Facile preparation of a nanostructured functionalized catalytically active organosalt

Article abstract of DOI:10.1039/c3ta13484a

We report a novel nanostructured organosalt, based on sulfonic acid functionalized pyrazinium {[H-pyrazine-SO₃H]Cl₂} that was synthesized and characterized by several techniques including Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG) analysis, transmission electron microscopy (TEM), mass spectrometry (MS), proton NMR (¹H NMR), carbon-13 NMR (¹³C NMR) and also electron diffraction (ED) patterns. Results proved that the unprecedented sulfonated pyrizinium organosalt is indeed nanostructured and highly crystalline as supported by TEM, ED and XRD studies, having an average nanoparticle size of 50 nm according to TEM micrographs. The novel nano-organocatalyst was proved to be an efficient catalyst in the synthesis of 1,2,4,5-tetrasubstituted imidazoles by a one-pot multi-component condensation of benzil, a broad range of aldehydes, primary amines and ammonium acetate at 90 °C under solvent-free conditions.

Full text of DOI:10.1039/c3ta13484a

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Paper
Facile preparation of a nanostructured functionalized catalytically
active organosalt
Ahmad Reza MoosaviꢀZare,*a Mohammad Ali Zolfigol,*b Vahid Khakyzadeh,b Christoph Böttcher,c
Mohammad Hassan Beyzavi,d Abdolkarim Zare,e Alireza Hasaninejadf and Rafael Luqueg
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
We report a novel nanostructured organosalt, based on sulfonic acid functionalized pyrazinium {[HꢀPyrazine–SO3H]Cl2} that
was synthesized and characterized by several techniques including Fourier transform infrared spectroscopy (FTꢀIR), Xꢀray
diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), transmission electron
10 microscopy (TEM), Mass spectra (MS), Proton NMR (1HNMR), Carbonꢀ13 NMR (13 CNMR) and also electron diffraction
(ED) patterns. Results proved that the unprecedented sulfonated pyrizinium organosalt is indeed nanostructured and highly
crystalline as supported by TEM, ED and XRD studies, having an average nanoparticle size of 50 nm according to TEM
micrographs. The novel nanoꢀorganocatalyst was proved to be an efficient catalyst in the synthesis of 1,2,4,5ꢀtetra substituted
imidazoles by a oneꢀpot multiꢀcomponent condensation of benzil, a broad range of aldehydes, primary amines and ammonium
15 acetate at 90 ºC under solventꢀfree conditions.
design and development of novel acidic functionalised ILs and
solid salts for organic transformations, we have now prepared and
characterized a novel nanostructured organosalt (sulfonic acid
Introduction
The design and application of high performing catalysts in
50 pyrazinium chloride)
(Scheme 1). The synthesized
synthetic organic protocols
including metalꢀfree organic
organocatalyst was successfully employed in the synthesis of
different polyꢀsubstituted imidazole derivatives exhibiting
various important properties (Scheme 2).
molecules (organocatalysis) and organometallic catalysts has
20 attracted significant efforts from the scientific community in
order to develop increasingly attractive methodologies for the
preparation of more complex molecules.1 Organocatalysis had a
significant impact and direct benefit in the production of
pharmaceutical intermediates when compared with (transition)
25 metal catalysts.
In addition, organocatalysts are commonly inexpensive, stable
and readily available, show low toxicity and no sensitivity
towards moisture or oxygen.2 Another advantage of
organocatalysts relates to their favourable surface to volume ratio
30 which enhances the contact between reactants and catalyst
support and in turn increases the catalytic activity.3 In spite of
their controversy as greener compounds, Ionic liquids (ILs) can
be considered as organocatalysts.4 In this context, we have
recently reported a novel family of ionic liquids based on acidic
35 sulfonic acid functionalized imidazolium salts (SAFIS).5ꢀ14 SꢀN
bond formation yielding imidazole derivatives as five member
heterocyclic ring compound was reported for the first time by
employing such acidic ILs as catalyst. Importantly, the catalytic
activities of these acidicꢀfunctionalized organocatalysts was
40 further extended to chemistries involving the preparation of
55 Scheme 1 The preparation of sulfonic acid functionalized pyrazinium salt
{[HꢀPyrazine–SO3H]Cl2}.
Scheme 2 The preparation of 1,2,4,5ꢀtetra substituted imidazoles (R and
Ar groups are given in Table 1).
