4-Fluorophenylhydrazine hydrochloride → 1-(4-Fluorophenyl)-3-isopropyl-6-oxo-5-phenyl-4,6-dihydro-1H-pyrazolo[3,4-c]pyrrole

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Reaction Steps

A mixture of 3-hydroxy-4-isobutyryl-2-oxo-1-phenyl-2,5-dihydropyrrole (0.350 g, 1.43 mmole), 4-fluorophenylhydrazine hydrochloride (0.245 g, 1.50 mmole) and sodium methoxide (39 mg, 0.72 mmole) in ethanol (10 ml) was heated to reflux. After 16 hours the solvent was removed by rotory evaporation under reduced pressure, and the crude residue was chromatographed on a silica column using 1:3 ethyl acetate/hexane as eluent to give 210 mg of the title compound along with 80 mg of the 2-(4-fluorophenyl)-3-isopropyl-6-oxo-5-phenyl-4,6-dihydro-2H-pyrazolo[3,4-c]pyrrole regioisomer (M.P. 223°-224° C.). The title compound was recrystallized from ether to give a pale yellow solid. M.P. 150°-151° C.; 1H NMR (250 Mhz, CDCl3) δ1.38 (d, J=7.0 Hz, 6H), 3.18 (heptet, J=7.0 Hz, 1H), 4.78 (s, 2H), 7.15 (dd, J=8.3, 9.1 Hz, 2H), 7.21 (m, 1H), 7.43 (t, J=7.9 Hz, 2H), 7.74 (d, J=7.8 Hz, 2H), 8.20 (dd, J=4.8, 9.1 Hz, 2H); MS m/z (M+) 336.

Provenance & Evidence