[CH2:1]([C:5]([C:16]1[CH:21]=[CH:20][C:19]([N+:22]([O-:24])=[O:23])=[C:18]([C:25]([F:28])([F:27])[F:26])[CH:17]=1)(C(OCC)=O)[C:6]([O:8]CC)=[O:7])[CH:2]([CH3:4])[CH3:3].O.OS(O)(=O)=O>C(O)(=O)C>[CH3:3][CH:2]([CH3:4])[CH2:1][CH:5]([C:16]1[CH:21]=[CH:20][C:19]([N+:22]([O-:24])=[O:23])=[C:18]([C:25]([F:26])([F:27])[F:28])[CH:17]=1)[C:6]([OH:8])=[O:7]To a solution of diethyl 2-isobutyl-2-(4-nitro-3-(trifluoromethyl)phenyl)malonate (74.4 g, 184 mmol) in acetic acid (500 mL) were added water (157 mL) and concentrated H2SO4 (55 mL) carefully. The reaction mixture was refluxed for three days and then concentrated under reduced pressure. The residue was diluted with water (400 mL) and extracted with ethyl acetate (6×100 mL). The combined organic extracts were washed with water (400 mL), dried over sodium sulfate, and concentrated under reduced pressure to give a brown oil. The residue was purified by silica-gel flash chromatography eluting with heptane/EtOAc (5:1 and then 2:1) to give 4-methyl-2-(4-nitro-3-trifluoromethyl-phenyl)-pentanoic acid (42.5 g, 76%) as a yellowish oil: 1H NMR (300 MHz, CDCl3): δ 11.51 (s, 1H, br), 7.87 (d, 1H, J=8.4 Hz), 7.78 (s, 1H), 7.71 (d, 1H, J=8.4 Hz), 3.84 (t, 1H, J=7.8 Hz), 2.06 (m, 1H), 1.72 (m, 1H), 1.49 (m, 1H), 0.95 (d, 3H, J=6.6. Hz), 0.94 (d, 3H, J=6.3 Hz); 13C NMR (75 MHz, CDCl3): δ 178.76, 147.09, 143.94, 132.66, 127.70 (q, J=5 Hz), 125.40, 123.95 (q, J=34 Hz), 121.74 (q, J=271 Hz), 42.16, 25.96, 22.44, 22.09.
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