An improved procedure for oxidative cleavage of oximes to the corresponding carbonyl compounds with chromic acid supported on kieselguhr under viscous conditions

Article abstract of DOI:10.1080/15533174.2013.763268

An improved and efficient oxidative cleavage of oximes to the corresponding carbonyl compounds with chromic acid supported on kieselguhr reagent at room temperature under viscous conditions in the yield between 82% and 96% is described. The present procedure can overcome the problems that existed in the common solvent-free reactions as for the difficulty for the solid molecular collision to react. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2013.763268

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1518–1520, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.763268
An Improved Procedure for Oxidative Cleavage of Oximes
to the Corresponding Carbonyl Compounds With Chromic
Acid Supported on Kieselguhr Under Viscous Conditions
1
1
1
1
1,2
Fang Lin, Jianan Lin, Wenjin Zheng, Xiu Lian Lu, and Ji-Dong Lou
1
College of Life Sciences, China Jiliang University, Hangzhou, Zhejiang, P. R. China
Sirnaomics, Inc., Gaithersburg, MD, USA
2
[
10]
pyridinium fluorochromate-hydrogen peroxide,
2,6-dicar-
[
11]
An improved and efficient oxidative cleavage of oximes to the boxypyridinium chlorochromate,
γ -picolinium chlorochro-
benzyltriphenylphosphonium chlorochromate,
corresponding carbonyl compounds with chromic acid supported
on kieselguhr reagent at room temperature under viscous condi-
tions in the yield between 82% and 96% is described. The present
procedure can overcome the problems that existed in the common
solvent-free reactions as for the difficulty for the solid molecular
collision to react.
[12]
[13]
mate,
[14]
quinolinium fluorochromate,
tetramethylammonium fluo-
rochromate (VI), benzyltrimethylammonium fluorochromate
[15]
16]
[17]
(
VI),[ imidazolium dichromate, dicarboxypyridinium flu-
[
18]
[19]
orochromate,
tetrabutylammonium chromate,
chromic
glycinium
acid,[
20]
chromium trioxide-NaHSO4·H2O,
[21]
[22]
Keywords carbonyl compounds, chromic acid, kieselguhr, oxidative chlorochromate-silica gel, and ammonium chlorochromate-
cleavage, oximes, viscous conditions
[23]
montmorillonite K10.
Although some of the reported
chromium(VI) or chromium(VI)-based reagents are carried
out under mild conditions, most of them are often hazardous,
expensive, or use not readily available reagents or use reagents
INTRODUCTION
Oxime derivatives of carbonyl compounds are highly crys- that are needed to be freshly prepared. Furthermore, some of
talline and are widely used for the characterization and purifi- these methods require long reaction times with the poor yields
cation of carbonyl compounds. The regeneration of carbonyl of the products, or have tedious workup procedures. Therefore,
compounds from the corresponding oximes under mild condi- some existed procedures may be modified to more modern,
tions is important and of considerable interest. Therefore, the elegant, and safe versions.
cleavage of these derivatives to the parent carbonyl compounds
So far, a considerable attention has been paid to the solvent-
[
1,2]
has been extensively investigated.
So far, several procedures free reactions in organic synthesis. Solvent-free reactions are
for the deoximation have been reported, for example, hydrolytic, not only of interest from ecological point of view, but in many
[
3]
oxidative, and reductive reactions and sometimes these trans- cases also offer considerable synthetic advantages in terms of
formations can be undertaken in both homogeneous and hetero- yield, selectivity, simplicity of the procedure, and operation at
geneous conditions. However, the development of milder and the room temperature. These factors are especially important
more efficient methods for the selective cleavage of derivatives in the industry. Unfortunately, under solvent-free conditions, in
containing a carbon-nitrogen double bond–like oximes to af- general, it is not satisfied for the reaction between solid sub-
ford carbonyl compounds continues to be a significant aspect of strates and solid reagents, such as oximes and chromium(VI)
organic chemistry.
oxidants, performed at the room temperature because both of
One of the most important procedures for the deoximation molecules are in crystal forms that are of difficulty for collision
process is oxidation with hexavalent chromium derivatives, such to reach the reaction, so that such reactions are normally carried
[
4]
as Jones reagent, methylammonium chlorochromate-alumi out at the temperature near or over the substrate melting point
[
5]
[6]
na, chromium trioxide-silica gel, pyridinium fluorochro- by either heating or other technologies in advance in order to
mate,[ quinolinium dichromate, potassium dichromate,
7]
[8]
[9]
dissolve the solid substrates into the liquid forms to increase the
reaction rate. Of those chromium(VI) or chromium(VI)-based
reagents for the oxidation of oximes described above only a few
experiments were carried out under solvent-free conditions,[
and basically the reaction procedure is that the solid mixture of
substrate and oxidants in a mortar was ground with a pestle and
9,18]
Received 4 December 2011; accepted 29 December 2012.
Address correspondence to Ji-Dong Lou, College of Life Sciences,
China Jiliang University, Hangzhou, Zhejiang 310018, P. R. China.
E-mail: lou@cjlu.edu.cn
1518

