ml, added dropwise to 800 ml of ice-cold water and stirred for 2 hours while cooling with ice. The white suspension is filtered with suction, and the filtration residue is washed with water and dried, yielding 4-chloro-5-(2-chlorophenylsulphonyl)-1,2-benzenediol in the form of white crystals having a melting point of 226°-229°.