Sulfuric Acid → 1-Benzyl-4-phenylpiperidine-4-carboxamide

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반응 단계

A mixture of 3 kg of commercial 1-benzyl-4-cyano-4-phenylpiperidine, 6 l of water, 8.98 l of toluene and 1.35 kg of an aqueous 35% sodium hydroxide solution is heated under nitrogen at 60° C. and the aqueous phase is separated out by settling at this temperature. The toluene phase is dried by azeotropic distillation and the solution thus obtained containing the 1-benzyl-4-cyano-4-phenylpiperidine base is added to a mixture of 2.83 kg of 95% sulfuric acid, 1.73 kg of glacial acetic acid and 3 l of toluene. The mixture thus obtained is heated for 6 hours, the heating is then stopped, the mixture is cooled to 60° C. and 3 l of water are added at this temperature. The mixture is allowed to cool to room temperature (about 20° C.) and is then poured into 8.65 l of 30% sodium hydroxide and 6.75 l of water. The temperature rises gradually to 75° C. The phases are separated by settling while hot and the organic phase is washed with water and dried azeotropically. The toluene solution is concentrated to half its volume and then cooled gradually to 60° C. and the crystallization is initiated. The crystallization is completed by cooling to 0° C. over 2 hours. The precipitate thus obtained is filtered off, washed and dried under vacuum at 60° C. 2.68 kg of 1-benzyl-4-phenyl-4-piperidinecarboxamide are thus obtained;

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