K3[Fe(CN)6]·3H2O supported on silica gel: An efficient and selective reagent for the cleavage of oximes to their corresponding carbonyl compounds in aqueous medium

Article abstract of DOI:10.1007/s12039-015-0801-6

K₃[Fe(CN)₆]·3H₂O supported on silica gel, a new oxidant, for efficient, simple and selective cleavage of ketoximes and aldoximes to their corresponding carbonyl compounds in aqueous medium is described. Further oxidation of aldehydes to carboxylic acid and formation of by-products were not observed. α-β unsaturated oxime was deoximated smoothly without oxidation of the double bond. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s12039-015-0801-6

J. Chem. Sci. Vol. 127, No. 3, March 2015, pp. 493–497. ꢀc Indian Academy of Sciences.
DOI 10.1007/s12039-015-0801-6
K [Fe(CN) ].3H O supported on silica gel: An efficient and selective
3
6
2
reagent for the cleavage of oximes to their corresponding carbonyl
compounds in aqueous medium
∗
ABBAS AMINI MANESH and BEHZAD SHIRMARDI SHAGHASEMI
Department of Chemistry, Payame Noor University, 19395-4697 Tehran, I. R. of IRAN
e-mail: a_aminima@yahoo.com
MS received 5 June 2014; revised 27 August 2014; accepted 29 August 2014
Abstract. K3[Fe(CN)6].3H2O supported on silica gel, a new oxidant, for efficient, simple and selective cleav-
age of ketoximes and aldoximes to their corresponding carbonyl compounds in aqueous medium is described.
Further oxidation of aldehydes to carboxylic acid and formation of by-products were not observed. α − β
unsaturated oxime was deoximated smoothly without oxidation of the double bond.
Keywords. K3[Fe(CN)6].3H2O, Silica gel; oxime; aldehyde; ketone.
1
. Introduction
K [Fe(CN) ].3H O supported on SiO as a new oxidant
3 6 2 2
(
scheme 1).
Oximes can be prepared from carbonyl and non-
carbonyl compounds, and compounds having active
methylene groups.1 These solid compounds are used
for isolation, purification and characterization of the
parent carbonyl compounds. Carbonyl groups can be
protected by oximation, and in turn, these oximes
,2
2
. Experimental
3
2
.1 General methods and materials
can serve as an intermediate for the preparation of In this study, all of the oximes were prepared as reported
4
25
nitriles of amides via the Beckmann rearrangement elsewhere, except benzaldehyde oxime, which pur-
5
1
or to activate the carbonyl group. Thus, there has chases from Merck (Darmstadt, Germany). IR and H
been an increasing interest in the development of NMR spectra were recorded using a Shimadzu Infrared
methods for the conversion of oximes into their cor- Spectrophotometer FT-IR Model IR Prestige 21 (KBr
responding carbonyl compounds and a number of pellets) and a 90 MHz Jeol FT-NMR spectrometer,
methods and compounds such as 1,3-Dibromo-5,5- respectively. H NMR chemical shifts were measured
dimethylhydantoin, microwave, CeO –ZrO , Potas- relative to TMS. Silica-supported K [Fe(CN) ].3H O
1
6
7
8
2
2
3 6 2
9
sium bromide and Ammonium heptamolybdate, Sil- (oxidant B) was prepared by impregnating 2.0 g of sil-
ica Sulfuric acid,10 Bi(OTf) ·4H O, Ionic liquid,
11
12
ica with aqueous solutions of K
[Fe(CN) ].3H O (1 g
O). The mixture was stirred overnight at
3
2
3
6 2
13
poly[4-vinyl-N, N-dichlorobenzenesulfonamide], me- in 30 mL H
2
14
15
talloporphyrins, 1,3-Dichloro-5,5-dimethylhydantoin,
reflux temperature, followed by drying using a rotary
-Nitro-4,5-dichloropyridazin-3(2H)-one, N-bromo- evaporator at 110 C which gives yellow powders.
16
◦
2
17
N-benzoyl-4-toluenesulfonamide, Tetra-n-alkylammo-
nium bromates have been explored.
18
In a nutshell, the regeneration of carbonyl com- 2.2 General Procedure for Deoximation
pounds from oximes can be achieved using a variety
of methods, including oxidative, reductive, and pho- To a solution of oxime (1 mmol) in ethanol (10 mL),
tochemical techniques.19 In continuation of our sys- 0.1 g oxidant B (0.393 mmol) was added. Then H
O
2
20–24
tematic study and research on oxidation methods,
(1 mL) was added to the solution. The resulting mix-
we report a new, simple and selective method for the ture was stirred at reflux conditions and the progress
conversion of aliphatic, aromatic and cyclic oximes of the reaction monitored by thin layer chromatography
to their corresponding aldehydes and ketones by (hexane-acetone, 8:2 v/v). After completion of the reac-
tion, the oxidant was removed by filtration and washed
∗
For correspondence
with 2 × 5 mL ethanol. The solvent was removed from
493

