The preparation and characterization of flower-like boehmite nanoparticles-SA: A new and reusable nanocatalyst for the synthesis of 2-aryl-1H-benzimidazoles

Article abstract of DOI:10.1080/15533174.2016.1186097

The efficient synthesis of 2-arylbenzimidazole derivatives is described by condensation of aldehydes and o-phenylenediamines in a single pot using AlOOH-SO3 nanoparticles (BNPs’SA) as a catalytic in excellent isolated yields. The variables investigated su

Full text of DOI:10.1080/15533174.2016.1186097

Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry
ISSN: 1553-3174 (Print) 1553-3182 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt20
The preparation and characterization of flower-
like boehmite nanoparticles-SA: as new and
reusable nanocatalyst for the synthesis of 2-
aryl-1H-benzimidazoles
Changiz Karami, Mozaffar Abdollahifar, Farahnaz Jahani, Azita Farrokhi &
Mohammad Ali Taher
To cite this article: Changiz Karami, Mozaffar Abdollahifar, Farahnaz Jahani, Azita Farrokhi
&
Mohammad Ali Taher (2016): The preparation and characterization of flower-like
boehmite nanoparticles-SA: as new and reusable nanocatalyst for the synthesis of 2-aryl-1H-
benzimidazoles, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal
Chemistry, DOI: 10.1080/15533174.2016.1186097
To link to this article: http://dx.doi.org/10.1080/15533174.2016.1186097
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The preparation and characterization of flower-like boehmite nanoparticles-SA: as new and
reusable nanocatalyst for the synthesis of 2-aryl-1H-benzimidazoles
*
,a
*,a
a
a
Changiz Karami , Mozaffar Abdollahifar , Farahnaz Jahani , Azita Farrokhi . and Mohammad
b
Ali Taher
a
Department of Chemistry, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
b
Department of Chemistry, Faculty of Science, Shahid Bahonar University of Kerman, kerman,
Iran.
*
Coresponding author. E-mail: Changiz.Karami@gmail.com (C. Karami)
Abstract
The efficient synthesis of 2-arylbenzimidazole derivatives is described by condensation of
aldehydes and o-phenylenediamines in a single pot using AlOOH-SO3 nanoparticles (BNPs'SA)
as a catalytic in excellent isolated yields. The variables investigated such as the amount of
catalyst, reaction temperature and the effect of various solvents are also studied, and
Structural properties of BNPs'SA is characterized by powder X-ray diffraction, FESEM, TEM, and
FT-IR spectroscopy. The average of crystalline size of AlOOH-SO3 nanoparticles 30-50 nm. The
present procedure offers several advantages such as short reaction time, simple workup,
recovery and reusability of the catalyst.
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Keywords
Nano boehmite, Sulfonic acid, Nano catalyst, Green chemistry, Benzimidazoles, Mild conditions
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Introduction
In recent years, the synthesis of nanoscale materials with special morphologies has been
shown to be of great significance in material science [1]. The intrinsic properties of nanoscale
materials are mainly determined by their composition, structure, crystallinity, size and
morphology [2]. In particular, nanoscale materials including nanowires and nanotubes have
attracted intensive interest due to their distinctive geometries, novel physical and chemical
properties, and potential applications in many areas [3,4].
In addition to, boehmite on of the nanofibre martials was first synthesized by John Bugosh in
1961 [5] and several methods such as sol--gel, hydrothermal, precipitation, and spray have
been used to synthesize of this nanofibre [6-9]. Furthermore, alumina can be employed as
catalyst [10], adsorbent [11] and composite materials [12].
However, the functionalization of solid state has been a significant evolution in the
heterogeneous catalysis, and these materials have developed for various special applications
like catalysis[13]. The sulfonic acid group functionalized is an important subgroup in the
heterogeneous catalysis class, and have been used in numerous types of reactions including,
bisphenol synthesis [14,15], esterification and selective acylation reactions [16], hydrolysis of
cellulose [17], and postsynthetic oxidation [18] esterification and transesterification [19].
