[H-].[Na+].C[C:4](P(OC)(O)=O)([C:6]([O-:8])=[O:7])[CH3:5].[CH3:14][N:15]1[CH2:20][CH2:19]C(=O)[CH2:17][CH2:16]1.O.[CH2:23]1COCC1>[Cl-].[Na+].O>[CH3:23][O:8][C:6](=[O:7])[CH:4]=[C:5]1[CH2:19][CH2:20][N:15]([CH3:14])[CH2:16][CH2:17]1
NaH (7.08 g, 177 mmol) (60% in oil) was washed with hexanes (3× under N2), suspended in 250 mL of THF and cooled to 0° C. To this mixture was added 20.1 g (115 mmol) of trimethylphosphonoacetate in 20 mL of THF and the resulting mixture was stirred at 20° C. for 30 min. 1-Methylpiperid-4-one (10 g, 88.5 mmol) in 25 mL of THF was added and stirring was continued for 4 h. Water (5 mL) was carefully added and the mixture was poured into brine, extracted with 800 mL EtOAc. Drying and evaporation gave crude (1-methyl-piperidin-4-ylidene)-acetic acid methyl ester as a 1:1 mixture of isomers.
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