494
Abbas Amini Manesh and Behzad Shirmardi Shaghasemi
Table 1. Optimization of Oxidant A.
Entry Oxidant A (g) Conditions Time (h) Yield (%)
1
2
3
4
5
0.2
0.2
0.1
0.3
0.25
r.t.
5
0
reflux
reflux
reflux
reflux
2.5
3.5
3.45
2.5
73
65
57
85
Scheme 1. Cleavage of oximes by K3[Fe(CN)6].3H2O
supported on SiO2.
Table 2. Optimization of solvent.
the filtrate and the product was purified by column
chromatography.
Entry
Solvent
Time (h)
Yield (%)
1
2
3
4
5
CH3CN
EtOH
CH2Cl2
Hexan
MeOH
2:30
2:15
5
5
2:30
85
91
0
0
86
3
. Results and Discussion
In order to optimize the reaction conditions, first of all,
0.2 g oxidant A (0.787 mmol K [Fe(CN) ].3H O) was
3
6
2
added to a solution of acetophenone oxime (1 mmol,
.135 g) in acetonitrile (10 mL). According to the pro- Table 3. Preparation of oxidant.
0
posed mechanism, H O (1 mL) was added to the solu-
2
Oxidant
SiO2(g)
K3[Fe(CN)6].3H2O(g)a
tion (scheme 2). The resulting mixture was stirred at
reflux conditions (the reaction did not proceed after pro-
longed time at room temperature) and the progress of
the reaction was monitored by thin layer chromatogra-
phy (hexane-acetone, 8:2 v/v). Several trials of oxidant
A were tried to find the suitable amount of oxidant for
the reaction (table 1).
A
B
C
2
2
2
2
1
0.5
aK3[Fe(CN)6].3H2O was dissolved in 30 mL of H2O.
During the optimization of the reaction conditions,
we compared the effect of different solvents on the rate
and yields of the reactions. Our findings showed that
EtOH was generally the best of the solvents tested in
terms of yield and time (table 2).
After using oxidant A in EtOH as the suitable sol-
vent, we conducted the reaction for different amounts
of oxidant B and oxidant C (table 3). Having analyzed
these results, we conclude that the best reaction condi-
tions were achieved when we used 0.1 g of oxidant B in
EtOH media in reflux condition. It is noteworthy that,
Figure 1. XRD pattern of A: SiO2, B: K3[Fe(CN)6].3H2O
supported on silica gel.
addition of more H O to the reaction mixture, does not
2
improve the reaction.
Different conditions for the preparation of oxidant A,
B and C are shown in table 3.
3.1 Characterization of the oxidant
The XRD profiles of the samples at 298 K are shown in
figure 1. Powder X-ray diffraction (XRD) patterns were
Figure 2. IR (KBr) Spectrum of K3[Fe(CN)6].3H2O sup-
ported on silica gel.
Scheme 2. Optimization of the reaction in acetonitrile.

