Water → 4-Piperidyl-1-acetoxypent-3-ene

関与物質

反応手順

A mixture of 0.5 moles of 1-acetoxypentan-4-one and 0.5 moles of piperidine in benzene is refluxed using a water separator until no more water distills from the reaction mixture. The reaction mixture is then cooled, washed and dried to afford the 4-piperidyl-1-acetoxypent-3-ene (XIX). A mixture of 5 g. of XIX in 100 ml. of dioxane is treated with an excess of methyl iodide at 20°C for 18 hours and then heated at 70°C for 6 hours. The reaction mixture is concentrated to a small volume, diluted with water and 1-acetoxy-3-methylpentan-4-one isolated by extraction with ethyl acetate. A mixture of 0.5 g. of this ketone, 100 mg. of p-toluenesulfonic acid, 3 ml. of ethyleneglycol and 100 ml. of benzene is refluxed using a water separator for 24 hours. The reaction mixture is cooled and then 100 ml. of ethanol and 2 g. of potassium hydroxide are added. This mixture is refluxed for 6 hours, cooled, diluted with water and the corresponding ethylene ketal is isolated by extraction with ethyl acetate. A solution of 0.1 moles of the ketal in 50 ml. of dimethylformamide containing 0.1 moles of triphenylphosphine is reacted with 0.1 moles of carbon tetrabromide at room temperature for 18 hours. The mixture is diluted with water and extracted with ether. The ether extracts are combined, washed with water, dried and evaporated. The residue is chromatographed on 400 g. of alumina eluting with hexane-benzene and benzene to give the ethylene ketal of 1-bromo-3-methylpentan-4-one. ##EQU16##

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