[Synthesis]
General procedure for the synthesis of 6-bromo-1-hydroxynaphthalene from 6-bromo-3,4-dihydronaphthalen-1(2H)-one: 6-bromo-3,4-dihydronaphthalen-1(2H)-one (350 mg, 1.57 mmol) was dissolved in a solvent mixture of methylene chloride (2 mL) and methanol (2 mL). A solution of tetrabutylammonium tribromide (832 mg, 1.73 mmol) in dichloromethane (4 mL) was slowly added dropwise at room temperature, and the dropwise process was controlled to be completed within 1 hour. After the dropwise addition, the reaction mixture was continued to be stirred at room temperature for 15 hours. Upon completion of the reaction, the reaction solution was concentrated. The residue was redissolved in dichloromethane and washed three times with saturated sodium bicarbonate solution. The organic layer was separated and concentrated and the residue was dissolved in dimethylformamide (10 mL). Lithium carbonate (286 mg, 3.29 mmol) and lithium bromide (372 mg, 5.02 mmol) were then added and the reaction mixture was stirred at 140 °C for 1.5 hours. After completion of the reaction, it was cooled to room temperature, the solid was filtered and washed with ethyl acetate. The filtrate was washed four times with water and dried with anhydrous sodium sulfate. 6-Bromo-1-hydroxynaphthalene was finally obtained as a brown solid (195 mg, 56% yield).1H NMR (400 MHz, CDCl3) δ: 8.06 (d, J = 9.2Hz, 1H), 7.97 (d, J = 2.4Hz, 1H), 7.54 (dd, J = 8.8Hz, 2.0Hz, 1H), 7.35-7.29 (m. 2H), 6.80 (dd, J = 6.0 Hz, 1.6 Hz, 1H), 5.20 (s, 1H). |