Triethyl oxalylsuccinate

B. a-Ketoglutaric acid. A mixture of 225 g. (0.82 mole) of triethyl oxalylsuccinate, 330 ml. of 12N hydrochloric acid, and 660 ml. of water is heated under reflux for 4 hours, and the mixture is distilled to dryness under reduced pressure at a bath temperature of 60-70° (Note 4). The liquid residue, which solidifies readily on standing, is warmed with 200 ml. of nitroethane on a steam bath until it is in solution. The warm solution is filtered, the funnel is washed with 40 ml. of nitroethane, and the filtrate is stirred at 0-10° for 5 hours. a-Ketoglutaric acid is separated by filtration and dried at 90° under reduced pressure for 4 hours. It is obtained as a tan solid weight 88-99 g. (73-83%) m.p. 103-110° (Note 5). 

Triethyl oxalylsuccinate begins to decompose at 84° at 760 mm. It cannot be distilled without decomposition even at a pressure of 1 mm. 

Triethyl oxalylsuccinate, conversion to a-ketoglutaric acid, 44, 67-68 Triethyl phosphite for ethylation of hexachlorocydopentadiene, 43, 90... 

A. Triethyl oxalylsuccinate. In a 2-1. 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 present procedure is a modification of one reported in an earlier volume of Organic Syntheses The methods used to prepare triethyl oxalylsuccinate and a-ketoglutaric acid are summarized in that volume. 

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