Potassium permanganate oxidation of organic compounds

Article abstract of DOI:10.1081/SCC-200049792

It has been discovered that potassium permanganate is an effective heterogeneous oxidant, even without resorting to the use of a solid support, if acetonitrile is employed as the solvent. Primary benzylic and secondary alcohols are converted to the corresponding aldehydes and ketones, alkyl arenes are oxidized to the corresponding α-ketones in good yields using this procedure, and both alkyl and aryl sulfides are smoothly converted to the corresponding sulfones, also in excellent yields. When methylene chloride is used as the solvent, instead of acetonitile, the yields of aldehydes, ketones, α-ketones, and sulfones are reduced. However, the oxidation of thiols to disulfides proceeds satisfactorily when methylene chloride is the solvent.

Full text of DOI:10.1081/SCC-200049792

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Potassium Permanganate Oxidation of Organic
Compounds
a
a
b
Ahmad Shaabani , Farahnaz Tavasoli‐Rad & Donald G. Lee
a
Chemistry Department, Shahid Beheshti University, Tehran, Iran
Department of Chemistry, University of Regina, Regina, Canada
b
Version of record first published: 12 Apr 2011
To cite this article: Ahmad Shaabani, Farahnaz Tavasoli‐Rad & Donald G. Lee (2005): Potassium
Permanganate Oxidation of Organic Compounds, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 35:4, 571-580
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w
Synthetic Communications , 35: 571–580, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200049792
Potassium Permanganate Oxidation of
Organic Compounds
Ahmad Shaabani and Farahnaz Tavasoli-Rad
Chemistry Department, Shahid Beheshti University, Tehran, Iran
Donald G. Lee
Department of Chemistry, University of Regina, Regina, Canada
Abstract: It has been discovered that potassium permanganate is an effective hetero-
geneous oxidant, even without resorting to the use of a solid support, if acetonitrile is
employed as the solvent. Primary benzylic and secondary alcohols are converted to the
corresponding aldehydes and ketones, alkyl arenes are oxidized to the corresponding
a-ketones in good yields using this procedure, and both alkyl and aryl sulfides are
smoothly converted to the corresponding sulfones, also in excellent yields. When
methylene chloride is used as the solvent, instead of acetonitile, the yields of
aldehydes, ketones, a-ketones, and sulfones are reduced. However, the oxidation of
thiols to disulfides proceeds satisfactorily when methylene chloride is the solvent.
Keywords: Oxidation, permanganate, alkyl arene, sulfide, thiol, alcohol
INTRODUCTION
Potassium permanganate is a commercially available reagent, widely used for
[
1]
the oxidation of organic compounds. The process is recognized as friendly
to the environment because manganese dioxide, a coproduct formed by the
[2]
reduction of permanganate, can be recycled.
Received in the UK 25 August 2004
Address correspondence to Ahmad Shaabani, Chemistry Department, Shahid
Beheshti University, P.O. Box 19396-4716, Tehran, Iran. Fax: þ98-21-2403041.
E-mail: a-shaabani@cc.sbu.ac.ir

5
72
A. Shaabani, F. Tavasoli-Rad, and D. G. Lee
In spite of considerable knowledge with respect to the oxidation of
organic compounds by KMnO under heterogeneous conditions, practical
4
problems have been observed under some conditions. For example, over-oxi-
dations and degradations, with the formation of a host of products, are known
to occur occasionally. Reaction conditions, particularly the solvents, catalysts,
and solid supports used are crucial to controlling the specificity of the products
obtained.
It has recently been shown that organic compounds are oxidized selec-
tively when treated under heterogeneous conditions with KMnO adsorbed
4
[6]
[3]
[3–5]
[7]
.
on solid supports such as CuSO 5H O, Al O ,
zeolites, SiO2,
4
2
2 3
[9]
[8]
ion exchange resins, and montmorillonite K10. Product yields are rela-
tively good, but MnO must be separated from the solid supports before it
2
can be recycled. Although copper sulfate can be easily separated from
[
MnO2, separation of MnO from most of the other solid supports such as
2]
2
silica, montmorillonite K10, alumina, ion exchange resin, and zeolites is
very difficult. Therefore, the discovery of new conditions for the selectively
transformation of organic compounds with KMnO , in which there is no
4
need to separate MnO from supports, is of prime importance in synthetic
2
organic chemistry.
In a continuation of our previous work on organic transformations using
[
9–11]
potassium permanganate as an oxidant,
describe the selectively oxidation of alcohols, alkyl arenes, sulfides, and thiols
we wish to report results which
by KMnO under heterogeneous conditions without the use of solid supports.
4
In these reactions, acetonitile was found to be a superior solvent for the
oxidation of alkyl arenas, sulfides, and primary benzylic and secondary
alcohols.
RESULTS AND DISCUSSION
Alkyl arenes are converted into the corresponding carbonyl compounds in
good yields when oxidized heterogeneously by potassium permanganate in
acetonitrile at room temperature. The products are identical to those
obtained under heterogeneous conditions when the KMnO is supported on
4
[
3]
[3,4]
.
CuSO4 5H O
or alumina.
However, as indicated by the data in
2
Table 1, the yields are reduced if methylene chloride is used as the
solvent. The reaction exhibited a strong selectivity for the oxidation of
a-methylene groups. No reaction was observed for the oxidation of toluene
derivatives where the a-carbon is primary. The observation that no
oxidation occurs when dihydrobenzofuran, a-phenylacetophenone, or o-
ethylpyridine are the reductants is reminiscent of other heterogeneous
[
3,5]
oxidations.
As indicated by the data in Table 2, alkyl and aryl sulfides are also
converted into the corresponding sulfones in excellent yields at room

