1,8-Dibromonaphthalene

204-03-5

17135-74-9

The general procedure for the synthesis of 1,8-dibromonaphthalene from 1H-naphtho[1,8-de][1,2,3]triazine was as follows: solid sodium nitrite (NaNO2, 3.5 g, 0.05 mol) was dissolved in 20 mL of water and cooled down to 0 °C. The sodium nitrite solution was added dropwise to a solution of 1H-naphtho[1,8-de][1,2,3]triazine (6.8 g, 0.04 mol) dissolved in 6.9 M sulfuric acid (H2SO4, 100 mL) at -5 °C. The reaction mixture was stirred vigorously with a mechanical stirrer at -5°C for 2 hours, followed by continued stirring at the same temperature for 2 hours. Next, a solution of cuprous bromide (CuBr, 14.6 g, 0.1 mol) dissolved in 47% aqueous hydrobromic acid (HBr, 50 mL) was added dropwise to the above mixture and stirred for 2 hours at -5°C. The reaction mixture was gradually warmed to 85°C and stirring was continued for 1 hour. Upon completion of the reaction, the reaction mixture was extracted with dichloromethane, the organic phases were combined and dried over anhydrous sodium sulfate (Na2SO4). Subsequently, the solvent was removed by vacuum evaporation to give the crude product. The crude product was purified by silica gel column chromatography using petroleum ether as eluent to afford pure 1,8-dibromonaphthalene (2.61 g, 23% yield) as light yellow crystals. The melting point of the product was 104-106 °C. 1H NMR (300 MHz, CDCl3): δ 7.92 (d, J = 7.5 Hz, 2H), 7.79 (d, J = 9.0 Hz, 2H), 7.24 (m, 2H).