[CH3:1]C([O-])(C)C.[K+].[CH2:7]1[C:9]2([CH2:16][CH2:15][CH2:14][CH2:13][CH2:12][CH2:11][C:10]2=O)[CH2:8]1.COC(C)(C)C.O>[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.O1CCCC1>[CH2:1]=[C:10]1[CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH2:16][C:9]21[CH2:7][CH2:8]264.3 g (180 mmol) of methyltriphenylphosphonium bromide was added while stirring under nitrogen to a solution of 19.1 g (170 mmol) of potassium tert-butylate in 350 ml of dry tetrahydrofuran and the mixture was heated to reflux. Then, a solution of 22.8 g (150 mmol) of spiro[2.7]decan-4-one in 50 ml of dry tetrahydrofuran was added dropwise to the boiling reaction mixture. The mixture was heated under reflux for a further 2 hours. After cooling, the reaction mixture was poured into 11 of tert-butyl methyl ether/water (1:1). The organic phase was separated and the aqueous phase was extracted twice with 500 ml of tert-butyl methyl ether. The organic extracts were combined, dried over sodium sulfate and concentrated on a rotary evaporator. After flash chromatography (n-pentane, Rf=0.97) on silica gel, there was obtained 17.1 g (76%) of 4-methylenespiro[2.7]decane (V, n=2) as a colorless liquid with the following properties:
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