1-Piperazinecarboxylic acid, ethyl ester → 1-Ethoxycarbonyl-4-[2-(4-fluorophenyl)-2-oxoethyl]piperazine

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Reaction Steps

4.3 g of 2-Chloro-4′-fluoroacetophenone and 8.0 g of 1-ethoxycarbonylpiperazine were dissolved in 30 ml of chloroform and refluxed with heating for 2 hours. After cooling to room temperature, the reaction solution was concentrated under reduced pressure, and 25% aqueous ammonia solution was added, followed by extraction with ether. The organic layer was dried over anhydrous sodium sulfate. After removal of the drying agent by filtration, the filtrate was concentrated under reduced pressure to give a crude 1-ethoxycarbonyl-4-[2-(4-fluorophenyl)-2-oxoethyl]piperazine, which was then dissolved in 40 ml of ethanol, and a solution prepared by adding 1 drop of 5% potassium hydroxide and 1.0 g of sodium borohydride to 5 ml of water was added, followed by heating at 50° C. for an hour. After concentration of the reaction solution under reduced pressure, water was added, followed by extraction with ether, and the organic layer was dried over anhydrous sodium sulfate. After removal of the drying agent by filtration, the filtrate was concentrated under reduced pressure. To the residue was poured 50 ml of 4M hydrogen chloride/ethyl acetate solution, the solution was concentrated under reduced pressure, and the resulting solid was washed with ether to give 8.3 g of 1-ethoxycarbonyl-4-[2-(4-fluorophenyl)-2-hydroxyethyl]piperazine hydrochloride.

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