Ethylene Glycol → 1,4-Dioxaspiro[4.5]decane-6-acetic acid, ethyl ester

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Under an argon atmosphere, ethylene glycol (7.6 ml, 135.87 mmol) and para-toluenesulfonic acid (516 mg, 2.72 mmol) were added to a solution of (±)-2-(ethoxycarbonylmethyl)cyclohexanone (5.00 g, 27.17 mmol) in toluene (136 ml). The mixture was heated to reflux in a Dean Stark apparatus for 4 h and then allowed to cool to room temperature and quenched with sodium bicarbonate (5 g) and a saturated sodium bicarbonate solution (150 ml). The organic phase was separated from the aqueous phase which was extracted with ethyl acetate (3×100 ml). The combined organic phases were washed with a saturated sodium bicarbonate solution (100 ml) and brine (100 ml). The organic phase was dried over magnesium sulphate and the solvent was evaporated under reduced pressure to give the crude product which was purified using flash column chromatography with hexane-ethyl acetate (9:1) to give (±)-6-(ethoxycarbonylmethyl)-1,4-dioxaspiro[4.5]decane (4.59 g, 74% yield) as a colourless oil. Rf 0.18 (hexane-ethyl acetate, 9:1).

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