N#N.[H-].[Na+].[F:5][C:6]1([F:20])[C:11](=O)[CH2:10][CH2:9][N:8]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:7]1.[OH2:21].[CH2:22]1[CH2:26][O:25][CH2:24][CH2:23]1>>[CH2:24]([O:25][C:26](=[O:21])[CH:22]=[C:11]1[CH2:10][CH2:9][N:8]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:7][C:6]1([F:20])[F:5])[CH3:23]In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), to NaH (45 mg, 1.12 mmol, 60% dispersion in oil washed with heptane) was added a solution of triethyl phosphonoacetate (262 mg, 1.17 mmol) in dry THF (10 mL) at 0° C. The reaction mixture was stirred at 0° C. for 30 min. Molecular sieves were then added followed by a solution of tert-butyl 3,3-difluoro-4-oxopiperidine-1-carboxylate (220 mg, 0.93 mmol) in THF (5 mL). The reaction mixture was stirred at 0° C. for 30 min and at rt for 1 h. Water was then added and the mixture extracted with EA (3×). The combined org. extracts were dried over MgSO4, filtered, and concentrated under reduced pressure to give the title compound as a yellow oil (mixture of E and Z isomers). LC-MS-conditions 08: tR=0.88 and 0.93 min; [M-CH3+H]+=291.27.
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