Benzimidazole is a kind of substances that is found practical applications in organic synthesis
[20], and the benzimidazole nucleus are found in a variety of pharmaceuticals as, potential
antitumor [21], Histamine H4 receptor binders [22], anti-parasitic [23], cardiovascular [24],
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antimicrobials and anti -hypertensives [25]. Due to the high importance of 2-aryl-1H-
benzimidazoles for the preparation of biologically active molecules, their synthesis has been
received considerable attention.
Direct condensation of o-aryldiamines and aldehydes is not a good synthetic reaction, as
it is well known to yield a complex mixture. In this case, Iron(II) bromide-catalyzed [26], β-
cyclodextrin [27] allow a partial selective synthesis of benzimidazoles. In recent years,
solvent-free synthesis of benzimidazoles under microwave irradiation using Yb(OTf) [28],
3
lithium bromide catalyzed [29], Iridium-Catalyzed [30], PPA [31], copper-catalyzed [32], ionic
liquid under microwave irradiation [33] have been reported. In spite of, many methods
available for the synthesis of these compounds, there is still a scope to develop simpler,
recyclable and cost effective processes for this reaction.
Ordered boehmite materials (20--50 nm) are getting tremendous attention because of
their outstanding advantages such as large surface area, narrow pore size distributions within
the mesoporous range, as well as suitable surface acidic--basic properties can often result in
favorable enhancements in the catalytic performances [34]. Therefore, the aim of this paper is
focused mainly on the preparation, characterization by XRD, FESEM, TEM, and FT-IR., and
investigation of catalytic activity of sulfonic acid supported on boehmite nanoparticles
(BNPs'SA) for the preparation of 2-aryl-1H-benzimidazoles one derivatives (Scheme 1).
To the best of our knowledge, there are no reports on the use of nano boehmite flower-like
supported with sulfonic acid as a catalyst for this conversion
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Experimental
All the chemical materials used in the experiments were used without further purification. In a
typical procedure, Al(NO
grade) H . The sample powder was analyzed by X-ray diffraction (XRD). This instrument
Philips, xpertpro, nitherland) works with voltage and current settings of 40 kV and 30 mA,
3
)
3
·9H
2
O(Scharlau, Spain, extra pure), urea, (Scharlau, Spain, synthesis
2
O
2
(
respectively and uses Cu--Kαradiation (1.540510 Å). For the qualitative analysis, X-Ray powder
diffraction (XRD) analysis was conducted on a Bruker, model B8 Advance X-ray diffractometer
with CuKα radiation. TEM images of the samples were taken using a PHILIPS model CM30
transmission electron microscope operated at an accelerating voltage of 250 kV. FESEM images
were obtained using a HITACHI S-4160 field emission scanning electron microscope. The FT-IR
spectra of the samples (as KBr pellets) were recorded using a Rayleigh WQF-510
−1
spectrophotometer in the range of 400--4000 cm . Melting points were determined using
1
Barnstead -Electrothermal 9300 Melting Point. HNMR spectra were recorded on Bruker 200
MHz NMR spectrometer.
Preparation of flower-like nano boehmite
In a typical procedure, 18.75 g of Al(NO
3
)
3
·9H O (A) and 6 g of urea (B) were dissolved in 100 mL
2
and 30 mL of distilled water, respectively, at room temperature in beakers and magnetically
stirred to obtain homogeneous solutions. Then solution B was added to solution A and stirred
at room temperature for 15 min before the mixed solution was transferred into a 200 mL
Teflon-lined stainless autoclave and heated at 200°C for 24h under autogenous pressure. After
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reaching room temperature, the white resultant colloidal product was centrifuged and washed
three times with deionized water, and then the product was dried at 60°C for 24 h.
Preparation of the sulfonic acid supported on boehmite nanoparticles (BNPs'SA)
The BNPs'SA were prepared by using the published method [35], nano boehmite modifies
sulfonic acid prepared by reacting nano boehmite with neat chlorosulfonic acid at room
temperature. A 50 mL suction flask equipped with a constant-pressure dropping funnel and a
gas inlet tube for conducting of HCl gas over an adsorbing solution (i.e. water) were used. It was
charged with nano boehmite (1 g). chlorosulfonic acid (0.04 g) was added drop wise over a
period of 30 min at room temperature. HCl gas immediately evolved from the reaction vessel.
After the addition was completed, the mixture was shaken for 30 min. A white solid of nano
boehmite sulfuric acid was obtained.
