CC(C)([O-])C.[K+].CN(C=O)C.[Cl:12][C:13]1[CH:18]=[CH:17][C:16]([CH2:19][C:20]([O:22][CH3:23])=[O:21])=[CH:15][CH:14]=1.[CH:24]1(Br)[CH2:28][CH2:27][CH2:26][CH2:25]1>O>[CH3:23][O:22][C:20](=[O:21])[CH:19]([C:16]1[CH:15]=[CH:14][C:13]([Cl:12])=[CH:18][CH:17]=1)[CH:24]1[CH2:28][CH2:27][CH2:26][CH2:25]1
A suspension of 3.65 g (32.5 mmol) of potassium tert-butoxide in 65 ml of abs. DMF was cooled to 0° C., and a solution of 5.0 g (27.08 mmol) of methyl 4-chlorophenylacetate in about 2 ml of abs. DMF was added dropwise. The mixture was stirred at 0° C. for 30 min, and 4.84 g (32.5 mmol) of cyclopentyl bromide were then slowly added dropwise. The reaction mixture was stirred at 0° C. for 1 h and then added to water and extracted with ethyl acetate. The organic phase was dried over sodium sulphate and concentrated under reduced pressure, and the residue was dried under high vacuum. The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 100:1). This gave 6.28 g of the target compound (91.8% of theory).
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