[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[O:8]C(=O)[CH2:6][C:5]2([CH3:14])[CH3:13].[CH2:15]([Mg]Br)C.Cl.C([O:23][CH2:24][CH3:25])(=O)C>O1CCCC1.CCCCCC>[Br:1][C:2]1[CH:11]=[CH:10][C:9]([OH:8])=[C:4]([C:5]([CH3:13])([CH3:14])[CH2:6][C:24]([OH:23])([CH3:25])[CH3:15])[CH:3]=1
A solution of 6-bromo-4,4-dimethyl-chroman-2-one (1 g, 3.92 mmol) in anhydrous tetrahydrofuran (20 mL) was treated with 3M solution of ethyl magnesium bromide (2.6 mL) and stirred at ambient temperature for 2 hours. The reaction mixture was poured into cold dilute hydrochloric acid and extracted with ethyl acetate (×2). The combined organic extract was dried over anhydrous sodium sulfate, filtered and evaporated in vacuo to afford a residue which was subjected to flash column chromatography over silica gel (230-400 mesh) using 10% ethyl acetate in hexane as the eluent to afford the title compound as a pale yellow solid (1.1 g, 100%).
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