[CH2:1]([O:3][C:4](=[O:11])[CH2:5][C:6](=[O:10])[CH2:7][CH2:8][CH3:9])[CH3:2].Cl([O-])(=O)(=O)=O.[Mg+2].Cl([O-])(=O)(=O)=O.[Br:23]N1C(=O)CCC1=O>C(OCC)(=O)C.C(OCC)C>[CH2:1]([O:3][C:4](=[O:11])[CH:5]([Br:23])[C:6](=[O:10])[CH2:7][CH2:8][CH3:9])[CH3:2]3-Oxo-hexanoic acid ethyl ester (4.0 mL, 25 mmol) and magnesium perchlorate (1.7 g, 7.6 mmol) were placed in 500 mL of ethyl acetate and allowed to stir for 5 minutes. N-Bromosuccinimide (4.7 g, 26 mmol) was added and the reaction mixture was allowed to stir for 15 minutes, at which time thin-layer chromatography (10% ethyl acetate in hexanes, silica gel, 254 nm irradiation) indicated the reaction was complete. The reaction mixture was diluted with 500 mL of ethyl ether and washed three times with an equal volume of saturated aqueous sodium chloride. The organic layer was then dried over sodium sulfate and evaporated to dryness. This material was used in the next step without further purification.
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