Triethylamine → trans-Ethyl 8-fluoro-3-phenyl-3a,4-dihydro-3h-pyrazolo[5,1-c][1,4]benzoxazine-2-carboxylate

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Reaction Steps

Ethyl (2E)-chloro[(5-fluoro-2-{[(2E)-3-phenylprop-2-enyl]oxy}phenyl)hydrazono]ethanoate (5-3, 3.1 g, 8.23 mmol) was dissolved in anhydrous toluene (20 mL) and treated with triethylamine (11.5 mL, 83 mmol). The reaction was heated at reflux for 24 h, and cooled. EtOAc (100 mL) was added and the organic layer was washed with 5% NaHCO3. The organic layer was dried (MgSO4), filtered and concentrated under reduced pressure. The crude was purified by flash column chromatography (120 g SiO2 Redisep, 0-30% EtOAc/hexanes gradient) to give pure trans-ethyl 8-fluoro-3-phenyl-3a,4-dihydro-3H-pyrazolo[5,1-c][1,4]benzoxazine-2-carboxylate (5-4). 1H NMR (300 MHz, CDCl3) δ 7.32 (m, 6H), 6.86 (dd, J=8.9, 5.0 Hz, 1H), 6.68 (app dt, J=7.9, 3.1 Hz, 1H), 4.34-4.12 (m, 5H), 3.62 (t, J=10.7 Hz, 1H), 1.23 (t, J=7.0 Hz, 2H); MS (M+H+, C19H17FN2O3) 340.1 found 340.4 required.

Provenance & Evidence