Br[C:2]1[CH:7]=[CH:6][C:5]([CH2:8][C:9]([CH3:12])([OH:11])[CH3:10])=[CH:4][CH:3]=1.C([Li])(C)(C)C.CCCCC.[C:23](=[O:25])=[O:24]>C1COCC1.CCOCC.CCOC(C)=O>[OH:11][C:9]([CH3:12])([CH3:10])[CH2:8][C:5]1[CH:6]=[CH:7][C:2]([C:23]([OH:25])=[O:24])=[CH:3][CH:4]=1
1-(4-bromophenyl)-2-methyl-propan-2-ol (2.77 g, 12.1 mmol) was dissolved in dry THF (30 mL) and the solution was cooled to −78° C. Tert-butyllithium in pentane (15 mL of 1.7 M, 25.4 mmol) was added dropwise over 10 minutes and the reaction mixture was stirred at −78° C. for 2 hours. The reaction mixture was added via cannula to crushed solid CO2 (53.2 g, 1.21 mol) in Et2O under a flow of nitrogen gas. The reaction mixture was allowed to warm to room temperature, diluted with EtOAc and washed with water. The aqueous phase was acidified (pH 2) with 1N HCl solution and the aqueous layer was extracted with EtOAc. The organics were dried over sodium sulfate, filtered and concentrated in vacuo to give 4-(2-hydroxy-2-methyl-propyl)benzoic acid (620 mg, 26%) as a white solid. ESI-MS m/z calc. 194.0. found 195.3 (M+1)+; Retention time: 0.93 minutes (3 min run).
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