2. Contents:
Sr No Topics Slide No
1 Introduction to die none phenol
rearrangment
03
2 Examples 04
3 Mechanism of die none phenol
rearrangment
05-06
4 Applications 06
5
References
07
2
3. Introduction:
3
The die none–phenol rearrangement is
a reaction in organic chemistry first
reported in 1921 by Karl von
Auwers and Karl Ziegler. A common
example of dienone–phenol
rearrangement is 4,4-
disubstituted cyclohexadienone converti
ng into a stable 3,4-
disubstituted phenol in presence of acid.
A similar rearrangement is possible with
a 2,2-disubstituted cyclohexadienone to
its corresponding disubstituted phenol.
Dienone–phenol rearrangement
of 4,4-disubstituted
cyclohexadienone into
3,4‐disubstituted phenol
4. • common example of dienone–phenol
rearrangement is 4,4-
disubstituted cyclohexadienone
converting into a stable 3,4-disubstituted
phenol in presence of acid A similar
rearrangement is possible with a 2,2-
disubstituted cyclohexadienone to its
corresponding disubstituted phenol.
4
5. Mechanism of Dienone phenol
Rearrangements
• On protonation of the oxygen, a carbocation is generated' which is stabilized
by de localization of the positive charge. In one of the canonical structures,
the positive charge is on a carbon adjacent to a highly substituted carbon.
Hence, a carbocation rearrangement occurs. Subsequent loss of a proton
gives the 3, 4-disubstituted phenol. The ease of dienone-phenol
rearrangement is due to the creation of a stable aromatic system.
• When one of the alkyl group forms a part of the cyclic system, either the alkyl
group or the ring methylene group may migrate. The course of the reaction
depends on the structural or electronic factors and on the conditions of
reaction. A reverse rearrangement, i.e., phenol--dienone rearrangement has
been observed during the electrophilic substitution in phenols in some cases.
5
6. • The reaction mechanism of 4,4-disubstituted
cyclohexadienones to 3,4-disubstituted phenol
6
7. Applications of Dienone phenol Rearrangements
• The rearrangement has useful
applications. A classic example is the
rearrangement of santonin to
deisotope santonin.
7
