[Br:1][C:2]1[C:7]([CH3:8])=[CH:6][C:5]([CH2:9][CH2:10][CH:11]=[O:12])=[CH:4][C:3]=1[CH3:13].[CH3:14][Mg]Br>O1CCCC1.O1CCCC1.C1(C)C=CC=CC=1>[Br:1][C:2]1[C:7]([CH3:8])=[CH:6][C:5]([CH2:9][CH2:10][CH:11]([OH:12])[CH3:14])=[CH:4][C:3]=1[CH3:13]To a solution of 3-(4-bromo-3,5-dimethylphenyl)propanal (120 mg) in tetrahydrofurane (2 mL) is added at 0° C. methylmagnesium bromide (800 μL of a 1.4 M solution in tetrahydrofurane/toluene 1:3). After stirring for 30 minutes the mixture is partitioned between saturated aqueous NH4Cl solution and diethylether. The organic phase is dried (MgSO4) and concentrated. The residue is chromatographed on silica gel (cyclohexane/ethyl acetate 99:1→70:30) to give the title compound. Yield: 130 mg; LC (method 8): tR=0.37 min; Mass spectrum (ESI+): m/z=274 [M+NH4]+.
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