Org. Synth. 1957, 37, 34
DOI: 10.15227/orgsyn.037.0034
[Malonic acid, tert-butyl ethyl ester]
Submitted by R. E. Strube1
Checked by William S. Johnson and Duff S. Allen, Jr..
1. Procedure
A 2-l. three-necked flask, equipped with a sealed stirrer, a dropping funnel and a reflux condenser provided with a calcium chloride drying tube, is charged with 100 g. (0.625 mole) of diethyl malonate (Note 1) and 400 ml. of commercial absolute ethanol. Stirring is started, and a solution of 35 g. of potassium hydroxide pellets (Note 2) in 400 ml. of commercial absolute ethanol is added at room temperature during a period of 1 hour. A white crystalline precipitate forms during the addition, and, after all the hydroxide has been added, stirring is continued for an additional 2 hours. After the mixture has stood overnight, it is heated to boiling on the steam bath and filtered while hot with suction (Note 3). Precipitation of the potassium ethyl malonate is completed by cooling the filtrate in an ice bath. The salt is collected by suction filtration, washed with a small amount of ether, and dried under reduced pressure at room temperature. An additional amount of the potassium salt is obtained by concentrating the mother liquors on the steam bath to about 100–125 ml. The total yield is 80–87 g. (75–82%).
A 250-ml. three-necked flask provided with a stirrer, a dropping funnel, and a thermometer is charged with 80 g. (0.470 mole) of potassium ethyl malonate and 50 ml. of water. The mixture is cooled to 5° with an ice bath, and 40 ml. of concentrated hydrochloric acid is added over a 30-minute period while the temperature is maintained below 10°. The mixture is filtered with suction, and the precipitate of potassium chloride washed with 75 ml. of ether. The aqueous layer of the filtrate is separated and washed with three 50-ml. portions of ether. The combined ether solutions are dried over anhydrous magnesium sulfate; then most of the solvent is removed by distillation at atmospheric pressure, and the remainder under reduced pressure. Finally, the liquid residue of monoethyl malonate is dried at 50°/1 mm. for 1 hour. The yield is 58–62 g. (93–100%).
A 500-ml. Pyrex heavy-walled, narrow-mouthed pressure bottle is charged with 100 ml. of ether and 3.5 ml. of concentrated sulfuric acid. The solution is cooled with an ice bath to 5°, and 56 g. (0.42 mole) of monoethyl malonate and approximately 60 ml. (about 0.75 mole) of isobutylene (Note 4) are added. The bottle is immediately closed with a rubber stopper, which is clamped or wired in place, and is shaken mechanically at room temperature overnight (Note 5). The bottle is chilled in an ice-salt bath and then opened. The reaction mixture is poured into a 1-l. Erlenmeyer flask containing a cooled solution of 50 g. of sodium hydroxide in 200 ml. of water and 200 g. of ice. The mixture is swirled a few times and then transferred to a separatory funnel (Note 6). The layers are separated, and the aqueous portion is extracted with two 75-ml. portions of ether. The organic layers are combined and dried over anhydrous magnesium sulfate. The solution is concentrated in a 125-ml. round-bottomed flask (Note 7) and distilled at reduced pressure through a 10-cm. Vigreux column. The fraction distilling at 98–100°/22 mm. or 107–109°/24 mm. is collected. The yield is 42–47 g. (53–58%), nD25 1.4128, nD23 1.4142.
2. Notes
1. Diethyl malonate as supplied by the Eastman Kodak Company (white label grade) or by Abbott Laboratories may be used without further purification.
2. Potassium hydroxide (85% minimum assay) obtained from the Mallinckrodt Chemical Works is satisfactory.
3. A steam-heated Büchner or a warmed sintered glass funnel is recommended.
4. Technical grade isobutylene supplied by Matheson Company was used. The isobutylene gas is liquefied by passage into a large test tube immersed in a Dry Ice-acetone bath.
5. For convenience, the reaction was carried out overnight. The reaction time may probably be shortened (compare the preparation of di-tert-butyl malonate, p. 261).
6. The mixture may be filtered, if necessary, to remove ice.
7. Since traces of acid will decompose the ester during the distillation, it is essential to wash the distillation apparatus carefully with a sodium hydroxide solution before rinsing and drying. The addition of some potassium carbonate or magnesium oxide before distillation is recommended (see Note 5 on p. 262).
3. Discussion
Ethyl tert-butyl malonate has been prepared by adding tert-butyl acetate and ethyl carbonate to sodium triphenylmethyl,2 and from ethyl malonyl chloride and tert-butyl alcohol.3 The present procedure is an adaptation of that for the preparation of di-tert-butyl malonate (p. 261).
This preparation is referenced from:

References and Notes
  1. The Upjohn Company, Kalamazoo, Michigan.
  2. Hauser, Abramovitch, and Adams, J. Am. Chem. Soc., 64, 2714 (1942).
  3. Breslow, Baumgarten, and Hauser, J. Am. Chem. Soc., 66, 1287 (1944).

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

sodium triphenylmethyl

ethanol (64-17-5)

potassium carbonate (584-08-7)

sulfuric acid (7664-93-9)

hydrochloric acid (7647-01-0)

ether (60-29-7)

sodium hydroxide (1310-73-2)

potassium hydroxide (1310-58-3)

diethyl malonate (105-53-3)

monoethyl malonate (1071-46-1)

potassium chloride (7447-40-7)

magnesium sulfate (7487-88-9)

ethyl carbonate

magnesium oxide (1309-48-4)

isobutylene (9003-27-4)

tert-butyl alcohol (75-65-0)

potassium ethyl malonate (6148-64-7)

ethyl malonyl chloride

tert-Butyl acetate (540-88-5)

Di-tert-butyl malonate (541-16-2)

Ethyl tert-butyl malonate,
Malonic acid, tert-butyl ethyl ester (32864-38-3)