C(NC(C)C)(C)C.C([Li])CCC.[Cl:13][C:14]1[CH:19]=[CH:18][C:17]([CH2:20][C:21]([O:23][CH3:24])=[O:22])=[CH:16][CH:15]=1.[C:25]1(=[O:30])[CH2:29][CH2:28][CH:27]=[CH:26]1.[Cl-].[NH4+]>C1COCC1.CCCCCC.C(OCC)(=O)C.C1CCCCC1.C(OCC)(=O)C>[Cl:13][C:14]1[CH:15]=[CH:16][C:17]([CH:20]([CH:27]2[CH2:28][CH2:29][C:25](=[O:30])[CH2:26]2)[C:21]([O:23][CH3:24])=[O:22])=[CH:18][CH:19]=1Under argon, 14.8 ml (105.6 mmol) of diisopropylamine were initially charged in 150 ml of THF, the mixture was cooled to −30° C. and 42.3 ml (105.75 mmol) of a 2.5 M solution of n-butyllithium in hexane were added slowly. The reaction solution was then warmed to −20° C., 15 g (81.25 mmol) of methyl (4-chlorophenyl)acetate, dissolved in 90 ml of THF, were added slowly and the mixture was stirred at this temperature for 2 h. The reaction solution then cooled to −78° C., and 7.2 ml (86.1 mmol) of 2-cyclopenten-1-one, dissolved in 60 ml of THF, were added slowly. After the addition had ended, the solution was stirred at −78° C. for another hour. After TLC (mobile phase cyclohexane/ethyl acetate 9:1), saturated aqueous ammonium chloride solution was added and the product was taken up in ethyl acetate. The aqueous phase was extracted twice with ethyl acetate. The combined organic phases were dried over magnesium sulphate. After filtration, the solvent was removed under reduced pressure. The crude product was purified chromatographically on silica gel (mobile phase cyclohexane/ethyl acetate 4:1). This gave 15.65 g (58.67 mmol, 72% of theory) of the title compound as a yellowish oil.
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