60
Imidazoles are one of the most important groups of five
membered nitrogen heterocycles which have attracted much
attention because of their participation in the structure and
activity of biological molecules including histidine, histamine or
biotin.15 Importantly, there is high demand of these compounds
bis(indolyl)methanes,5 Nꢀsulfonyl imines,6 nitro aromatic
8
compounds,7,
1ꢀamidoalkylꢀ2ꢀnaphthols,9 Xanthenes,10 1ꢀ
carbamatoalkylꢀ2ꢀnaphthols,11 4,4'ꢀ(arylmethylene)ꢀbis(3ꢀmethylꢀ
1ꢀphenylꢀ1Hꢀpyrazolꢀ5ꢀol)s,12 tertꢀbutyl aryl carbamates13 and
45 hexahydroquinolines.14
65 from the pharmaceutical viewpoint the imidazole moiety is the
core structure of important drugs such as Losartan, Olmesartan,
In continuation of previous research endeavours related to the
Eprosartan
and
Trifenagrel
(Figure
1).16
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Figure 1 The structure of a few exemplary drugs such as Losartan, Olmesartan, Eprosartan and Trifenagrel, which incorporate an imidazole moiety.
5
Figure 2 IR spectrum of sulfonic acid functionalized pyrazinium salt {[HꢀPyrazine–SO3H]Cl2}
monoꢀfunctionalized [HꢀPyrazine–SO3H]Cl2 as main product
Moreover, they are very popular as ILs17 and Nꢀheterocyclic
(Scheme 3).
carbenes (NHCs) in organometallic chemistry has been increased.
18, 19
35
Characterization of {[HꢀPyrazine–SO3H]Cl2} was carried out
10
Several catalytic methods have been reported to improve the
yields for the synthesis of polysubstituted imidazoles. Catalysts
employed in this process include heteropolyacids,20 silica gel and
1
using various analytical techniques including IR, H NMR, 13C
NMR and mass spectrometry.
IR spectrum of the catalyst showed
a broad peak at
zeolites,21 alumina,22 HClO4ꢀSiO2,23 I2,24 BF3 ꢁ SiO2,25 InCl3
ꢁ
2650ꢀ3500 cmꢀ1 which could contain the overlaid NH+Clꢀ
3H2O,26 K5CoW12O40
ꢁ
3H2O,27 copper acetate,28 or
40 stretching peak (2800 cmꢀ1, bs),31 and the OꢀH stretching of
SO3H. Moreover, the two peaks observed at 1069 cmꢀ1 and 1174
cmꢀ1 correspond to vibrational modes of NꢀSO2 and OꢀSO2 bonds.
Another peak at 1010 could be correlated to S=O bonds (Figure
2).
15 trifluoroacetic acid using microwave irradiation.29 Other
examples for the synthesis of polysubstituted imidazoles have
also been reported in the literature.30
However, most of the reported protocols have inherent
drawbacks related to laborious and complex reaction workup,
20 tedious purification steps, generation of significant amounts of
waste, employment of strongly acidic conditions, side reactions,
poor yields and the use of expensive or sophisticated catalysts.
Comparatively, the utilization of the proposed organosalt as
catalyst in the synthesis of substituted imidazoles can provide
25 additional advantages in terms of reaction efficiency, selectivity
and the possibility to recycle the catalyst for further uses. To the
best of our knowledge, this is also the first report of the
preparation of a catalytically active nanostructured organosalt.
45
Results and Discussion
Scheme 3 The preparation of sulfonic acid functionalized pyrazinium salt
{[HꢀPyrazine–SO3H]Cl2}.
30 The expected diꢀsulfonic acid functionalized pyrazinium salt {i.e.
[SO3HꢀPyrazine–SO3H]Cl2} was surprisingly not observed in the
synthesis of the sulfonic acid functionalized pyrazinium salt, with
1
The important peak found in H NMR spectra of the catalyst is
50 related to the acidic hydrogen of SO3H which was observed at
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13.23 ppm (Figure 3b). 1HNMR spectra of ClSO3H (starting
material) as well as [HꢀPyrazine–H]Cl2 in DMSO {[Hꢀ Pyrazine–
H][ClSO3]2 was not commercially available and [HꢀPyrazine–
H]Cl2 has the same type of acidic H environments} were run to
further confirm the presence of SO3H hydrogen in the catalyst
(and not to unreacted starting material or possible byproducts).
support the proposed asymmetric structure of catalyst from
Scheme 3 (Figure 4).
5
In these spectra, the peaks of the acidic hydrogens of [Hꢀ
Pyrazine–SO3H]Cl2, ClSO3H and [HꢀPyrazine–H]Cl2 were
observed at 13.23, 10.75 and 9.25 ppm, respectively (Figure 3a).
10
The difference between the peaks of the acidic hydrogens in
the compounds confirmed that the peak observed at 13.23 ppm of
the 1H NMR spectra of [HꢀPyrazine–SO3H]Cl2 is correctly
related to the hydrogen of SO3Hꢀfunctionalized pyrazinium salt.
