New nitrite ionic liquid (IL-ONO) and nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica as nitrosonium sources for electrophilic aromatic nitrosation

Article abstract of DOI:10.1016/j.crci.2011.09.012

An improved method for the synthesis of nitrosoarenes has been developed using a new nitrite ionic liquid (IL-ONO) and immobilized nitrite ionic liquid. These ionic liquids play as nitrosonium sources for electrophilic aromatic nitrosation of active aromatics at 0-5 °C. Their action was accomplished in water and the satisfactory results were obtained under the mild conditions in short reaction time.

Full text of DOI:10.1016/j.crci.2011.09.012

C. R. Chimie 14 (2011) 1103–1108
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Full paper/Memoire
New nitrite ionic liquid (IL-ONO) and nanoparticles of
organosilane-based nitrite ionic liquid immobilized on silica as
nitrosonium sources for electrophilic aromatic nitrosation
*
Hassan Valizadeh , Mohammad Amiri, Ashkan Shomali
Department of Chemistry, Faculty of Sciences, Azarbaijan University of Tarbiat Moallem, 53714-161 Tabriz, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
An improved method for the synthesis of nitrosoarenes has been developed using a new
nitrite ionic liquid (IL-ONO) and immobilized nitrite ionic liquid. These ionic liquids play as
nitrosonium sources for electrophilic aromatic nitrosation of active aromatics at 0–5 8C.
Their action was accomplished in water and the satisfactory results were obtained under
the mild conditions in short reaction time.
Received 12 May 2011
Accepted after revision 26 September 2011
Available online 1 November 2011
Keywords:
ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Electrophilic aromatic nitrosation
Task-specific ionic liquid
Nitrosonium source
Immobilized nitrite ionic liquid
1. Introduction
for in situ generation of HNO2 for the nitrosation of
secondary amines [6]. Ionic liquids have interesting
Nitrosoarenes are an important class of chemical
compounds which are used for the preparation of some
organic intermediates. These compounds also find appli-
cations in analysis as reagents [1,2]. Because of the low
electrophilicity of nitrosating agents, there are fewer
reports about the nitrosation reaction in comparison with
nitration reaction. One of the most common procedures for
the synthesis of nitrosoarenes is the electrophilic aromatic
nitrosation reaction using HNO2 as nitrosating agent [3]. A
major problem in this reaction is the instability of the
aromatic nitroso-compounds formed. These compounds
can decompose by oxidation by NO2 [4], or by nitration
with the nitric acid which was produced from the aerobic
oxidation of nitrous acid [5]. Zyk et al. reported the
synthesis of nitrosoarenes via the nitrosation of O-
alkylphenols and N,N-dialkylanilines using nitrosonium
ethyl sulfate as nitrosonium reagent [2]. Zolfigol et al. used
inorganic acidic salts such as aluminum hydrogen sulfate
physical properties and are used as solvents in organic
chemistry [7]. They are usually an ion pair of weakly
coordinated organic cations such as 1-butyl-3-methylimi-
dazolium, N-alkylpyridinium or tetraalkylammonium
with inorganic anions such as ClÀ, BF4 or HSO4 and a
classical example is the readily available 1-butyl-3-
methylimidazolium tetrafluoroborate [bmim][BF4] [8].
Ionic liquids containing chemically active functional
groups on their cations or anions are known as task-
specific ionic liquids (TSILs). Functional groups are
covalently bonded to cation or anion in these compounds.
TSILs have been increasingly used as solvents and reagents
or catalysts due to their specific properties [9–13]. In
continuation of our interest to use ionic liquids (IL’s), water
or solventless systems as green reaction media [14–23], in
this report, we wish to highlight our results on using new
nitrite ionic liquid (IL-ONO) and new immobilized ionic
liquid as nitrosonium source reagents in nitrosation
reaction to produce nitrosoarenes in good to excellent
yields at 0–5 8C in aqueous media (Scheme 1).
À
À
Nanoparticles and ionic liquids are very important in
materials chemistry. The combination of properties of
* Corresponding author.
E-mail address: h-valizadeh@azaruniv.edu (H. Valizadeh).
1631-0748/$ – see front matter ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.09.012

