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

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Reaction Steps

The concentrated resolution mother liquors from Scheme B, step b, (302.3 g, assayed 38.5 wt % diastereomeric salt (116 g, 147 mmol of salt)) were concentrated on the rotary evaporator to a solution which was approximately 0.67 g/mL. This solution was added dropwise to a suspension of toluene (250 mL), water (175 mL) and potassium carbonate (25.58 g, 0.185 mol). The mixture was stirred for about 30 minutes at 40° C. (The organic phase contained 14.1 wt %, 49.8 g (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c) by assay. The aqueous phase1 contained 1.3 wt %, 5 g of (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c) by assay). The toluene was removed by evaporation to give a white solid (60 g). This residue was dissolved in tetrahydrofuran (174 mL), water (75 mL) and sulphuric acid (47.6 g, 0.48 mol). (The pale yellow solution was assayed, 14.8 wt %, 50.3 g of (S)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (3c)). The mixture was heated at reflux for 32 hours. After 16 hours, an additional portion (6.5 g, 66 mmol) of sulphuric acid was added. The reaction mixture was cooled to ambient temperature and carefully neutralized with 50% aqueous sodium hydroxide (87.92 g, 1.1 mol). The tetrahydrofuran was removed by vacuum distillation on the rotary evaporator, toluene (175 mL) and water (55 mL) were added and the mixture was stirred at 60-70° C. for about 30 minutes. The phases were decanted at 60° C. and the aqueous phase was extracted a second time with toluene (80 mL). The toluene phases were combined and concentrated on the rotary evaporator to remove water. The solution was assayed (29.7%, 43.2 g α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol) (5), heated to reflux and slowly cooled. Seeding at 50° C. was required. The slurry was digested at 50° C. prior to cooling to 0-5° C. prior to isolation by filtration. The filter cake was washed with chilled toluene (30 mL) and dried to a constant weight to obtain α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (5) (40.25 g, 81%, 97.5% assay). 1The aqueous phase which contained the (2S,3S)-(+)-di-(p-anisoyl)tartaric acid was added dropwise to a solution of 32% HCl (42.57 g, 0.37 mol) and water (234 mL) at 40° C. The (2S,3S)-(+)-di-(p-anisoyl)tartaric acid precipitated as a white solid. The solution was cooled to room temperature overnight and in an ice bath for 45 minutes prior to isolation by filtration. The recovered solid was washed with cold water, suction filtered, and finally dried to a constant weight in a vacuum oven to give 47.55 g of product (77% recovery).

Provenance & Evidence