Diethyl Malonate → 1-[2-(4-Fluorophenyl)ethyl]-4-methyl-2,6-dioxopiperidine-3-carboxylic Acid Ethyl Ester

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Reaction Steps

Sodium (1.5 g, 65.1 mmol) was dissolved in ethanol (50 mL) and the solution was concentrated under vacuum. The residue was suspended in toluene (50 mL) and bis(2-methoxyethyl)ether (30 mL). Diethyl malonate (4.0 mL, 26.5 mmol) was added, followed by a suspension of trans-2-butenoic acid [2-(4-fluoro-phenyl)ethyl]amide (5.00 g, 24.1 mmol) in bis(2-methoxyethyl)ether (20 mL). The mixture was heated at reflux for 6 hours. The cooled mixture was washed with 1.0 N aqueous hydrochloric acid, then with water, and dried over sodium sulfate and concentrated under vacuum. The residue was purified by flash chromatography, eluting with 25% ethyl acetate in hexane, to provide a pale yellowish oil which slowly crystallized (5.81 g, 75%). This appeared to be a mixture of cis and trans isomers (approximately 15% cis). 1H NMR (300 MHz, CDCl3) δ7.20 (m, 2H), 6.99 (t, J=9 Hz, 2H), 4.28 (m, 2H), 4.00 (m, 2H), 3.66 (d, J=5 Hz, 0.15H), 3.27 (d, J=10 Hz, 0.85H), 2.82 (m, 3H), 2.53 (m, 1H), 2.33 (dd, J=17, 10 Hz, 1H), 1.34 (m, 3H), 1.09 (d, J=7 Hz, 3H). Mass spec (AP+) m/z 322.0 (M+H+, 100%).

Provenance & Evidence