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H. Valizadeh et al. / C. R. Chimie 14 (2011) 1103–1108
of N-methyl imidazole with (3-chloropropyl) trimethox-
ysilane at 80 8C. The solution of ionic liquid 3 in CH2Cl2 was
then added to the suspension of freshly prepared silica
nanoparticles in CH2Cl2. After stirring the mixture for 3
days at 40–50 8C, the ionic liquid immobilized on silica 4
was prepared. Immobilized nitrite ionic liquid (Im-IL) 5
was obtained in 98% yield as a white powder by stirring of
4 with excess amount of NaNO2 in deionized water for 24 h
at room temperature (Scheme 2).
The SEM image of silica nanoparticles was obtained and
compared with the SEM images of immobilized nitrite
ionic liquid 5 (Figs. 1 and 2). Comparing the two SEM
images showed that the size of the silica nanoparticles is
larger than immobilized nitrite ionic liquid 5.
Ionic liquid, 1-(4-nitritobutyl)-3- methylimidazolium
chloride was synthesized according our very recently
published article [29].
Scheme 1. Electrophilic aromatic nitrosation reaction using immobilized
To examine its activity as nitrosonium source, this ionic
liquid (IL-ONO) was used for the nitrosation of N,N-
dimethylaniline in the presence of HCl 37%, at 0–5 8C. The
experimental results revealed that nitrite-functionalized
IL- ONO, exhibits a very high activity and 4-nitroso-N,N-
dimethylaniline 2a was prepared in excellent yield.
Optimization of the reaction conditions was studied with
different molar ratios of the ionic liquid, N,N-dimethylani-
line and HCl. The best ratio was found to be 1:1:1.5.
Increasing the amount of ionic liquid led to the mixture of
products. To examine the versatility of this procedure, IL-
ONO was then used for nitrosation of other aromatic
compounds.
As it can be seen from Table 1, active aromatic
compounds, containing electron releasing groups react
faster and afforded the related nitroso products in higher
yields in comparison with toluene. Nitrobenzene and
benzoic acid were not nitrosated under these conditions.
Phenol, phenethol, N,N-dialkylaniline and anisole nitro-
ionic liquid and nitrite IL-ONO.
nanoparticles and ionic liquids has already been studied by
some researchers [24]. The ionic liquid 1-methyl-3-(20-
mercaptoacetoxyethyl) imidazolium chloride was used to
stabilize palladium nanowires [25] and organosilanes
containing covalently bonded catalyst were used as a
linker or coupling agent to an oxide support [26]. Catalytic
properties of the ionic liquids were transferred to a solid
catalyst in immobilization process [27]. Immobilized ionic
liquids should be more widely applicable than their neat
precursors because of their miscibility with the organic
solvent. Ionic liquids immobilized on silica can successful-
ly be studied by optimized multinuclear one- and two-
dimensional 1H and 13C HRMAS NMR spectroscopy of their
suspensions in a suitable solvent, such as DMSO. In
comparison to the pure ionic liquids, immobilized ionic
liquids offer the additional features that they facilitate
recovery of the catalyst and can be used in gas phase
reactions [28].
sated regioselectively at 4 position as showed in Table 1.
Naphtol nitrosated regioselectively at position.
b
a
-
-
a
2. Results and discussion
Naphtol was nitrosated at 2 and 4 positions with 56:35
ratio (Table 1, entry 4). Despite previous reports, the
nitroso products were stable during the reaction and no
oxidated nitro product was observed under these condi-
tions [5]. Dealkylation is very often observed in the
nitrosation of alkyl phenyl ethers [35]. However, using the
nitrite IL-ONO for the nitrosation of anisole and phenethol
in virtually afforded to related pure nitroso products and
the reactions were not accompanied by dealkylation. All of
products were characterized by comparing their (1H, 13C
NMR and IR) spectroscopic data and melting points with
literature values.
N-methyl-3-(3-trimethoxysilylpropyl) imidaz- olium
chloride 3, [MTMSPIM]ClÀ, was prepared from the reaction
The plausible mechanism for acid-catalyzed nitrosation
of 2-naphtol in IL-ONO was depicted in Scheme 3.
Initially, the nitrosonium ion was formed from proton-
ated IL-ONO. Electrophilic substitution of nitrosonium ion
at a-position of 2-naphtol was accrued to afford 1-nitroso-
2-naphtol. In the present study, we investigated that IL-OH
can be recycled. After removal of the mixture of product,
possible impurities and unreacted materials, the remain-
ing IL-OH was reused for the preparation of IL-ONO and
consecutive three cycles without significant loss in its
efficiency (Table 2).
Scheme 2. Preparation of immobilized nitrite ionic liquid 5.

