[C:1](Cl)(=[O:4])[CH2:2][CH3:3].[CH2:6]([O:8][C:9]1[CH:10]=[CH:11][C:12]2[C:13]([CH3:22])([CH3:21])[CH2:14][CH2:15][C:16]([CH3:20])([CH3:19])[C:17]=2[CH:18]=1)[CH3:7].[Cl-].[Cl-].[Cl-].[Al+3]>ClCCl>[CH2:6]([O:8][C:9]1[C:10]([C:1](=[O:4])[CH2:2][CH3:3])=[CH:11][C:12]2[C:13]([CH3:21])([CH3:22])[CH2:14][CH2:15][C:16]([CH3:20])([CH3:19])[C:17]=2[CH:18]=1)[CH3:7]Propionyl chloride (1.44 mL, 16.6 mmol) was added to a stirring solution of 3-ethoxy-5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene (Intermediate 2, 3.5 g, 15.1 mmol) in dichloromethane (100 mL), and the solution was cooled to 0° C. Aluminum trichloride (2.21 g, 16.6 mmol) was added over two to three minutes, the ice-bath was removed, the yellow solution was stirred for 1 h at room temperature. The solution was poured over ice in a separatory funnel, and the products were extracted three times with ether. The combined organic layers were washed with 10% aqueous sodium hydroxide, brine and dried over magnesium sulfate. The solvent was removed in vacuo to give the title compound as a solid.
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