[CH3:1][C:2]1([CH3:9])[CH2:7][C:6](=[O:8])[CH2:5][CH2:4][O:3]1.[Br:10]N1C(=O)CCC1=O.C([O-])(=O)C.[NH4+]>CCOCC.C(OCC)(=O)C>[Br:10][CH:5]1[CH2:4][O:3][C:2]([CH3:9])([CH3:1])[CH2:7][C:6]1=[O:8]Into around-bottom flask, was placed a solution of 2,2-dimethyloxan-4-one (1.00 g, 7.80 mmol, 1.00 equiv) in ether (20 mL). N-Bromosuccinimide (1.50 g, 25.5 mmol, 3.26 equiv) was added in portions, followed by the addition of ammonium acetate (60.0 mg, 0.78 mmol, 0.10 equiv). The resulting mixture was stirred overnight at 25° C., then diluted with ethyl acetate (20 mL). The resulting mixture was washed brine (2×40 mL), dried (Na2SO4), filtered and concentrated in vacuo. The residue was purified by silica gel chromatography with ethyl acetate/petroleum ether (1:30) as the eluent to obtain the title compound as a yellow oil (508 mg, 31%).
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