Water → Ethyl 8-oxo-1,4-dioxaspiro[4.5]decane-7-carboxylate

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Sodium hydride (60% dispersion; 45 g, 1.17 mol) was washed with 500 ml of hexane (2×), suspended in 750 mL of THF and treated with diethylcarbonate (112.5 g, 0.94 mol). The suspension was heated to reflux and treated drop-wise with a solution of 1,4-cyclohexanedione mono-ethylene ketal (60.0 g, 0.384 mol) in THF (250 mL). After the addition was complete the suspension was heated to reflux for an additional 4 hours. The mixture was cooled in an ice bath to 0° C. and then poured, while vigorously stirring, into a mixture of ice (1 L), water (100 mL) and acetic acid (100 mL). The resulting mixture was extracted with hexane (2 L total) and the extracts washed with water and brine. The hexane extract was dried over Na2SO4, filtered and concentrated to give 8-oxo-1,4-dioxa-spiro[4.5]decane-7-carboxylic acid ethyl ester as a pale yellow oil. This was used without further purification. 1H NMR (300 MHz, CDCl3) 6 (TMS): 12.25 (s, 1H), 4.20 (q, J=7 Hz, 2H), 4.06-3.96 (m, 4H), 2.53-2.48 (m, 4H), 1.84 (t, J=6.6 Hz, 2H), 1.29 (t, J=7 Hz, 3H).

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