Deoximation by silica supported K3[Fe(CN)6].3H2O
495
Table 4. The results of the conversion of oximes to the carbonyl compounds by oxidant.
Entry
Oxime
Product
Time (min)
Yield (%)a,b
1
2
50
50
95
90
3
45
95
4
5
45
65
95
87
6
7
50
55
90
90
8
9
60
75
105
–
86
93
85
–
10
11
12
–
–
13
–
–
a
Products were characterized by their physical constants, comparison with authentic samples and melting points of 2,4-dinitro
b
phenyl hydrazone derivatives and IR and NMR spectra; Isolated yields
recorded on a Philips PW-1840 X-ray diffractometer K [Fe(CN) ].3H O supported on silica gel are con-
3
6
2
(
XRD) with Cu Kα radiation. The intensity data were nected to the similarity of bands associated with the
◦
collected over a 2θ range of 10–90 . The XRD results inorganic backbone including (i) a broad band between
revealed the presence of K [Fe(CN) ].3H O over amor- 3400 and 3200 cm , which is assigned to the O-
−1
3
6
2
phous SiO matrix in the case of K [Fe(CN) ].3H O- H stretching mode of silanol groups and also to the
2
3
6
2
◦
SiO (see 2θ = 20 − 40 ), and some overlapped remaining adsorbed water, (ii) the intense band related
2
−1
regions.
to siloxane stretching of these groups at 1100 cm , (iii)
The particles size of the K [Fe(CN) ].3H O on a band assigned to Si-O stretching mode of the silanol
3
6
2
−1
−1
SiO2 is 82 nm (figure 1). The main features of group at 800 cm and (iv) the band around 1650 cm ,

496
Abbas Amini Manesh and Behzad Shirmardi Shaghasemi
Scheme 3. Proposed mechanism of deoximation by the oxidant.
assigned to the water bending mode, and (v) an intense 4. Conclusion
−1
band assigned to CN band at 2117 cm (figure 2).
It is noteworthy that in this study, over oxidation of
aldehydes to carboxylic acid and formation of by-
products were not observed. α- β unsaturated oxime
3.2 Proposed mechanism
(
Entry 7) was deoximated smoothly without oxida-
Various methods were adopted for the deoximation
processes to effectively and suitably obtain the parent
or new aldehydes and ketones. Deoximation can be
achieved using various processes like oxidation, hydrol-
ysis, hydrogenation, etc., using organic and inorganic
reagents. Besides, some surface templated processes
and photochemical processes were also used to give
products in a remarkably effective way.26
tion of the double bond. Furthermore, acid sensitive
groups (Entry 4 and 8) remained unaffected during
the oxidation reaction. The water insolubility of the
reagent and by-products made product recovery easy.
Due to sterical hindrance, benzoin oxime (Entry 11),
Camphor oxime (Entry 12), and 2-hydroxy acetophe-
none oxime (Entry 13) could not be converted to
their corresponding carbonyl compounds. Also, the
reactions did not proceed using K [Fe(CN) ].3H O or
Mechanism of deoximation by the K [Fe(CN) ].
3
6
3
6
2
3
H O supported on silica gel is similar to other
2
SiO alone, even after a prolonged period of time.
2
electron transfer type mechanisms that are described
The striking features of our method are short reac-
tion times, heterogeneous reaction conditions, absence
of formation of over oxidation products due to high
selectivity and mild nature of oxidant, easy work-
up procedure, high yields and preservation of carbon-
carbon double bond functional group in the oxime
structure.
27
elsewhere. Proposed mechanism for deoximation of
variety of oximes to their corresponding aldehydes and
ketones (table 4) is shown in scheme 3. The first step is
simply the formation of the radical cation (I) of oxime
by electron transfer from oxime to the potassium ferri-
cyanide. Alternatively, a sequence can be written invol-
ving removal of a proton from (I) followed oxidation
of iminoxyl radical (II) or nitroso radical (III) by potas-
sium ferricyanide to give the nitroso carbocation (IV).
Hydration of the carbocation (IV) produces the inter-
Supplementary Information
mediate (V), and finally decomposition of the (VI) The electronic supporting information can be seen at
produces carbonyl compounds. www.ias.ac.in/chemsci.

Deoximation by silica supported K3[Fe(CN)6].3H2O
497
Acknowledgement
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The authors acknowledge the support of the Hamedan
Payame Noor University to this work.
5
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