25
Figure 4 13CNMR of sulfonic acid functionalized pyrazolium salt {[Hꢀ
Pyrazine–SO3H]Cl2}.
XRD patterns of the catalyst {[HꢀPyrazine–SO3H]Cl2} was
investigated in a domain of 10ꢀ90 degree (Figure 5). As shown at
30 Figure 5, patterns exhibited diffraction lines of a highly
crystalline structure at 2θ ≈ 14.48◦, 16.97◦, 18.50◦, 18.80◦, 19.09◦,
22.38◦, 25.08◦, 26.03◦, 27.86◦, 28.45◦, and several small lines in
the 30ꢀ60º range. Peak width (FWHM), size and interꢀplanar
distance studies of the catalyst could be worked out in the 14.5 to
35 33. 3 degree and results have been summarized in Table 1. As
example, calculations for the highest diffraction line 26.03◦
proved that an FWHM of 0.126, a crystallite size of ca. 120 nmꢀ
calculated via the Scherrer equation [D =Kλ/(βcosθ)] and an
interꢀplanar distance of 0.343 nm (calculated using the Bragg
40 equation:
dhkl = λ/(2sinθ), (λ : Cu radiation (0.154178 nm) were
obtained. Most importantly, crystallite sizes as obtained from the
various diffraction lines using the Scherrer equation were found
to be in the nanometer range (50ꢀ160 nm), a most relevant finding
for the synthesized organosalt.
15 Figure 3 a) 1HNMR of pyrazinium chloride {[HꢀPyrazine–H]Cl2}; b)
1HNMR of sulfonic acid functionalized pyrazinium salt {[HꢀPyrazine–
SO3H]Cl2}.
45
Results were also in good agreement with mass spectra of [Hꢀ
Pyrazine–SO3H]Cl2, which indicated a parent peak of 233 m/z,
20 the expected mass of the catalyst (supporting information).
Another evidence of the structure of catalyst was obtained from
13CNMR spectra. Two peaks present at 144.26 and 150.75
Figure 5 XRD pattern of the nanostructured organosalt
.
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c)
b)
a)
Figure 6 a) Transmission electron micrographs (TEM) of the catalyst particles; b) Histogram of size distribution of 307 catalyst particles taken from (a);
c) Electron diffraction (ED) patterns of the catalyst
Table 1 XRD data for the catalyst {[HꢀPyrazine–SO3H]Cl2}.
Peak width
[FWHM]
Size
Inter planer
Entry
2θ
[nm]
distance [nm]
1
2
3
4
5
6
7
8
9
14.50
16.99
18.79
19.10
22.41
25.10
26.01
28.30
33.30
0.212
0.163
0.258
0.198
0.146
0.108
0.126
0.184
0.152
54
77
0.610853
0.521848
0.472243
0.464649
0.396712
0.354771
0.342563
0.315343
0.269048
43
60
93
157
119
69
93
Figure 7 TG/DTG of the [HꢀPyrazine–SO3H] Cl2.
To further confirm the nanostructure of the synthesized
organosalt, TEM measurements were performed as depicted in
Figure 6a.
TEM micrograph (Figure 6a) confirmed the presence of more
or less spherical nanoparticles with a mean diameter of 51 nm
(figure 6b, from the analysis of 307 particles via image
5
30
Upon detailed characterization and stability studies, [Hꢀ
Pyrazine–SO3H]Cl2 was subsequently investigated as catalyst for
organic transformations.
The synthesis of polysubstituted imidazoles was selected as
test reaction for the organocatalyst. Preliminary experiments were
10 processing program of Figure 6a). TEM imaging was
complemented by electron diffraction (ED) patterns (Figure 6c)
to check the materials crystalline nature. The most prominent ED
rings corresponded to real spacings at 0.5219 nm, in good
agreement with XRD results (Table 1, entry 2. Additional
15 prominent diffraction rings could be observed at 0.438 nm (no
analogous value in XRD), 0.397 nm (Table 1, entry 5) and 0.317
nm (Table 1, entry 8). ED results further confirmed the nanoscale
nature of the synthesized organosalt.
The stability of the catalyst was further investigated by thermal
20 gravimetric (TG) and differential thermal gravimetric (DTG)
analysis. TG and DTG plots from Figure 7 indicate that weight
losses of [HꢀPyrazine–SO3H]Cl2 occurred in a single step after
280ºC, so that [HꢀPyrazine–SO3H]Cl2 is in principle stable up to
35 aimed to screen and optimize reaction conditions for the model
reaction of benzil (1 mmol), 4ꢀchlorobenzaldehyde (1 mmol),
benzylamine (1 mmol) and ammonium acetate (1 mmol) under
mild temperature (80–95 °C). Results summarized in Figure 8
pointed out that optimum results were obtained using catalytic
40 amounts (1 mol %) [HꢀPyrazine–SO3H]Cl2 at 90 ºC. In principle,
this reaction could be then considered as solventless. The use of
[HꢀPyrazineꢀH]Cl2 as well as H2SO4 as alternative catalysts in the
reaction provided comparably lower yields to the target product
under investigated reaction conditions (Figure 8).
