Highly selective oxidation of primary and secondary benzylic alcohols by KMnO4/ZrOCl2·8H2O in diethyl ether

Article abstract of DOI:10.1081/SCC-100108237

Zirconyl chloride octahydrate-potassium permanganate is used for highly selective and efficient oxidation of primary and secondary benzylic alcohols to the corresponding carbonyl compounds under mild condition. Over-oxidation of aldehydes to carboxylic acids and damage to carbon-carbon double bond is not observed by this method.

Full text of DOI:10.1081/SCC-100108237

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HIGHLY SELECTIVE OXIDATION OF PRIMARY AND
SECONDARY BENZYLIC ALCOHOLS BY KMnO /ZrOCI
4
2
8
H O IN DIETHYL ETHER
2
a
a
a
Habib Firouzabadi , Mahmood Fakoorpour & Hassan Hazarkhani
a
Department of Chemistry, College of Sciences, Shiraz University, Shiraz, 71454, Iran
Published online: 09 Nov 2006.
To cite this article: Habib Firouzabadi , Mahmood Fakoorpour & Hassan Hazarkhani (2001) HIGHLY SELECTIVE OXIDATION
OF PRIMARY AND SECONDARY BENZYLIC ALCOHOLS BY KMnO /ZrOCI 8H O IN DIETHYL ETHER, Synthetic Communications:
4
2
2
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 31:24, 3859-3862, DOI: 10.1081/
SCC-100108237
To link to this article: http://dx.doi.org/10.1081/SCC-100108237
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SYNTHETIC COMMUNICATIONS, 31(24), 3859–3862 (2001)
HIGHLY SELECTIVE OXIDATION OF
PRIMARY AND SECONDARY BENZYLIC
ALCOHOLS BY KMnO /ZrOCl E8H O IN
4
2
2
DIETHYL ETHER
Habib Firouzabadi,* Mahmood Fakoorpour,
and Hassan Hazarkhani
Department of Chemistry, College of Sciences,
Shiraz University, Shiraz 71454, Iran
ABSTRACT
Zirconyl chloride octahydrate-potassium permanganate is
used for highly selective and efficient oxidation of primary
and secondary benzylic alcohols to the corresponding carbo-
nyl compounds under mild condition. Over-oxidation of alde-
hydes to carboxylic acids and damage to carbon–carbon
double bond is not observed by this method.
Potassium permanganate has long been used as an oxidant for a vari-
1
,2
ety of organic functional groups, either in aqueous or non-aqueous media.
Nevertheless, potassium permanganate has found relatively little application
in the oxidation of alcohols to aldehydes and ketones, especially for the
oxidation of primary alcohols to aldehydes. Precautions, in such cases,
must be taken that aldehyde is not further oxidized to the carboxylic acid.
*
Corresponding author. Fax: Int. (071) 20027; E-mail: firouzabadi@chem.susc.ac.ir
859
3
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
3
860
FIROUZABADI, FAKOORPOUR, AND HAZARKHANI
3
One way to halt oxidation is by distillation of the aldehyde as it is formed.
ꢀ
In order to control the oxidation power of MnO anion, modifications have
4
1
,4–6
been devised and reported.
Heterogeneous oxidation of unsaturated primary and secondary alco-
hols by permanganate mixed with solid support, such as copper sulfate penta-
hydrate is reported. By this procedure, primary alcohols are converted to
7
their carboxylic acids in high yields. Solid sodium permanganate monohy-
drate has also been used for the oxidation of primary alcohols to their
8
carboxylic acids.
Now, we wish to report that zirconyl chloride octahydrate (ZrOCl ꢁ
2
8H O) is a suitable support for the highly selective and high yield oxidation
of benzylic, aryl allylic alcohols by KMnO in diethyl ether at room tem-
2
4
perature (Table, Scheme 1).
Oxidation of primary and secondary benzylic alcohols in the presence
of saturated ones, shows high selectivity of the presented method. We have
shown this selectivity in a single molecule bearing benzylic and saturated
hydroxyl functional groups (Scheme 2). Vicinal diols, benzylic silyl and THP
ethers remain unreacted in the presence of KMnO /ZrOCl ꢁ8H O. Water of
4
2
2
hydration of zirconyl chloride plays a crucial role in the activity of the
solid support. We have observed that when ZrOCl ꢁ8H O was left in
2
2
ꢂ
an oven at 140 C overnight the rate of the reaction dropped drastically.
Table. Oxidation of Alcohols by KMnO /ZrOCl ÁH O in Et O at Room
4
2
2
2
Temperature
Oxidant/
a
Promoter Ratio
Time
(h)
Yield
(%)
Alcohol
Product
b
PhCH OH
2
2–3/0.7
2–3/0.7
2–3/0.7
2–3/0.7
2–3/0.7
3–4/0.7
2–3/0.7
3.5 PhCHO
95
93
94
94
92
90
85
4
4
4
4
4
9
-H
3
C-C
6
H
4
-CH
-CH
2
OH
3.5 4-CH
4-CH
3
-C
6
H
4
-CHO
-H
-Cl-C H -CH OH
-Br-C
-HOCH
-Hydroxymethyl
anthracene
3
CO-C
6
H
4
2
OH
3
3
O-C H -CHO
6 4
3.5 4-Cl-C H -CHO
6 4
6
4
2
6
H
4
-CH
-C
2
OH
-CH
3.5 4-Br-C
5.5 4-OHC-C
9-Anthraldehyde
6
H
4
-CHO
2
6
H
4
2
OH
H -CHO
6 4
6
PhCH(OH)CH
PhCH(OH)Ph
2
CH
3
3–4/0.7
3–4/0.7
2–3/0.7
3–4/0.7
2–3/0.7
4.5 PhCOCH
4.5 PhCOPh
2
CH
3
95
94
91
90
92
PhCH(OH)COPh
OH
6
12
6
PhCOCOPh
PhCH¼CHCHO
PhCH¼CHCH
2
PhCH¼CHCH(OH)Ph
PhCH¼CHCOPh
a
b
Oxidant/promoter ratio per one mmol of substrate. Benzaldehyde was isolated as
its 2,4-dinitrophenylhydrazine derivative.

