[Mg].Br[C:3]1[CH:8]=[CH:7][C:6]([O:9][CH2:10][CH3:11])=[C:5]([CH3:12])[CH:4]=1.[Br-].[CH3:14][C:15]([C:17]1[CH:22]=[CH:21][CH:20]=[C:19]([Br:23])[CH:18]=1)=O>O1CCCC1.BrCCBr>[Br:23][C:19]1[CH:18]=[C:17]([C:15]([C:3]2[CH:8]=[CH:7][C:6]([O:9][CH2:10][CH3:11])=[C:5]([CH3:12])[CH:4]=2)=[CH2:14])[CH:22]=[CH:21][CH:20]=1To a suspension of magnesium turnings (963 mg, 39.6 mmol, 1.2 eq) in 5 mL of dry tetrahydrofuran, 0.1 mL of 1,2-dibromoethane were added followed by 5 mL of a tetrahydrofuran solution of 4-bromo-1-ethoxy-2-methyl-benzene (7.8 g, 36.3 mmol, 1.1 eq in 25 mL tetrahydrofuran). The resulting mixture was gently heated to initiate the reaction. The remaining solution of bromide was added dropwise at such a rate that the reaction could reflux without external heating. After the addition the reaction mixture was heated at reflux for further 2 hours. The mixture was cooled to 0° C. and a solution of 3-bromoacetophenone (6.56 g, 33.0 mmol, 1.0 eq) in tetrahydrofuran (30 mL) was added dropwise. After 2 hours LCMS showed complete conversion to the desired product. 50 mL of water were added followed by 35 mL of 1M aqueous HCl. The organic fraction was washed with brine, dried over sodium sulfate and concentrated to give a yellow oil. The oil was dissolved in 10 mL of acetic acid. 0.3 mL of 98% sulfuric acid were added and the dark solution was stirred at room temperature. After 30 min LCMS showed complete conversion to the desired product. Crushed ice was added to the reaction mixture which was then extracted with dichloromethane. The organic fraction was collected, washed with water, saturated sodium bicarbonate solution and dried with over sodium sulfate. The crude product was purified by flash chromatography eluting with cyclohexane. 7.5 g of clean product was obtained as colorless liquid (yield: 63%)
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