Br[C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][C:11]=1/[CH:12]=[CH:13]\[CH2:14][CH2:15][CH2:16][CH3:17])[C:8]([CH3:19])([CH3:18])[CH2:7][CH2:6][C:5]2([CH3:21])[CH3:20].[Li]CCCC.[C:27](=[O:29])=[O:28]>O1CCCC1>[CH:12](/[C:11]1[C:2]([C:27]([OH:29])=[O:28])=[CH:3][C:4]2[C:5]([CH3:20])([CH3:21])[CH2:6][CH2:7][C:8]([CH3:19])([CH3:18])[C:9]=2[CH:10]=1)=[CH:13]/[CH2:14][CH2:15][CH2:16][CH3:17]3.72 g of (Z)-6-bromo-7-hex-1-enyl-1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene (75% pure) were placed in 25 ml of abs. tetrahydrofuran and treated at -75° with 8.25 ml of 1.55M n-BuLi (hexane) (1.2 eq.). After 1/2h., a CO2 stream was conducted vigorously through the solution for 30 min., with the temperature rising to -60° in spite of constant cooling. The mixture was left to warm to room temperature, poured on to ice/HCl solution, extracted with diethyl ether, washed with H2O, dried over Na2SO4 and the solvent was removed in a vacuum. Two-fold flash chromatography on SiO2 (hexane/ethyl acetate=85/15, then 9/1) yielded 1.06 g of (Z)-3-hex-1-enyl-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalene-2-carboxylic acid as colorless crystals.
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