The document summarizes the Dienone-Phenol rearrangement reaction. It begins by classifying rearrangement reactions based on the migrating group or atom. It then provides examples of the Dienone-Phenol rearrangement where disubstituted cyclohexadienones rearrange to the corresponding disubstituted phenols. The mechanism involves the generation of a carbocation through protonation, followed by rearrangement and loss of a proton to form the phenol product. The rearrangement is driven by aromatization. It notes applications in synthesizing anthracenes, phenanthrenes, and steroids like santonin. References on reaction mechanisms and rearrangements are also provided.

1. TUMKUR UNIVERSITY
DEPARTMENT OF STUDIES AND RESEARCH IN CHEMISTRYUNIVERSITY COLLEGE OF SCIENCE, TUMKUR.
2021-2022
SEMINAR TOPIC : Mechanism and synthetic use of Dinone-Phenol rearrangement
(CPT 3.1 Reaction, Rearrangement and Heterocyclic chemistry)
sUBMITTEDBY SuBMITTEDto guidEDBY
KEERTHIKUMAR C Dr .RAMESH T.N Dr .SHIVANANDHA M.K
II MSc , III Semester Co- Ordinator ASSSTANT PROFESSOR
DOS&R IN CHEMISTRY UNIVERSITY COLLEGE OF SCIENCE, DOS&R IN CHEMISTRY
UNIVERSITY COLLEGE OF SCIENCE TUMKUR UNIVERSITY COLLEGE OF SCIENCE
TUMKUR TUMKUR
1

2. INTRODUCTION
• Rearrangement reactions involve the migration of a group or an
atom from one center (migration origin) to another(migration
terminus) in within a molecule or between the two molicule
• Rearrangements roughly classified on the basis of the nature of the
migrating group/atom
1.Nucleophilic :- migrating group migrates with electron pair
2.Electrophilic :- migrating group migrates without electron pair
3.Free radical :- migrating group migrates with only one electron
2

3. Dienone–phenol Rearrangement
• The Dienone–phenol rearrangement is a reaction developed by Auwers and
Ziegler in 1921
• Example 1:- 4,4-disubstituted cyclohexadienone will be converted into a stable
3,4-disubstituted phenol
• Example 2 :- 2,2-disubstituted cyclohexadienone will be converted into its
corresponding disubstituted phenol
3
O
R R
OH
R
R
H+
O
O
H
R
R
H
+
R
R

4. • Example 3:-
• Example 4:-
4
O
H
O
R
H
+
O
H
O
H
R
O
H
+
O
H

5. MECHANISM:-
• On protonation of oxygen, a carbocation is generated which is stabilized by delocalization of the
positive charge
• The positive charge is on the carbon adjacent to a highly substituted carbon hence rearrangement
occurs. Subsequent loss of proton gives 3,4-disubstituted phenol
• Driving force for this reaction is aromatization of the ring
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O
R R
H +
R R
+
O H
R R
O H
+
O H
+
R
R
H
H +
OH
R
R
R R
O H
+

6. When one of the alkyl group forms a part of the cyclic system, either the alkyl group or
the ring methylene group may migrate.
Alkyl migration:-
Migration of ring methylene group:-
6
R
O
R
HO
1.(CH3CO)O + H2SO4
2. H2O
C
H
3
C
H
3
O
C
O
C
H
3
O
(
C
H
3
C
O
)
2
O
H
2
S
O
4

7. • The course of the reaction depends on the structural and electronic
factors and condition of reaction.
A reverse rearrangement i.e., phenol-dienone rearrangement has
been observed during the electrophilic substitution in phenols in some
cases.
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Br Br
Br
Br Br
Br Br
O
+ Br : Br
OH
+ HBr

8. APPLICATIONS:-
• Dienone-phenol rearrangement used in the synthesis of anthracenes,
phenanthrenes, steroids
• Example for synthesis of steroids:-Rearrangement of santonin to desmotropo
santonin.
8
O
H O
O
O
H C l
O
O
s a n t o n in d e s m o t r o p o s a n t o n in

9. •References:-
1. Reaction rearrangement and reagents
By Sanyal
Bharati bhavan publishers
2. Organic reaction mechanisms
By V.K Ahluwalia, Rakesh Kumar Parashar
Narosa Publishing house New Delhi
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