反应详情

To a solution of MeCN (7.28 mL, 139 mmol) in anhydrous THF (130 mL) at −78° C. under N2 was added n-butyllithium (2.4 mol/L) in hexanes (58 mL, 139 mmol) dropwise. The mixture was stirred at −78° C. for 30 min then cis-ethyl-2-fluorocyclo-propanecarboxylate (1.5 g; 87.0 mmol) was added dropwise with stirring while maintaining the temperature at −78° C. The resulting solution was stirred at 25° C. for 2 h, quenched by the addition of 50% satd. aq. NH4Cl solution and extracted with EtOAc (3×50 mL). The combined organic layers were dried (Na2SO4), filtered and concentrated under vacuum to afford 7.7 g of crude cis-3-(2-fluorocyclopropyl)-3-oxopropanenitrile as a red oil. Crude cis-3-(2-fluoro-cyclopropyl)-3-oxopropanenitrile was dissolved in EtOH (130 mL) and hydrazine (8.45 mL, 261 mmol) was added. The reaction mixture was heated at reflux for 16 h then concentrated in vacuo. The resultant orange solid was triturated with DCM (ca. 50 mL). The precipitate was filtered, rinsed with DCM, and dried in vacuo to obtain 7.48 g (60.9%) of cis-5-(2-fluorocyclopropyl)-1H-pyrazol-3-amine as a tan solid. 1H NMR (400 MHz, DMSO-d6) δ 11.18 (br s, 1H), 5.16 (s, 1H), 4.81 (ddd, J=66.3, 9.5, 5.2 Hz, 1H), 4.46 (br s, 2H), 1.99-1.81 (m, 1H), 1.23-1.02 (m, 2H).

1. temperatureThe reaction mixture was heated
2. temperatureat reflux for 16 h
3. concentrationthen concentrated in vacuo
4. customThe resultant orange solid was triturated with DCM (ca. 50 mL)
5. filtrationThe precipitate was filtered
6. washrinsed with DCM
7. customdried in vacuo