[Br-].O=[C:3]1[CH2:8][CH2:7][N:6]([C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH2:5][CH2:4]1.[C:16](O[K])(C)(C)C>O1CCCC1>[CH2:16]=[C:3]1[CH2:8][CH2:7][N:6]([C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH2:5][CH2:4]147.2 g of methyltoluphenylphosphonium bromide and 21.9 g of tert-butyl 4-oxo-1-piperidinecarboxylate were added to a mixture of 14.8 g tert-butoxy potassium and 300 ml tetrahydrofuran, and stirred for 40 min at room temperature. The reaction solution was evaporated, diethyl ether was added thereto, and then filtered through Celite. The filtrate was washed with water and brine, dried over anhydrous magnesium sulfate, and then filtered. The filtrate was evaporated, and the resulting residue was subjected to silica gel column chromatography to give 20.8 g of tert-butyl 4-methylene-1-piperidinecarboxylate.
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