A clean conversion of carbonyl compounds to oximes using silica gel supported hydroxylamine hydrochloride

Article abstract of DOI:10.1080/10426500490459821

The efficient condensation of carbonyl compounds with hydroxylamine hydrochloride under solvent free conditions is described.

Full text of DOI:10.1080/10426500490459821

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Phosphorus, Sulfur, and Silicon and the Related
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A CLEAN CONVERSION OF CARBONYL COMPOUNDS TO
OXIMES USING SILICA GEL SUPPORTED HYDROXYLAMINE
HYDROCHLORIDE
Ali Reza Kiasat a , Foad Kazemi a & Kazem Nourbakhsh a
a Shahid Chamran University, Ahvaz, Iran
Published online: 16 Aug 2010.
To cite this article: Ali Reza Kiasat , Foad Kazemi & Kazem Nourbakhsh (2004): A CLEAN CONVERSION OF CARBONYL
COMPOUNDS TO OXIMES USING SILICA GEL SUPPORTED HYDROXYLAMINE HYDROCHLORIDE, Phosphorus, Sulfur, and Silicon and
the Related Elements, 179:6, 1193-1196
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Phosphorus, Sulfur, and Silicon, 179:1193–1196, 2004
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ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490459821
A CLEAN CONVERSION OF CARBONYL
COMPOUNDS TO OXIMES USING SILICA GEL
SUPPORTED HYDROXYLAMINE HYDROCHLORIDE
Ali Reza Kiasat, Foad Kazemi, and Kazem Nourbakhsh
Shahid Chamran University, Ahvaz, Iran
(Received October 14, 2003; accepted October 16, 2003)
The efficient condensation of carbonyl compounds with hydroxylamine
hydrochloride under solvent free conditions is described.
Keywords: Carbonyl compound; condensation; oxime; protection; silica
gel; solvent free
Organic reactions on supported reagents recently have received con-
siderable attention from synthetic chemists because of their high
efficiency, environmentally benign conditions, and convenient work-
up procedure.1 In particular, silica gel has been shown to be the
most useful inorganic solid for effecting a variety of functional group
transformation.1−3 The catalytic activity of silica gel is now recognized
to be the results of water present in this reagent as a form of silicic acid,
a so-called Bro¨nsted acid.3 One of the major advantages of using silica
gel as a reagent is its weakly acidic character (pH 5.5–7.5).3
Protection of carbonyl compounds as oximes is of great interest
to organic chemists, as they are readily prepared and highly stable
compounds.4 Oximes are employed as ketone and aldehyde functional
group equivalent in synthesis, both because they provide convenient
protection for the carbonyl group and because they are important syn-
thetic intermediates.5
The addition of hydroxylamine hydrochloride to carbonyls to yield
oximes is one of the best understood examples of a nonenzymatic
addition-elimination reaction.6 The process of this addition-elimination
reaction usually was catalyzed by sulfuric acid that is highly corrosive
The authors acknowledge the partial support of this work by Shahid Chamran Ahvaz
University Research Council.
Address correspondence to Ali Reza Kiasat, Chemistry Department, College of Sci-
ence, Shahid Chamran University, Ahvaz, Iran.
1193

1194
A. R. Kiasat et al.
TABLE I Conversion of Carbonyl Compounds to Oximes Using SiO2/
NH2OHHCl
Time
(min)
Yielda,b
(%)
Entry
1
Substrate
Product
9
78c
2
3
11
9
91
86
4
9
90
5
6
8
83
70
11
7
8
11
8
80
80c
9
9
74c
85
10
11
11
9
93
aYields refer to pure isolated products.
bProducts were characterized by comparison of their physical data, IR, NMR spectra
with known samples.
cIn the production isolation step, addition of water, and recrystallization steps were
not performed.

Oximes
1195
and poses severe environmental hazards.7 In 1988, a patent by Roffia
et al.8 outlined the preparation of the cyclohexanone oxime, as key in-
termediate for the preparation of nylon by liquid-phase ammoximation
of cyclohexanone using ammonia hydrogen peroxide as the oxidizing
agent and titanium silicite as the catalyst. But the economic attrac-
tiveness of this process, however, may be limited by the use of H2O2.
9
Very recently Sharghi et al. have reported CaO,4 CuSO4,9 and K2CO3
can be used as catalyst for the addition of hydroxylamine hydrochloride
to carbonyl compounds in solvent free conditions at high temperature.
The remarkable ability of the silica gel to promote the various re-
actions together with the importance of protection reactions in organic
synthesis gave us impetus for testing the oximation reaction of car-
bonyl compounds by hydroxylamine hydrochloride supported on silica
gel. Our new approach reported herein involves the use of the cheap and
commercially available silica gel as catalyst in the absence of solvent
for mild and efficient conversion of carbonyl compounds to oximes.
Hydroxylamine hydrochloride supported on silica gel was prepared
by simply cogrinding silica gel with NH2OHHCl in the ratio 4:1 (w/w)
in an agate mortar. In this simple and efficient method the starting car-
bonyl compounds were converted to the corresponding oximes in a mor-
tar with grinding by a pestle in the presence of supported NH2OHHCl
on silica gel. It is proved that for rapid and clean conversion of carbonyl
compounds to oximes, addition of small drops of t-BuOH in the reaction
media is essential.
As reported in Table I satisfactory results have been obtained in the
condensation of a variety of aldehydes and ketones with hydroxylamine
hydrochloride under solvent free conditions in the presence of silica
gel. It can be emphasized that the reaction is clean, the work-up is
straightforward and, from economical and environmental points of view,
use of solvent free conditions is favorable.
CONCLUSION
In conclusion we have developed a rapid and solvent less method for
protection of carbonyl compounds as their corresponding oximes. We
believe that the present procedure provides an easy, mild, efficient, ver-
satile, and general methodology for the protection of different classes

1196
A. R. Kiasat et al.
of carbonyl compounds, and we feel that it may be a suitable addition
to methodologies already present in the literature.
EXPERIMENTAL
General
All products are known compounds and are identified by comparison
of their physical and spectral data with those of authentic samples.
The purity determination of the products and reaction monitoring were
accomplished by TLC on silica gel polygram SILG/UV 254 plates.
General Procedure for the Preparation of Oximes
A mortar was charged with SiO2 (2 g) and NH2OHHCl (0.5 g, 7.2 mmol);
the mixture was ground with a pestle of 1 min. A neat carbonyl com-
pounds (1 mmol) and twelve drops of t-BuOH were added to this mix-
ture. The reaction mixture was ground for the time specified in the
Table I. The progress of reaction was monitored by TLC using ether-
CCl4. After the disappearance of starting material, the reaction mix-
ture was mixed with ether. The mixture was filtrated to remove silica
gel and then mixed with water and extracted. The solvent was removed
in vaccuo to give the product which was recrystallized from a suitable
solvent to afford the TLC and 1HNMR pure products in 70–93% isolated
yields.
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[2] V. A. Basiuk, Russ. Chem. Rev., 64, 1003 (1995).
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