[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8](=[O:16])[CH2:9][C:10]([CH3:15])([CH3:14])[C:11]([OH:13])=[O:12])=[CH:4][CH:3]=1.[CH3:17]OC(OC)(C)C.Cl>CO.O1CCOCC1>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([C:8](=[O:16])[CH2:9][C:10]([CH3:14])([CH3:15])[C:11]([O:13][CH3:17])=[O:12])=[CH:6][CH:7]=1To a solution of 4-(4-bromophenyl)-2,2-dimethyl-4-oxobutanoic acid (8.33 g, 29.2 mmol) and 2,2-dimethoxypropane (3.95 g, 37.9 mmol) in methanol (100 mL) was added 1 M HCl in dioxane (2.0 mL). The reaction mixture was stirred at 50° C. for 22 h. The mixture was concentrated under reduced pressure. Toluene (2×60 mL) was added and the mixture concentrated again (2×) to afford methyl 4-(4-bromophenyl)-2,2-dimethyl-4-oxobutanoate as an off-white, semi-solid (8.60 g, 99%). This material was used in the next step without further purification. LC-MS: ret. time 3.23 min; m/z 298.8 (MH+); 1H NMR (300 MHz, CDCl3) δ 1.34 (s, 6H), 3.28 (s, 2H), 3.67 (s,3H), 7.58 (d, 2H), 7.78 (d, 2H).
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