Potassium Permanganate Oxidation
573
Table 1. Oxidation of alkyl arenes to the corresponding carbonyl compounds by
at room temperature
Product
KMnO
4
in CH
3
CN and CH
2
Cl
2
CH
Yield %)
3
CN
2 2
CH Cl
(
(Time, h)
(Yield %)
(Time, h)
Entry
1
Reactant
56(29)
20(51)
9(54)
2
3
58(30)
58(32)
14(53.5)
4
5
75(24)
80(24)
8(27)
23(60)
6
7
8
9
78(27)
77(22)
72(15)
0(24)
15(143)
10(28)
31(41)
0(24)
No reaction
(
continued)

5
74
A. Shaabani, F. Tavasoli-Rad, and D. G. Lee
Table 1. Continued
CH
Yield %)
3
CN
(
(Time, h)
2 2
CH Cl
(Yield %)
(Time, h)
Entry
Reactant
Product
1
0
No reaction
0(24)
0(24)
1
1
No reaction
0(24)
0(24)
1
1
2
3
No reaction
No reaction
0(24)
0(24)
0(24)
0(24)
1
4
No reaction
0(24)
0(24)
temperature when acetonitrile is used as the solvent. This is a highly useful
reaction for the preparation of sulfones, which are important intermediates
[12]
in the synthesis of many organic compounds.
As can be seen from the results reported in Table 3, primary benzylic and
secondary alcohols are converted into the corresponding carbonyl compounds
in relatively high yields in CH CN at room temperature; however, the yields of
3
these reactions are reduced if CH Cl is used and the reaction is completely
2
2
inhibited when the electron withdrawing group is in para-position of alcohol
(
Entry 6).
Under homogenous conditions, thiols are converted into sulfonic
[
13,14]
acids.
However, under heterogeneous conditions, both aromatic and
aliphatic thiols are oxidized to the corresponding disulfides in good yields
at room temperature, as indicated by the data in Table 4. For these
reactions, methylene chloride proved to be a satisfactory solvent.
The oxidation of alkene (trans-stilbene) and alkyne (diphenylacetylene)
gives cleavage product (benzaldehyde) in high yields (GC yield) in CH CN
3

Potassium Permanganate Oxidation
575
Table 2. Oxidation of sulfides to sulfones by KMnO in CH CN and CH Cl at room
4
3
2
2
temperature
CH
Yield %) (Yield %)
3
CN
(
(Time, h)
2 2
CH Cl
Entry
Reactant
Product
(Time, h)
1
2
3
4
5
C
C
2
H
H
5
-S-C
-S-C
2
3
H
H
5
7
C
C
2
H
H
5
-SO
-SO
2
-C
-C
2
H
H
5
85(5)
92(6)
92(7)
93(7)
93(4)
48(16)
40(18)
42(23)
35(8)
8(6)
3
7
3
7
2
3
7
C H -S- C H
4
C H -SO -C H
4
9
4
9
9
2
4
9
C
8
H
17-S- C
8
H
17
C
8
H
17-SO
2
-C
8
H
17
6
7
95(4)
32(5)
95(55)
25(72)
8
9
96(22)
85(24)
14(22)
38(28)
at room temperature. However, these reactions are completely inhihibited in
CH Cl after a few days.
The oxidation of oximes and aromatic amines was also investigated.
2
2
However, the oxidation of these compounds does not result in the formation
of significant amount of useful product.
In conclusion we have introduced an economically and environmentally
friendly procedure for the selectively oxidation of organic compounds by
KMnO in CH CN or CH Cl without using of any solid supports. We have
4
3
2
2
found in CH CN sulfones are obtained from sulfides, a-ketones from
3
arenas, aldehydes, and ketones from primary benzylic and secondary
alcohols, benzaldehyde from alkene or alkyne and in CH Cl disulfides are
obtained from thiols.
2
2

