Diethyl carbonate (146 mL, 1.2 mol) and 150 mL of dry tetrahydrofuran were added to a 1000 mL three-necked flask. NaH (60%, 63 g, 1.6 mol) was added with stirring. After reflux for 1 h, a THF solution of cyclohexanone (50 mL, 0.48 mol) was added dropwise over approximately 0.5 h. After the addition was complete, reflux was continued for another 1.5 h. After cooling, the solution was adjusted to neutral with 3N hydrochloric acid, then poured into brine and extracted with dichloromethane (75 mL × 3). After drying the organic layer, vacuum distillation yielded a brown oily liquid (66 g, 80% yield), which was crude Ethyl 2-oxocyclohexanecarboxylate, and could be used directly in the next reaction.
