A.
Ethyl oxalylsuccinate.
Potassium (39.5 g., 1 gram atom) is cut into pieces under
xylene (Note
1) in a wide
evaporating dish. The
xylene is poured off, and the metal is washed with three
50-ml. portions of absolute ether. The
potassium is then transferred quickly to a
2-l. three-necked flask containing
650 ml. of anhydrous ether and fitted with a
reflux condenser, a
mercury-sealed mechanical stirrer (Note
2), and a
dropping funnel containing
150 ml. of anhydrous ethanol. The
ethanol is added over a period of about 1.5 hours; stirring is unnecessary. After most of the
ethanol has been added, the flask is heated on a
water bath to ensure complete solution of the
potassium. This usually takes from 3 to 4 hours. After the reaction is completed, the flask is cooled to room temperature, and
146 g. (1 mole) of ethyl oxalate is added rapidly through the dropping funnel, with stirring, to the solution of
potassium ethoxide in
ether. A yellow color develops at this point. The stirring is continued for an additional 10 minutes. Then
174 g. (1 mole) of ethyl succinate is added rapidly, with vigorous stirring (Note
3). After a few minutes, the potassium salt crystallizes, making further stirring impracticable. It is collected on a filter and washed with ether until the salt is colorless.
The salt is dissolved in 270 ml. of water, and
100 ml. of concentrated hydrochloric acid is added. The
ethyl oxalylsuccinate separates as an oil and rises to the surface. It is removed by extracting the mixture with
100-ml. portions of ether until the aqueous solution is almost colorless. The extracts are dried over
sodium sulfate, and the
ether is distilled under reduced pressure. The
ethyl oxalylsuccinate remains in the flask as a yellow oil. The yield is
225–227 g. (
82–83%) (Note
4).