Org. Synth. 1966, 46, 60
DOI: 10.15227/orgsyn.046.0060
2-(p-METHOXYPHENYL)-6-PHENYL-4-PYRONE
[4H-Pyran-4-one, 2-(p-methoxyphenyl)-6-phenyl-]
Submitted by Marion L. Miles and Charles R. Hauser
1.
Checked by Victor Nelson, Wayland E. Noland, and William E. Parham.
1. Procedure
In a 50-ml. Erlenmeyer flask is placed 10 ml. of concentrated (36N) sulfuric acid (Note 1), and the flask is then immersed in an ice water bath. When the temperature of the acid reaches 0°, 2.96 g. (0.010 mole) of 1-(p-methoxyphenyl)-5-phenyl-1,3,5-pentanetrione (Note 2) is added in small portions. As each portion is added, the flask is swirled until the triketone dissolves. After the addition is completed, the solution is kept at 0° for 1 hour and then poured into 500 ml. of cold water. To the resulting slurry is added solid sodium bicarbonate until a pH of 7–8 (Note 3) is obtained. The mixture is filtered, and the filter cake is washed with cold water and then recrystallized from 15 ml. of 95% ethanol to give 2.46–2.72 g. (88–98%) of 2-(p-methoxyphenyl)-6-phenyl-4-pyrone, m.p. 161–163°.
2. Notes
1.
Regular commercial grade of concentrated sulfuric acid (sp. gr. 1.84) obtained from the General Chemical Division of Allied Chemical Corporation was used.
2.
For the preparation of this compound see this volume,
p. 718.
3.
This pyrone has a tendency to form a salt in aqueous
sulfuric acid. The submitters used "Hydrion" paper to check the pH.
3. Discussion
The method is an adaptation of the procedure of Light and Hauser.
2 2-(p-Methoxyphenyl)-6-phenyl-4-pyrone has been prepared in
50% yield by a Claisen-type acylation of
p-methoxyacetophenone with
ethyl phenylpropiolate accompanied by cyclization.
34. Merits of the Preparation
This procedure offers an extremely simple and fairly general method for the preparation of 2,6-disubstituted 4-pyrones. Pyrones which have been prepared
2 by this procedure are:
2-methyl-6-phenyl-4-pyrone (
60%),
2-(p-chlorophenyl)-6-methyl-4-pyrone (
90%),
2,6-diphenyl-4-pyrone (
91%),
2-(p-chlorophenyl)-6-phenyl-4-pyrone (
90%),
2-phenyl-6-(3-pyridyl)-4-pyrone (
91%),
5,6,7,8-tetrahydroflavone (
76%),
4'-methoxy-5,6,7,8-tetrahydroflavone (
70%),
cyclopenteno[b]-6-(p-methoxyphenyl)-4-pyrone (
59%), and
flavone (
63%).
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
cyclopenteno[b]-6-(p-methoxyphenyl)-4-pyrone
ethanol (64-17-5)
sulfuric acid (7664-93-9)
sodium bicarbonate (144-55-8)
ethyl phenylpropiolate (2216-94-6)
Flavone (525-82-6)
2-methyl-6-phenyl-4-pyrone
2,6-diphenyl-4-pyrone
2-phenyl-6-(3-pyridyl)-4-pyrone
5,6,7,8-tetrahydroflavone
p-Methoxyacetophenone (100-06-1)
1-(p-Methoxyphenyl)-5-phenyl-1,3,5-pentanetrione (1678-17-7)
2-(p-Methoxyphenyl)-6-phenyl-4-pyrone,
4H-Pyran-4-one, 2-(p-methoxyphenyl)-6-phenyl- (14116-43-9)
2-(p-chlorophenyl)-6-methyl-4-pyrone
2-(p-chlorophenyl)-6-phenyl-4-pyrone
4'-methoxy-5,6,7,8-tetrahydroflavone
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