A mixture of 12 g. (0.50 gram atom) of magnesium turnings, 130 g. (1.0 mole) of ethyl acetoacetate, 200 g. of benzene (dried over sodium), and 120 g. (1.50 moles) of acetyl chloride is heated under reflux for 2 hours in a 1-l. round-bottomed flask provided with a condenser closed by a calcium chloride tube and supported in an oil bath (85–90°) (Note 1). The yellow reaction mixture is cooled in an ice bath, and the liquid portion is decanted into a separatory funnel. The residue in the flask is washed twice with 50-ml. portions of ether, and the ethereal solution is poured over ice. The ether-water mixture is then added to the benzene solution in the separatory funnel, and the mixture is shaken thoroughly (Note 2); the aqueous layer is drawn off and discarded. The benzene-ether solution is washed once with 500 ml. of 5% sodium bicarbonate solution and once with 50 ml. of water, and finally is dried over calcium chloride. The ether and most of the benzene are removed by distillation from a water bath, and the remainder of the benzene is driven off at 50°/50 mm. The ethyl diacetylacetate is then precipitated from the residue as the copper derivative by the addition of 1.2 l. of a saturated aqueous solution of copper acetate (Note 3). After addition of the copper acetate solution, the contents of the flask are shaken vigorously now and then and allowed to stand for an hour to ensure complete precipitation of the copper derivative. The blue copper derivative is filtered on a Büchner funnel, washed with two 50-ml. portions of water, and transferred directly to a separatory funnel where it is mixed with 600 ml. of ether.

Four hundred milliliters of 25% sulfuric acid is added, and the contents of the funnel are shaken continually until the copper derivative has disappeared (5–10 minutes). After separation of the ethereal layer, the aqueous layer is extracted twice with 100-ml. portions of ether, and the combined ethereal extracts are dried over calcium chloride. The ether is removed on the steam bath and the residual ester distilled under diminished pressure. A few drops come over up to 90°, but the bulk of the material distils at 92–98°/12 mm. Redistillation yields pure ethyl diacetylacetate boiling at 95–97°/12 mm. The yield is 80–90 g. (46–52%).