A simple, rapid, and efficient oxidation of oximes to ketones and aldehydes with manganese dioxide catalyzed by kieselguhr under solvent-free conditions

Article abstract of DOI:10.1007/s11164-012-0573-2

A simple, rapid, and efficient oxidation of oximes to the corresponding ketones and aldehydes with manganese dioxide catalyzed by kieselguhr under solvent-free conditions at room temperature in the yields between 82 and 98 is described. It seems that kieselguhr in the present procedure can highly expedite the reaction rate. By comparing to other methods described previously, the main advantages of this oxidation are that the oxidations are more efficient, the reaction conditions are milder, the reaction times are shorter, and the work-up is easier. Furthermore, the amount of manganese dioxide used in this oxidation is largely decreased.

Full text of DOI:10.1007/s11164-012-0573-2

Res Chem Intermed (2013) 39:499–504
DOI 10.1007/s11164-012-0573-2
A simple, rapid, and efficient oxidation of oximes
to ketones and aldehydes with manganese dioxide
catalyzed by kieselguhr under solvent-free conditions
Wenjin Zheng
Yi-Feng Zhou
•
Chen Huang
Ji-Dong Lou
•
Changhe Zhang
•
•
Received: 10 April 2012 / Accepted: 21 April 2012 / Published online: 13 May 2012
Ó Springer Science+Business Media B.V. 2012
Abstract A simple, rapid, and efficient oxidation of oximes to the corresponding
ketones and aldehydes with manganese dioxide catalyzed by kieselguhr under
solvent-free conditions at room temperature in the yields between 82 and 98 is
described. It seems that kieselguhr in the present procedure can highly expedite the
reaction rate. By comparing to other methods described previously, the main
advantages of this oxidation are that the oxidations are more efficient, the reaction
conditions are milder, the reaction times are shorter, and the work-up is easier.
Furthermore, the amount of manganese dioxide used in this oxidation is largely
decreased.
Keywords Oxidation Á Oximes Á Manganese dioxide Á Kieselguhr
W. Zheng Á Y.-F. Zhou (&) Á J.-D. Lou
College of Life Sciences, China Jiliang University, Hangzhou 310018, Zhejiang, China
e-mail: zhouyifeng@cjlu.edu.cn
C. Huang
China Pharmaceutical University, Nanjing 210009, Jiangsu, China
C. Zhang
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),
Apartado 1013, 5001-801 Vila Real, Portugal
J.-D. Lou (&)
Sirnaomics, Inc, 401 Professional Drive, Gaithersburg, MD 20879, USA
e-mail: jidonglou@sirnaomics.com
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Introduction
Oxime compounds are useful protecting groups in organic syntheses [1] and have
found extensive application in the isolation, purification, and characterization of the
carbonyl compounds [2, 3]. Oximes have been used as intermediates for a number
of synthetic products, and have proven to be important and useful reagents in
organic syntheses as well [4–6]. So far, many methods and reagents have been
reported for regeneration of carbonyl compounds such as aldehydes and ketones
from oxime derivatives, for instance, hydrolytic, reductive, and oxidative reactions,
and the deoximation process can be undertaken in both homogeneous and
heterogeneous conditions [7–9]. It is well known that the oxidation is one of the
most important procedures for this transformation. However, although some of the
methods reported are carried out under mild reaction conditions, most of them
require drastic conditions, for example, high temperature, long reaction times, toxic
reagents, and tedious work-up procedures. Therefore, the development of mild and
efficient methods for the selective cleavage of derivatives containing carbon–
nitrogen double-bond-like oximes to afford carbonyl compounds continues to be a
significant aspect of organic chemistry.
Results and discussion
Manganese dioxide, a relatively environmentally friendly oxidative reagent, has
been extensively used for the oxidation of a variety of functional groups in synthetic
chemistry, even though during the work-up of the reaction the isolation of products
from the residues is rendered more difficult and the oxidation is also accompanied
by the formation of minor contaminants [10]. To the best of our knowledge, only
one report has noted manganese dioxide to be applied in the selective oxidation of
oximes into the corresponding aldehydes and ketones under heterogeneous
conditions [11].
In continuation of our previous investigations related to reactions with reagents
supported on kieselguhr [12–25], we report here an efficient procedure for the
oxidation of oximes (1) to the corresponding aldehydes and ketones (2) using
manganese dioxide catalyzed by kieselguhr under solvent-free conditions at room
temperature (Scheme 1), which offers a simple, rapid, and efficient oxidation
method for the regeneration of carbonyl compounds from the corresponding oxime
derivatives.
It has been found that reagents supported on insoluble solid supports are
particularly convenient for solving many problems in organic synthesis [26–28].
One important aspect of reactions with solid-supported reagents is that in many
Scheme 1 Oxidation of
oximes
OH
R2
N
MnO - kieselguhr
O
2
R1
solvent-free, RT
R1
R2
(1)
(2)
1
23

