Org. Synth. 1944, 24, 6
DOI: 10.15227/orgsyn.024.0006
4-AMINO-2,6-DIMETHYLPYRIMIDINE
[Pyrimidine, 4-amino-2,6-dimethyl-]
Submitted by Anthony R. Ronzio and William B. Cook.
Checked by C. G. Stuckwisch and Henry Gilman.
1. Procedure
Seventy grams (1 mole) of freshly prepared potassium methoxide (Note 1) and 41 g. (1 mole) of freshly purified acetonitrile (Note 2) are placed in a 500-ml. distilling flask. A cold-finger condenser which extends into the bulb of the flask is inserted through a rubber stopper in the neck of the flask, and a short piece of rubber tubing carrying a Hofmann clamp is connected to the side arm of the flask. The tubing is connected to an aspirator, and suction is applied until the acetonitrile begins to boil, whereupon the tubing is closed by means of the clamp and the flask is heated for 5 hours in an oil bath maintained at 140°.
At the end of the heating period the contents of the flask will have solidified. To the cold mixture 40 ml. of water is added to hydrolyze the potassium methoxide and precipitate the pyrimidine; the fine crystals are filtered and dried. The crude product is placed in a 500-ml. distilling flask with 250 ml. of purified kerosene (Note 3). On distilling the kerosene, the pyrimidine codistils and solidifies in the receiving flask to a snow-white mass of crystals. These are filtered, washed well with petroleum ether, and dried in an oven at 100°. The yield of pure material, melting at 182–183°, is 27.5–28.7 g. (67–70%) (Note 4).
2. Notes
1.
To prepare the
potassium methoxide 39 g. (1 gram atom) of metallic potassium, cut
under toluene (
Caution!) in 1-cm. cubes, is placed in a
1-l. three-necked flask which has been swept with
nitrogen. The flask, fitted with a
reflux condenser,
mechanical stirrer, and
dropping funnel, is immersed in a cooling bath at −30°, and absolute
methanol is added through the funnel until all the
potassium has dissolved. The excess
methanol is removed by heating on the steam bath, finally under reduced pressure, and the
potassium methoxide is dried overnight in a
vacuum desiccator over
sulfuric acid.
2.
Commercial
acetonitrile is treated with solid
sodium carbonate until no more
carbon dioxide is evolved. The nitrile is then distilled over
phosphorus pentoxide and stored in tightly
stoppered bottles. Before use, the nitrile is redistilled over
phosphorus pentoxide.
3.
Kerosene is purified by shaking for 24 hours with concentrated
sulfuric acid. The
kerosene is separated from the acid, washed several times with dilute
sodium hydroxide then with water, and finally dried over
calcium chloride and distilled using an air condenser. Purified
kerosene is a water-white, sweet-smelling liquid.
4.
The percentage yield decreases when larger or smaller quantities of material are used.
3. Discussion
4-Amino-2,6-dimethylpyrimidine has been prepared by heating the reaction product obtained from
acetic anhydride and
acetamidine;
1 by treating
4-chloro-2,6-dimethylpyrimidine with
ammonia;
2 and by heating
acetonitrile either with
sodium ethoxide in a
sealed tube3 or with
sodium.
4,5
It has been reported that this trimerization may be carried out with equally good results through the use of a small amount of
sodium methoxide in place of a large amount of
potassium methoxide.
6
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
kerosene
metallic potassium
calcium chloride (10043-52-4)
sulfuric acid (7664-93-9)
ammonia (7664-41-7)
methanol (67-56-1)
acetic anhydride (108-24-7)
acetonitrile (75-05-8)
sodium hydroxide (1310-73-2)
sodium carbonate (497-19-8)
nitrogen (7727-37-9)
carbon dioxide (124-38-9)
sodium methoxide (124-41-4)
toluene (108-88-3)
sodium (13966-32-0)
sodium ethoxide (141-52-6)
potassium (7440-09-7)
pyrimidine (289-95-2)
4-Amino-2,6-dimethylpyrimidine,
Pyrimidine, 4-amino-2,6-dimethyl- (461-98-3)
potassium methoxide (865-33-8)
acetamidine (143-37-3)
4-chloro-2,6-dimethylpyrimidine
phosphorus pentoxide (1314-56-3)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved