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

Participants

Reaction Steps

In a 5 L round bottom flask, sodium 4-(ethoxycarbonyl)-2-(methoxycarbonyl)-3-methylcyclo-penta-1,3-dienolate (485 g, 1954 mmol), KCl (204 g, 2736 mmol, JT Baker), and AcOH (392 mL, 6839 mmol, JT Baker) in toluene (1200 mL) and water (1200 mL) were heated at reflux for about 6 h. The reaction mixture was allowed to cool to ambient temperature for about 16 h. The reaction mixture was then poured into a 12 L flask and diluted with water (3 L). Solid NaHCO3 (450 g, 5.3 mol) was added cautiously portionwise with stirring over about 1 h. After about an additional 30 min of stirring, the basic aqueous phase was separated and further extracted with Et2O (4×400 mL). The combined organic layers were washed with water (4×500 mL) and brine (500 mL), dried over anhydrous MgSO4, filtered, and concd under reduced pressure to yield a yellow oil that was purified by vacuum distillation (92-94° C., 0.4 mmHg) to give ethyl 2-methyl-4-oxocyclopent-2-enecarboxylate (229 g, 69%) as a yellow oil: 1H NMR (CDCl3) δ 6.04-6.01 (m, 1H), 4.26-4.17 (m, 2H), 3.67 (m, 1H), 2.72 (m, 1H), 2.62 (m, 1H), 2.16 (s, 3H), 1.32-1.27 (t, J=7.1 Hz, 3H).

Provenance & Evidence