H. Valizadeh et al. / C. R. Chimie 14 (2011) 1103–1108
1105
Table 1
Electrophilic aromatic nitrosation using new nitrite ionic liquid (IL-ONO) and new immobilized ionic liquid (Im-IL).
Entry Ar-H
Product
Time (minute)
M.P (8C)
Yielda (%)
Reported (reference) IL (ONO) Im-IL
IL (ONO) Im-IL Found
1
65
60
60
57
92–94
92 [2]
91
93
NMe2
1a
2
103–106 109 [30]
92
92
OH
NO
OH
1b
2b
3
4
75
55
72
55
135–138 133 [31]
89
90
OH
OH
1c
2c
ON
155–157 142–144 [32]
56b
56b
OH
1d
5
6
60
62
61
58
82–84
70–73
84–84 [2]
71–72 [2]
91
90
90
92
NEt2
NEt2
2e
1e
ON
ON
N(i-Pr)2
N(i-Pr)2
1f
2f
7
65
60
35–36
30–32 [2]
94
95
OEt
OEt
1g
2g
ON
8
9
65
60
23
23–24 [2]
88
87
OMe
OMe
2h
1h
ON
ON
50
68
42
63
156–159
–
32
35
OH
OH
1i
2i
HO
ON
HO
10
156–158 160–162 [33]
63c
63c
OH
2j
Me

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H. Valizadeh et al. / C. R. Chimie 14 (2011) 1103–1108
Table 1 (Continued )
Entry Ar-H
Product
Time (minute)
M.P (8C)
Yielda (%)
IL (ONO) Im-IL Found
Reported (reference) IL (ONO) Im-IL
11
75
72
Liquid
Liquid [34]
31
37
NO
1k
2k
Me
Me
a
Isolated yield.
b
Total yield of reaction was 91% and 4-nitroso-1-naphtol was also isolated in 35%, yield in this reaction.
Total yield of reaction was 93% and 2-nitrosocresol was also isolated in 30% yield in this reaction.
c
Scheme 3. Plausible mechanism for nitrosation of 2-naphtol.
Table 2
The comparison of efficiency of recycled IL-OH for the preparation of new
nitrite ionic liquid (IL-ONO) and consecutive electrophilic aromatic
nitrosation.
Run
Yielda (%)
2a
2b
2g
2j
1
2
3
91
89
90
92
91
90
94
92
93
93
91
92
Fig. 1. The SEM image of immobilized nitrite ionic liquid 5.
a
Yields of recrystallized product.
For comparison, Im-IL 5 was used in place of IL-ONO in
this procedure at the same optimized conditions as
described above. The results were shown in Table 1. After
removal of the mixture of product, possible impurities and
unreacted materials, the immobilized ionic liquid in the
feed was washed tree times with ethanol and reused after
exchanging of the chlorid anion with nitrite ionic liquid. No
significant decrease in yield after three cycles of the
immobilized ionic liquid.
3. Conclusions
In conclusion, it was found that IL-ONO and immobi-
lized nitrite ionic liquids are convenient reagents for
electrophilic aromatic nitrosation of aromatic compounds.
Reactions of these reagents with arenes are not accompa-
nied by side processes such as oxidation or dealkylation.
Regioselectivity, easy and clean work-up procedure and
high yields make this method attractive for organic
chemists. Thus, it provides a more practical alternative
to the existing methodologies.
Fig. 2. The SEM image of silica nanoparticles.