45
Upon optimization of reaction conditions, the scope and
efficiency of the process was subsequently explored for a range
of structurally diversed aromatic aldehydes as well as amines
(aliphatic or aromatic). Gratifyingly, the proposed reaction
catalysed by the nanostructured organosalt was amenable to
280ºC. The TG pattern coincides with
a single stage
25 decomposition of the organosalt in which no additional
intermediate was identified.
50 several susbtrates under very mild reaction conditions and short
times of reaction (typically 90ºC, Table 2).
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Figure 8 Effect of different amounts of the catalyst loading and temperature on the reaction of benzil, 4ꢀchlorobenzaldehyde,
benzylamine and ammonium acetate.
Table 2 The synthesis of 1,2,4,5ꢀtetrasubstituted imidazoles using [HꢀPyrazine–SO3H]Cl2 (1 mol %) under solventꢀfree conditions at
90°C.a
Yield b (%)
Entry
Ar
R
Time (min)
M.P. (°C)Found/(reported)Ref.
C6H5
C6H5
C6H5
10
15
86
87
219ꢀ220/ (218ꢀ219)20
155ꢀ158/(158ꢀ160)20
1a
1b
C6H5CH2
4ꢀCH3ꢀC6H4
4ꢀCH3ꢀC6H4
4ꢀClꢀC6H4
C6H5
25
15
10
25
15
10
10
15
25
10
20
15
15
15
15
25
15
80
90
85
80
90
95
90
80
80
85
85
85
92
95
85
85
87
189ꢀ191/(189ꢀ190)20
164ꢀ167/(165ꢀ166)20
188ꢀ189/(189ꢀ191)18
146ꢀ149/(149ꢀ151)18
216ꢀ219/(215ꢀ217)18
157ꢀ159/(161ꢀ163)18
195ꢀ199/(198ꢀ201)18
190ꢀ193/(194ꢀ196)18
131ꢀ132/(128ꢀ130)23
147ꢀ150/(148ꢀ150)31
133ꢀ136/(134ꢀ135)23
155ꢀ167/(157ꢀ160)22
279ꢀ282/(280ꢀ281)25
197ꢀ199/(198ꢀ201)18
231ꢀ233/(230ꢀ232)27
198ꢀ201/(199ꢀ202)18
199ꢀ202/(198ꢀ201)18
1c
1d
1e
1f
C6H5CH2
4ꢀClꢀC6H4
4ꢀCH3ꢀC6H4
4ꢀCH3ꢀC6H4
C6H5CH2
4ꢀFꢀC6H4
4ꢀCH3ꢀC6H4
C6H5CH2
C6H5
3ꢀNO2ꢀC6H4
4ꢀNO2ꢀC6H4
4ꢀClꢀC6H4
1g
1h
1i
4ꢀClꢀC6H4
4ꢀCH3ꢀC6H4
3ꢀOCH3ꢀC6H4
4ꢀClꢀC6H4
1j
1k
1l
4ꢀOHꢀC6H4
4ꢀOCH3ꢀC6H4
4ꢀOHꢀC6H4
4ꢀCNꢀC6H4
3ꢀOHꢀC6H4
2ꢀThienyl
C6H5CH2
C6H5CH2
C6H5
1m
1n
1o
1p
1q
1r
1s
4ꢀCH3ꢀC6H4
4ꢀCH3ꢀC6H4
4ꢀCH3ꢀC6H4
4ꢀOHꢀC6H4
2ꢀThienyl
a
1HNMR and 13CNMR of products insert in supporting information.
b Yield of purified product.
5
A number of substituted imidazole products could be obtained
accept nucleophiles. In particular, we believe that the differences
in good to excellent yields in the absence of byproducts under the 15 in acidity of the SO3H hydrogen from [HꢀPyrazine–SO3H]Cl2 as
investigated conditions.
compared to those of [HꢀPyrazine–H]Cl2 and H2SO4 may
account for the observed improved catalytic activity in Figure 8.