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KMnO
4
/ZrOCl
2
E8H
2
O IN DIETHYL ETHER
3861
Scheme 1.
Scheme 2.
This observation is in agreement with that reported for oxidation by
7
KMnO /CuSO ꢁ5H O.
4
4
2
In conclusion, in this investigation we have presented a new method
for the highly efficient and selective oxidation of benzylic alcohols with
KMnO in diethyl ether.
4
EXPERIMENTAL
General Procedure. To a solution of alcohol (10 mmol) in Et O (25 mL)
2
was added KMnO /ZrOCl ꢁ8H O (20–30 mmol/0.7 mmol). The resulting
4
2
2
mixture was stirred at room temperature for the appropriate reaction time
(monitored by TLC, table). After completion of the reaction, the reaction
mixture was filtered through a silica-gel pad and the filter cake was further
washed with Et O (2 ꢃ 10 mL). The ethereal solutions were combined
2
together and evaporated to give the desired product in good to excellent
yield (table). Further purification was accomplished by column chromato-
graphy packed with silica gel with the appropriate solvent.
ACKNOWLEDGMENTS
The authors are grateful to National Research Council of I.R. for
grant No. 464 and Shiraz University Research Council for the partial sup-
port of this work.

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FIROUZABADI, FAKOORPOUR, AND HAZARKHANI
REFERENCES
1
2
. Fatiadi, A.J. Synthesis 1987, 85.
. a) Hudlicky, M. Oxidation in Organic Chemistry, American Chemical
Society, Washington, DC, 1990, b) Augustine, R.L.; Dekker, M.
Oxidation, New York, 1969.
3. Vogel, A.R., Vogel’s Textbook of Practical Organic Chemistry, 5th ed.,
Longman Scientific and Technical, 1989.
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5
. Firouzabadi, H.; Vessal, B.; Naderi, M. Tetrahedron Lett. 1982, 1847.
. Firouzabadi, H.; Sardarian, A.R.; Naderi, M.; Vessal, B. Tetrahedron
1984, 40, 500.
6. Firouzabadi, H.; Mottaghinejad, E.; Seddighi, M. Synthesis 1989, 378.
7. Noureldin, N.A.; Lee, D.J. J. Org. Chem. 1982, 47, 2790.
8. Menger, F.M.; Lee, C. Tetrahedron Lett. 1981, 1655.
Received in the Netherlands February 10, 2001

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