1,3-Dibromobenzene → 5-[1-(3-Bromo-phenyl)-vinyl]-2,3-dihydro-benzofuran

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Reaction Steps

A 1.6 M solution of n-butyllithium in hexane (22.3 mL, 35.7 mmol, 1.16 eq.) was added dropwise to a solution of 1,3-dibromobenzene (8.0 g, 33.9 mmol, 1.1 eq) in 30 mL of dry tetrahydrofuran at −78° C. under nitrogen, and the mixture was stirred for 20 min. After this time, a solution of 1-(2,3-dihydro-benzofuran-5-yl)-ethanone (5.0 g, 30.8 mmol, 1.0 eq, prepared as shown in Scheme 4) in 20 mL of dry tetrahydrofuran was added over 10 minutes and the resulting solution was further stirred for 45 min. The reaction mixture was examined LCMS which showed complete conversion to the desired product. 20 mL of a saturated aqueous solution of ammonium chloride was added and the cooling bath was removed. The mixture was poured into 100 mL of a 1:1 diisopropyl ether/water mixture. The organic fraction was 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 poured in the reaction mixture which was then extracted with dichloromethane. The organic fraction was collected, washed with water, sodium bicarbonate solution and dried with over sodium sulfate. The crude product was purified by flash chromatography eluting with cyclohexane. 3.5 g of clean product was obtained as colorless liquid (yield: 38%)

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