Organic Syntheses, CV 5, 785
Submitted by A. W. Johnson, E. Markham, and R. Price
1.
Checked by Virgil Boekelheide and M. Kunstmann.
1. Procedure
A mixture of
65.2 g. (0.65 mole) of pentane-2,4-dione,
113 g. (0.80 mole) of methyl iodide,
84 g. of anhydrous potassium carbonate (Note
1), and
125 ml. of acetone is placed in a
500-ml. round-bottomed flask fitted with a reflux condenser and a calcium chloride guard tube. The mixture is heated under reflux for 20 hours and is then allowed to cool. The insoluble material is removed by filtration and washed with
acetone (Note
2). The combined filtrate and
acetone washings are concentrated on the
steam bath (Note
3), and the residual oil is distilled. There is collected
56-57 g. (
75-77%) of a colorless oil, b.p.
170–172°/760 mm..,
nD24 1.4378 (Note
4).
2. Notes
2. Thorough washing of the inorganic residues is essential and requires about
200 ml. of acetone.
4. It has been reported by A. M. Roe and J. B. Harbride (private communication) that this procedure yields a product containing 20–25% of
3,3-dimethylpentane-2,4-dione as shown by gas chromatography. The amount of the dialkylation product is said to be reduced to 5–10% when the reflux period is shortened from 20 to 4.5 hours. The impurity is not readily removed, but it does not interfere with the preparation of
2,3,4,5-tetramethylpyrrole [this volume, p.
1022].
The same authors report that the work-up of the reaction may be improved by adding
250 ml. of petroleum ether (b.p.
40–60°) to the cold reaction mixture before filtering, and washing the solids with a 1:1 mixture of
acetone and
petroleum ether. With this change it is not necessary to decant the product from the precipitated
potassium iodide as recommended in (Note
3).
3. Discussion
4. Merits of Preparation
The method presented here has also been used for the preparation of 3-ethyl- and 3-isopropylpentane-2,4-diones and is probably of general applicability in the preparation of 3-alkylpentane-2,4-diones.
This preparation is referenced from:
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
petroleum ether
sodium derivative of pentane-2,4-dione
3-ethyl- and 3-isopropylpentane-2,4-diones
potassium carbonate (584-08-7)
potassium iodide (7681-11-0)
acetone (67-64-1)
sodium (13966-32-0)
potassium (7440-09-7)
Methyl iodide (74-88-4)
pentane-2,4-dione (123-54-6)
2,3,4,5-Tetramethylpyrrole (1003-90-3)
3-Methylpentane-2,4-dione,
2,4-Pentanedione, 3-methyl- (815-57-6)
3,3-dimethylpentane-2,4-dione (3142-58-3)
2-aminopenten-4-one
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