Poly[N-(4-pyridinumdichromate)-p-styrenesulphonamide] as an efficient reagent for the cleavage of C=N bonds of oximes

Article abstract of DOI:10.1080/10426500490257032

Poly[N-(4-pyridinumdichromate)-p-styrenesulphonamide] (PPDSS) was found to be an efficient oxidant for the conversion of C=N of oximes to their corresponding carbonyl compounds in excellent yields.

Full text of DOI:10.1080/10426500490257032

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Phosphorus, Sulfur, and Silicon and the Related
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POLY[N-(4-PYRIDINUMDICHROMATE)-P-
STYRENESULPHONAMIDE] AS AN EFFICIENT REAGENT
FOR THE CLEAVAGE OF C=N BONDS OF OXIMES
Ramin Ghorbani Vaghei a & Ardeshir Khazaei a
a Department of Chemistry, Faculty of Science, Bu-Ali Sina University , Hamadan, Iran
Published online: 11 Aug 2010.
To cite this article: Ramin Ghorbani Vaghei & Ardeshir Khazaei (2004) POLY[N-(4-PYRIDINUMDICHROMATE)-P-
STYRENESULPHONAMIDE] AS AN EFFICIENT REAGENT FOR THE CLEAVAGE OF C=N BONDS OF OXIMES, Phosphorus, Sulfur, and
Silicon and the Related Elements, 179:1, 55-59, DOI: 10.1080/10426500490257032
To link to this article: http://dx.doi.org/10.1080/10426500490257032
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Phosphorus, Sulfur, and Silicon, 179:55–59, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490257032
POLY[N-(4-PYRIDINUMDICHROMATE)-
P-STYRENESULPHONAMIDE] AS AN EFFICIENT
REAGENT FOR THE CLEAVAGE
OF C N BONDS OF OXIMES
Ramin Ghorbani Vaghei and Ardeshir Khazaei
Department of Chemistry, Faculty of Science, Bu-Ali Sina
University, Hamadan, Iran
(Received June 24, 2003; accepted July 15, 2003)
Poly[N-(4-pyridinumdichromate)-p-styrenesulphonamide] (PPDSS)
was found to be an efficient oxidant for the conversion of C
N
of oximes to their corresponding carbonyl compounds in excellent
yields.
Keywords: Carbonyl compounds; deoximation; deprotection; PPDSS
Protection of carbonyl compounds as C N derivatives is of great
interest to organic chemists, as they are highly stable and read-
ily prepared compounds.1 Oximes are extensively used to not only
isolate and purify of carbonyl compounds but also to activate
the carbonyl group.2 Oximes also serve as the intermediates for
many reactions such as the preparation of nitriles3 or amides
via Beckmann rearrangement.4 Their synthesis from noncarbonyl
compounds5 provides an alternative pathway to aldehydes and ke-
tones. Although a number of methods for the conversion of C N
derivatives to carbonyl compounds are available, the discovery of
a milder, selective, nonhazardous reagent is still in demand. Some
of the methods reported earlier for deoximation of carbonyl com-
pounds consist of oxidative6 or reductive,7 clay-supported ammo-
nium chlorochromate,8 bis-(trimethylsilyl) chromate,9 silica gel sup-
ported chromium trioxide,10 N-methoxyimidoxyl bromides,11 copper
(II) chloride dihydrate,12 2-iodoxybenzoic acid (IBX) and Dess-Martin
periodinane (DMP),13 quinolinium fluorochromate,14 and ammonium
persulphate-silica.15 Some of these reagents suffer from disadvantages
Address correspondence to Ramin Ghorbani Vaghei, Department of Chemistry,
Faculty of Science, Bu-Ali Sina University, Hamadan, Iran. E-mail: ghorbani@basu.ac.ir
55

56
R. G. Vaghei and A. Khazaei
like long reaction time, difficulties in isolation of products; also some
may be expensive and cause explosion under excessive heating dur-
ing preparation. Moreover, many of the methods cited in the liter-
ature do not describe the deoximation of aldoximes, give low yields
of aldehydes, or the liberated aldehydes are overoxidized. Benzal-
doxime, for example, was deoximated in poor yield by pyridinium
chlorochromate (PCC),16 in 35% yield by PCC-H2O2,7 in 56% yield
by trimethylammonium chromate,17 and in 72% yield by chromium
trioxide-chlorotrimethylsilane.18
RESULTS AND DISCUSSION
We previously reported a convenient method for the deoximation of ke-
tone and aldehyde oximes to their corresponding carbonyl compounds
with N,Nꢁ-dibromo-N,Nꢁ-1,2-ethanediylbis (p-toluenesulfonamide)19
and poly[4-vinyl-N,N-dichlorobenzenesulfonamide].20
Herein, we report a convenient method for the deoximation of
ketone and aldehyde oximes to their corresponding carbonyl com-
pounds using a new reagent PPDSS21 that was prepared from sodium
p-styrenesulfonate 1 (Scheme 1).
SCHEME 1
Poly[N-(4-pyridinumdichromate)-p-styrenesulphonamide] (PPDSS)
was prepared by the reaction of 1 with PCl5 and 4-aminopyridine,