OXIDATIVE CLEAVAGE OF OXIMES
1519
then the products were produced, which can be performed in the which are described in Table 1, show that it is an efficient oxi-
laboratory but might be not satisfied to carry out in a large scale. dation route for oximes, and gives the corresponding carbonyl
compounds in high yields. The oxidized products are all known
compounds and identified by spectroscopic comparison with
authentic samples.
EXPERIMENTAL
The main advantages of the present procedure are that under
viscous conditions the oxidation of the solid substrates can be
carried out very efficient with mild process. As an example, the
Oxidative Cleavage of Benzophenone Oxime
to Benzophenone: Typical Procedure
Benzophenone oxime (197 mg, 1 mmol) was dissolved
results for oxidation of benzaldehyde oxime to benzaldehyde
in dichloromethane (0.2 mL) to form a viscous liquid, and
[26]
then chromium trioxide-kieselguhr (450 mg, kieselguhr pur-
chased from Tianjin Fu Chen Chemical Reagent Factory) was
added. The mixture was shaken mechanically at room tem-
perature. The progress of the reaction was monitored by TLC
TABLE 1
Oxidative cleavage of oximes to the corresponding carbonyl
compounds with chromic acid supported on kieselguhr under
viscous conditions
(silica gel GF254) using hexane:ethyl acetate (7:3) as eluent. Af-
ter 4 h the reaction mixture was washed with dichloromethane
Producta
Yield (%)
95
b
Entry
1
Oxime
Time (h)
4
(
3 × 10 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 benzophenone
(172 mg; 95%).
2
3
4
4
86
90
86
RESULTS AND DISCUSSION
We have described oxidative cleavage of oximes to the car-
bonyl compounds with chromic acid supported on kieselguhr
reagent at reflux under heterogeneous conditions,
dation of benzoins to the benzils with manganese dioxide at
[
24]
and oxi-
4.5
4.5
[
25]
room temperature under viscous conditions. In continuation
of previous work,[
24,25]
we now report here an improved and
more efficient procedure for the oxidation of oximes (1) to the
corresponding aldehydes and ketones (2) using chromic acid
supported on kieselguhr at room temperature under viscous con-
ditions (Scheme 1), which can overcome the problems existed
in the common solvent-free reactions of the difficulty for the
solid molecular collision to react. The present procedure offers
a simple and efficient oxidation method for the regeneration of
carbonyl compounds from the corresponding oximes.
5
6
4
82
95
3.5
7
4
92
SCH. 1.
8
9
4
96
86
Under our experiments, some typical oximes were oxidized
and 1 to 1.5 molar ratio of the substrate to the oxidant (50%:
[
26]
w/w; chromium trioxide to kieselguhr ) was employed. The
oxidation was very simple: first the solid substrate was dissolved
with a very minimum amount of dichloromethane to form a vis-
cous liquid, and then the oxidant was added in one portion.
The mixture was shaken magnetically at room temperature un-
til thin-layer chromatography (TLC) analysis indicated a com-
3.5
aAll products were identified by comparison of their physical and
pleted reaction, and the product was then purified by preparative spectral data with those of authentic samples.
b
TLC. All the reactions were completed within 4.5 h. The results,
Yield of isolated pure product.

