Org. Synth. 1960, 40, 16
DOI: 10.15227/orgsyn.040.0016
DEOXYANISOIN
[Acetophenone, 4'-methoxy-2-(p-methoxyphenyl)-]
Submitted by P. H. Carter, J. Cymerman Craig, Ruth E. Lack, and M. Moyle
1.
Checked by Max Tishler and E. M. Chamberlin.
1. Procedure
A 500-ml. round-bottomed flask, equipped with a reflux condenser, is charged with 40 g. (0.33 mole) of powdered tin (Note 1) and (Note 2), 52 g. (0.19 mole) of anisoin (Note 3), 52 ml. of concentrated hydrochloric acid (Note 4), and 60 ml. of 95% alcohol. After the mixture is refluxed for 24 hours (Note 5), the boiling solution is decanted from undissolved tin, cooled to 0°, and the white crystals are filtered by suction. The filtrate is heated to boiling and then used to wash the tin by decantation. The combined washings are cooled to 0°, and the crystalline solid is collected by suction filtration. Recrystallization of the combined solids from 450 ml. of boiling 95% ethanol (Note 6) and (Note 7) gives, on cooling to 0°, colorless crystals of deoxyanisoin melting at 108–111°. The yield is 42–45 g. (86–92%).
2. Notes
1.
A reduction in the amount of
tin lowers the yield. Best results are obtained using powdered
tin of between 100 and 200 mesh size. Use of
tin coarser than 100 mesh results in the presence of unchanged anisoin, while
tin finer than 200 mesh tends to conglomerate, causing lower yields. The checkers used
tin obtained from E. H. Sargent Co., Chicago, labeled 200 mesh.
2.
No advantage is gained by using amalgamated
tin.
3.
This procedure is generally applicable to the preparation of symmetrical deoxybenzoins. The submitters have prepared (
a)
deoxybenzoin (m.p.
56–58°) in
80–84% yield from
53 g. of benzoin (0.25 mole),
53 ml. of concentrated hydrochloric acid,
50 ml. of 95% alcohol, and
53 g. of powdered tin (0.44 mole), recrystallizing from
160 ml. of boiling 95% alcohol and cooling to 0°; (
b)
deoxypiperoin (m.p. and mixed m.p.
112–114°) in
89% yield from
14.3 g. of piperoin (0.048 mole),
13 ml. of concentrated hydrochloric acid,
30 ml. of 95% alcohol, and
10 g. of powdered tin (0.083 mole), recrystallizing from
140 ml. of boiling 95% alcohol and cooling to 0°.
4.
A reduction in the amount of
hydrochloric acid lowers the yield.
5.
Lower yields are obtained by using reflux periods of 16 or 18 hours.
6.
The checkers recommend washing the product with cold
95% alcohol; otherwise the product tends to discolor on standing.
7.
Addition of water to the filtrate does not yield any further crystalline products.
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3. Discussion
The synthesis of
deoxybenzoin from
phenacetyl chloride and
benzene by the Friedel-Crafts reaction has been described.
2 For symmetrically substituted deoxybenzoins, direct reduction of the readily accessible
benzoin is a more convenient method. Reduction of
benzoin by
zinc dust and
acetic acid,
3 and by
hydrochloric acid and granulated
tin4,5 or amalgamated powdered
tin6 has been reported. The present method is based on a publication of the authors.
7
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Deoxyanisoin
anisoin
deoxypiperoin
piperoin
phenacetyl chloride
ethanol (64-17-5)
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
Benzene (71-43-2)
tin (7440-31-5)
Benzoin (119-53-9)
zinc (7440-66-6)
deoxybenzoin (451-40-1)
Acetophenone, 4'-methoxy-2-(p-methoxyphenyl)- (120-44-5)
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