C[Si](C)(C)[N-][Si](C)(C)C.[K+].[Cl:11][C:12]1[CH:13]=[C:14]([CH:19]([CH2:22][CH2:23][CH2:24][O:25][CH:26]2[CH2:31][CH2:30][O:29][CH2:28][CH2:27]2)[C:20]#[N:21])[CH:15]=[CH:16][C:17]=1[Cl:18].Br[CH2:33][CH2:34][C:35]([O:37][CH2:38][CH3:39])=[O:36]>C1COCC1>[CH2:38]([O:37][C:35](=[O:36])[CH2:34][CH2:33][C:19]([C:20]#[N:21])([C:14]1[CH:15]=[CH:16][C:17]([Cl:18])=[C:12]([Cl:11])[CH:13]=1)[CH2:22][CH2:23][CH2:24][O:25][CH:26]1[CH2:31][CH2:30][O:29][CH2:28][CH2:27]1)[CH3:39]Potassium hexamethyldisilazide (0.5 M in toluene, 285 mL, 0.143 mol) was added dropwise to a solution of (4) (39 g, 0.119 mol) in THF (240 mL) under nitrogen and stirred at room temperature for 1 hour. A solution of ethyl 3-bromopropionate (22.8 mL, 0.178 mol, 1.5 eq) in THF (45 mL) was added to the reaction mixture all at once. After stirring at room temperature for 4 hours, the reaction was quenched with saturated NH4Cl solution (20 mL). The organic solution was dried over MgSO4, and solvent is evaporated. The crude oil was purified by flashed chromatography (hexane-AcOEt/8:1) to give light yellow oil (48.03 g, 94.4% yield).
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