Organic Reactions, Volume 2

CONDITIONS OF REARRANGEMENT 23
the allylic isomers can be separated by careful distillation, the chlorides
are much more useful for synthetic work.
The Williamson synthesis, using a sodium phenoxide and allyl bromide
in methanol solution, is more rapid than the procedure using acetone
and potassium carbonate and gives good results. 16 ' 3B ' **• 66 Aqueous acetone
also has been used as the reaction medium with allyl bromide and
sodium hydroxide; this method likewise is rapid and sometimes leads
to better yields than the procedure using potassium carbonate and
acetone. 34 Allylation of 2-hydroxy-l,4-naphthoquinone has been carried
out by treating the silver salt, in benzene, with allyl bromide; 84
some C-alkylation as well as O-alkylation was observed.
The extent of C-alkylation as a side reaction in etherification varies;
about 1% of allyl 2-allylphenyl ether is formed when phenol is used in
the acetone and potassium carbonate method with allyl bromide; * with
cinnamyl bromide or 7,7-dimethylallyl bromide the extent of C-alkylation
is greater. 16 A complicated mixture of C- and O-alkylation products
results from the treatment of phenol with 4-bromo-2-hexene and 4chloro-2-hexene."
4-Hexenylresorcinol has been obtained in about 40%
yield from the reaction of l-bromo-2-hexene, resorcinol, and potassium
carbonate in boiling acetone. 99 " An appreciable amount of C-alkylation
occurs when 2,6-dimethylphenol is treated with allyl bromide and
sodium ethoxide in ethanol. 70 Since, in general, the ampunt of C-alkyiation
is greatly increased by carrying out the alkylation on the sodium
salt of the phenol in benzene, 16 this method is unsuitable for the preparation
of allyl aryl ethers.
In preparing ethers of o-carbomethoxyphenols it has been found that
the slow dropwise addition of aqueous sodium hydroxide or potassium
carbonate to a refluxing mixture of the proper phenol and halide in
methyl ethyl ketone gives a smoother reaction with yields much better
than those obtained when all the alkali is added before refluxing is
begun. 46 "
Conditions of Rearrangement
The simpler allyl aryl ethers can be rearranged by refluxing at atmospheric
pressure until the boiling point becomes constant; since the
boiling point(of the product is higher than that of the ether, the boiling
point rises until the reaction is complete." The rearrangement is nearly
always exothermic—so much so that it may become troublesome when
large batches are run without solvent.
* See p. 78 of the article cited in reference 11.
99 Smith, TTngnade, Lauer, and Leekley, J. Am. Chem. Soc., 61, 3079 (1939).
"" Hurd and McNamee, J. Am. Chem. Soc., 59. 104 (1937).