7-Bromo-1,1-dimethyl-1,2,3,4-tetrahydronaphthalene (Compound 2, 1.1 g, 4.62 mmol) was used as a starting material and dissolved in 10 mL of dichloromethane. To this solution was added chromium (VI) oxide (72 mg, 0.46 mmol) and 5 mL of tert-butyl hydroperoxide solution (TBHP). The reaction mixture was stirred at room temperature for 8 hours. Upon completion of the reaction, the mixture was diluted with 20 mL of water and subsequently extracted with ether (3 x 10 mL). The combined organic phases were washed with brine (10 mL), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to remove the solvent. The crude product was purified by fast chromatography (eluent ratio 90:10 hexane/ethyl acetate) to afford 6-bromo-4,4-dimethyl-3,4-dihydronaphthalen-1(2H)-one (920 mg, 79% yield) as a white solid. The product was characterized by 1H NMR (CDCl3, 300 MHz): δ 7.87 (d, J = 8.1 Hz, 1H), 7.54 (d, J = 2.1 Hz, 1H), 7.42 (dd, J = 2.1, 8.1 Hz, 1H), 2.70 (dd, J = 6.3, 7.5 Hz, 2H), 2.01 (dd, J = 6.3, 7.5 Hz, 2H), 1.38 (s, 6H).
