Ethyl piperidine-2-carboxylate → 1-(2-Fluoro-4-chloro-5-isopropoxycarbonylphenyl)aminocarbonyl-2-ethoxycarbonylpiperidine

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Reaction Steps

5.15 g (0.02 mol) of 2-fluoro-4-chloro-5-isopropoxycarbonylphenyl isocyanate were added to a solution of 3.2 g (0.02 mol) of ethyl pipecolate dissolved in 30 ml of benzene. The mixture was stirred at a temperature of 40° to 50° C. for an hour, washed with water, dried over anhydrous sodium sulfate, and then concentrated. The resulting crystals were recrystallized from a mixed solvent of n-hexane and ethyl acetate to give 6.9 g (yield 83.2%) of 1-(2-fluoro-4-chloro-5-isopropoxycarbonylphenyl)aminocarbonyl-2-ethoxycarbonylpiperidine. This compound was dissolved in 70 ml of toluene and hydrogen chloride was blown thereinto. The mixture was stirred at room temperature for three hours, washed with a saturated solution of sodium hydrogen carbonate, washed with water, dried over anhydrous sodium sulfate and then concentrated. The resulting crystals were recrystallized from a mixed solvent of toluene and ethyl acetate to give 2.6 g (yield 71.9%) of the desired product as white crystals with a melting point of 128°-129° C.

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