A.
Triethyl oxalylsuccinate. In a
2-l. three-necked flask equipped with a sealed stirrer and a reflux condenser bearing a calcium chloride drying tube is placed
356 ml. (276 g., 6.00 moles) of anhydrous ethanol (Note
1).
Sodium (23 g., 1.0 g. atom) is added in small portions at a rate sufficient to keep the
ethanol boiling. External heating is required to dissolve the last portions of the metal. After all the
sodium has dissolved, the excess
ethanol is removed by distillation at atmospheric pressure; as the mixture becomes pasty,
dry toluene is added in sufficient amounts to permit stirring and to prevent splattering of the salt. Distillation and addition of
toluene is continued until all the
ethanol is removed and the contents of the flask reach a temperature of 105° (Note
2). The
sodium ethoxide slurry is cooled to room temperature and
650 ml. of anhydrous ether is added, followed by
146 g. (1.00 mole) of diethyl oxalate. To the yellow solution there is added
174 g. (1.00 mole) of diethyl succinate, and the mixture is allowed to stand at room temperature for at least 12 hours.
The mixture is hydrolyzed by the addition of 500 ml. of water with stirring. The layers are separated, the
ether layer is washed with 150 ml. of water, and the
ether layer is discarded. The combined aqueous layers are acidified with
100 ml. of 12N hydrochloric acid, and the layers are separated. The aqueous layer is extracted with three
150-ml. portions of ether, which are added to the oily layer. The ethereal solution is dried over
anhydrous magnesium sulfate, and the
ether is removed by evaporation under water-pump pressure at a bath temperature of 35–45°.
Triethyl oxalylsuccinate, a yellow oil weighing
235–250 g. (
86–91%), remains in the flask (Note
3).