Ethyl 4-oxo-cyclohexanecarboxylate (52.8 g, 0.31 mol), ethylene glycol (67.4 g, 1.08 mol) and p-toluenesulfonic acid (0.7 g) were dissolved in toluene (160 mL) and the reaction mixture was stirred at room temperature. After the reaction was completed, the reaction solution was poured into ether (300 mL), washed sequentially with water, sodium bicarbonate solution and sodium chloride solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give a colorless liquid product. The product was directly used in the next reaction without further purification, yield: 66.5 g (100%).1H-NMR (CDCl3) δ: 1.24 (t, 3H), 1.53 (m, 2H), 1.76 (m, 4H), 1.92 (m, 2H), 2.31 (m, 1H), 3.91 (s, 4H), 4.11 (q, 2H).13C- NMR (CDCl3) δ: 14.28 (q), 26.32 (t), 33.76 (t), 41.59 (d), 60.14 (t), 64.21 (t), 107.90 (d), 174.77 (s). Sec-butanediol (1.08 mol) and p-toluenesulfonic acid (0.7 g) were added to a solution of ethyl 4-oxo-cyclohexanecarboxylate (0.31 mol) in toluene (160 mL) and stirred for 20 hr at 25 °C. At the end of the reaction, ethyl acetate (300 mL) was added, and the organic phase was separated, washed sequentially with water, saturated aqueous sodium bicarbonate solution, and sodium chloride solution, dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting product can be used in the next reaction without further purification.
![ethyl 1,4-dioxaspiro[4.5]decane-8-carboxylate](/CAS/GIF/1489-97-0.gif)