A partial contribution of the nanocrystallinity of the organosalt
cannot be either ruled out but this (if any) would be in principle
The proposed catalytic routes have been depicted in Scheme 4,
10 which are consistent with literature reports.14,
The
19, 32
nanoꢀorganosalt [HꢀPyrazine–SO3H]Cl2 has two acidic hydrogens
can participate in hydrogen bonding. Consequently, both 20 expected to be not very significant. Also, the formation of several
aldehydes and benzil were activated by [HꢀPyrazine–SO3H]Cl2 to
hydrogenꢀbonds between substrates and catalyst could facilitate a
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more efficient catalysis in the reaction. High reaction rates could
also be influenced by the organosalt nanostructure, which will be
investigated in due course.
ammonium acetate under mild reaction conditions to give 1,2,4,5ꢀ
Tetrasubstituted Imidazoles. Excelling features of the proposed
35 methodology include high efficiency, versatility, short times of
reaction, high yields to products, cleaner reaction profiles and
simplicity, making it an attractive alternative for the clean
synthesis of substituted imidazoles as biologically and
pharmaceutically relevant materials.
40 Experimental Section
Materials: All chemicals were purchased from Merck or Fluka
Chemical Companies. Known products were identified by
comparison of their melting points and spectral data with those in
1
the authentic samples. H NMR (500 MHz) and 13C NMR (125
45 MHz) were run on a Bruker Avance DPXꢀ250 FTꢀNMR
spectrometer (δ in ppm). Melting points were recorded on a
Büchi Bꢀ545 apparatus in open capillary tubes. The crystal
structure of synthesized materials was determined by an Xꢀray
diffractometer (Italstructure ADP2000 XRD) at ambient
50 temperature. Mass spectra were recorded on a Shimadzu GC MSꢀ
QP 1000 EX 85 apparatus. Thermal gravimetry (TG) and
differential thermal 88 gravimetric (DTG) were recorded on a
Perkin Elmer Model: 89 Pyris 1. Transmission electron
microscopy imaging was carried out using a Tecnai F20 (FEI
55 company, Oregon, USA) with field emission illumination
operated at an acceleration voltage of 160kV.
5
Scheme 4 Proposed reaction mechanism for the synthesis of
1,2,4,5ꢀtetrasubstituted imidazoles using [HꢀPyrazine–SO3H]Cl2
Procedure for the preparation of sulfonic acid functionalized
pyrazinium salt {[HꢀPyrazine–SO3H]Cl2} (Scheme 3):
Chlorosulfonic acid (1.177 g, 10.2 mmol) was added dropwise to
60 a roundꢀbottomed flask (50 mL) containing pyrazine (0.400 g,
5 mmol) in CH2Cl2 (20 mL) over a period of 30 min at room
temperature. Upon complete addition, the reaction mixture was
stirred and heated under reflux conditions for 12 h. Upon cooling
down very slowly to room temperature, CH2Cl2 was decanted.
65 The solid residue was then washed with dry CH2Cl2 (3 × 20 mL)
and dried under vacuum to give [HꢀPyrazine–SO3H]Cl2 as a gray
solid powder in 98% yield, 1.14 g.
The recovery and reuse of the catalyst was also examined for
10 the reactions of benzil, 4ꢀchlorobenzaldehyde, benzylamine and
ammonium acetate by means of a hot filtration test.33 The reaction
mixture was filtered off half way through reaction, extracted
using hot absolute ethanol or ethyl acetate and separated out from
the catalyst. The reused catalyst upon filtration was subsequently
15 employed in another reaction run with fresh reagents while the
filtrate of the reaction mixture was left reacting for several hours.
The catalytic activity of the nanoꢀorganocatalyst was found to be
almost preserved after five successive runs, with a slight decrease
in rate constant (by a factor of two, assuming a first order
20 kinetics). Nevertheless, products were obtained in excellent yield
after five uses in a short time of reaction (typically 10ꢀ15 mins,
Table 3). The analogous reaction from the filtrate did not react
further under similar reaction conditions even after 1 h reaction.
Procedure for the synthesis of 1,2,4,5ꢀtetrasubstituted
imidazoles using [HꢀPyrazine–SO3H]Cl2 as catalyst (1aꢀs): A
70 mixture of benzil (1 mmol), aldehyde (1 mmol), primary amine (1
mmol), ammonium acetate (1 mmol, as precursor for the inꢀsitu
generation of ammonia) and [HꢀPyrazine–SO3H]Cl2 (1 mol %) in
a 10 mL roundꢀbottomed flask connected to a reflux condenser
was stirred in an oilꢀbath at 90 °C. After reaction completion, as
75 monitored by TLC, the mixture was cooled to room temperature.
Crude products were soluble in warm ethanol or warm ethyl
acetate and separated off from the catalyst, which was then
filtered off. The remaining solid was washed with ethyl acetate (5
mL) and dried under reduced pressure ([HꢀPyrazine–SO3H]Cl2
80 was recovered in 95% yield). Then, the pure product was
obtained by the recrystallization of the reaction mixture in
ethanol or ethyl acetate.
