[Br:1][C:2]1[CH:18]=[CH:17][C:5]([C:6]([C@H:8]2[CH2:13][CH2:12][CH2:11][CH2:10][C@H:9]2[C:14]([OH:16])=[O:15])=[O:7])=[CH:4][CH:3]=1.[CH3:19]OC(OC)(C)C.Cl>CO>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([C:6]([C@H:8]2[CH2:13][CH2:12][CH2:11][CH2:10][C@H:9]2[C:14]([O:16][CH3:19])=[O:15])=[O:7])=[CH:17][CH:18]=1To a solution of cis-2-(4-bromobenzoyl)-1-cyclohexanecarboxylic acid (4.0 g, 12.85 mmol) in MeOH (50 mL) was added 2,2-dimethoxypropane (2.01 g, 19.28 mmol) and HCl (4.0 M in dioxane, 1.20 mL). The resulting solution was stirred at 40° C. for 3 days, and then evaporated to dryness. The resulting residue was purified by flash chromatography (Biotage Flash 40M) using 3 to 6% ethyl acetate in hexanes to afford methyl cis-2-(4-bromobenzoyl)cyclohexane-carboxylate (1.76 g, 42%). LC-MS ret. time 3.40; m/z 326 (MH+); 1H NMR (400 MHz, CD2Cl2) δ 1.35–1.51 (m, 3H), 1.72–1.86 (m, 2H), 1.91–2.05 (m, 2H), 2.11–2.20 (m, 1H), 2.74 (m, 1H), 3.58 (s, 3H), 3.82 (q, 1H), 7.62 (m, 2H), 7.73 (m, 2H).
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