Rearrangement

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:-
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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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