H. Valizadeh et al. / C. R. Chimie 14 (2011) 1103–1108
1107
4. Experimental
anions, was removed by washing the mixture with
deionized water (3 Â 30 mL). Immobilized nitrite ionic
liquid was obtained typically in 98% yield as a white
powder. Immobilized nitrite ionic liquid nanoparticles
were examined under scanning electron microscopy.
4.1. 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 Elmer FT-
IR spectrometer. 1H NMR spectra were recorded on a
Bruker Avance AC-400 MHz using DMSO-d6 or CDCl3 as the
deuterated solvents and TMS as internal standard. All
melting points measured in open glass-capillaries using
Stuart melting point apparatus.
4.2. General procedure
4.2.1. Electrophilic aromatic nitrosation
Aromatic compound (50 mmol) and freshly prepared
IL-ONO or immobilized nitrite ionic liquid (50 mmol) were
added to water (5 mL) and mixed thoroughly at 0–5 8C.
Then HCl 37% (75 mmol, 2.3 mL) was added to the mixture
continuously and stirred for a time as shown in Table 1. The
participated products were filtered and washed three
times with cold water to afford the crude nitrosoarenes.
The crude products were purified by recrystallization from
ethyl acetate/n-hexane. Product 2h was purified by flash
chromatography on silica gel.
4.1.1. Synthesis of 1-methyl-3-(3-trimethoxysilylpropyl)
imidazolium chloride 1-Methylimidazole
N-Methylimidazole (20 mL, 0.25 mol) and (3-chloropro-
pyl) trimethoxysilane (6.04 g, 0.25 mmol) were refluxed at
80 8C for three days in the absence of any catalyst and
solvent. The unreacted materials were washed by diethyl
ether (3 Â 8 mL). The diethyl ether was removed under
reduced pressure at room temperature, followed by heating
under high vacuum, to yield a yellowish viscous liquid.
Isolated yield was 98%. IR (KBr): 1656, 1612, 1584/cm. 1H
4.3. Selected spectroscopic data
4.3.1. 1-Nitroso-2-naphthol 2b
NMR (400 MHz, CDCl3):
d
= 10.22 (1H, broad, Ar-H), 7.59
m.p. 103-106 8C. IR (KBr): 3405, 1625, 1530–1600/cm.
(1H, dd, Ar-H), 7.26 (1H, dd, Ar-H), 4.06 (2H, t, -NCH2), 3.86
(3H, s, -NCH3), 3.30 (9H, s, -OCH3), 1.74 (2H, tt, CH2), 0.37
(2H, t, SiCH2).
1H NMR (400 MHz, CDCl3):
d = 14.08 (1H, s, OH), 8.83 (1H,
d), 7.66–7.64 (1H, d), 7.6–7.49 (3H, m), 6.40–6.38 (1H, d).
Anal. Calc. for C10H7NO2: C 69.36; H 4.07; N 8.09%. Found:
C 70.05; H 4.10; N 8.00%.
4.1.2. Synthesis of silica nanoparticles
Ammonia solution 25% (750
mL, 10 mmol) and water
4.3.2. 2-Nitroso-1-naphthol 2d
(1.98 mL) were added into a 250 mL round bottom flask
containing absolute methanol (100 mL). The solution is
stirred for 10 min at room temparature. While stirring of the
solution, tetraethoxysilane, TEOS (10.41 g, 500 mmol) was
added dropwise. The final solution is stirred continously for
three days at ambient temperature. The particle size was
examined under scanning electron microscopy.
m.p. 155-157 8C. IR (KBr): 3201, 1669, 1594–1627/cm.
1H NMR (400 MHz, DMSO-d6):
d = 13.49 (1H, s, OH) 7.81–
7.61 (4H, m), 7.15–7.12 (1H, d), 7.06–7.04 (1H, d). Anal.
Calc. for C10H7NO2: C 69.36; H 4.07; N 8.09%. Found: C
70.12; H 4.01; N 8.12%.
4.3.3. 2-Nitroso hydroquinone 2i
m.p. 156-159 8C. IR (KBr): 3221, 1631, 1500–1600/cm.
4.1.3. Procedure for the immobilization of chloride ionic
liquid onto silica nanoparticles
1H NMR (400 MHz, DMSO-d6):
d = 13.62 (1H, s, OH), 8.63
(1H, s, OH), 6.88 (1H, s), 6.56 (2H, s). Anal. Calc. for
C6H5NO3: C 51.80; H 3.62; N 10.07%. Found: C 52.05; H
3.64; N 9.99%.
The silica nanoparticles suspension are precipitated
with n-hexane and extracted through centrifugation
(twice at 6000 rpm) before being re-suspended in dichlor-
omethane. Silica (1.016 g) was suspended in CH2Cl2 (5 mL)
and the solution of 1-methyl-3-(3-trimethoxy silylpropyl)
imidazolium chloride (300 mg, 0.929 mmol) in CH2Cl2 was
then added. The mixture was stirred for 3 days at 40–50 8C.
In the following step, the solvent and the methanol created
in the grafting step were distilled off and the remaining
solid dried under high vacuum and the excess of 1-methyl-
3-(3-trimethoxy silylpropyl) imidazolium chloride re-
moved by extraction with boiling dichloromethane. After
drying of residue under vacuum at room temperature, the
nanoparticles of immobilized chloride ionic liquid on to
silica was prepared.
4.3.4. 4-Nitroso-m-cresol 2j
m.p. 156-158 8C. IR (KBr): 3120, 1633, 1570–1594/cm.
1H NMR (400 MHz, DMSO-d6):
d = 13.54 (1H, s, OH), 7.66–
7.63 (1H, d), 6.39–6.36 (1H, dd), 6.32 (1H, s), 2.09 (3H, s,
CH3). Anal. Calc. for C7H7NO2: C 61.31; H 5.14; N 10.21%.
Found: C 61.51; H 5.16; N 10.18%.
Acknowledgements
The partial financial assistance from the Research Vice
Chancellor of Azarbaijan University of Tarbiat-Moallem is
gratefully acknowledged.
4.1.4. Anion exchange in the immobilized ionic liquid
Immobilized chloride ionic liquid 4 and an excess
amount of NaNO2 were added into the deionized water and
stirred for 24 h at room temperature. NaCl which was
prepared during the exchange of chloride with nitrite
References
[1] H. Feuer, The chemistry of nitro and nitroso groups. Part I, Interscience,
New York, 1969.
[2] N.V. Zyk, E.E. Nesterov, A.N. Khiobystov, N.S. Zefirov, Russ. Chem. Bull.
48 (1999) 506.