5
76
A. Shaabani, F. Tavasoli-Rad, and D. G. Lee
Table 3. Oxidation of alcohols to the corresponding carbonylcompounds by KMnO4
3 2 2
in CH CN and CH Cl at room temperature
CH
Yield %)
3
CN
(
(Time, h)
2 2
CH Cl
(Yield %)
(Time, h)
Entry
1
Reactant
Product
98(1)
45(3.30)
2
3
77(0.40)
78(0.35)
67(3.15)
68(3)
4
5
75(0.45)
70(0.30)
60(4.30)
58(5)
6
7
75(3.30)
98(0.50)
No reaction(5)
72(3.30)
(
continued)

Potassium Permanganate Oxidation
Table 3. Continued
577
CH
Yield %)
3
CN
(
(Time, h)
2 2
CH Cl
(Yield %)
(Time, h)
Entry
8
Reactant
Product
85(1)
78(2.15)
17(192)
9
81(6)
10
85(1.30)
65(4)
1
1
1
2
70(0.30)
65(6)
47(5)
5(6)
1
1
3
4
40(16)
60(6)
No reaction(18)
10(6)
EXPERIMENTAL
Oxidation of Fluorene in Acetonitrile. A Typical Procedure
Fluroene (0.16 g, 1.0 mmol) was dissolved in 25 mL of CH CN and placed in
3
a round-bottomed flask. Finely ground KMnO (1.0 g, 6.3 mmol) was added
4

5
78
A. Shaabani, F. Tavasoli-Rad, and D. G. Lee
Table 4. Oxidation of thiols by KMnO in CH Cl at room temperature
4
2
2
% Yield
Time (min)
Entry
1
Reactant
Product
90(30)
2
3
81(35)
83(60)
4
5
6
93(40)
82(45)
95(53)
7
8
9
[C H ]SH
8 17
[C H ] S
8
94(60)
92(55)
78(45)
17 2
2
5
[C H
11]SH
[C
5
H
11
]
S
2 2
[C
3
H
7
]SH
3 7 2 2
[C H ] S
in small portions over a period of 15 min. The mixture was stirred vigorously
at room temperature for 15 h. The product was filtered through a celite pad
and the residue washed successively with CH CN (2 ꢀ 10 mL). The filtrate
3
.
2
was treated with three to four drops of NH -NH 2HCl in order to reduce
2
any residual oxidant. After filtering and evaporating the solvent, pure 9-fluor-
enone (0.13 g, 0.72 mmol, 72%), mp ¼ 83–848C (Lit.
[15]
82.5–858C) was
isolated.
Oxidation of Diphenylsulfide in Acetonitrile: A Typical Procedure
Diphenyl sulfide (0.16 g, 1.0 mmol) was dissolved in 25 mL of CH CN and
3
placed in a round-bottomed flask. Finely ground KMnO (1.0 g, 6.3 mmol)
4
was added in small portions over a period of 15 min. The mixture was
stirred vigorously at room temperature for 22 h. The product was filtered

Potassium Permanganate Oxidation
579
through a celite pad and the residue washed successively with CH CN
3
(
2 ꢀ 10 mL). The filtrate was treated with three to four drops of NH -
2
.
NH 2HCl in order to reduce any residual oxidant. After filtering and evapor-
2
ating the solvent, pure diphenyl sulfone (0.21 g, 0.98 mmol, 98%),
16]
[
mp ¼ 127–1288C (Lit.
126–1288C) was isolated.
Oxidation of 1-Indanol in Acetonitrile: A Typical Procedure
1
-Indanol (0.134 g, 1 mmol) was dissolved in 25 mL of CH CN and placed in a
3
round-bottomed flask and cooled to þ58C using an ice-water bath and stirred
magnetically. Finely ground KMnO (1.0 g, 6.3 mmol) was added in small
4
portions over a period of 15 min and after stirring for 5 min, the flask was
removed from the cooling bath and stirred for an additional 50 min. The
product was filtered through a celite pad and the residue washed successively
with CH CN (2 ꢀ 10 mL). The filtrate was treated with three to four drops of
3
.
2
NH -NH 2HCl in order to reduce any residual oxidant. After filtering and
2
evaporating the solvent, pure 1-indanone (0.129 g, 0.98 mmol, 98%),
[
17]
mp ¼ 41–428C (Lit.
428C) was isolated.
Oxidation of Benzyl Thiol in Methylene Chloride: A Typical
Procedure
Benzyl thiol (0.24 g, 2.0 mmol) was dissolved in 25 mL of CH Cl and placed
2
2
in a round-bottomed flask with a magnetic stirring bar. Finely ground KMnO4,
1.0 g, 6.3 mmol) was added in small portions over a period of 15 min. The
(
mixture was stirred vigorously at room temperature for 35 min. The product
was filtered through sintered glass and the residue washed successively with
CH Cl (3 ꢀ 20 mL). The solvent was evaporated to give product (0.20 g,
2
2
0
.81 mmol, 81%), which produced only one TLC spot and was identified as
[18]
dibenzyl disulfide, mp ¼ 70–718C (Lit.
71–728C).
ACKNOWLEDGMENT
Financial support on the Research Council of Shahid Beheshti University is
acknowledged.
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