Organic Reactions, Volume 2

SIDE REACTIONS 15
1,3-pentadiene and ethyl 4-hydroxybenzoate. 62 2-Cyclohexenyl phenyl
ether (LII) gives a 50-60% yield of phenol and cyclohexadiene, with 5%
of the expected rearrangement product (LIII) and 15% of hexahydrodibenzofuran
(LIV). 63 The very highly substituted ether, a,a,7,7-tetra-
LIV
methylallyl phenyl ether (LV) undergoes only the cleavage reaction
without any rearrangement, 33% of the diene being obtained after one
hour at 160-170 0 . 61 It has been reported, 36 ' M but without experimental
details, that 7,7-dimethylallyl phenyl ether yields phenol and isoprene on
heating, but that when heated with sodium carbonate it undergoes rearrangement.
Recently it has been shown 640 that pyrolysis of 7,7dimethylallyl
4-carbethoxyphenyl ether (LVo) gives
OCH2CH=C(CH3)2
(CH3)2
HCHS
COOC2H5
LVo LV6
mainly the cleavage products, isoprene and ethyl 4-hydroxybenzoate;
the dihydrobenzofuran derivative (LVb) is produced in small yield,
apparently as the result of an abnormal rearrangement with attachment
by the |8-carbon, followed by ring closure. The cleavage of a substituted
allyl ether and formation of the phenol have been observed also in an
attempted catalytic reduction at low temperature and pressure with a
palladium 6 or a platinum catalyst. 66 - 18
The other side reaction which is sometimes troublesome is illustrated
by the formation of LIV (see p. 18). The rearrangement of allyl phenyl
ether itself yields, in addition to 2-allylphenol,* a small amount (4-6%)
of the methyldihydrobenzofuran (LVI), which is probably produced
0
7 N
LVI
* See p. 79 of the article cited in reference 11.
6a
Lauer and Ungnade^ J. Am. Chem. Soc., 61, 3047 (1939).
ea
Cornforth, Hughes, and Lions, J. Proc. Royal Soc. N. S. Wales, 71, 323 (1938) [C. A
•33, 148 (1939)].
M
Claisen, J. prakt. Chem., [2] 105, 65 (1922).
Mo
Lauer and Moe, J. Am. Chem. Soc, 65, 289 (1943).
66
Tarbell and Wilson, unpublished observation.