[C:1]1([CH3:9])[CH:6]=[CH:5][C:4]([Mg]Br)=[CH:3][CH:2]=1.[Br:10][C:11]1[CH:12]=[C:13]2[C:18](=[CH:19][CH:20]=1)[C:17](=O)[CH2:16][CH2:15][C:14]2([CH3:23])[CH3:22].C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C(OCC)C.ClCCl>[Br:10][C:11]1[CH:12]=[C:13]2[C:18]([C:17]([C:4]3[CH:5]=[CH:6][C:1]([CH3:9])=[CH:2][CH:3]=3)=[CH:16][CH2:15][C:14]2([CH3:23])[CH3:22])=[CH:19][CH:20]=1p-Tolyl magnesium bromide (1 M solution in diethyl ether, 4.2 mL, 4.17 mmol) was added slowly to a solution of 6-bromo-4,4-dimethyl-3,4-dihydro-2H-naphthalen-1-one (Compound 3, 350 mg, 1.39 mmol) in 10 mL of diethyl ether at 0° C. After stirring and warming to room temperature for 2 h, the mixture was quenched with water at 0° C., extracted with diethyl ether (3×5 mL), washed with brine (1×5 mL), dried (MgSO4) and concentrated at reduced pressure to give a light yellow oil. The crude oil was then dissolved in 10 mL of dichloromethane and stirred with 100 mg of para-toluenesulfonic acid at room temperature for 2 h. Water (10 mL) was then added and the organic layer was washed with brine (1×5 mL), dried (MgSO4) and concentrated at reduced pressure. Purification by flash chromatography (hexane) gave the title compound (295 mg, 65% yield) as a colorless oil:
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