25 Table 3 Reuses of [HꢀPyrazine–SO3H]Cl2 in the reaction between benzil,
4ꢀchlorobenzaldehyde, benzylamine and ammonium acetate at 90 ºC.
Run
1
2
3
4
5
Time [min]
Yield [%] [a]
a Isolated yield
10
95
10
93
12
93
13
91
15
90
Conclusions
A novel nanostructured sulfonic acid functionalized pyrazinium
salt {[HꢀPyrazine–SO3H]Cl2} was synthesized, characterized and
Characterization methods
30 tested as
a
reusable nanoꢀorganosalt in the oneꢀpot
Due to the radiation sensitivity of the organic material, the
85 diffraction spacings quickly faded upon irradiation. Lowꢀdose
fourꢀcomponent reaction of aldehydes (heteroꢀaromatic and
aromatic aldehydes), amines (aliphatic or aromatic), benzil and
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‡ Footnotes should appear here. These might include comments relevant
to but not central to the matter under discussion, limited experimental and
60 spectral data, and crystallographic data.
techniques implemented in the microscopes’ software were
therefore used in order to allow for imaging of the diffraction
data.
Thermal gravimetric analysis (TGA) of the sulfonic acid
functionalized pyrazinium salt was also studied at a range of 25
up to 800 ºC, with a temperature increase rate of 10 ºC minꢀ1 in a
nitrogen atmosphere (Figure 8).
Samples for TEM were generally prepared by ultrasonication
of 10 mg solid in hexane for 30 minutes, which gave a turbid
10 suspension in all cases. The solid was treated beforehand in an
achate mortar for milling larger particles. Droplets of the
suspension were applied to carbon foil covered microscopical 400
mesh copper grids (BALꢀTEC GmbH, Witten, Germany) and
dried in air. No additional staining materials were used. The grids
1
2
Y. YuꢀDong, Lu. Xu, T. Etsuko, S. Norio, J. Fluorine Chem. 2012,
143, 204ꢀ209.
5
a) P. C. B. Page, M. M. Farah, B. R. Buckley, A. J. Blacker, J. Org.
Chem, 2007, 72, 4424ꢀ4430; b) J. MarcoꢀMartínez, V. Marcos, S.
Reboredo, S. Filippone, N. Martín, Angew. Chem., Int. Ed, 2013, 52,
5115ꢀ5119; c) R. GramageꢀDoria, J.N.H. Reek, ChemCatChem,
2013, 5, 677ꢀ679; d) C. Gomez, J.ꢀF. Betzer, A. Voituriez, A.
Marinetti, ChemCatChem, 2013, 5, 1055ꢀ1065; e) C.ꢀC. Hsiao, H.ꢀH.
Liao, E. Sugiono, I. Atodiresei, M. Rueping, Chem. Eur. J, 2013,
DOI: 10.1002/chem.201300766; f) J. Alemán, S. Cabrera, Chem.
Soc. Rev, 2013, 42, 774ꢀ793; g) Z. Du, Z. Shao, Chem. Soc. Rev,
2013, 42, 1337ꢀ1378; h) Q. Dai, H. Arman, J.C.ꢀG. Zhao, Chem. Eur.
J, 2013, 19, 1666ꢀ1671; i) B. Bradshaw, C. LuqueꢀCorredera, J.
Bonjoch, Org. Lett, 2013, 15, 326ꢀ329; j) E. Mayans, A. Gargallo,
Á. ÁlvarezꢀLarena, O. Illa, R.M. Ortuño, Eur. J. Org. Chem, 2013,
1425ꢀ1433; k) Y. Sohtome, T. Yamaguchi, S. Tanaka, K. Nagasawa,
Org. Biomol. Chem, 2013, 11, 2780ꢀ2786;
65
70
75
15 were consecutively transferred into
a Tecnai F20 FEG
transmission electron microscope (FEI company, Oregon, USA)
operated at 160kV acceleration voltage. Images were taken at
various magnifications ranging from 2k up to 19k. Data were
recorded by the use of an Eagle 2k CCD camera (FEI company)
20 at full resolution (binning 1). The application of the microscopes
low dose routine was necessary for image and diffraction pattern
recordings as the crystal ultrastructure turned out to suffer from
radiation damage. Diffraction pattern were recorded at a camera
length of 520 mm. Calibration was done using a Thallium
25 chloride standard (Plano GmbH, Wetzlar, Germany).
