Submitted by C. R. Hauser, J. T. Adams, and R. Levine.
Checked by Arthur C. Cope and Frank S. Fawcett.
1. Procedure
Approximately
300 ml. of commercial anhydrous liquid ammonia is added to a
500-ml. three-necked round-bottomed flask equipped with a
mercury-sealed stirrer and a
reflux condenser connected to a
soda-lime drying tube (Note
1). The drying tube is attached to a gas-absorption
trap, or the apparatus is assembled in a
well-ventilated hood. The third neck of the flask is closed with a
stopper. Freshly cut
sodium (13.8 g., 0.6 gram atom) is weighed under
xylene or
kerosene, and a small amount is added to the liquid
ammonia, with stirring, until a permanent blue color is produced. A few small crystals of
ferric nitrate are added to catalyze the conversion of
sodium to
sodium amide (Note
2), and when the blue color has disappeared the remainder of the
sodium is added in small pieces. When the
sodium is converted completely to
sodium amide, as indicated by change of the blue solution to a gray suspension, the
ammonia is evaporated by warming the flask on a
steam bath. During this operation sufficient dry
ether is added through a
dropping funnel (attached to the third neck of the flask) so that the volume of the liquid remains approximately 300 ml. After practically all the
ammonia has been evaporated, as indicated by refluxing of the
ether, the
sodium amide suspension is stirred and heated under reflux for a few minutes and then cooled to room temperature. The procedure to this point requires approximately 1 hour.
A solution of
30 g. (0.3 mole) of redistilled methyl isobutyl ketone in
50 ml. of absolute ether is added to the stirred suspension of
sodium amide during 5–10 minutes. After an additional 5 minutes, a solution of
78 g. (0.6 mole) of redistilled ethyl isovalerate in
50 ml. of dry ether is added during about 15 minutes. Stirring is continued for 2 hours while the mixture is heated under reflux on the steam bath. The gelatinous suspension of the
sodium salt of diisovalerylmethane is poured into 300 ml. of water, made neutral to litmus by dilute
hydrochloric acid, and extracted with three
100-ml. portions of ether. The solvent is removed by distillation under reduced pressure, and the residue is dissolved in an equal volume of
methanol. A solution prepared from
44 g. of cupric acetate monohydrate and 350 ml. of water is heated nearly to the boiling point, filtered, and added to the
methanol solution. The resulting mixture is allowed to stand until it has cooled to room temperature. The blue
copper salt of diisovalerylmethane is collected on a
Büchner funnel, pressed as dry as possible, washed on the funnel with
100 ml. of petroleum ether (b.p.
30–60°), and again sucked dry. The yield of the copper salt after air drying is
44–51 g. (
69–79%); it melts in the range
150–155° (Note
3).
The
diisovalerylmethane is regenerated by shaking the copper salt vigorously with
500 ml. of 10% sulfuric acid and
200 ml. of ether until all the salt has dissolved. The aqueous acid layer is extracted with two
100-ml. portions of ether, and the combined
ether solutions are dried over anhydrous
sodium sulfate. The solvent is removed, and the residue is distilled under reduced pressure. The yield of
diisovalerylmethane is
32–42 g. (
58–76%, based on
methyl isobutyl ketone), b.p.
115–116°/20 mm.,
nD25 1.4565 (Note
4) and (Note
5).
2. Notes
1. Apparatus fitted with standard-taper ground-glass joints is convenient for this preparation.
2. It may be helpful to provide additional catalysis of the conversion to
sodium amide of the small amount of
sodium added initially by bubbling dry air through the solution.
1
3. After recrystallization from
methanol or
95% ethanol the fluffy light blue copper salt melts at
157–158°.
5.
Acetone may be acylated with
ethyl laurate by either procedure (with excess ester or excess ketone).
Lauroylacetone (m.p.
31.5–32°) is obtained in
75% yield
3 by either procedure.
3. Discussion
Copyright © 1921-2002, Organic Syntheses, Inc. All Rights Reserved