Org. Synth. 1952, 32, 54
DOI: 10.15227/orgsyn.032.0054
DIETHYL ETHYLIDENEMALONATE
[Malonic acid, ethylidene-, diethyl ester]
Submitted by William S. Fones
1
Checked by Arthur C. Cope, Harris E. Petree, and E. R. Trumbull.
1. Procedure
In a 1-l. three-necked flask, equipped with a thermometer and a reflux condenser, are placed 60 g. of paraldehyde (0.45 mole, equivalent to 1.35 moles of acetaldehyde) and 100 ml. (1.06 moles) of acetic anhydride. Ice water is circulated through the condenser, and the reaction mixture is protected from atmospheric moisture by a drying tube containing Drierite. The temperature of the mixture is raised slowly by heating with an electric mantle to 125°, at which point gentle refluxing begins. Then 100 g. (0.62 mole) of diethyl malonate is added in 15-ml. portions at a rate of 1 portion every 30 minutes. During the addition of diethyl malonate, the temperature gradually drops to about 100°, and the mixture is heated so as to maintain a reflux rate of 30–60 drops per minute. After the addition is complete, the reaction mixture is heated under reflux for 4 hours at the specified rate.
The reflux condenser is replaced by a Claisen distillation head, and the reaction mixture is distilled until the temperature of the vapor reaches 140°. The residue is transferred to a smaller flask and fractionated through a 30-cm. column packed with glass helices. A low-boiling fraction containing ethylidene diacetate and diethyl malonate is collected first, followed by 79–89.5 g. (68–77%) of diethyl ethylidenemalonate; b.p. 102–106°/10 mm.; n25D 1.4394 (Note 1) and (Note 2).
2. Notes
1.
The submitter obtained a yield of
70% when three times the above quantities were used, in which case the
diethyl malonate was added at a rate of 90 ml. per hour.
2.
Horton
2 has reported that a higher yield of
diethyl ethylidenemalonate has been obtained by the following procedure. A mixture of
50 g. of redistilled malonic ester,
50 g. of acetic anhydride and
28.5 g. of acetaldehyde, enclosed in a
hydrogenation bomb, was mixed and heated at 100° for 24 hours without shaking. The bomb contents were transferred with the aid of
benzene, and three pooled runs were distilled through a
15-in. Vigreux column at 18–20 mm. A fore-run of
diethyl malonate was removed, and then
149.8 g. (
86.2%) of
diethyl ethylidenemalonate was collected at
106–109°/13 mm. The product was stored at 5°.
3. Discussion
Diethyl ethylidenemalonate has been prepared by heating
acetaldehyde,
diethyl malonate, and
acetic anhydride;
3,4 by heating the same reagents plus
zinc chloride;
5 by treating
acetaldehyde and
diethyl malonate with
sodium ethoxide or
piperidine;
6 and by heating
diethyl malonate,
ethylidene bromide, and ethanolic
sodium ethoxide.
7
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
acetaldehyde (75-07-0)
Benzene (71-43-2)
acetic anhydride (108-24-7)
piperidine (110-89-4)
sodium ethoxide (141-52-6)
zinc chloride (7646-85-7)
diethyl malonate (105-53-3)
Diethyl ethylidenemalonate,
Malonic acid, ethylidene-, diethyl ester (1462-12-0)
ethylidene diacetate (542-10-9)
ethylidene bromide (557-91-5)
paraldehyde (123-53-7)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved