[CH2:1]([C@H:3]1[C:12]([CH3:14])([CH3:13])[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([CH3:15])[CH:10]=2)[C:5]([CH3:17])([CH3:16])[CH2:4]1)[CH3:2].[C:18](Cl)(=[O:20])[CH3:19].[Cl-].[Al+3].[Cl-].[Cl-].Cl>ClCCCl>[C:18]([C:8]1[CH:7]=[C:6]2[C:11]([C:12]([CH3:14])([CH3:13])[C@H:3]([CH2:1][CH3:2])[CH2:4][C:5]2([CH3:16])[CH3:17])=[CH:10][C:9]=1[CH3:15])(=[O:20])[CH3:19]
To a solution of (R)-3-ethyl-1,1,4,4,6-pentamethyl-1,2,3,4-tetrahydronaphthalene ([α]546 +2.2° (C=0.95 in ethanol)) (36.5 g; 0.159 mol) and acetyl chloride (13.7 g; 0.174 mol) in 1,2-dichloroethane (100 ml), anhydrous aluminum chloride (25.3 g; 0.190 mol) was added at 20° C., and the resulting mixture was stirred for 1 hour. The reaction mixture was treated with dilute hydrochloric acid while cooling with ice. The organic layer was washed with dilute hydrochloric acid, saturated sodium carbonate solution and saturated sodium chloride solution in order, dried over anhydrous sodium sulfate and concentrated t give (R)-7-acetyl-3-ethyl-1,1,4,4,6-pentamethyl-1,2,3,4-tetrahydronaphthalene (41.5 g; 0.153 mol; 96%). B.P., 120° C./0.1 mmHg. [α]365 -46.1° (C=0.97 in ethanol).
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