反应详情

To a solution of 0.41 g (2.02 mmol) of 4-amino-5-chloro-2-methoxybenzoic acid in 10 mL of dry DMF was added 0.29 g (2.89 mmol) of triethylamine at room temperature under N2-atmosphere. After stirring for 10 min at rt, a solution of 0.22 g (2.02 mmol) of ethyl chloroformate in 2 mL of DMF was added dropwise at rt and stirring was continued for 30 min, while the temperature was maintained at rt (cooling with waterbath at rt). Then 0.27 g (2.02 mmol) of hydroxybenzotriazole was added as a solid in one portion at rt and the solution was stirred for 30 min. Subsequently, a solution of 0.42 g (1.93 mmol) of amine 5 in 3 mL of DMF was added dropwise at rt and the reaction mixture was stirred overnight at rt. Afterwards, the mixture was poured in 20 mL of brine and extracted with EtOAc (3×25 mL). The combined organic fraction was washed with brine, dried over MgSO4, filtered and evaporated under reduced pressure. The crude mixture was subjected to flash silicagel chromatography (hex/EtOAc/Et3N 1:1:0.1) to yield 0.72 g (93%) of pure trans-tert-butyl 4-(4-amino-5-chloro-2-methoxybenzoylamino)-3-fluoropiperidine-1-carboxylate 6 as a solid. 1H NMR (CDCl3): δ 1.47 (9H, s); 2.17-2.28 (1H, m); 2.96-3.19 (2H, m); 3.74 (1H, dm, J=13.7 Hz); 3.90 (3H, s); 3.92-4.40 (3H, m); 4.45 (1H, ddt, J=4.4 Hz, 8.3 Hz, J=48.4 Hz); 6.30 (1H, s); 7.82 (1H, d, J=7.2 Hz); 8.08 (1H, s). 19F NMR (CDCl3): δ −189.0 (d, J=44.7 Hz). 13C NMR (CDCl3): δ 28.4 (3×), 29.1 (br), 41.5 (br), 45.6 (br), 50.1 (br), 56.4, 80.4, 88.2 (d, J=182.3 Hz), 97.9, 111.8, 112.1, 133.2, 147.1, 154.7, 157.6; 164.5. IR (ATR, cm−1): ν=3478, 3378, 1683, 1619, 1593, 1420, 1247, 1146. MS (ES+) m/z (%): 346/48 (M+H+, 100); 402/404 (M+H+, 60).

1. stirringstirring
2. waitwas continued for 30 min, while the temperature
3. temperaturewas maintained at rt
4. temperature(cooling with waterbath at rt)
5. stirringthe solution was stirred for 30 min
6. stirringthe reaction mixture was stirred overnight at rt
7. extractionextracted with EtOAc (3×25 mL)
8. washThe combined organic fraction was washed with brine
9. dry with materialdried over MgSO4
10. filtrationfiltered
11. customevaporated under reduced pressure