Synthesis
Sodium sulfide nonahydrate (96 g, 400 mmol) and sulfur (12.8 g, 400 mmol) in a mixture of water and ethanol was heated at reflux under nitrogen for 1 h. The solution was added to a stirred suspension of 2-bromo-4,6-dinitrobenzenamine (104.8 g, 400 mmol) and ammonium chloride (20.8 g, 400 mmol) in a solution of 400 mL of water and 700 mL of ethanol. The mixture was stirred at 65° C for 30 min. Then 400 mL of 2N NaOH solution was added dropwise during 30 min and the mixture was then stirred for 15 minutes at 65° C. After cooling, the mixture was poured onto a mixture of 2N HCl (400 mL), 1 kg ice and 1 L of water, stirred for 15 min to complete the reaction and extracted with ethyl acetate (1 L*3). The combined organic layers were dried over sodium sulphate and evaporated to give the crude product (3-Bromo-5-nitrobenzene-1,2-diamine) (90 g, 97%) as a rust-colored solid, which was used for the next step without further purification.
