[Li+].C[Si]([N-][Si](C)(C)C)(C)C.[Cl:11][C:12]1[CH:17]=[CH:16][C:15]([CH:18]=[C:19]([CH3:24])[C:20](=[O:23])[CH2:21][CH3:22])=[CH:14][CH:13]=1.[C:25]([O:32][CH2:33][CH3:34])(=[O:31])[C:26]([O:28]CC)=O>C1COCC1>[Cl:11][C:12]1[CH:13]=[CH:14][C:15]([CH:18]=[C:19]([CH3:24])[C:20](=[O:23])[CH:21]([CH3:22])[C:26](=[O:28])[C:25]([O:32][CH2:33][CH3:34])=[O:31])=[CH:16][CH:17]=1To a solution of LiHMDS (1N solution in THF, 5.48 mmol, 5.17 mL) in THF (16 mL) at −78° C. was added a solution of 46b (4.98 mmol, 1.04 g) in THF (2.5 mL) drop wise. After stirring at −78° C. for 1 h, the mixture was treated with a solution of diethyl oxalate (4.98 mmol, 0.73 g) in THF (2.5 mL). After stirring at −78° C. for 1 h, then the mixture was warmed up to room temperature and stirred overnight. The solvent was evaporated and the crude product was taken up in EtOAc, and washed with 1N HCl and brine. The organic layer was dried over Na2SO4 and concentrated to give 1.5 g of 46c.
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