1,2-Dibromoethane → Ethyl 1-(2-bromoethyl)-3-(4-fluorophenyl)-1H-pyrazole-5-carboxylate

Participants

Reaction Steps

To a solution of Intermediate 1B (135 g, 576 mmol) and potassium carbonate (159 g, 1153 mmol) in acetonitrile (1400 mL) was added 1,2-dibromoethane (59.6 mL, 692 mmol) and the resulting reaction mixture was refluxed for 4 h. Acetonitrile was removed under reduced pressure and the residue was diluted with water. The aqueous layer was extracted with DCM (2×500 mL) The combined organic layer was washed with brine, dried over Na2SO4, filtered and concentrated. The residue was purified by ISCO using 880 g REDISEP® column and 1% methanol in chloroform as eluent. Combined fractions were concentrated to afford Intermediate 1C (90 g, 45%). MS(ES): m/z=343 [M+H]+; 1H NMR (400 MHz, DMSO-d6) δ ppm 7.91-7.97 (m, 2H), 7.41 (s, 1H), 7.24-7.30 (m, 2H), 4.96 (t, J=6.34 Hz, 2H), 4.36 (q, J=7.11 Hz, 2H), 3.90 (t, J=6.34 Hz, 2H), 1.35 (t, J=7.12 Hz, 3H).

Provenance & Evidence