An eco-friendly system for oximation of organic carbonyl compounds under microwave irradiation

Article abstract of DOI:10.13005/ojc/300241

The oximation of a variety of organic carbonyl compounds was efficiently carried out with NH2OH?HCl under microwave irradiation. The reactions were performed in water or water-ethanol as green solvents to give Z-aldoxime isomers from the corresponding aldehydes and E-ketoxime isomers from the corresponding ketones in a perfect selectively with excellent yields.

Full text of DOI:10.13005/ojc/300241

ISSN: 0970-020 X
CODEN: OJCHEG
2014, Vol. 30, No. (2):
Pg. 699-703
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
An Eco-Friendly System for Oximation of Organic
Carbonyl Compounds Under Microwave Irradiation
HANABATMANI and DAVOOD SETAMDIDEH*
Department of Chemistry, College of Sciences, Mahabad Branch,
Islamic Azad University, Mahabad, Iran.
*Corresponding author E-mail: d.setamdideh@iau-mahabad.ac.ir
http://dx.doi.org/10.13005/ojc/300241
(Received: April 11, 2014; Accepted: May 15, 2014)
ABSTRACT
The oximation of a variety of organic carbonyl compounds was efficiently carried out with
NH2OH·HCl under microwave irradiation. The reactions were performed in water or water-ethanol
as green solvents to give Z-aldoxime isomers from the corresponding aldehydes and E-ketoxime
isomers from the corresponding ketones in a perfect selectively with excellent yields.
Key words: Oximes, Z-aldoximes, E-acetophenone oximes, H2NOH.HCl, microwave irradiation.
INTRODUCTION
Microwave irradiation
creates economic and ecological concerns.
Consequently replacement of volatile organic
solvents from reaction medium has been a major
emphasis of green chemistry2. So, the use of water
as a green solvent can be the best medium of choice
to perform chemical reactions. In the last decades,
a large number of publications have demonstrated
the value of performing chemical reactions in water
or aqueous media 3a-b. We have reported a fast and
efficient method for the reduction of varieties of
carbonyl compounds such as aldehydes, ketones,
conjugated aldehydes and ketones, á-diketones
and acyloins to their corresponding alcohols under
microwave irradiation in water as green solvent3c.
Recently, the oximation methods has been
as
an
unconventional energy source has been widely
used to carry out many kinds of chemical reactions.
Many reviews and papers have demonstrated its
importance. It is now clear that the microwave
dielectric heating effect uses the ability of liquids to
transform electromagnetic energy into heat and so
drive chemical reactions effectively and quickly1.
This in situ mode of energy conversion has attracted
much attentions of chemists and has resulted in
the development of many techniques to perform
microwave-assisted organic reactions using
domestic microwave ovens. On the other hand, the
use of large amounts of conventional volatile
solvents required to conduct a chemical reaction
4
reviewed . The lack of information for systematic
the oximation of carbonyl compounds in water

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BATMANI & SETAMDIDEH, Orient. J. Chem., Vol. 30(2), 699-703 (2014)
under microwave irradiation and our ongoing benzaldehyde. The reaction was completed in 90
attentions to the development of modified methods sec with excellent yield (95%). The results show
in organic synthesis 5-23 encouraged us to investigate that the use of 1 molar equivalents of NH2OH.HCl is
this transformation with NH2OH·HCl under sufficient and no other additives are required for
microwave irradiation in water as a green and good this conversion. In order to evaluate the generality
solvent for transferring electromagnetic energy into of the process a variety of aldehydes were ground
heat and so driving an oximation reaction effectively. with hydroxylamine hydrochloride under microwave
Herein, we describe a fast and efficient method for irradiation in water. In this approach, the
the oximation of varieties of carbonyl compounds corresponding Z-aldoximes were obtained in
such as aldehydes, ketones to the corresponding quantitative yield. The general reaction has been
oximes with NH2OH·HCl/H2O/MWI system.
shown in scheme 1 and the results have been
reported in table1 (entries 1-7).
RESULTS AND DISCUSSIONS
The reaction of different aromatic
The oximation of unsymmetrical carbonyl aldehydes gave Z-aldoximes in excellent yields and
compounds usually give a mixture of the two stereoselectivity. The purity of the products was
geometrical isomers (Z and E) of their corresponding determined by 1H-NMR which showed the exclusive
oximes which have different physical properties and formation of the corresponding Z-aldoximes. The
biological activities24. Thus, there is considerable Z-stereochemistry of the products was determined
1
interest in finding more selective methods for oximes from the H-chemical shift 4 of the C(H)=N group
synthesis. We now report a simple and efficient which appeared around 8-8.5 ppm as a singlet
method for the preparation of oximes from their whereas the 1H-chemical shift of the C(H)=N group
corresponding carbonyl compounds with for E-aldoximes appears in 7.30 and 7.60 ppm. In
NH2OH·HCl/H2O/Microwave irradiation system.
all the 1H-NMR spectra (CDCl3, 25 ºC) by
comparison of H-NMR of these isomers, we have
1
In order to determine an appropriate observed the C(H)=N signal in 8.10 -8.49 ppm. The
reaction conditions for the oximation of aldehydes 1H-chemical shift of the C(H)=N groups appears for
and ketones a model study was carried out on the (Z)-benzaldehyde oxime in  8.18 ppm, (Z)-4-
oximation of bezaldehyde and acetophene. The bromobenzaldehyde oxime in  8.10 ppm, (Z)- N,
results showed that using NH2OH.HCl (1mmol) in N-dimethylbenzaldehyde oxime in  8.07 ppm, (Z)-
H2O (5 ml) and 30% power amplitude of microwave 4-methylbenzaldehyde oxime in  8.15 ppm,
oven (300 W) was the best for the oximation of (Z)-3-methylbenzaldehyde oxime in  8.15 ppm, (Z)-
Scheme 1:
Scheme 2:

