Org. Synth. 1945, 25, 49
DOI: 10.15227/orgsyn.025.0049
o-EUGENOL
Submitted by C. F. H. Allen and J. W. Gates, Jr..
Checked by W. E. Bachmann and N. C. Deno..
1. Procedure
A. Guaiacol allyl ether. A mixture of 63 g. (0.5 mole) of guaiacol, 66 g. (0.55 mole) of allyl bromide, 70 g. of anhydrous potassium carbonate (0.5 mole), and 100 ml. of dry acetone in a 500-ml. round-bottomed flask is refluxed on a steam bath for 8 hours and cooled. The mixture is diluted with 200 ml. of water and extracted with two 100-ml. portions of ether. The combined extracts are washed with two 100-ml. portions of 10% sodium hydroxide (Note 1) and dried with 50 g. of anhydrous potassium carbonate. After removal of the solvent, the residual oil (Note 2) is distilled under reduced pressure. The yield of guaiacol allyl ether boiling at 110–113°/12 mm. is 66–75 g. (80–90%).
B. o-Eugenol. The allyl ether (70 g.) is cautiously (Note 3) brought to boiling in a 500-ml. round-bottomed flask, refluxed for 1 hour, and cooled. The oil is dissolved in 100 ml. of ether (Note 4), and the solution is extracted with three 100-ml. portions of 10% sodium hydroxide. The combined alkaline extracts are then acidified with 100 ml. of concentrated hydrochloric acid diluted with 100 ml. of water, and the mixture is extracted with three 100-ml. portions of ether. The combined ether extracts are dried with 50 g. of anhydrous sodium sulfate and evaporated, and the residual oil is distilled under reduced pressure. The yield of o-eugenol boiling at 120–122°/12 mm. (Note 5) is 56–63 g. (80–90%).
2. Notes
1.
A small amount of
guaiacol may be recovered by acidifying the alkaline wash and extracting with
ether.
2.
When this crude
guaiacol allyl ether was rearranged without prior distillation, the yields of
o-eugenol were about 10% lower than those obtained with the distilled
ether.
3.
This rearrangement is sometimes quite vigorous and needs little heat once it is started.
Dimethylaniline is said to be a good solvent for use in this type of rearrangement.
14.
Benzene may be substituted for
ether throughout.
5.
Other boiling points are
250–251°/760 mm.,
125°/14 mm., and
115°/9 mm.
3. Discussion
Guaiacol allyl ether has been prepared from
guaiacol,
ethanolic potassium hydroxide, and
allyl iodide;
2 or from
guaiacol,
allyl bromide, and
potassium carbonate in
acetone.
3,4 o-Eugenol has been prepared by the rearrangement of
guaiacol allyl ether;
3,4 from
3-methoxy-2-allyloxybenzaldehyde by heating to 210°;
5 and from
3-methoxy-2-allyloxybenzoic acid by heating above 110°.
6
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ethanolic potassium hydroxide
potassium carbonate (584-08-7)
hydrochloric acid (7647-01-0)
Benzene (71-43-2)
ether (60-29-7)
sodium hydroxide (1310-73-2)
Allyl bromide (106-95-6)
sodium sulfate (7757-82-6)
allyl iodide (556-56-9)
acetone (67-64-1)
Guaiacol (90-05-1)
dimethylaniline (121-69-7)
Guaiacol allyl ether (4125-43-3)
3-methoxy-2-allyloxybenzaldehyde
3-methoxy-2-allyloxybenzoic acid
o-Eugenol (579-60-2)
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