1,4-Dibromobutane → Benzyl 1-(4-bromobutyl)-2-oxo-cyclopentanecarboxylate

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Reaction Steps

In a 500 mL three-necked flask provided with magnetic stirring and a condenser, under an inert nitrogen atmosphere, sodium hydride 95% (2.2 g; 87.1 mmol; 1.25 eq.) is suspended in a mixture of anhydrous THF (115 mL) and HMPA (14.6 mL). A solution of benzyl 2-oxocyclopentanecarboxylate (15.3 g; 70.3 mmol) in 45 mL of anhydrous THF is added dropwise so as to keep the temperature below 45° C. The reaction mixture is stirred for 1 hour at ambient temperature. 1,4-Dibromobutane (12.6 mL; 105.4 mmol; 1.5 eq.) is added to the clear yellow solution. The reaction mixture is stirred again, for 14 hours, at reflux. After coming back to ambient temperature, 80 mL of saturated aqueous ammonium chloride solution are added. The mixture is poured into 500 mL of ether and the organic phase is washed five times with 100 mL of water and then with 100 mL of saturated aqueous sodium chloride solution. The organic phase is dried over MgSO4, filtered and concentrated.

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