Potassium Hydroxide → 4-(5-Fluoro-2-benzofuranyl)piperidine

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Reaction Steps

5.9 g (about 0.02 mole) of 4-(5-fluoro-2-benzofuranyl)-1-piperidinecarboxylic acid ethyl ester is dissolved in 65 ml of ethylene glycol. After the addition of 19.4 g of 86% potassium hydroxide, the cloudy solution formed is heated, with vigorous stirring, for 18 hours at 160°. The reaction solution is thereupon cooled to 100°, diluted with 65 ml of toluene and then cooled to 20°. The organic phases are firstly extracted twice with one liter of water each time, then four times with 200 ml of a 10% solution of methane sulphonic acid in water. The methanesulphonic acid solution is thereupon brought to the pH-value of 12 by the addition of 30% sodium hydroxide solution, and is subsequently extracted with one liter of chloroform. The chloroform solution is dried with sodium sulphate, filtered and concentrated by evaporation to thus obtain crude 4-(5-fluoro-2-benzofuranyl)-piperidine. The base is distilled by molecular distillation in high vacuum. The fraction distilling at 190°-200° and 0.05 Torr is 4-(5-fluoro-2-benzofuranyl)-piperidine. The hydrochloride is prepared with hydrogen chloride in ethyl acetate and recrystallised from ethyl acetate, whereupon it melts at 235°-237°.

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