Ethanol → 4-Methyl-2-(4-nitro-3-trifluoromethyl-phenyl)-pentanoic acid ethyl ester

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Reaction Steps

To a solution of 4-methyl-2-(4-nitro-3-trifluoromethyl-phenyl)-pentanoic acid (42.3 g, 139 mmol) in absolute ethanol (300 mL) was added concentrated sulfuric acid (95-98%, 9.0 mL) and the solution was heated at reflux overnight. The reaction mixture was concentrated under reduced pressure; the residue was treated with a solution of sodium carbonate (5%, 300 mL) and the mixture was extracted with ethyl acetate (300 mL). The organic layer was washed with brine (300 mL), dried over sodium sulfate, and concentrated under reduced pressure. Purification by silica-gel flash chromatography eluting with heptane/EtOAc (10:1) gave 4-methyl-2-(4-nitro-3-trifluoromethyl-phenyl)-pentanoic acid ethyl ester (38.4 g, 83%) as a yellowish oil: 1H NMR (300 MHz, CDCl3): δ 7.90 (d, 1H, J=8.4 Hz), 7.82 (s, 1H), 7.74 (dd, 1H, J=8.4, 1.5 Hz), 4.18 (m, 2H), 3.83 (t, 1H, J=7.5 Hz), 2.06 (m, 1H), 1.70 (m, 1H), 1.50 (m, 1H), 1.27 (t, 3H, J=7.2 Hz), 0.97 (d, 3H, J=6.6 Hz), 0.96 (d, 3H, J=6.3 Hz); 13C NMR (75 MHz, CDCl3): δ 172.24, 146.83, 145.04, 132.40, 127.51 (q, J=5 Hz), 125.28, 123.80 (q, J=32 Hz), 121.78 (q, J=272 Hz), 61.45, 49.45, 42.65, 26.03, 22.41, 22.17, 14.10.

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