Nitrite ionic liquids (IL-ONO and [bmim]NO2) as effective nitrosonium sources for the synthesis of α-oximinoketones under mild heterogeneous conditions

Article abstract of DOI:10.1002/cjoc.201180452

Ketones and β-diketones were nitrosated and converted to their corresponding α-oximinoketones using task-specific ionic liquids, 1-(4-nitritobutyl)-3-methylimidazolium chloride, IL-ONO, and 1-butyl-3-methylimidazolium nitrite at room temperature. The results from two ionic liquids are comparable and showed that these IL's are effective nitrosonium sources for the preparation of oximinoketones. The protocol is rapid, the yields are excellent, and the method is simple. Copyright

Full text of DOI:10.1002/cjoc.201180452

FULL PAPER
DOI: 10.1002/cjoc.201180452
Nitrite Ionic Liquids (IL-ONO and [bmim]NO2) as Effective
Nitrosonium Sources for the Synthesis of α-Oximinoketones
under Mild Heterogeneous Conditions
Valizadeh, H.*
Shomali, A.
Gholipour, H.
Department of Chemistry, Faculty of Sciences, Azarbaijan University of Tarbiat Moallem, Tabriz, Iran
Ketones and β-diketones were nitrosated and converted to their corresponding α-oximinoketones using
task-specific ionic liquids, 1-(4-nitritobutyl)-3-methylimidazolium chloride, IL-ONO, and 1-butyl-3-methyl-
imidazolium nitrite at room temperature. The results from two ionic liquids are comparable and showed that these
IL's are effective nitrosonium sources for the preparation of oximinoketones. The protocol is rapid, the yields are
excellent, and the method is simple.
Keywords β-diketones, ketones, malonodiamide, oximinoketones, ionic liquids
Introduction
istry.[28-32] In this work we wish to report the two nitrite
functionalized ionic liquids as new reagents for the ni-
trosation of ketons and β-diketones (Figure 1).
Large number of organic compounds especially het-
erocyclic one containing an oximino group have phar-
macological properties.[1,2] Some oxime derivatives pre-
sent a fungi toxic and herbicide effect,[3,4] or act as
growth regulators for plants.[5] Various important or-
ganic compounds such as amino acids,[6] nitrosopyra-
zoles[7] and 2-vinylimidazoles[8] have been synthesized
from α-oximinoketones. Nitrosation chemistry is very
attractive for organic and biological chemists[9-11] and
many works have been reported about the synthetic and
mechanistic aspects of nitrosation or transnitrosa-
tion.[12,13] Nitrous acid is the most general reagent which
is used for nitrosation and is generated from sodium
nitrite and a mineral acid.[14,15] Alkyl nitrites,[16,17] ni-
trosyl salts,[18,19] Fremy’s salt,[20] bis(triphenylpho-
sphine)nitrogen (1＋) nitrite,[21] alkyl thionitrite and
thionitrate,[22] polymer-supported nitrosation reagent,[23]
nitrosonium ethyl sulfate,[24] and [NO＋•Crown•
H(NO3 )－2 ][25] have been used as nitrosating agents.
Figure 1 Synthesis of oximinoketones using IL-ONO or
[bmim]NO2.
Weekly coordination of organic cations such as
1-butyl-3-methylimidazolium, N-alkylpyridinium or
tetraalkylammonium with inorganic anions such as Cl－,
Results and Discussion
The task-specific nitrite ionic liquids, 1-(4-nitritobu-
tyl)-3-methylimidazolium chloride (3) and 1-butyl-3-
methylimidazolium nitrite (4) were prepared according
to our recently published paper[33] and from the anion
exchange of [bmim]Cl respectively. First of all, we
found that activated methylene compounds, such as
benzoylacetone (1a) and dibenzoylmethane (1b) could
be transformed into the corresponding oximes 2a and 2b
respectively by simply grinding (45—50 min) at room
temperature (in a mortar with a pestle) with 1 equiv. of
BF－ or HSO－4 produced ionic liquids, which have
4
attracted chemist's interest due to their interesting
physical and chemical properties.[26,27] Many of these
compounds known as task-specific ionic liquids (TSILs)
are able to play dual roles as catalyst and/or reagent and
solvent, which have been reported in the literature.
