Synthesis
General procedure for the synthesis of 2,4-dibromo-1-aminonaphthalene from 1-naphthylamine: a mixture of 1-naphthylamine (286 mg, 2 mmol), potassium bromide (309 mg, 2.6 mmol), acetic acid (9 mL), water (1 mL), and dichloromethane (5 mL) was added sequentially to a three-necked flask equipped with a condenser and a thermometer. ZnAl-BrO3-LDHs (3.6 g, 3.6 mmol) was slowly added over 15 min in a thermostatically heated magnetic stirring water bath. The reaction temperature was controlled to be 25 °C for 5 h. The reaction was carried out at a constant temperature with magnetic stirring. After completion of the reaction, the reaction mixture was washed with sodium sulfite solution. It was subsequently extracted with dichloromethane (3 × 10 mL), the organic phases were combined and silica gel (200-300 mesh) was added to the organic phase. The organic solvent was removed by distillation under reduced pressure and the residue was purified by column chromatography (eluent was petroleum ether: ethyl acetate = 13:1) to afford 566 mg of the target product 2,4-dibromo-1-aminonaphthalene as a reddish brown solid in 94% yield.
References
[1] Canadian Journal of Chemistry, 2005, vol. 83, # 2, p. 146 - 149
[2] Patent: CN107417543, 2017, A. Location in patent: Paragraph 0056-0058; 0062
[3] Patent: WO2017/201161, 2017, A1. Location in patent: Paragraph 0215; 0246
[4] Synthetic Communications, 2004, vol. 34, # 24, p. 4597 - 4604
[5] ChemMedChem, 2018, vol. 13, # 11, p. 1092 - 1097
