C(NC(C)C)(C)C.C([Li])CCC.[C:13]([O:17][C:18](=[O:22])[CH:19]([CH3:21])[CH3:20])([CH3:16])([CH3:15])[CH3:14].[Br:23][C:24]1[CH:29]=[C:28]([CH2:30]Br)[CH:27]=[CH:26][C:25]=1[Cl:32].[Cl-].[NH4+]>C1COCC1.C(OCC)(=O)C>[Br:23][C:24]1[CH:29]=[C:28]([CH2:30][C:19]([CH3:21])([CH3:20])[C:18]([O:17][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:22])[CH:27]=[CH:26][C:25]=1[Cl:32]
Under argon, 4.0 ml (28.8 mmol) of diisopropylamine were dissolved in 50 ml of dry THF, and the mixture was cooled to −30° C. 11.5 ml (28.8 mmol) of n-butyllithium solution (2.5 M in hexane) were added dropwise. The resulting mixture was warmed to 0° C. and then cooled to −70° C. A solution of 2.77 g (19.2 mmol) of tert-butyl-2-methylpropanoate in 20 ml of THF was then added, the temperature being kept below −60° C. After 4 h of stirring at −60° C., a solution of 6.0 g (21.1 mmol) of 2-bromo-4-(bromomethyl)-1-chlorobenzene in 30 ml of THF was added, the reaction temperature once more being kept below −60° C. The reaction mixture was stirred overnight slowly warming to RT, and saturated aqueous ammonium chloride solution and ethyl acetate were then added. After phase separation, the aqueous phase was extracted twice with ethyl acetate. The combined organic phases were dried over magnesium sulphate and concentrated under reduced pressure. The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 10:1→4:1). This gave 5.6 g (84% of theory) of the title compound.
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