Organic Reactions, Volume 2

CONDITIONS OF REARRANGEMENT 25
able -para substitution and disubstitution, and does not give a high yield
of a pure product. In the only instance 108a noted in the literature in
which an acid catalyst was used to rearrange an allyl phenyl ether, allyl
2-methoxyphenyl ether (LXXIX) rearranged at 78° in the presence of
boron fluoride and acetic acid to give 38% of eugenol (LXXX), with
guaiacol, 6-allyleugenol, and the allyl ether of allylguaiacol as byproducts.
When the rearrangement of LXXIX is carried out thermally,
OC3H6 OH OH
)CHS '
LXXIX LXXXI
an excellent yield of LXXXI is obtained (Table I). The presence of acids
in the Claisen rearrangement might be disadvantageous because the 2allylphenols
might be isomerized to the heterocyclic compounds (see
p. 18).
Experience with a variety of allyl ethers has indicated that in general
it is not necessary to heat etchers above 200° to effect rearrangement, and
that many preparations in the literature probably would give better
yields if they were run at lower temperatures. Allyl 4-methylphenyl
ether rearranges completely in thirteen hours at 200° without solvent, 67
and the corresponding 2,4- and 2,6-dimethyl compounds react more
rapidly. The allyl ethers of 2-phenanthrol and 3-phenanthrol rearrange
at 100 0 . 61 Allyl 2-nitrophenyl ether gives a 73% yield after heating five
hours at 180°, but the 4-nitro compound rearranges much more^lowly.
The allyl ethers of the isomeric hydroxynaphthoquinones (LXXXII and
LXXXIII) rearrange in a few minutes at 136-145° to give the same
compound (LXXXIV). 84
iOC3HB
Substitution in the a- or 7-position of the allyl group increases the
rate of rearrangement; the crotyl ether of 2,4-dichlorophenol rearranges
more rapidly than the allyl ether. 46 a-Ethylcrotyl phenyl ether rearranges
to the extent of 10% in twenty-four hours at 120°." a-Ethyl-
io3« Bryusova and Joffe. J. Gen. Chem. U.S.S.R., 11, 722 (1941) \C. A., 36,430 (1942)1.