Manganese dioxide supported on aluminum silicate: A new reagent for oxidation of alcohols under heterogeneous conditions

Article abstract of DOI:10.1080/00397911.2011.582596

Manganese dioxide supported on aluminum silicate, under heterogeneous conditions at reflux, selectively oxidized aromatic primary and secondary alcohols into the corresponding aldehydes and ketones, respectively, in yields of 87-96%. The present method failed to oxidize aliphatic alcohols.

Full text of DOI:10.1080/00397911.2011.582596

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Manganese Dioxide Supported on
Aluminum Silicate: A New Reagent
for Oxidation of Alcohols Under
Heterogeneous Conditions
a
a
b
c
Li-Hong Huang , Yi-Chun Ma , Changhe Zhang , Qiang Wang
,
a
c
Xiao-Nan Zou & Ji-Dong Lou
a
College of Life Sciences, China Jiliang University, Hangzhou,
Zhejiang, China
b
Centre for the Research and Technology of Agro-environmental and
Biological Sciences (CITAB)/Department of Biology and Environment,
Universidade de Trás-os-Montes e Alto Douro (UTAD), Vila Real,
Portugal
c
Sirnaomics, Inc., Gaithersburg, Maryland, USA
Accepted author version posted online: 11 Nov 2011.Published
online: 18 Jul 2012.
To cite this article: Li-Hong Huang , Yi-Chun Ma , Changhe Zhang , Qiang Wang , Xiao-Nan Zou & Ji-
Dong Lou (2012): Manganese Dioxide Supported on Aluminum Silicate: A New Reagent for Oxidation
of Alcohols Under Heterogeneous Conditions, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 42:22, 3377-3382
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1
Synthetic Communications , 42: 3377–3382, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.582596
MANGANESE DIOXIDE SUPPORTED ON ALUMINUM
SILICATE: A NEW REAGENT FOR OXIDATION OF
ALCOHOLS UNDER HETEROGENEOUS CONDITIONS
1
Li-Hong Huang, Yi-Chun Ma, Changhe Zhang,
1
2
3
Qiang Wang, Xiao-Nan Zou, and Ji-Dong Lou
1
3
1
College of Life Sciences, China Jiliang University, Hangzhou,
Zhejiang, China
2
Centre for the Research and Technology of Agro-environmental and
Biological Sciences (CITAB)=Department of Biology and Environment,
Universidade de Tr a´ s-os-Montes e Alto Douro (UTAD), Vila Real, Portugal
3
Sirnaomics, Inc., Gaithersburg, Maryland, USA
GRAPHICAL ABSTRACT
Abstract Manganese dioxide supported on aluminum silicate, under heterogeneous
conditions at reflux, selectively oxidized aromatic primary and secondary alcohols into
the corresponding aldehydes and ketones, respectively, in yields of 87–96%. The present
method failed to oxidize aliphatic alcohols.
Keywords Alcohols; aluminum silicate; manganese dioxide; oxidation; supported
reagent
INTRODUCTION
The oxidation of alcohols to the corresponding carbonyl compounds is one of
the most important reactions in organic chemistry, and has long been the objective of
many research papers. Although many methods are available for this oxidation,
convenient and mild procedures are important objectives of current relevance.
Consequently, introduction of new methods and reagents is still fraught with experi-
mental challenges, especially in the search for environmentally friendly, inexpensive,
versatile, and selective oxidation reagents.
Received February 15, 2011.
Address correspondence to Ji-Dong Lou, Sirnaomics, Inc., 401 Professional Drive, Gaithersburg,
MD 20879, USA. E-mail: jidonglou@sirnaomics.com
3
377

3378
L.-H. HUANG ET AL.
RESULTS AND DISCUSSION
It is well known that manganese dioxide, a relatively environmentally friendly
reagent, has been extensively used for the oxidation of a variety of functional groups
[1]
in synthetic chemistry. However, few manganese dioxide or manganese dioxide–
based reagents have been applied in the selective oxidation of aromatic primary
alcohols to the corresponding aldehydes, for instance, mainly solid manganese
[
2–4]
dioxide under heterogeneous conditions,
5,6]
manganese dioxide under solvent-free
and supported manganese dioxide reagent under microwave
[
conditions,
irradiations.
[
7,8]
So far, introduction of reagents on solid supports has circumvented some
problems and provided an attractive alternative in organic synthesis in view of the
selectivity and associated ease of manipulation. Therefore, a number of oxidants
impregnated on solid supports have been explored, considerably extending the
supported-reagent technique. Many organic reactions have been devised in which
the reagents are deposited on various inorganic solid supports. These novel reagents
have advantages over the conventional homogeneous solution techniques, for
instance, ease of setup and workup, mild experimental conditions, and gains in yield
and=or selectivity. The variety and the versatility of these heterogeneous methods are
[
9,10]
evident from a recent number of relative publications.
These factors are
especially important in industry. Likewise, in most cases, solid-supported reagents
have been found superior to the unsupported reagents.
Previously, we described aluminum silicate as a good inorganic solid support of
[
11,12]
[13]
hexavalent chromium derivatives,
[
potassium permanganate,
and ferric
14]
nitrate for the selective oxidation of alcohols to carbonyl compounds and manga-
nese dioxide supported on kieselguhr as an efficient reagent for the oxidation of
[
15]
[11–15]
benzoins.
In connection with our previous studies,
we report here that
manganese dioxide supported on aluminum silicate is a new reagent suitable for
the selective oxidation of aromatic primary and secondary alcohols (1) into the
corresponding aldehydes and ketones (2), respectively (Scheme 1).
The manganese dioxide supported on aluminum silicate reagent is easily pre-
pared by mixing potassium permanganate, manganese sulfate monohydrate, and
ꢀ
aluminum silicate at 60 C. The active manganese dioxide is prepared according to
[
1]
Ref. After contact of aromatic primary or secondary alcohols with the reagent
under heterogeneous and reflux, the expected products are obtained. In our cases,
commercial potassium permanganate, manganese sulfate monohydrate, and alumi-
num silicate can be used without further purification, and the solid support, alumi-
num silicate, is readily available and inexpensive as well. Under our investigations, a
1:3 molar ratio of the substrate to the oxidant is employed, and the oxidation of all
aromatic alcohols is completed within 12 h with good yields. The progress of the
Scheme 1. Oxidation of alcohols.