3
4
5
V. Polshettiwar, R. S. Varma, Green Chem. 2010, 12, 743ꢀ754.
J. P. Hallett, T. Welton, Chem. Rev. 2011, 111, 3508ꢀ3576.
80
M. A. Zolfigol, A. Khazaei, A. R. MoosaviꢀZare, A. Zare, Org. Prep.
Proced. Int. 2010, 42, 95ꢀ102.
6
7
8
M. A. Zolfigol, A. Khazaei, A. R. MoosaviꢀZare, A. Zare, J. Iran.
Chem. Soc. 2010, 7, 646ꢀ651.
85
A. Khazaei, M. A.Zolfigol, A. R. MoosaviꢀZare, A. Zare, Scientia
Iranica: Trans. C: Chem. Chem. Engin. 2010, 17, 31ꢀ36.
Acknowledgments
M. A. Zolfigol, A. Khazaei, A. R. MoosaviꢀZare, A. Zare, H. G.
Kruger, Z. Asgari, V. Khakyzadeh, M. KazemꢀRostami, J. Org.
Chem. 2012, 77, 3640ꢀ3645.
The authors gratefully acknowledge partial support of this work
by the Research Affairs Office of BuꢀAli Sina University (Grant
number 32ꢀ1716 entitled development of chemical methods,
30 reagents and molecules), and Center of Excellence in
Development of Chemical Method (CEDCM), Hamedan, I.R.
Iran. Rafael Luque gratefully acknowledges MICINN for the
concession of a Ramon y Cajal Contract (ref. RYCꢀ2009ꢀ04199)
and funding from projects CTQ2011ꢀ28954ꢀC02ꢀ02 (MEC) and
35 P10ꢀFQMꢀ6711 (Consejeria de Ciencia e Innovacion, Junta de
Andalucia).
90
9
M. A. Zolfigol, A. Khazaei, A. R. MoosaviꢀZare, A. Zare, V.
Khakyzadeh, Appl. Catal AꢀGen., 2011, 400, 70ꢀ81.
10 M. A. Zolfigol, V. Khakyzadeh, A. R. MoosaviꢀZare, A. Zare, S. B.
Azimi, Z. Asgari, A. Hasaninejad, C. R. Chim. 2012, 15, 719ꢀ736.
11 A. Zare, T. Yousofia, A. R. MoosaviꢀZare, RSC. Adv. 2012, 2, 7988ꢀ
95
7991.
12 A. Khazaei, M. A. Zolfigol, A. R. MoosaviꢀZare, Z. Asgari, M.
Shekouhy, A. Zare, A. Hasaninejad, RSC. Adv. 2012, 2, 8010ꢀ8013.
13 M. A. Zolfigol, V. Khakyzadeh, A. R. MoosaviꢀZare, G. Chehardoli,
F. DerakhshanꢀPanah, A. Zare, O. Khaledian Scientia Iranica: Trans.
C: Chem. Chem. Engin. 2012, 19, 1584ꢀ1590.
100
Notes and references
14 A. Zare, F. Abi, A. R. MoosaviꢀZare, M. H. Beyzavi, M. A. Zolfigol
a
Department of Chemistry, University of Sayyed Jamaleddin Asadabadi,
J. Mol. Liq. 2013, 178, 113–121.
Asadabad, 6541835583, Iran, Fax: +988123237450, Eꢀmail:
15 S. A. Laufer, W. Zimmermann, K. J. Ruff, J. Med. Chem. 2004, 47,
40 moosavizare@yahoo.com.
b
6311ꢀ6325.
Faculty of Chemistry, BuꢀAli Sina University, Hamedan, 6517838683,
Iran, Eꢀmail: mzolfigol@yahoo.com, mr.khakyzadeh@yahoo.com.
Research Center of Electron Microscopy, Institute for Chemistry and
Biochemistry, Freie Universität Berlin, Fabeckstraße 36a, 14195 Berlin,
105 16 C. Leister, Y. Wang, Z. Zhao, C. W. Lindsley, Org. Lett. 2004, 6,
c
1453ꢀ1456.
45 Germany.
17 P. Wasserscheid, T. Welton, Ionic Liquids in Synthesis, WileyꢀVCH,
Weinheim, 2008.
d
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3,
14195 Berlin, Germany.
e
18 L. H. Lee, M. Bang, C. S. Pak, Tetrahedron Lett. 2005, 46, 7139ꢀ
Department of Chemistry,Payame Noor University, 19395ꢀ4697 Tehran,
110
7142.
Iran.
f
50 Department of Chemistry, Faculty of Sciences, Persian Gulf University,
19 A. Hasaninejad, A. Zare, M. Shekouhi, J. Ameri Rad, J. Comb.
Chem. 2010, 12, 844.
Bushehr 75169, Iran.
g
Departamento de Quimica Organica, Universidad de Córdoba, Edif.
