Green oxidations. Manganese(II) sulfate aided oxidations of organic compounds by potassium permanganate

Article abstract of DOI:10.1007/s00706-007-0667-5

The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable. Springer-Verlag 2007.

Full text of DOI:10.1007/s00706-007-0667-5

Monatshefte f u¨ r Chemie 138, 649–651 (2007)
DOI 10.1007/s00706-007-0667-5
Printed in The Netherlands
Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic
Compounds by Potassium Permanganate
Ahmad Shaabani1 , Abbas Rahmati , Masoumeh Sharifi , Jafar Mogimi Rad ,
;ꢀ
1
1
1
2
1
3;ꢀ
Behnaz Aghaaliakbari , Elham Farhangi , and Donald G. Lee
1
Department of Chemistry, Shahid Beheshti University, Tehran, Iran
2
Department of Chemistry, University of Kashan, Kashan, Iran
3
Department of Chemistry and Biochemistry, University of Regina, Regina SK, Canada
Received January 23, 2007; accepted February 14, 2007; published online May 11, 2007
#
Springer-Verlag 2007
Summary. The oxidation of arenes and sulfides by potas-
sium permanganate was accomplished in good yields under
solvent free and heterogeneous conditions when manga-
nese(II) sulfate is used as a solid support. After extraction of
the organic products, the inorganic products can be reoxidized
to permanganate. This result is important because it provides
an approach to oxidation reactions that is, in theory, infinitely
sustainable.
permanganate, as outlined in the following reac-
tion [1].
Therefore, if ways to recover the manganese diox-
ide (in sufficiently pure form) can be found, the pro-
cess becomes infinitely sustainable. An approach to
the exploitation of this idea that we have previously
discussed in literature involves the use of potassium
permanganate as an oxidant under solvent free or
heterogeneous conditions [2]. When used under such
conditions, potassium permanganate must be acti-
vated using a solid support. Unfortunately, many of
the common solid supports (such as alumina [3, 4],
silica [5], zeolite [6], montmorillonite K10 [7], cation
exchange resins [8], molecular sieves [9], or copper
sulfate pentahydrate [10]) interfere with the reoxida-
tion process. However, we have found that activated
manganese dioxide is an excellent solid support that
can be recycled, as in the following example [11].
Keywords. Oxidation; Solvent free; Permanganate; Arene;
Sulfide.
Introduction
Although oxidation reactions play a central role in
organic chemistry, many are known to be envir-
onmentally destructive because they require vigor-
ous reagents and harsh conditions. Therefore, there
are substantial benefits to be realized from the de-
velopment of oxidation processes that are sustain-
able and, as a consequence, more environmentally
acceptable.
In an attempt to find sustainable oxidation pro-
cedures, we have previously examined the use of
potassium permanganate under various conditions.
It is a most attractive oxidant on which to base a
sustainable process because its reduction product,
manganese dioxide, can be reoxidized to potassium
ꢀ Corresponding author. E-mail: a-shaabani@cc.sbu.ac.ir