TSILs contain functional groups which are covalently
bonded to cation or anion in these compounds. TSILs
have been increasingly used in synthetic organic chem-
*
E-mail: h-valizadeh@azaruniv.edu; Tel: ＋98-411-3856447; Fax: ＋98-4124327541
Received March 3, 2011; accepted June 21, 2011.
Chin. J. Chem. 2012, 30, 163—166
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
163

Valizadeh, Shomali & Gholipour
FULL PAPER
Table 1 Synthesis of oximinoketones using task-specific nitrite
ionic liquids IL-ONO or [bmim]NO2
IL-ONO over acidic alumina. For optimization, differ-
ent factors such as reaction temperature, reactants ratios
and solid supports (silica gel, neutral alumina and mo-
lecular sieves 3 Å) in the presence of various Lewis ac-
ids (AlCl3, ZnCl2 and TiCl4) were studied. No signifi-
cant improvement in the yields of products 2a and 2b
were observed under different grinding conditions. So,
we decided to examine this reaction under heterogene-
ous aqueous condition in the presence of HCl. Under
these conditions, dibenzoylmethane was converted to
related oximinoketone 2b, using one equivalent of
IL-ONO in 80% yield over 4 h. Also, there was no need
to heat the reaction mixture. For optimization, the reac-
tion was studied with different molar ratios of the
dibenzoylmethane, IL-ONO and HCl. The best ratio
was found to be 1∶1.1∶1.25 and the related product
2b was prepared in 89% yield over 2.5 h. Increasing the
amount of ionic liquid led to the mixture of products
such as nitrosoarene derivatives via electrophilic aro-
matic nitrosation of benzene ring. With optimized con-
ditions in hand, we examined the nitrosation of some
other ketones and diketones (Table 1). Acetophenone 1e
afforded the product 2e in 82% yield over 2.5 h.
O-Hydroxyacetophenone 1g led to the related oximi-
noketnoe product in lower yield (65%) in comparison
with acetophenone and nitrosoarene derivative product
was also isolated in this reaction. Diketones (1f, 1h and
1i) containing two sites for nitrosation, were nitrosated
selectively at activated site but the nitrosated product at
other site was also isolated in very lower yield for these
reactants. Excellent results were obtained with malono-
diamide 1c and dimethylmalonate 1d. H NMR and C
NMR spectroscopic data showed that two syn and anti
isomers of products 2a and 2e—2i were formed in this
procedure. The spectroscopic data of the major isomer
were given in the experimental section.
1-Butyl-3-methylimidazolium nitrite was also ex-
amined to transform the activated methylene com-
pounds, benzoylacetone (1a) and dibenzoylmethane (1b)
into their related oximes 2a and 2b under above de-
scribed optimized conditions. It was found that there are
no significant differences in the results from the using
of two ILs in this procedure. For comparison, the results
of the nitrosation of some ketones and diketones using
two ILs are gathered in Table 2. In order to evaluate the
preparative value of the present methodology we carried
out these reactions with 0.5 mol of benzoylacetone and
oximinoketone 2a was obtained in high yield.
a
Entry Ketone/Diketone
1
Product
m.p./℃
129—131
2
145—149
3
168—170
4
129—132
5
123—125
6
—
—
—
—
—
—
7
1
13
8
9
10
11
a Excess HCl was used for the reaction of 1c.
Experimental
In conclusion, the task-specific nitrite containing
ionic liquids, IL-ONO and [bmim]NO2, act as excellent
alternative reagents for the synthesis of oximinoketones.
Easy and clean work-up, and high yields make this pro-
cedure an attractive method for organic synthesis. This
simple procedure is highly selective and contamination
by-products is avoided. We believed that the present
methodology is an important addition to existing meth-
odologies.
