[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2([C:18](OC)=[O:19])[CH2:17][CH2:16][C:11]3([O:15][CH2:14][CH2:13][O:12]3)[CH2:10][CH2:9]2)=[CH:4][CH:3]=1.ClCCl.CC(C[AlH]CC(C)C)C.S([O-])([O-])(=O)=O.[Mg+2]>C1(C)C=CC=CC=1>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2([CH2:18][OH:19])[CH2:9][CH2:10][C:11]3([O:12][CH2:13][CH2:14][O:15]3)[CH2:16][CH2:17]2)=[CH:4][CH:3]=1
To a round bottom flask containing methyl 8-(4-bromophenyl)-1,4-dioxaspiro[4.5]decane-8-carboxylate (5.30 g, 14.92 mmol) was added anhydrous dichloromethane (60 ml) at room temperature. The content was then cool to −78° C. under a dry ice-acetone bath and DIBAL-H (31.1 ml, 37.30 mmol) in toluene was added dropwise slowly. When the addition was completed, the mixture was stirred at −78° C. for 30 minutes or until the consumption of the starting material as indicated by thin layer chromatography (TLC). The reaction was then quenched by the slow addition of a pH 8 buffered solution (prepared by mixing 0.53 mL ammonium hydroxide solution and 8.8 mL of saturated ammonium chloride solution) at −78° C. The mixture was then allowed to warm back up to room temperature and stirred for a further 45 minutes. Solid magnesium sulfate (8 g) was added and the mixture stirred at room temperature for another 30 minutes to afford free flowing slurry. The content was filtered and concentrated to afford the title compound as clear oil, which was used in the next step without purification (4.88 g). LC/MS, ESI-MS: non-ionizable, RT: 1.05 (Condition E).
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