6
50
A. Shaabani et al.
After the organic product (acetophenone in this
The yields under three sets of conditions are
reported in Table 1. The first column gives the yields
obtained when an oxidant consisting of equal
amounts (by weight) of KMnO and MnSO ꢁ H O
example) has been extracted, the manganese product
can be oxidized to potassium permanganate, making
the process infinitely sustainable, in theory.
4
4
2
One of the difficulties with this approach is the
need to prepare activated manganese dioxide by the
oxidation of manganese(II) sulfate with potassium
permanganate. In an attempt to bypass this step, and
thereby improve the efficiency of this process, we
have now investigated the use of manganese(II) sul-
fate as a solid support for these reactions under both
solvent free and heterogeneous conditions.
was used under solvent free conditions. The second
column gives the yields obtained when KMnO4
and MnSO ꢁ H O were combined in a 5:1 ratio (by
4
2
weight) and used under solvent free conditions. The
third column gives the yields obtained when equal
amounts (by weight) of KMnO and MnSO ꢁ H O
4
4
2
were combined and used under heterogeneous con-
ditions with methylene chloride as the solvent. In
the absence of any added manganese(II) sulfate, the
yields were abysmally low.
Results and Discussion
Although there are individual variations, it ap-
pears that the use of an oxidant consisting of KMnO4
and MnSO ꢁ H O in a 5:1 ratio (by weight) under
The results obtained from the oxidation of a number
of products of these reactions are the corresponding
ketones and sulfones, as indicated in the following
equations.
4
2
solvent free conditions is generally the most satis-
factory approach. The yields are comparable to
those obtained when equal amounts of KMnO and
4
MnSO ꢁ H O were used under solvent free condi-
4
2
tions and the reaction times are much shorter than
those required for similar yields under heteroge-
neous conditions. Therefore, the use of KMnO and
4
MnSO ꢁ H O in a 5:1 ratio is environmentally ap-
4
2
pealing for two reasons: (1) less material is used,
and (2) the reduced oxidant can be recycled.
Table 1. Yields=% (react time=h) obtained from the manganese(II) sulfate aided oxidations of arenes and sulfides by potassium
permanganate
Reductant
KMnO :MnSO ꢁ H O ¼ 1:1
KMnO :MnSO ꢁ H O ¼ 5:1
KMnO :MnSO ꢁ H O ¼ 1:1
4
4
2
4
4
2
4
4
2
(
solvent free)
(solvent free)
(heterogeneous)
Ethylbenzene
Propylbenzene
Butylbenzene
Diphenylmethane
Indane
Tetralin
Phthalan
Isochroman
Xanthene
Fluorene
Diphenylsulfide
Benzylphenylsulfide
Methylphenylsulfide
Methyl(4-nitrophenyl)sulfide
Bis(4-hydroxyphenyl)sulfide
Phenoxathin
Dibenzylsulfide
Dipropylsulfide
Dibutylsulfide
Tetrahydrotiophene
90 (4.45)
75 (5.30)
79 (5.45)
55 (5)
80 (6)
85 (4)
81 (4)
90 (5)
85 (4)
91 (3.30)
92 (1)
96 (1)
83 (0.75)
100 (0.5)
80 (2)
86 (0.5)
95 (1.25)
90 (0.17)
95 (0.25)
93 (0.25)
67 (5.4)
70 (6)
80 (6)
70 (35)
32 (45)
50 (47)
87 (43)
61 (53)
80 (56)
65 (20)
70 (51)
100 (24)
68 (51)
95 (10)
86 (42)
90 (1.15)
100 (12)
64 (11)
95 (11)
90 (51)
33 (5)
96 (6)
76 (18)
80 (7.30)
65 (4)
82 (10)
80 (5)
89 (5.30)
93 (2)
95 (1)
87 (0.5)
97 (1.10)
86 (1.30)
95 (0.75)
90 (1.30)
92 (1.10)
91 (1.20)
18 (6)
45 (5)
30 (5)

Green Oxidations
651
Experimental
References
The oxidant for the reactions reported in the first column of
Table 1 was prepared by grinding together potassium perman-
ganate (1.0 g) and MnSO ꢁ H O (1.0g). This oxidant was
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4
2
placed in a round bottom flask (in the absence of solvent)
and reductant (1.0mmol) was added. The reactants were stir-
red continuously at room temperature using a magnetically
controlled stirring bar. Progress of the reactions was monitored
by TLC until the reductant had completely reacted or until a
reasonable amount of time had elapsed. Methylene chloride
3
15 cm ) was then added to the flask and the reaction mixture
(
was filtered through a sintered glass funnel. The residue was
3
washed with additional methylene chloride (2ꢂ10 cm ) and
the solvent collected was combined and evaporated on a flash
evaporator. The yields were determined by GC analysis or
1
from the integrals of the H NMR spectrum of the material
obtained when most of the solvent had been evaporated. All
1
products are known compounds with well-defined H NMR
spectra [11].
The results reported in the second column of Table 1 were
obtained in the same way except that the oxidant consisted of
KMnO (1.0g) and MnSO ꢁ H O (0.20 g).
4
4
2
The results reported in the third column of Table 1 were
obtained using heterogeneous conditions. KMnO (1.0g) and
4
MnSO ꢁ H O (1.0g) were ground together and placed in a
4
2
3
round bottom flask, followed by methylene chloride (15 cm )
and reductant (1.00 mmol). The reaction was then monitored
and worked up as described above.
[9] Shaabani A, Lee DG (2001) Tetrahedron Lett 42: 5833
10] a) Regen SL, Koteel C (1977) J Am Chem Soc 99: 3837;
b) Lai S, Lee DG (2001) Synthesis 1645
[11] Shaabani A, Mirzaei P, Naderi S, Lee DG (2004)
Tetrahedron 60: 11415
[
Acknowledgements
Financial assistance from the Research Council of Shahid
Beheshti University of Iran is gratefully acknowledged.