General information
All reagents were purchased from Merck Company
and used without further purification. Infrared spectra
were recorded in KBr and were determined on a Perkin
1
Elmer FT-IR spectrometer. H NMR spectra were ob-
tained in DMSO-d6 solution from Bruker Avance
AC-400 MHz and 13C NMR spectra at 100 MHz on the
164
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 163—166

Nitrite Ionic Liquids as Effective Nitrosonium Sources for the Synthesis of α-Oximinoketones
Synthesis of oximinoketones using IL-ONO or
[bmim]NO2
Table 2 Comparison of the results of nitrosation using IL-ONO
with [bmim]NO2
.
Yielda/%
Diketone or ketone (12 mmol) and concentrated hy-
Time/h
Product
drochloric acid (15 mmol) were added in water or in
mixed alcohol-water (10 mL) and mixed vigorously at
room temperature. While stirring the mixture, a solution
of ionic liquid (13.2 mmol) in water (8 mL) is added
slowly. The reaction mixture was left to stirring at room
temperature for a time as shown in Table 1. The par-
ticipated products were filtered and washed three times
with cold water to afford the crude oximinoketone (2a
— 2i). The crude solid products were purified by
recrystallization from water/ethanol.
[bmim]NO2 IL-ONO
[bmim]NO2 IL-ONO
2a
2b
2c
2d
2e
2f
3
2.5
3.5
3
3
2.5
3.5
3
88b
90b
90
89
95
95
92
94
2.5
3
2.5
3
83b
85b
63b
88
82b
84b
65b
89
2g
2h
2i
3.5
3.5
3
3.5
3.5
3
Selected spectroscopic data
85b
85b
1-Phenyl-1,2,3-butanetrione-2-oxime (2a)
1H
2j
3
3
65
68
NMR (DMSO-d6, 400 MHz) δ: 7.61—7.68 (m, 4H,
PhH), 7.75—7.79 (m, 2H, PhH), 7.81—7.85 (m, 4H,
PhH), 12.87 (s, 1H, OH); 13C NMR (DMSO-d6, 150
MHz) δ: 114.05, 128.74, 130.00, 141.10, 154.87, 162.36;
IR (KBr) νmax: 3383 (br, OH), 1701, 1685, 1590, 1458,
2k
3
3
72
75
a Isolated yield. b Total yield of two isomeric products.
aforementioned instruments.
－
1
1370 cm . Anal. calcd for C10H9NO3: C 62.82, H 4.74,
N 7.33; found C 63.02, H 4.75, N 7.31.
Elemental analyses were carried out on
a
Perkin-Elmer 240C elemental analyzer and are reported
in percent atomic abundance. All melting points were
measured in an open glass-capillaries using Stuart melt-
ing point apparatus.
1,3-Diphenyl-1,2,3-propanetrione-2-oxime
(2b)
1H NMR (DMSO-d6, 400 MHz) δ: 2.51 (s, 3H, Me),
7.56—7.60 (m, 2H, PhH), 7.71—7.75 (m, 1H, PhH),
7.77—7.80 (m, 2H, PhH), 13.04 (s, 1H, OH); 13C NMR
(DMSO-d6, 150 MHz) δ: 19.78, 112.25, 127.12, 128.45,
144.80, 148.32, 158.14, 160.21; IR (KBr) νmax: 3379 (br,
Preparation of 1-butyl-3-methylimidazolium nitrite,
[bmim]NO2
－
1
OH), 1689, 1579, 1451, 1372 cm . Anal. calcd for
C15H11NO3: C 71.14, H 4.38, N 5.53; found C 71.23, H
4.39, N 5.52.
