Acetic Acid → Ethyl 2-methyl-4-oxocyclopent-2-ene-1-carboxylate

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Reaction Steps

A round-bottom flask was charged with sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclopenta-1,3-dienolate (105 g, 0.420 mol) and diglyme (1 L) to give a yellow suspension. AcOH (100 mL, 1.7 mol) was added to the resulting mixture and sodium iodide (280 g, 1.9 mol) was added portion-wise over about 5-10 min. The reaction mixture was then heated to reflux for about 3 h, cooled to room temperature, and poured over ice water (800 mL). The resulting material was extracted with Et2O (3×500 mL). The combined organic extracts were washed with brine (2×500 mL), dried over anhydrous MgSO4, and filtered. The solvent was removed under reduced pressure to give a brown liquid that was purified by vacuum distillation (80-85° C., 0.3 Torr) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (40.6 g, 57%) as a yellow oil: 1H NMR (CDCl3) δ 6.06-5.98 (m, 1H), 4.30-4.11 (m, 2H), 3.72-3.65 (m, 1H), 2.77-2.66 (m, 1H), 2.66-2.57 (m, 1H), 2.17 (s, 3H), 1.30 (t, J=7.1 Hz, 3H).

Provenance & Evidence