BATMANI & SETAMDIDEH, Orient. J. Chem., Vol. 30(2), 699-703 (2014)
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BATMANI & SETAMDIDEH, Orient. J. Chem., Vol. 30(2), 699-703 (2014)
2-methoxybenzaldehyde oxime in  8.49 ppm and
(Z)-4-methoxybenzaldehyde oxime in  8.11 ppm.
condenser. All substrates and reagents were
purchased from commercially sources with the best
quality. IR and H NMR spectra were recorded on
1
The oximation of ketones was also
performed well by NH2OH·HCl/H2O-EtOH/
Microwave irradiation system but due to the lower
reactivity of ketones relative to aldehydes, the
oximation requires higher molar amounts of
NH2OH·HCl (2 mmol) vs. 1mmol of the substrates.
E-acetophenone oximes (table 1, entries 8-11) were
also obtained in high to excellent yields as shown
in scheme 2.
Perkin-Elmer FT-IR RXI and 300 MHz Bruker
spectrometers, respectively. The products were
characterized by their H NMR or IR spectra and
1
comparison with authentic samples (melting points).
All yields referred to isolated pure products. The
1
purity of products was determined by TLC and H
NMR. Also, reactions were monitored by TLCs
utilizing plates cut from silica gel 60 F254 aluminum
sheets.
The E-stereochemistry of acetophenone
oxime derivatives was determined from the H-
A typical procedure for the oximation of
aldehydes with NH2OH·HCl/H2O/Microwave
irradiation system
1
chemical shift of the CH3 group which appeared
around 2.3 ppm as a singlet whereas the 1H-chemical
shift of the CH3 group for Z-ketoximes appeared around
2.6 ppm. In all the 1H-NMR spectra (CDCl3, 25 ºC) by
comparison of 1H-NMR of these isomers 4, we have
In a round-bottomed flask (10 mL) a
mixture of benzaldehyde (0.106 g, l mmol) in water
(5 mL) was prepared. NH2OH·HCl (0.07 g, 1 mmol)
was added. After fitting the flask to the external
condenser at the inside of the oven the mixture
was irradiated with a microwave oven (30% power
amplitude  300 W) for 90 sec. The progress of the
reaction was monitored byTLC (eluent:CCl4/Et2O:5/
2). After completion of the reaction, the precipitate
Z-benzalde oxime (0.115 g, 95 % yield, table1, entry
1) was filtered and washed with water and air-dried
without further purification.
1
observed the CH3 signal in 2.30-2.34 ppm. The H-
chemical shift of the CH3 groups appears for (E)-
benzalacetone oxime in  2.34 ppm, (E)-4-
methylacetophenone oxime in  2.38 ppm,
(E)-4-methoxyacetophenone oxime in  2.30 ppm
and (E)-benzalacetone oxime (as ,-unsaturated )
in  2.18.The Symmetric ketones (table 1, entries 12-
14). i.e. Benzophenone, 9H-fluoren-9-one and
cyclohexanone were ground with hydroxylamine
hydrochloride under microwave irradiation in water
to their corresponding ketoximes in quantitative yields.
A typical procedure for the oximation of ketones
with NH2OH·HCl/H2O/Microwave irradiation
system
In order to show chemoselectivity of the
presented oximation system a mixture of one
equivalents of benzaldehyde and one equivalents
of acetophenone was treated with NH2OH.HCl
(1mmol) under microwave irradiation in water. The
oximation of aldehyde with respect to ketone was
not satisfactory. In the most cases the selectivity
ratios were not excellent. Therefore this
methodology could not be used selectively for the
preparation of aldoximes of compounds that contain
both aldehyde and ketone functional groups.
In a round-bottomed flask (10 mL) a
solution of acetophenone (0.120 g, l mmol) in water-
ethanol (96%) (5:1 mL) was prepared. NH2OH·HCl
(0.14 g, 2 mmol) and was added. After fitting the
flask to the external condenser at the inside of the
oven the mixture was irradiated with a microwave
oven (30% power amplitude  300 W) for 130 sec.
The progress of the reaction was monitored by TLC
(eluent:CCl4/Et2O:5/2). After completion of the
reaction the precipitate i.e.E-acetophenone oxime
(0.126 g, 93% yield, table 1, entry 8) was filtered
and washed with water and air-dried without further
purification.
EXPERIMENTAL
All microwave assisted reactions were
carried out in a Yusch household microwave oven
(1000 W). The instrument was modified for
laboratory applications with an external reflux
CONCLUSION
In conclusion, the oximation of a variety of
carbonyl compounds such as aldehydes, ketones

BATMANI & SETAMDIDEH, Orient. J. Chem., Vol. 30(2), 699-703 (2014)
703
was carried out efficiently with NH2OH·HCl/H2O/ Therefore, this new protocol for the oximation of
Microwave irradiation system. The reactions were carbonyl compounds could be a useful addition to
performed in water and water-ethanol to give the present methodologies.
Z-aldoximation isomers of aldehydes and E-
oximaton of ketones in a perfect selectively. The
oximation of aldehydes over ketones has not been
accomplished successfully by this system. Also, this
ACKNOWLEDGEMENTS
The authors gratefully appreciated the
oximation system has the easily worked up. financial support of this work by the research council
of Islamic Azad University branch of Mahabad.
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