1,4-Dibromobenzene → 1,4-Di-2-ethylhexylbenzene

Beteiligte Stoffe

Reaktionsschritte

A 500 ml two-necked flask equipped with a reflux condenser attached to a nitrogen gas inlet was charged with 10.1 g (0.422 mol) of magnesium turnings. After heating the reaction mixture for 3 minutes under vacuum and cooling it to room temperature, 200 mL of dry Et2O was filled and then 54.3 g (0.281 mol) of 2-ethylhexyl bromide in 50 mL dry ether was added dropwise. The solution was refluxed for 3 hours and cooled to room temperature. The prepared 2-ethylhexylmagnesium bromide solution was added dropwise, over 1 h, to an ice-cooled and stirring mixture of 1,4-dibromobenzene (24.5 g, 0.104 mol) and Ni(dppp)Cl2 (0.564 g, 1.04 mmol) in dry ether (300 mL). The cooling bath was removed and the temperature was increased to room temperature. The reaction solution was then refluxed overnight, cooled to 0° C. and carefully quenched with water (50 mL), followed by 2N HCl (300 mL). After separation of the organic layer, the organic layer was washed with water (300 mL) two times and dried with anhydrous sodium sulfate and evaporated in vacuo. Column chromatography (silica gel, hexane) yielded the pure compound 20a (18.2 g, 58%). 1H NMR (CDCl3): δ 0.84-0.92 (12H, m), 1.25-1.35 (16H, m), 1.50-1.58 (2H, m), 2.50 (4H, d), 7.04 (4H, s). MS (EI): calcd, 302.5. found M+, 302.3.

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