4-Toluenesulfonyl chloride → tert-butyl (3R,4S)-3-fluoro-4-hydroxypiperidine-1-carboxylate

Participants

Reaction Steps

To a solution of 0.60 g (2.74 mmol) of cis-1-Boc-3-fluoro-4-hydroxypiperidine 3 in 15 mL DCM was added 0.42 g (4.11 mmol) of triethylamine and 37 mg (0.3 mmol) of 4-(N,N-dimethylamino)pyridine (DMAP) at rt. Then a solution of 0.57 g (3.01 mmol) of p-toluenesulfonyl chloride in 2 mL of DCM was added under a dry atmosphere (CaCl2-tube) at rt. After stirring for 15 h at rt, the solution was poured in brine (20 mL) and extracted with DCM (3×25 mL). After drying over MgSO4, filtration and evaporation of the solvent, the crude mixture was used as such in the next step without further purification. The obtained tosylate was dissolved in 5 mL of dry DMSO and 0.36 g (5.48 mmol) of NaN3 was added. The mixture was stirred under N2-atmosphere at 90° C. for 15 h. After cooling, the mixture was poured in brine (10 mL) and extracted with EtOAc. The combined extract were washed with brine, dried over MgSO4, filtered and evaporated in vacuo. trans-4-Azido-1-Boc-3-fluoropiperidine 4 was obtained as a colorless oil in 92% yield from 4-hydroxypiperidine 3 and was sufficiently pure for further use. 1H NMR (CDCl3): δ 1.43 (9H, s); 1.44-1.64 (1H, m); 1.97 (1H, ddd, J=4.3 Hz, 8.4 Hz, 18.0 Hz); 2.99 (1H, ddd, J=3.3 Hz, 10.5 Hz, 13.8 Hz); 3.00-3.15 (2H, m); 3.57-3.68 (1H, m); 3.79 (1H, dt, J=13.8 Hz, J=4.4 Hz); 4.00-4.19 (1H, m); 4.33 (tdd, J=47.9 Hz, J=8.3 Hz, J=4.4 Hz). 19F NMR (CDCl3): δ −188.1 (1F, d(br), J=47.4 Hz). 13C NMR (CDCl3): δ 28.3 (4×), 41.2 (br), 45.5 (br), 61.4 (d, J=20.7 Hz), 80.6, 88.9 (d, J=182.3 Hz), 154.4. IR (ATR, cm−1): ν=2099, 1693, 1417, 1236, 1161, 1141. MS (ES+) m/z (%): 227 (M+H+, 100).

Provenance & Evidence