Org. Synth. 1936, 16, 33
[Malonic acid, phenyl-, diethyl ester]
Submitted by P. A. Levene and G. M. Meyer.
Checked by Louis F. Fieser and C. H. Fisher.
In a 2-l. three-necked flask, fitted with a mercury-sealed stirrer, reflux condenser, and dropping funnel, is placed 500 cc. of absolute ethyl alcohol (Note 1), and 23 g. (1 gram atom) of cleanly cut sodium is added in portions. When the sodium has dissolved the solution is cooled to 60°, and 146 g. (1 mole) of ethyl oxalate (Note 2) is added in a rapid stream through the funnel with vigorous stirring. This is washed down with a small quantity of absolute alcohol and is followed immediately by the addition of 175 g. (1.06 moles) of ethyl phenylacetate. Stirring is discontinued at once, the reaction flask is lowered from the stirrer, and a 2-l. beaker is made ready. Within four to six minutes after the ethyl phenylacetate has been added crystallization sets in. The contents of the flask are transferred immediately to the beaker at the first sign of crystallization, which is nearly instantaneous.
The nearly solid paste of the sodium derivative is allowed to cool to room temperature and then stirred thoroughly with 800 cc. of dry ether. The solid is collected by suction and washed repeatedly with dry ether. The phenyloxaloacetic ester is liberated from the sodium salt with dilute sulfuric acid (29 cc. of concentrated sulfuric acid in 500 cc. of water). The almost colorless oil is separated, and the aqueous layer is extracted with three 100-cc. portions of ether, which are combined with the oil. The ethereal solution is dried over anhydrous sodium sulfate, and the ether is distilled. The residual oil, contained in a modified Claisen flask having a fractionating side arm, is heated under a pressure of about 15 mm. in a bath of Wood's metal. The temperature of the bath is brought gradually to 175° and kept there until the evolution of carbon monoxide is complete. During this process the heating is momentarily discontinued in the event of a temporary increase in pressure. At the end of the reaction (five to six hours) the oil which has distilled is returned to the flask, and the ethyl phenylmalonate is distilled at reduced pressure. The fraction boiling at 158–162°/10 mm. weighs 189–201 g. (80–85 per cent of the theoretical amount).
A high grade of absolute alcohol
is essential. Ordinary "absolute" alcohol
may be treated with about 5 per cent of its weight of sodium
and distilled directly into the reaction flask.
To ensure absolutely dry and neutral reagents the ethyl oxalate (Org. Syn. Coll. Vol. I, 1941, 261)
and ethyl phenylacetate (Org. Syn. Coll. Vol. I, 1941, 270)
were shaken with anhydrous potassium carbonate
and distilled carefully under reduced pressure, after a preliminary heating under atmospheric pressure until their boiling points were reached.
The procedure is based upon the standard method of Wislicenus.1 Ethyl phenylmalonate
has also been obtained from benzyl cyanide
and ethyl carbonate
.2 Phenylmalonic acid
has been prepared by carbonation of the enolate of phenylacetic acid
Chemical Abstracts Nomenclature (Collective Index Number);
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
carbon monoxide (630-08-0)
sodium sulfate (7757-82-6)
Benzyl cyanide (140-29-4)
Phenylacetic acid (103-82-2)
Ethyl phenylacetate (101-97-3)
Ethyl phenylmalonate (83-13-6)
Malonic acid, phenyl-, diethyl ester (83-13-6)
Phenylmalonic acid (2613-89-0)
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