A solution of
sodium ethoxide is prepared by adding 138 g. (6.0 g. atoms) of fresh-cut sodium in small pieces to 2.5 l. of absolute ethanol in a
5-l. round-bottomed flask fitted with an
efficient reflux condenser capped with a
calcium chloride drying tube (Note
1). In a
three-necked 5-l. round-bottomed flask, equipped with a reflux condenser capped with a calcium chloride tube, a
rubber-sealed mechanical stirrer, and an inlet tube for addition of the
sodium ethoxide solution, are mixed
480 g. (3.0 moles) of diethyl malonate (Note
2) and
472 g. (3.0 moles) of trimethylene chlorobromide (Note
3). The mixture is heated to 80° and vigorously stirred while the
sodium ethoxide solution is slowly forced into the flask by means of dry air pressure. The rate of addition is regulated so that the reaction mixture refluxes smoothly. After the addition is complete (this requires about 1.5 hours), the mixture is refluxed, with continued stirring (Note
4), for an additional 45 minutes. Upon completion of the reflux period, the alcohol is removed by distillation (Note
4), 90–95% of the alcohol being recovered. The reaction mixture is cooled, and 900 ml. of cold water is added. After the sodium halides are completely dissolved, the organic layer is separated and the aqueous layer is extracted with three
500-ml. portions of ether. The organic layer and the
ether extracts are combined, shaken with 50 ml. of saturated salt solution, and dried over
100 g. of anhydrous sodium sulfate. The solution is filtered, the ether is removed by distillation on a
steam bath, and the residue, which weighs
600–625 g., is distilled through a
short Vigreux column. The yield of product boiling at
91–96°/4 mm. is
320–330 g. (
53–55%) (Note
5).