1-Butyl-3-methylimidazolium chloride was prepared
from the reaction of N-methylimidazole with
n-butylchloride at 80 ℃ under neat conditions.[34] So-
dium nitrite (23 mmol) was added to a solution of this
freshly prepared ionic liquid (20 mmol) in dichloro-
methane (10 mL) and stirred for 24 h at room tempera-
ture. The suspension was filtered to remove the precipi-
tated sodium chloride salt and the organic layer washed
with water (8 mL×3) until no precipitation of AgCl
occurred in aqueous phase on addition of a concentrated
AgNO3 solution. The solvent and other volatile materi-
als were removed from organic layer in vacuum and the
resulting ionic liquid was stirred with activated charcoal
for 12 h, after which the ionic liquid was passed through
a short alumina column(s) (acidic and/or neutral) to give
a colorless ionic liquid, which was dried at 100 ℃ in
vacuum for 24 h or until no visible signs of water pre-
sent in the IR spectrum. Yields were generally 75%—
Malonamide-2-one-2-oxime (2c)
1H NMR
(DMSO-d6, 400 MHz) δ: 7.73—7.79 (br, 2H, NH2),
7.32—7.36 (br, 2H, NH2), 12.04 (s, 1H, OH); 13C NMR
(DMSO-d6, MHz) δ: 138.63, 159.32, 162.52; IR (KBr)
νmax: 3431 (br, OH), 3310 (NH2), 3211 (NH2), 1680,
－
1
1675, 1437, 1261 cm . Anal. calcd for C3H5N3O3: C
27.49, H 3.84, N 32.05; found C 28.14, H 3.85, N 31.58.
Methyl 4-methoxy-2,3-dione-2-oxime butanoate
(2d) 1H NMR (DMSO-d6, 400 MHz) δ: 3.25 (s, 3H,
OCH3), 3.68 (s, 3H, OCH3), 3.75 (s, 2H, OCH2), 12.68
(s, 1H, OH); 13C NMR (DMSO-d6, 150 MHz) δ: 59.65,
60.25, 68.89, 135.25, 161.87, 163.45; IR (KBr) νmax
3330 (br, OH), 1743, 1691, 1627, 1437, 1388 cm .
:
－
1
Anal. calcd for C6H9NO5: C 41.15, H 5.18, N 8.00;
found C 42.10, H 5.16, N 7.98.
1-Phenyl-1,2-ethanedione-2-oxime (2e) 1H NMR
(DMSO-d6, 400 MHz) δ: 7.73—7.77 (m, 2H, PhH),
7.81—7.85 (m, 3H, PhH), 12.75 (s, 1H, OH); 13C NMR
(DMSO-d6, 150 MHz) δ: 112.32, 117.65, 125.63,
128.45, 148.63, 161.54; IR (KBr) νmax: 3421 (br, OH),
1
82%. H NMR (400 MHz, CDCl3) δ: 1.05 (t, J＝8.24
Hz, 3H, CH3), 1.41—1.43 (m, 2H, CH2), 1.76—1.78 (m,
2H, CH2), 3.83 (s, 3H, NCH3), 3.97 (t, J＝8.14 Hz, 2H,
CH2), 7.21 (d, J＝7.24 Hz, 1H, ArH), 7.40 (d, J＝7.24
Hz, 1H, ArH), 9.12 (broad, 1H, ArH); 13C NMR (CDCl3,
100 MHz) δ: 11.7, 18.3, 25.6, 36.4, 37.8, 124.7, 126.8,
140.0; IR (KBr) ν: 1652, 1617, 1532, 1350, 1190 cm .
Anal. calcd for C8H15N3O2: C 51.88, H 8.16, N 22.69;
found C 52.12, H 8.21, N 22.58.
－
1
1688, 1685, 1614, 1450, 1318 cm . Anal. calcd for
C8H7NO2: C 64.42, H 4.73, N 9.39; found C 64.87, H
4.71, N 9.35.
