[CH3:1][Si:2]([CH3:15])([CH3:14])[CH2:3][CH2:4][O:5][CH2:6][O:7][C:8]1[CH:9]=[N:10][CH:11]=[CH:12][CH:13]=1.[Li]C(C)(C)C.C1C=CC(S(N(S(C2C=CC=CC=2)(=O)=O)[F:31])(=O)=O)=CC=1.CCCCCC.CC(C)=O>CCOCC.C1COCC1>[F:31][C:13]1[CH:12]=[CH:11][N:10]=[CH:9][C:8]=1[O:7][CH2:6][O:5][CH2:4][CH2:3][Si:2]([CH3:15])([CH3:14])[CH3:1]
To a stirred solution of 9 (12.39 g, 0.055 mol) in ether (200 mL) cooled to ≦−70° C. under an atmosphere of argon was slowly added t-BuLi (40 mL, 1.5 M pentane solution). During the addition, the reaction temperature was maintained at ≦−68° C. After the addition was complete the mixture was stirred an additional 60 minutes at ≦−70° C., then transferred via cannula to a stirred solution of N-fluorobenzenesulfonimide (18.92 g) in dry THF (200 mL) which was also cooled to ≦−70° C. under argon. After the addition was complete, the cooling bath was removed and the reaction mixture was allowed to warm up to room temperature. Water (100 mL) was added and the organic phase was separated, dried (MgSO4) and concentrated to give a brown oil. Chromatography (silica gel, hexane-acetone, 9:1) gave the desired product 10 as an orange oil (7.5 g) which contained about 15% starting material. This crude mixture was used directly in the next reaction.
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