To
500 g. (3.85 moles) of freshly distilled ethyl acetoacetate in a
1-l. flask, set in ice and well cooled, are added
152 g. (2 moles) of 40 per cent aqueous formaldehyde solution and 20–25 drops of
diethylamine. The flask and contents are kept cold for six hours and are then allowed to stand at room temperature for forty to forty-five hours. At the end of this time two layers are present, a lower oily layer and an upper aqueous layer. The layers are separated, and the aqueous layer is extracted with
50 cc. of ether. The
ether solution is added to the oily layer, and the resulting solution is dried over
30 g. of calcium chloride. The
ether is then removed by distillation on a
steam bath. The residue, amounting to approximately 500 g., is diluted with an equal volume of alcohol and is thoroughly cooled in an
ice bath.
Ammonia is then passed into the mixture until the solution is saturated. This requires from four to eight hours, and during this time the flask is kept packed in ice. The ammoniacal alcoholic solution is allowed to stand at room temperature for forty to forty-five hours. Most of the alcohol is now evaporated; the residue is cooled, and the solid
1,4-dihydro-3,5-dicarbethoxy-2,6-dimethylpyridine is removed from the remaining alcohol on a
suction filter. The dried ester melts at
175–180° and weighs
410–435 g. (
84–89 per cent of the theoretical amount).