In a 600-cc. beaker 210 g. (0.88 mole) of ethyl bromomalonate (p. 245) (Note 1) and 165 g. (0.89 mole) of potassium phthalimide (p. 119) are intimately stirred together. The mixture is stirred approximately every ten minutes. If no spontaneous reaction starts within one-half hour (Note 1), it is necessary to initiate the reaction by heating to 110–120°. The mixture then becomes liquid and can be stirred easily. It turns to a light brown color, especially near the top where it comes in contact with the air. When the temperature begins to drop, the mixture is heated in an oil bath at 110° for one hour to insure completion of the reaction.

The mixture is then poured into a mortar where it solidifies to a solid mass (Note 2). When cold, the mixture is ground up with water to remove most of the potassium bromide and filtered. The precipitate is then reground with water and refiltered, finally being washed well with water. The solid material on the filter consists of some potassium bromide, some phthalimide, and the ethyl phthalimidomalonate. Without drying, it is put into a 1-l. flask with 400 cc. of benzene and heated to boiling. After cooling, the insoluble bromide and phthalimide are removed by filtration. The filtrate contains some water, which is removed by means of a separatory funnel.

The benzene solution is dried with 20 g. of calcium chloride and the benzene removed by distillation under diminished pressure on a water bath. The residue is poured into a mortar where it solidifies. The crystalline mass is then ground with small amounts of ether (200 cc. in all), filtered, and washed with ether (about 100 cc.) until pure white. The yield of ethyl phthalimidomalonate melting at 73–74° is 155–162 g. From the ether filtrate after distilling the ether, there may be recovered a further amount by washing with a small amount of ether to remove the brown color. The total weight of ester obtained in the two crops is 180–190 g. (67–71 per cent of the theoretical amount).