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%).