A simple, rapid, and efficient oxidation
501
cases, both the reagent and the product into which it is converted during reaction are
strongly adsorbed on the surface of the solid support or remain intercalated in it,
therefore, there is very little or probably no contamination of organic products or
solvents by solid materials. Furthermore, it should be possible in many cases
involving solid-supported reagents to regenerate the active reagent directly from the
spent support system by standard inorganic reactions. In most cases, solid-supported
reagents have been found superior to the non-supported reagents. On the other hand,
solvent-free reactions are not only of interest from an ecological point of view, but
in many cases also offer considerable synthetic advantages in terms of yield,
selectivity, and simplicity of the reaction procedures [29, 30]. These factors are
especially important in industry. Therefore, some of the traditional organic synthetic
methods, which have long been carried out in solvent, may be modified to more
modern, elegant, and safe versions.
In the present oxidation, a 1:2 molar ratio of the substrate to the oxidant is
employed. After mixing alcohols and manganese dioxide supported on kieselguhr
reagent with a pestle and mortar under solvent-free conditions at room temperature,
the corresponding aldehydes and ketones are obtained. All the reactions are
completed within 3 min in high yields. The progress of the reaction is monitored
with TLC, and the crude product is purified by preparative TLC. The obtained
products are all known compounds and identified by spectroscopic comparison with
authentic samples. Our results are listed in Table 1.
The promoting effect of kieselguhr was definitely confirmed by comparing our
results with those previously reported [11] that applied manganese dioxide in the
absence of inorganic support for the oxidation of oximes to the corresponding
aldehydes and ketones in heterogeneous conditions at room temperature. Kieselguhr
in the present procedure can highly expedite the reaction rate. For example, the
oxidation of benzaldehyde oxime to benzaldehyde with manganese dioxide was
completed under heterogeneous condition after 15 min in 84% yield [11], while
with manganese dioxide supported on kieselguhr under solvent-free conditions,
the required time for completion of oxidation reaction is only 2 min in 96% yield.
Furthermore, the amount of manganese dioxide used in this oxidation is largely
decreased (Table 2).
In addition, the present method has manipulative advantages over heterogeneous
oxidations, for instance, the oxidations are more efficient and selective, the reaction
conditions are milder, the reaction times are shorter, and the work-up is easier.
We consider that the mechanism for this oxidation is the same as that described
previously in the literature (Scheme 2) [11].
Experimental
Oxidation of benzaldehyde oxime to benzaldehyde: typical procedure
Manganese dioxide supported on kieselguhr (2,600 mg; 2 mmol; kieselguhr
purchased from Tianjin Fu Chen Chemical Reagent Factory) [12] and benzaldehyde
oxime (121 mg, 1 mmol) were well ground at room temperature using a pestle.
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Table 1 Oxidative cleavage of oximes to their corresponding carbonyl compounds with manganese
dioxide catalyzed by kieselguhr under solvent-free conditions
a
b
Yield (%)
Entry
1
Oxime
Time (min)
2
Product
OH
OH
O
O
96
N
N
2
2
98
Cl
Cl
Cl
Cl
3
4
5
3
3
2
96
90
86
OH
O
N
OH
OH
O
O
N
N
6
7
OH
N
3
2
O
84
96
N
CHO
OH
OH
8
N
2
3
CHO
90
82
OCH3
OCH3
9
CHO
N
OH
a
All products were identified by comparison of their physical and spectral data with those of authentic
samples
b
Isolated yields
The progress of the reaction was monitored by TLC (plates: aluminum-backed silica
gel Merck 60 GF254) using hexane:ethyl acetate (7:3) as eluent. After 2 min, the
reaction was complete. The solid was filtered and washed with dichloromethane
(
3 9 5 mL). The combined filtrates were evaporated to give crude product, which
was purified by preparative TLC (silica gel GF254) with hexane:ethyl acetate (7:3) to
afford 102 mg (96%) benzaldehyde.
1
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A simple, rapid, and efficient oxidation
503
Table 2 Comparison of oxidation of benzaldehyde oxime to benzaldehyde with manganese dioxide
under different reaction conditions
Entry Supports
Reaction
conditions
Molar ratio substrate to
manganese dioxide
Reaction
time (min)
Yield References
(%)
1
2
Kieselguhr Solvent-free,
RT, grind
1:2
2
96
84
Current
work
a
No
Hexane, RT,
stirring
1:60
15
11
a
In reference [11] it is indicated that the molar ratio of benzaldehyde oxime to manganese dioxide is
:60. We assume that it may be 1:6 due to a typing error
1
MnO
H
O
O
O
O H
O
OH
R2
Mn
O
N
Mn
O
Mn
N
N
O
R1
R2
O
R1
R2
R1
R1
R2
Scheme 2 Possible mechanism for the oxidation
Conclusions
A simple, rapid, and efficient oxidation of oximes to ketones and aldehydes with
manganese dioxide catalyzed by kieselguhr under solvent-free conditions at room
temperature in the yields between 82 and 98 is described. Kieselguhr in the present
procedure can highly expedite the reaction rate. By comparing to other methods
described previously, the main advantages of this oxidation are that the oxidations
are more efficient, the reaction conditions are milder, the reaction times are shorter,
and the work-up is easier. Furthermore, the amount of manganese dioxide used in
this oxidation is largely decreased. The mechanism for this oxidation is discussed.
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