Hydrochloric Acid → (R)-(1-Methylpiperidin-2-yl)methanol

Beteiligte Stoffe

Reaktionsschritte

Following the known procedure of patent EP 0 429 984 A2 (reference example 8). The resolution was identical to the above given procedure except that 4 rounds of crystallization were performed instead of the two as sited above. To a mixture of (±)-1-methyl-2-piperidinemethanol (77 g, 596 mmol) in EtOH (615 mL) was added dibenzoyl-D-tartaric acid (205 g, 573 mmol). The resulting mixture was slowly heated until a solution was obtained at which time the solution was slowly cooled with gentle stirring. After 12 h the crystals were isolated and dried to afford 131.6 g. This process was repeated: (2) EtOH (533 mL) provided 92.5 g. (3) EtOH (225 mL) provided 68 g (4) EtOH (200 mL) provided 49 g. The resulting salt was treated with 3M HCl (200 mL) which was heated to induce it to dissolve. The still warn solution was poured into a separatory funnel and extracted with ethyl acetate. The remaining aqueous layer was adjusted to pH 10 with K2CO3. The solution was extracted with CH2Cl2, dried (MgSO4) and concentrated to give 12 g of the alcohol. This alcohol (12 g, 92.8 mmol) was suspended in CH2Cl2 (200 mL) and SOCl2 added. After stirring for 12 h, the solvent was removed to provide a crude HCl salt. This salt was dissolved in EtOH (100 mL) and treated with NH2NH2 (89 mL, 1.86 mol) and heated to reflux for 12 h. NaOH (74 g) in H2O (30 mL) was added and stirred for 1 h. Half the solvent was removed and the residue extracted with ether to give a crude oil. After distillation under reduced pressure (50–60° C.) the pure hydrazine product (4.87 g) was obtained. This hydrazine (1.6 g, 11.2 mmol) was dissolved in THF (10 mL) and triphenylmethylisocyanate (3.19 g, 11.2 mmol) was added slowly. The solution was then stirred overnight and filtered to provide 650 mg of the desired product in good purity. 1H NMR (DMSO-d6): δ 1.10 (m, 2H), 1.30–1.56 (m, 4H), 1.95 (t, 1H), 2.15 (s, 1H), 2.18 (s, 3H), 2.71(d, 1H), 3.25 (q, 1H), 3.55(q, 1H), 4.80 (s, 2H), 7.12–7.32 (m, 15 H), 8.02 (s, 1H). ESI-MS m/z 429.2 (100, M+H).

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