Acetic Acid → Ethyl 2-ethyl-4-oxocyclopent-2-enecarboxylate

Participants

Reaction Steps

In a 5 L round bottom flask, sodium 4-(ethoxycarbonyl)-3-ethyl-2-(methoxycarbonyl)cyclopenta-1,3-dienolate (316 g, 1205 mmol, [Example #1, step E]), KCl (126 g, 1687 mmol), and AcOH (241 mL, 4218 mmol, JT Baker) in toluene (1850 mL) and water (130 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 added dropwise to an aqueous solution of NaHCO3 (3.5 L, 8%). The aqueous layer was extracted with MTBE (2×1.5 L). The combined organic layers were washed with brine (1 L), dried over anhydrous MgSO4, filtered, and concd under reduced pressure. The crude material was purified by vacuum distillation (80-98° C., 0.6 mmHg) to give ethyl 2-ethyl-4-oxocyclopent-2-enecarboxylate (160.4 g, 69%): 1H NMR (400 MHz, CDCl3) δ 6.05-6.02 (m, 1H), 4.28-4.14 (m, 2H), 3.75 (m, J=0.9, 1.8, 3.8, 6.7, 1H), 2.69 (dd, J=3.1, 18.4, 1H), 2.61 (dd, J=6.9, 18.4, 1H), 2.52 (dq, J=7.4, 24.2, 1H), 2.40 (dq, J=7.4, 16.1, 1H), 1.30 (t, J=7.2, 3H), 1.21 (t, J=7.4, 3H).

Provenance & Evidence