－
1
Benzyl 2,3-dione-2-oxime butanoate (2f)
1H
NMR (DMSO-d6, 400 MHz) δ: 2.50 (s, 3H, Me), 3.95 (s,
2H, OCH2), 7.52—7.58 (m, 2H, PhH), 7.67—7.72 (m,
Chin. J. Chem. 2012, 30, 163—166
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www.cjc.wiley-vch.de
165

Valizadeh, Shomali & Gholipour
FULL PAPER
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1H, PhH), 7.75—7.78 (m, 2H, PhH), 13.08 (s, 1H, OH);
13C NMR (DMSO-d6, 150 MHz) δ: 36.78, 71.41, 113.63,
117.87, 119.56, 122.36, 149.79, 160.52, 163.53; IR
(KBr) νmax: 3331 (br, OH), 1746, 1698, 1627, 1498,
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N 6.33; found C 60.23, H 4.99, N 6.32.
－
1
1-(2-Hydroxyphenyl)-1,2-ethanedione-2-oxime
(2g) 1H NMR (DMSO-d6, 400 MHz) δ: 6.35 (br, 1H,
OH), 7.41—7.45 (m, 2H, PhH), 7.60—7.65 (m, 1H,
PhH), 7.75—7.78 (m, 2H, PhH), 12.82 (s, 1H, OH); 13C
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121.32, 122.52, 122.98, 149.96, 165.85; IR (KBr) νmax
:
－
1
3449 (br, OH), 1684, 1531, 1384 cm . Anal. Calcd for
C8H7NO3: C 58.18, H 4.27, N 8.48; found C 59.08, H
4.26, N 8.46.
Methyl 2,3-dione-2-oxime hexanoate (2h) 1H
NMR (DMSO-d6, 400 MHz) δ: 1.05 (t, J＝8.24 Hz, 3H,
CH3), 1.15—1.17 (m, 2H, CH2), 2.64 (t, J＝8.24 Hz, 2H,
CH2), 3.65 (s, 3H, OCH3), 12.89 (s, 1H, OH); 13C NMR
(DMSO-d6, 150 MHz) δ: 15.52, 18.45, 23.36, 62.52,
145.56, 158.89, 164.75; IR (KBr) νmax: 3354 (br, OH),
－
1
1726, 1694, 1627, 1458, 1374 cm . Anal. calcd for
C7H11NO4 C 48.55, H 6.40, N 8.09; found C 48.74, H
6.43, N 8.08.
Methyl 2,3-dione-2-oxime butanoate (2i) 1H
NMR (DMSO-d6, 400 MHz) δ: 2.35 (s, 3H, CH3), 3.78
(s, 3H, OCH3), 13.34 (s, 1H, OH); 13C NMR (DMSO-d6,
150 MHz) δ: 31.25, 62.53, 147.69, 161.53, 165.82; IR
(KBr) νmax: 3448 (br, OH), 1751, 1654, 1452, 1373
－
1
cm . Anal. calcd for C5H7NO4: C 41.38, H 4.86, N
9.65; found C 41.42, H 4.88, N 9.63.
2,4-Dione-3-oxime pentane 1H NMR (DMSO-d6,
400 MHz) δ: 2.15 (s, 3H, CH3), 13.04 (s, 1H, OH); 13C
NMR (DMSO-d6, 150 MHz) δ: 31.25, 137.79, 159.51,
161.72; IR (KBr) νmax: 3437 (br, OH), 1747, 1634, 1425,
－
1
1351 cm . Anal. calcd for C5H7NO3: C 46.51, H 5.46,
N 10.85; found C 46.53, H 5.47, N 10.83.
3,5-Dione-4-oxime heptane 1H NMR (DMSO-d6,
400 MHz) δ: 2.24 (s, 3H, CH3), 13.02 (s, 1H, OH); 13C
NMR (DMSO-d6, 150 MHz) δ: 30.16, 32.42, 136.70,
159.43, 160.63; IR (KBr) νmax: 3435 (br, OH), 1748,
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－
1
1641, 1430, 1356 cm . Anal. calcd for C5H11NO3: C
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53.49, H 7.05, N 8.91; found C 53.50, H 7.06, N 8.89.
Acknowledgments
The partial financial assistance from the Research
Vice Chancellor of Azarbaijan University of Tarbiat
Moallem is gratefully acknowledged.
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166
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 163—166