1108
H. Valizadeh et al. / C. R. Chimie 14 (2011) 1103–1108
[3] D.L.H. Williams, Nitrosation, Cambridge University Press, Cambridge,
1988.
[4] B.G. Gowenlock, B. King, J. Pfab, M.J. Witanowski, Chem. Soc. Perkin
Trans. 2 (1998) 483.
[5] B. Beake, R.B. Moodie, J. Chem. Soc. Perkin Trans. 2 (1995) 1045.
[6] M.A. Zolfigol, A.G. Choghamarani, A. Taqian-Nasab, H. Keypour, S.
Salehzadeh, Bull. Korean Chem. Soc. 24 (2003) 638.
[7] T. Welton, Chem. Rev. 99 (1999) 2071.
[8] P.A.Z. Suarez, J.E.L. Dullius, S. Einloft, R. De Souza, J. Dupont, Polyhedron
15 (1996) 1217.
[9] K. Gong, D. Fang, H.L. Wang, X.L. Zhou, Z.L. Liu, Dye. Pig. 80 (2009) 30.
[10] (a) L. Wang, H. Li, P. Li, Tetrahedron 65 (2009) 364 ;
(b) A. Yue, Y. Mao, M. Wei, Lu¨ , Catal. Commun. 9 (2008) 1571.
[11] L. Dhar, S. Yadav, R. Patel, V. Rai, K. Vishnu, P. Srivastava, Tetrahedron
Lett. 48 (2007) 7793.
[18] H. Valizadeh, A. Shockravi, Tetrahedron Lett. 46 (2005) 3501.
[19] H. Valizadeh, A. Shockravi, Heteroatom Chem. 20 (2009) 284.
[20] H. Valizadeh, H. Gholipour, J. Iran. Chem. Soc. 8 (2011) 123.
[21] H. Valizadeh, A. Fakhari, Mulecules 15 (2010) 2972.
[22] H. Valizadeh, H. Gholipour, Synth. Commun. (2010) 1477.
[23] H. Valizadeh, A.A. Azimi, J. Iran. Chem. Soc. 8 (2011) 123.
[24] M. Litschauer, M.A. Neouze, J. Mater. Chem. 18 (2008) 640.
[25] S. Gao, H. Zhang, X. Wang, W. Mai, C. Peng, L. Ge, Nanotechnology 16
(2005) 1234.
[26] S.M. Lee, H. Yoon, J.H. Kim, W.J. Chung, Y.S. Lee, Pure Appl. Chem. 79
(2007) 1553.
[27] M.H. Valkenberg, C. deCastro, W.F. Ho¨lderich, Green Chem. 4 (2002) 88.
[28] S. Brenna, T. Posset, J. Furrer, J. Blumel, Chem. Eur. J. 12 (2006) 2880.
[29] H. Valizadeh, A. Shomali, Dyes Pigments doi: 10.1016/j, (Available
online) 2010.
[12] I. Yavari, E. Kowsari, Mol. Divers. 13 (2009) 519.
[13] H. Valizadeh, M. Amiri, H. Gholipour, J. Heterocycl. Chem. 46 (2009)
108.
[14] H. Valizadeh, A. Shockravi, Synth. Commun. 39 (2009) 4341.
[15] H. Valizadeh, A. Fakhari, Heterocycl. Chem. 46 (2009) 1392.
[16] H. Valizadeh, S. Vaghefi, Synth. Commun. 39 (2009) 1666.
[17] H. Valizadeh, M.M. Heravi, M. Amiri, Mol. Divers. 14 (2010) 575.
[30] M.H. Jones, J.T. Woodcock, Anal. Chem. 48 (1976) 1915.
[31] W.R. Vaughan, G.K. Finch, J. O. C. 21 (1956) 1201.
[32] B. Foretic, N. Burger, Chemica. ACTA 75 (2002) 21.
[33] R.A. Baldvin, M.T. Cheng, United States Patent 3 714 (1973) 267.
[34] http://www.lookchem.com.
[35] B.C. Challis, R.J. Higgins, A.J. Lowson, J. Chem. Soc. Perkin Trans. 12 (2)
(1972) 183l.