1,1'-Carbonyldiimidazole → Tert-butyl 4-(2,2-dimethyl-5-oxo-1,3-dioxolan-4-yl)-3-oxobutanoate

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132 g of mono-tert-butyl malonate was dissolved in 1.5 μl of tetrahydrofuran, and 49.2 g of magnesium chloride and 134 ml of triethylamine were added thereto with stirring under cooling with ice. The mixture was stirred at room temperature for 3 hours. Added to this solution was a liquid separately prepared by stirring 60.0 g of 2,2-dimethyl-1,3-dioxolan-4-on-5-ylacetic acid (Tetrahedron Letter, vol. 28, p. 1685 (1987)) in a liquid mixture of 500 ml of tetrahydrofuran and 100 ml of dimethylformamide together with 64.2 g of 1,1'-carbonyldiimidazole at room temperature for 2 hours. The mixture was stirred at room temperature overnight. Insoluble matters were separated by filtration. Then, the filtrate was evaporated to dryness under reduced pressure. The residue was dissolved in a liquid mixture of ethyl ether and water and then adjusted to pH 3 to 4 by an addition of 1N hydrochloric acid. The organic layer was collected by separation, then washed with a saturated sodium chloride aqueous solution and dried over anhydrous magnesium sulfate. Then, the solvent was distilled off under reduced pressure. The residue was dissolved in ethyl acetate and then passed through a column of 300 g of activated aluminum oxide. The solution passed through the column was evaporated to dryness under reduced pressure to obtain 72.4 g (yield: 77%) of tert-butyl 4-(2,2-dimethyl-1,3-dioxolan-4-on-5-yl)-3-oxobutyrate.

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