OXIDATION OF ALCOHOLS WITH MAGNESIUM DIOXIDE
3379
reaction is monitored with thin-layer chromatography (TLC), and the product is
purified by preparative TLC. The obtained products are all known compounds
and identified by spectroscopic comparison with authentic samples.
Meanwhile, some typical saturated aliphatic alcohols are also investigated
under similar reaction conditions. However, they remain almost intact by this
method: after 24-h oxidation, for a secondary alcohol, 2-hexanol, the corresponding
2
-hexanone is obtained in 19% yield, and for a primary alcohol, 1-hexanol, the cor-
responding 1-hexanal is obtained in only 9% yield. Our results are listed in Table 1,
which shows the oxidation of aromatic alcohols is achieved in good yields because of
the p-electrons of the double bond.
To the best of our knowledge, no previous reports can be found in the litera-
ture for the selective oxidation of aromatic primary alcohols into the corresponding
Table 1. Oxidation of alcohols with manganese dioxide supported on aluminum silicate reagent
ꢀ
d
Mp ( C) of 2,4-DNP
a
b
c
Yield (%)
[16]
Reported
Substrate
Product
Reaction time (h)
Found
[
16]
1
1
1
2
2
2
89
96
92
254–256
255
237
254
[16]
235–236
255–256
232–234
263–265
[
[
[
16]
17]
16]
1
1
2
2
89
87
234
266
[
17]
1
1
2
2
90
96
245–247
46–47
249
e,[16]
48–49
[
17]
2
2
4
4
19
9
103–105
100–101
106
[16]
101–103
a
All the substrates are commercially available.
b
All the products are known compounds and were identified by comparison of their melting points with
1
the literature values as well as by H NMR and IR.
c
Yield of isolated pure product.
d
2,4-Dinitrophenylhydrazone derivative.
Mp of benzophenone.
e

3380
L.-H. HUANG ET AL.
Table 2. Oxidation of benzyl alcohol to benzaldehyde with manganese dioxide under different reaction
conditions
Reaction conditions
Time
Yield (%)
References
MnO
MnO
MnO
MnO
MnO
2
2
2
2
2
-aluminum silicate=CH
=CHCl =rt
2
Cl
2
=reflux
12 h
23 h
5 h
96
89
92
77
88
Present work
3
2
5
6
7
ꢀ
=solvent-free=90 C
=solvent-free=rt
-silica gel=solvent-free=microwave irradiation
48 h
20 m
Scheme 2. Possible mechanism of the oxidation.
aldehydes using supported manganese dioxide reagents under heterogeneous con-
ditions. Furthermore, it is well known that for the reaction with manganese dioxide
in the absence of support the isolation of products from the ensuing residues is
rendered more difficult, and the oxidation is also accompanied by the formation
of minor contaminants. However, the current procedure is very profitable in
workup, which becomes reduced to mere filtration.
In addition, compared with previous methods using manganese dioxide
oxidizing aromatic alcohols, the present procedure has some additional merits. As
a representative example, the oxidation of benzyl alcohol to benzaldehyde with
manganese dioxide under different reaction conditions is compared in Table 2. From
this table it is clear that the reaction time of the current procedure is relatively
shorter except for the reaction using microwave irradiation, and the yield of current
procedure is better as well.
We consider that the present oxidation is a free radical mechanism, which is the
same as that proposed by Goldman.
example (Scheme 2).
[18]
Here oxidation of benzyl alcohol is an
CONCLUSION
In conclusion, the present manganese dioxide supported on aluminum silicate
reagent under heterogeneous conditions is a new and efficient procedure for the
selective oxidation of aromatic primary and secondary alcohols to the corresponding
aldehydes and ketones, respectively. In the current procedure it turns out to be very
profitable in the workup, which becomes reduced to mere filtration.

OXIDATION OF ALCOHOLS WITH MAGNESIUM DIOXIDE
3381
EXPERIMENTAL
Preparation of Active Manganese Dioxide Supported on Aluminum
Silicate Reagent
[
1]
Active manganese dioxide is prepared according to Ref. Potassium per-
manganate (1.9 g) was dissolved in water (50 mL) at room temperature, aluminum
ꢀ
silicate (30 g) was added with stirring, and the water was evaporated at 60 C. The
residue was ground to a fine powder and then added to a solution of manganese sul-
fate monohydrate (4.7 g) in water (50 mL) with vigorous stirring. After the resulting
ꢀ
precipitate was filtered and dried at 100 C for 3 h, manganese dioxide supported on
aluminum silicate reagent was obtained.
Oxidation of Benzyl Alcohol to Benzaldehyde, Typical Procedure
The manganese dioxide supported on aluminum silicate reagent (3.8 g) was
placed in a flask together with dichloromethane (30 mL), and the mixture was mag-
netically stirred. A solution of benzyl alcohol (108 mg, 1 mmol) in dichloromethane
(5 mL) was added, and after 12 h at reflux the solid was filtered and washed with
dichloromethane (3 Â 5 mL). The combined filtrates were evaporated to give crude
product, which was purified by preparative TLC with hexane–ethyl acetate (8:2)
to afford 102 mg (96%) benzaldehyde.
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