Org. Synth. 1961, 41, 38
Submitted by S. Ramachandran and Melvin S. Newman1
Checked by Max Tishler, G. A. Stein, and G. Lindberg.
A mixture of 63.1 g. (0.5 mole) of 2-methyl-1,3-cyclohexanedione (Note 1), 52.6 g. (0.75 mole) of methyl vinyl ketone (Note 2), about 0.25 g. (3 pellets) of potassium hydroxide, and 250 ml. of absolute methanol is placed in a 500-ml. round-bottomed flask fitted with a reflux condenser and a drying tube (Note 3). The mixture is heated under reflux for 3 hours, and the dione gradually goes into solution. At the end of this period, methanol and the excess methyl vinyl ketone are removed by distillation under reduced pressure (Note 4) and (Note 5). The residual liquid is dissolved in 250 ml. of benzene, a Dean-Stark phase-separating head is attached, and 20 ml. of solvent is removed by distillation at atmospheric pressure to remove traces of water and methanol. The solution is cooled well below the boiling point, 3 ml. of pyrrolidine is added (Note 6) and the mixture held at reflux for about 30 minutes, during which time about 9 ml. of water collects in the trap. Refluxing is continued for an additional 15 minutes after the separation of water ceases. The water collected is removed, and then 50 ml. of solvent is distilled. The reddish reaction mixture is cooled to room temperature and diluted with 150 ml. of ether. This solution is washed with 100 ml. of distilled water containing 15 ml. of 10% hydrochloric acid and 100 ml. of water. The aqueous extracts are extracted with 50 ml. of ether (Note 7), and the combined organic layers are washed with three 100-ml. portions of water, then with saturated salt solution and dried over magnesium sulfate. The solvents are then removed, and on distillation of the residue (82–85 g.) (Note 8) at 0.5–1.0 mm. (Note 9) the material, b.p. 117–145°, is collected and diluted with 5 ml. of ether. The distillate is placed overnight in a refrigerator, the resulting crystals are then collected by rapid filtration and washed with about 25 ml. of cold ether (Note 10) and (Note 11). The first crop of diketone weighs 50–53 g. and is colorless. The combined mother liquors are redistilled to obtain a further 4–6 g. of crystalline product. A yield of 56–58 g. (63–65% based on dione) of 1,6-dioxo-8a-methyl-1,2,3,4,6,7,8,8a-octahydronaphthalene, m.p. 47–50°, suitable for most other purposes, is obtained (Note 12).
was prepared by the method described by Mekler et al., this volume, p. 743
Technical grade methyl vinyl ketone supplied by Matheson, Coleman and Bell Co., Cincinnati, Ohio
, was used without further purification.
The checkers found that stirring during reflux and concentration and in the cyclization step was advantageous.
The submitters report that the intermediate 2-methyl-2-(3'-oxobutyl)-1,3-cyclohexanedione
can be isolated in 85%
at this point if desired.
The checkers removed methanol
and methyl vinyl ketone
at 650 mm. pressure with a water bath
On adding pyrrolidine
an exothermic reaction occurs rapidly. Cooling is needed to prevent too rapid a reaction. The submitters report that piperidine
may be used in place of pyrrolidine
The checkers extracted the aqueous extracts twice with 75-ml. portions of ether
The checkers found the residual weights to amount to 87–100 g.
The checkers used a saddle-packed 5-in. column
and found b.p. 137–150°/0.6–0.7 mm.
; 123–150°/0.2–0.5 mm.
; and 132–141°/0.5–0.8 mm.
A successful crystallization yields relatively large crystals which may be rapidly filtered and washed with ether
with little loss. If fine crystals are obtained, it is preferable to redissolve and allow the material to crystallize again.
Because of the high solubility in ether (1 g. per 2.5 ml. at room temperature)
, the checkers washed the product with hexane
Purer product, m.p. 48.6–50.0°
, may be obtained by crystallization from ether
has been obtained through the reaction of 2-methyl-1,3-cyclohexanedione
with acetonedicarboxylic acid
,3 4-diethylamino-2-butanone methiodide
and by cyclization of 2-methyl-2-(3-oxobutyl)-1,3-cyclohexanedione
using either aluminum tert-butoxide
or piperidine phosphate
4. Merits of Preparation
has been employed as an intermediate in the synthesis of terpenes8,9
and in the projected synthesis of steroids.4,10
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
hydrochloric acid (7647-01-0)
potassium hydroxide (1310-58-3)
magnesium sulfate (7487-88-9)
methyl vinyl ketone (78-94-4)
1,6-Naphthalenedione, 1,2,3,4,6,7,8,8a-octahydro-8a-methyl- (20007-72-1)
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