Deoximation
57
polymerization with AIBN, and then addition of a suspension of
poly[N-(4-pyridine)-p-styrenesulphonamide] in water to a cold solution
of Na2Cr2O7 in a minimum amount of water. This orange-colored oxi-
dizing agent is a stable compound and can be stored for months without
losing its activity. It is not hygroscopic or light sensitive. The presence
of the dichromate anion in the reagent was confirmed by the IR spec-
trum having bands at 930 and 765 cm−1, and is characteristic for the
dichromate anion.22
The reaction of oximes 6 with PPDSS in CH3CN afforded carbonyl
compounds 7 without the formation of side products (Scheme 2).
SCHEME 2
The results of the conversion of various ketoximes and aldoximes to
ketones and aldehydes are presented in Table I.
The products of the reaction with 5 (PPDSS) were isolated simply
by filtering off PPDSS and evaporating the solvent from the filtrate.
The method has advantage in terms of yields, simplicity of reaction
conditions, short reaction times and no side products.
TABLE I Oxidative Cleavage of Oximes with PPDSS
Reaction times Yield
Entry
R1
R2
Producta
Acetophenone
p-Methoxyacetophenone
Benzophenone
p-Chlorobenzophenone
Benzaldehyde
o-Chlorobenzaldehyde
o-Hydroxybenzaldehyde
p-Chlorobenzaldehyde
Benzoin
(h)
(%)
1
2
3
4
5
6
7
8
9
CH3
CH3
C6H5
C6H5
H
H
H
H
C6H5
2.5
2.0
2.0
2.0
2.5
2.0
2.5
2.0
3.0
3.5
4.0
93
91
95
90
92
90
91
90
91
89
91
p-MeOC6H5
C6H5
p-ClC6H5
C6H5
o-ClC6H5
o-OHC6H5
p-ClC6H5
C6H5CH(OH)
C2H5
C6H5
C6H5
CH3
10
11
Propiophenone
2-Octanone
C6H13
aProducts were characterized by their physical constants, comparison with authentic
samples and IR spectra.

58
R. G. Vaghei and A. Khazaei
CONCLUSION
The procedure reported here is a convenient and high-yielding method
for the oxidation of oximes to the corresponding carbonyl compounds.
Furthermore, another important advantage of this work is that the
polymeric reagent can be stored for months without losing its activity. It
is not hygroscopic or light sensitive. The insoluble polymer was removed
by filtration after the reaction.
EXPERIMENTAL
General
Commercial sodium p-styrenesulfonate and 4-aminopyridine (Fluka,
A.G., Switzerland) were used as received.
Procedure for the Preparation of Poly[N-(4-pyridinumdi-
chromate)-p-styrenesulphonamide]
To a suspension of 0.05 mmol of poly[N-(4-pyridine)-p-styrenesul-
phonamide] in 100 ml of water was added a cold solution of 0.06 mmol
of Na2Cr2O7 in a minimum amount of water. Formation of the reagent
occurred very smoothly. After filteration, the reagent was washed
repeatedly with water until the filtrate was colorless.
General Procedure for Deoximation with Poly[N-(4-pyri-
dinumdichromate)-p-styrenesulphonamide]
A mixture of oxime (5 mmol), acetonitrile (15 ml) and poly[N-(4-
pyridinumdichromate)-p-styrenesulphonamide] was refluxed for 2–4 h
(Table I). The reaction was monitored by TLC. After completion, it was
diluted with ether (15 ml) and the insoluble polymeric reagent was
removed by filtration and washed with carbon tetrachloride (10 ml).
Removal of the solvent under reduced pressure gave the crude prod-
uct. Solid products were recrystalized from diethyl ether; oily prod-
ucts were dissolved in ether and the ether solution washed, dried, and
concentrated.
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Deoximation
59
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