Marie Curie, Ctra Nnal IVꢀA, Km 396, E14014, Córdoba (Spain). Eꢀmail:
q62alsor@uco.es.
55 † Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/b000000x/
20 M. M. Heravi, F. Derikvand, F. F. Bamoharram, J. Mol. Catal. Aꢀ
Chem. 2007, 263, 112ꢀ114.
115 21 S. Balalaie, A. Arabanian, Green Chem. 2000, 2, 274ꢀ276.
22 A. Y. Usyatinsky, Y. L. Khmelnitsky, Tetrahedron Lett. 2000, 41,
5031ꢀ5034.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 7

Journal of Materials Chemistry A
Page 8 of 8
View Article Online
DOI: 10.1039/C3TA13484A
23 S. Kantevari, S. V. N. Vuppalapati, D. O. Biradar, L. Nagarapu, J.
Mol. Catal. AꢀChem. 2007, 266 109ꢀ113.
24 M. Kidwai, P. Mothsra, V. Bansal, R. K. Somvanshi, A. S.
Ethayathulla, S. Dey, T. P. Singh, J. Mol. Catal. AꢀChem. 2007, 265,
177ꢀ179.
5
25 B. Sadeghi, B. B. F. Mirjalili, M. M. Hashemi, Tetrahedron Lett.
2008, 49, 2575ꢀ2577.
26 S. D. Sharma, P. Hazarika, D. Konwar, Tetrahedron Lett. 2008, 49,
2216ꢀ2220.
10 27 L. Nagarapu, S. Apuri, S. Kantevari, J. Mol. Catal. AꢀChem. 2007,
266, 104ꢀ108.
28 B. H. Lipshutz, M. C. Morey, J. Org. Chem. 1983, 48, 3745ꢀ3750.
29 M. R. Mohammadizadeh, A. Hasaninejad, M. Bahramzadeh, Synth.
Commun. 2009, 39, 3232ꢀ3242.
15 30 H. Huang, X. Ji, W. Wu, H. Jiang, Adv. Synth. Catal, 2013, 355, 170ꢀ
180; b) Z. Jiang, P. Lu, Y. Wang, Org. Lett, 2012, 14, 6266ꢀ6269; c)
B. Hu, Z. Wang, N. Ai, J. Zheng, X.ꢀH. Liu, S. Shan, Z. Wang, Org.
Lett, 2011, 13, 6362ꢀ6365; d) Y.ꢀB. Nie, L. Wang, M.ꢀW. Ding, J.
Org. Chem, 2012, 77, 696ꢀ700; e) D. Kumar, D.N. Kommi, N.
20
25
30
Bollineni, A.R. Patel, A.K. Chakraborti, Green Chem, 2012, 14,
2038ꢀ2049; f) C. Kison, T. Opatz, Chem. Eur. J, 2009, 15, 843ꢀ845;
g) W. Li, Y. Lam, J. Comb. Chem, 2005, 7, 644ꢀ647; h) A.R. Karimi,
Z. Alimohammadi, J. Azizian, A.A. Mohammadi, M.R.
Mohammadizadeh, Catal. Commun, 2006, 7, 728ꢀ732; i) K. Niknam,
A. Deris, F. Naeimi, F. Majleci, Tetrahedron. Lett, 2011, 52, 4642ꢀ
4645; j) S. Samai, G.C. Nandi, P. Singh, M.S. Singh, Tetrahedron,
2009, 65, 10155ꢀ10161; k) S. Ray, P. Das, A. Bhaumik, A. Dutta, C.
Appl. Catal. AꢀGen, 2013, 458, 183ꢀ195; l) L. Wang, X. Zhong, M.
Zhou, W.ꢀY. Zhou, Q. Chen, M.ꢀY. He, J. Chem. Res, 2013, 37, 236ꢀ
238; m) V. Kannan, K. Sreekumar, J. Mol. Catal. AꢀChem, 2013,
376, 34ꢀ39; n) S. Laufer, D. Hauser, T. Stegmiller, C. Bracht, K.
Ruff, V. Schattel, W. Albrecht, P. Koch, Bioorg. Med. Chem. Lett,
2010, 20, 6671ꢀ6675; p) M.M. Heravi, F. Derikvand, F.F.
Bamoharram, J. Mol. Catal. AꢀChem, 2007, 263, 112ꢀ114.
35 31 K. M. Harmon, S. Pillar, J. Mol. Struct. 2005, 740, 75ꢀ80.
32 X. B. Wang, L. He, T. Y. Jian, S. Ye, Chin. Chem. Lett. 2012, 23,
13ꢀ16.
33 I.W.C.E. Arends, R.A. Sheldon, Appl. Catal. A 2001, 212, 175ꢀ187.
8
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