In a
3-l. three-necked, round-bottomed flask, fitted with a
liquid-sealed mechanical stirrer and
dropping funnel, are placed
390 g. (3 moles) of ethyl acetoacetate (Org. Syn. Coll. Vol. I, 1941, 235) and
900 cc. of glacial acetic acid. The solution is cooled in an efficient freezing mixture to 5°, and a cold solution of
107 g. (1.47 moles) of 95 per cent sodium nitrite in 150 cc. of water is added dropwise with vigorous stirring at such a rate that the temperature remains between 5° and 7°. With efficient cooling about one-half hour is required to add the nitrite. The mixture is stirred for one-half hour longer and then allowed to stand for four hours, during which time it warms up to room temperature.
The
separatory funnel is replaced by a
wide-bore condenser, and the third neck of the flask is fitted with a
stopper. The solution is stirred and portions of
196 g. (3 gram atoms) of zinc dust (Note
1) are added quickly through the third neck of the flask until the liquid boils and then frequently enough to keep it boiling (Note
2). After the addition has been completed, the mixture is heated by a burner and refluxed for one hour (Note
3) and (Note
4). While still hot the contents of the flask are decanted from the remaining
zinc into a
crock containing 10 l. of water which is being vigorously stirred. The
zinc residue is washed with two
50-cc. portions of hot glacial acetic acid which are also decanted into the water. After standing overnight, the crude product is filtered by suction, washed on the filter with two 500-cc. portions of water, and dried in air to constant weight. The yield is
205–230 g. (
57–64 per cent of the theoretical amount) of material melting at
126–130°. On recrystallizing a 50-g. portion from
100 cc. of 95 per cent alcohol and washing twice with
20-cc. portions of cold alcohol, there is obtained
38.5 g. of pale yellow crystals melting at
136–137° (Note
5).