Hydrochloric Acid → (2,3-Dimethoxyphenyl)-[1-[2-(4-fluorophenyl)ethyl]piperidin-4-yl]methanol

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

In a 250 mL glass round bottom flask equipped with a magnetic stirrer, cold water condenser and a nitrogen line, 97.5% pure (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c) (10.49 g, 28 mmol), water (13 mL), glyme (40 mL) and 37% HCl (13.86 g, 140 mmol) were combined and heated to reflux. The solution was assayed initially and showed 14.4 wt % (10.39 g) (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c) in solution. The clear homogeneous solution was heated for 4-5 hours. Analysis of the reaction solution at the end of racemization showed an optical purity of 1.1% of (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c). The solution was cooled to room temperature and neutralized with 50% NaOH (11.25 g, 140 mmol). The solution was cooled before the base was added to help control the exotherm produced during the addition. The reaction mixture was stirred for 5-10 minutes. The glyme was removed by rotary evaporation. To the residue, toluene (53 mL) was added. The phases were agitated and heated to 70° C. The phases were separated at 60° C. The bottom aqueous phase was removed and extracted a second time with toluene (27 mL). The phases were heated and stirred for 15 minutes before being separated. The organic phases were combined and assayed at 9.5 wt % (8.2 g) α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (5) in solution. There was essentially no product left in the aqueous phase. The organic solution was stripped to a solid on the rotary evaporator. The residue was dissolved in 2-propanol (15 g) to give a 35 wt % solution of α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (5). The solution was heated to reflux and cooled to room temperature. The solution crystallized, the slurry was warmed and the crystals were digested at 45-50° C. for 30 minutes. The slurry was then cooled to room temperature and then chilled in an ice bath for 30 minutes. The crystals were suction filtered through a coarse sintered glass funnel. The wet cake was washed with 17 mL of 2-propanol before being dried in a vacuum oven at 60° C. The mother liquor showed 2.6 wt % (0.66 g) α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (5) in solution. Isolation of the α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (5) crystals were done in a 69.7% yield based on the initial amount of (S)-a-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c) used. Assay of the crystals was >100% and showed an optical purity of 1.2% (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c).

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