3-Bromo-5-nitro-4-pyridinol

Step 1. 3-Bromo-5-nitropyridin-4-ol To a suspension of 4-hydroxy-3-nitropyridine (7. 00g, 50 mmol) in water (50 ml) was added bromine (3. 23ml, 63 mmol) dropwise at room temperature. The resulting mixture was stirred for one hour then heated to 50°C for two hours. After cooling to room temperature and stirring for a further hour the product was filtered off, washed with water and dried under vacuum for two days, affording 9.54g (87percent)4-hydroxy-3-nitropyridine (40 g, 0.285 mol) was added to 200 ml of water and then bromine (18.44 ml, 0.36 mol) was slowly added thereto at room temperature. The reaction mixture was stirred under heating for 2 hours at 50Step 1. 3-Bromo-5-nitropyridin-4-ol To a suspension of 4-hydroxy-3-nitropyridine (7. 00g, 50 mmol) in water (50 ml) was added bromine (3. 23ml, 63 mmol) dropwise at room temperature. The resulting mixture was stirred for one hour then heated to 50°C for two hours. After cooling to room temperature and stirring for a further hour the product was filtered off, washed with water and dried under vacuum for two days, affording 9.54g (87percent)To a solution of 3-nitropyridin-4-ol (20 g, 142.76 mmol, 1 eq.) in 50 percent aqueous acetic acid (250 mL) bromine (113 g, 713 mmol, 5 eq.) was added dropwise. The resulting mixture was stirred for 20 hours at room temperature. The resulting precipitate was filtered and washed with water. 25 g of intermediate 8-b was obtained.To a solution of 3-nitropyridin-4-ol 17-a (20 g, 142.76 mmol, 1 eq.) in 50 percent aqueous acetic acid (250 mL) bromine (113 g, 713 mmol, 5 eq.) was added dropwise. The resulting mixture was stirred for 20 hours at room temperature. The resulting precipitate was filtered and washed with water. 25 g of intermediate 17-b was obtained.