C([O-])([O-])=O.[K+].[K+].[CH3:7][C:8]1([CH3:18])[CH2:13][CH2:12][CH2:11][C:10](=[CH2:14])[CH:9]1[C:15]([OH:17])=[O:16].[CH2:19](Br)[CH3:20].[OH-].[Na+]>CC(C)=O>[CH3:7][C:8]1([CH3:18])[CH2:13][CH2:12][CH2:11][C:10](=[CH2:14])[CH:9]1[C:15]([O:17][CH2:19][CH3:20])=[O:16]In a flask maintained under nitrogen and equipped with a mechanical stirrer, a suspension of K2CO3 (29.5 g, 0.241 mole) in an acetone (200 ml) solution of 2,2-dimethyl-6-methylene-1-cyclohexanecarboxylic acid (30.0 g, 0.179 ml) and ethyl bromide (23.3 g, 0.214 mole) was warmed up to reflux. After 2 h 30, the temperature was allowed to cool to 25° and the reaction mixture was poured on 5% NaOH, extracted with ether (twice), washed with H2O and sat. NaCl, dried over Na2SO4, filtered and the solvents evaporated. Distillation of the crude product yielded, at 90°/5.3×102Pa, 32.3 g of the desired ester (yield: 92%).
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