Acetic Acid → Ethyl 1-methylpiperidine-4-carboxylate

Ethyl isonipecotate (20) (5.00 g, 31.8 mmol) was dissolved in an ice-cold mixture of glacial acetic acid (3.80 g, 63.6 mmol) and water (11 mL). Then, a 37% aqueous formaldehyde solution (2.85 mL, 38.2 mmol) was added and the reaction mixture was hydrogenated over Pd/C (10%, 338 mg) at 58 psi H2 for 3.5 h at room temperature. The solid was removed by filtration through Celite, which was washed thoroughly with water (50 mL) and the filtrate was adjusted to pH 11 with 1 M NaOH under cooling. The resulting solution was extracted with Et2O (5×100 mL), the combined organic fractions were dried (MgSO4), and the solvent was removed under reduced pressure to provide 21 (5.44 g, quant.) as a colorless liquid that was used for the next step without further purification. 1H NMR (300 MHz, CDCl3): δ=1.25 (t, J=7.1 Hz, 3 H, OCH2CH3), 1.69-2.06 (m, 6 H, 2-Hax, 3-H2, 5-H2, 6-Hax), 2.18-2.32 (m, 1 H, 4-H), 2.27 (s, 3 H, NMe), 2.75-2.87 (m, 2 H, 2-Heq, 6-Heq), 4.13 (q, J=7.1 Hz, 2 H, OCH2CH3) ppm. —13C NMR (75.5 MHz, CDCl3): δ=14.1 (OCH2CH3), 28.2 (C-3, C-5), 40.5 (C-4), 46.3 (NMe), 54.9 (C-2, C-6), 60.2 (OCH2CH3), 175.0 (C═O) ppm. −MS (70 eV, EI): m/z (%)=171 (31) [M]+, 142 (59) [M-CH2CH3]+, 126 (40) [M-OCH2CH3]+, 98 (56) [M-CO2Et]+. —C9H17NO2 (171.24).

1. customThe solid was removed by filtration through Celite, which
2. washwas washed thoroughly with water (50 mL)
3. temperatureunder cooling
4. extractionThe resulting solution was extracted with Et2O (5×100 mL)
5. dry with materialthe combined organic fractions were dried (MgSO4)
6. customthe solvent was removed under reduced pressure

ORD record

ord-b993ce95c0584e28b3d3623a459ad5b6

Source dataset

uspto-grants-2015_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08940784B2