52927-23-8

345995-25-7

52927-23-8

91270-69-8

2,5-Dibromo-1-tetralone (16.08 g, 52.9 mmol) was used as feedstock and mixed with LiCl (5.61 g, 132 mmol) in 120 mL of anhydrous DMF and heated to reflux (155°C) under nitrogen protection. The reaction mixture gradually changed to dark brown color and HPLC monitoring showed that the feedstock was completely consumed within 0.5 h. The reaction was completed by cooling the mixture to a temperature of 0.5°C. Upon completion of the reaction, the mixture was cooled to room temperature, diluted with 1N HCl (200 mL) and subsequently extracted with ether (Et2O, 100 mL, 25 mL, 25 mL) in three fractions. The ether layers were combined to give a brown turbid mixture (partially forming an emulsion). Decolorized carbon (10 g, Calgon ADP) was added and stirred, and a clarified light yellow solution was obtained by hyflo supercel filtration. This solution was extracted with 3N NaOH (100 mL, 25 mL) to remove the non-naphthol by-products. The brown NaOH extracts were combined, acidified to pH 1 with concentrated hydrochloric acid and subsequently extracted with dichloromethane (CH2Cl2, 100 mL, 25 mL). The combined dichloromethane layers formed a dark red solution. Decolorized carbon (5 g, Darco G-60) was added again with stirring and the solution returned to a light yellow color by hyflo supercel filtration. An equal volume of heptane was added and CH2Cl2 was removed by distillation. a gray precipitate was observed to form when the temperature was raised to 75°C, with a significant increase in the amount of precipitate upon cooling to room temperature. Filtration and drying under vacuum at 50 °C gave a gray solid product mixture (5.92 g, 50.2% yield).HPLC analysis showed that the mixture contained 7-bromo-1-naphthol (48.3%) and 5-bromo-1-naphthol (50.8%), but the 1H NMR (CDCl3) integral showed that the actual ratio was about 9:15 (5-Br/7-Br). Separation by preparative reversed-phase HPLC gave a single peak of 5-bromo-1-naphthol as a white solid (3.22 g, 27.3% yield).