1520
F. LIN ET AL.
8. Sadeghi, M.M.; Mohammadpoor-Baltork, I.; Azarm, M.; Mazidi, M.R.
TABLE 2
Regeneration of carbonyl compounds from oximes, phenylhydrazones, p-
nitrophenylhydrazones, and semicarbazones by quinolinium dichromate
under nonaqueous conditions. Synth. Comm. 2001, 31, 435–438.
. Mohammadpoor-Baltork, I.; Sadeghi, M.M.; Adibi, A.-H. Efficient,
solvent-free oxidation of organic compounds with potassium dichromate
in the presence of Lewis acids. Molecules 2001, 6, 900–908.
0. Ganguly, N.C.; Sukai, A.K.; De, S.; De, P. Oxidative deprotection of oximes
using pyridinium fluorochromate (PFC) and hydrogen peroxide. Synth.
Comm. 2001, 31, 1607–1612.
1. Hosseinzadeh, R.; Tajbakhsh, M.; Niaki, M.Y. 2,6-Dicarboxypyridinium
chlorochromate (2,6-DCPCC): a mild, efficient and selective reagent for
oxidative deprotection of oximes to carbonyl compounds. Tetrahedron Lett.
2002, 43, 9413–9416.
Comparison of oxidation of benzaldehyde oxime
to benzaldehyde with chromium trioxide-kieselguhr reagent
under different reaction conditions
9
Molar ratio
substrate to
1
Reaction
chromium Reaction Yield
Entry
1
conditions
trioxide time (h) (%) References
1
Viscous
conditions/RT
CH2Cl2/reflux
1:1.5
1:1.5
3.5
3
95 This work
92 24
2
12. Salehi, P.; Khodaei, M.M.; Goodarzi, M. A mild and selective deoxima-
tion method using γ -picolinium chlorochromate (γ -PCC). Synth. Commun.
2
002, 32, 1259–1263.
using chromic acid supported on kieselguhr under different re-
action conditions are compared (Table 2). From this table it is
shown that even for the similar yields obtained of the product
and the similar reaction time used, the reaction under hetero-
geneous conditions was performed at reflux (entry 2), while it
under viscous conditions was at room temperature (entry 1).
In addition to milder reaction conditions, because the present
oxidation was carried out under a very minimum amount of sol-
vents, the contamination, toxicity, and environmental pollution
of the solvents were largely decreased. Overall, the benefits of
the current procedure are over those of some reported methods
using chromium(VI)-based reagents as oxidants.
1
3. Hajipour, A.R.; Mallakpour, S.E.; Mohammadpoor-Baltork, I.; Backnejad,
H. Conversion of oximes, phenylhydrazones, 2,4-dinitrophenylhydrazones
and semicarbazones to carbonyl compounds with benzyltriphenylphospho-
nium chlorochromate (BTPPCC) in the presence of aluminium chloride
under non-aqueous conditions. Indian J. Chem. 2002, 41B, 1740–1743.
4. Tajbakhsh, M.; Mohammadpoor-Baltork, I.; Ramzanian-Lehmali, F. Quino-
linium fluorochromate as a reagent for selective oxidative cleavage of
oximes and phenylhydrazones to their parent carbonyl compounds under
non-aqueous and aprotic conditions. J. Chem. Res. 2003, 710–711.
5. Mahjoub, A.R.; Ghammami, S.; Kassaee, M.Z. Tetramethylammonium flu-
orochromate(VI): a new and efficient oxidant for organic substrates. Tetra-
hedron Lett. 2003, 44, 4555–4557.
1
1
1
6. Kassaee, M.Z.; Hattami, M.; Moradi, L. Benzyltrimethylammonium fluo-
rochromate(VI): a novel, efficient and selective oxidant. Acta Chim. Slov.
2
004, 51, 743–750.
1
7. De, S.K. A mild and efficient method for cleavage of C N using imida-
zolium dichromate. Synth. Comm. 2004, 34, 2751–2755.
CONCLUSION
An improved and efficient procedure for oxidative cleav-
age of oximes to the corresponding aldehydes and ketones us-
ing chromic acid supported on kieselguhr reagent under vis-
cous conditions at room temperature is described, which can
overcome the problems existed in the common solvent-free
reactions of the difficulty for the solid molecular collision to
react.
1
8. Tajbakhsh, M.; Hosseinzadeh, R.; Ramzanian-Lahmali, F.; Sadatshahabi,
M. 2,6-dicarboxypyridinium fluorochromate: a mild and efficient reagent
for oxidative deprotection of oximes, phenylhydrazones, and semicar-
bazones to their corresponding carbonyl compounds under solvent-free
conditions. J. Chin. Chem. Soc. 2005, 52, 1005–1009.
9. Pourali, A.R.; Goli, A. Efficient conversion of oximes to the correspond-
ing carbonyl compounds with tetrabutylammonium chromate under aprotic
conditions. Bull. Korean Chem. Soc. 2006, 27, 587–588.
1
2
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