General procedure for the preparation of benzimidazoles
To a mixture of aldehyde (1.0 mmol),,2-phenylenediamine (1 mmol), and H
2
2
O (30%, 0.1 mL),
was added BNPs'SA (0.015 g) and heated at 80 ºC for an appropriate time (Table 1). The
reaction was monitored by TLC. After the progress of reaction was completed and monitored by
TLC, the reaction mixture was dissolved in EtOH (10 mL) then poured into ice water (30 mL).
The reaction mixture was filtered to remove the catalyst and the filtrate was poured into cold
water. The solid was suction filtered, washed with cold water (20 mL × 2) to afford pure
product.
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2
-(4-Chlorophenyl)-1H-benzimidazole (Table 2, entry 1): mp 290-293°C; 1H-NMR (200 MHz,
DMSO-d6,): δ = 7.10 (m, 2H), 7.30 (m, 2H), 7.6 (d, 2H, J = 8.4 Hz), 8.20 (d, 2H), 12.5 (s, 1H, NH):
3 C-NMR (50 MHz, DMSO-d6): δ = 115.4, 123.2, 128.6, 128.9, 129.4, 134.3, 138.9, 152.9.
1
Results and discussion
In this research, we developed novel, green, rapid, and one-pot method for synthesis of
benzimidazoles derivatives catalyzed by BNPs'SA as heterogeneous nanocatalyst. Nano AlOOH
was modified by covalently bonded sulfonic acid on the surface of it to provide the BNPs'SA
with Brønsted acid properties. This white nano powder was prepared from reaction of
chlorosulfonic acid with nano boehmite that its was named nano BNPs'SA, and the preparation
of this catalyst is safe, easy to handle, clean, and no special work up procedure,. The XRD
pattern of AlOOH is shown in Fig. 1. X-ray powder diffraction indicated that samples were
single-phase AlOOH, in accordance with the literature. All the sharp and strong reflection peaks
of samples are readily indexed as orthorhombic boehmite (AlOOH, JCPDS card No. 00-021-
1307, a = 3.700, b = 12.227, and c = 2.868 Å at 25°C.). No evidence could be found for the
existence of impurities in the synthesized AlOOH. The crystallite sizes calculated from the
FWHM of the (020) diffractions for AlOOH the Scherrer equation was found to be 12 nm.
Typical FT-IR spectra of the corresponding samples are shown in (Fig. 2 a) for boehmite and b
1
for boehmite sulfuric. (Fig. 2a) shows that bands at 3095 and 3301 cm belong to the υas(Al)O-
1
1
H and υs(Al)O-H stretching vibrations [36]. The bands at 1065 cm and 1156 cm are assigned
to the Δ
s
Al-O-H and Δas Al-O-H modes of AlOOH, respectively [37] The three bands at 480 and
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1
1
6
31cm represent the vibration mode of AlO6 [38] and the band at 747 cm assigned to the
OH torsional mode [39], which strongly support the formation of the synthesized sample. Fig.
2b shows the FTIR spectra BNPs'SA, In comparison with the unmodified AlOOH, the
1
distinguishing features of the BNPs'SA are the presence of new absorption bands at 1350 cm
1
and 1400 cm in the spectra, which are assigned to the typical symmetric stretching of the S =
O bond [40].
Field emission scanning electron microscopy (FESEM) and transmission electron microscopy
(
TEM) investigations were carried out to observe the morphology of the prepared nanocatalyst
Fig. 3 a, b). FESEM was used to obtain information on morphology and structure of products
(
that was shown the flower-like nanostructures of BNPs'SA. The TEM image in (Fig. 3b) reveals
the product consists of flower-like with an average size of 10--20 nm. In general, the FESEM
micrographs are in good agreement with the TEM observations.
To optimize the reaction condition, to illustrate the high efficiency and catalytic activity of
BNPs'SA, in the model o-phenylenediamine (1 mmol), 4-chlorobenzaldehyde (1 mmol), and
H
2
O
2
(30%, 0.1mL) under solvent-free conditions at 80°C, was used in the presence of 0.015 g
BNPs'SA in different percentage of SO H ratios. It was found that the catalytic conversion as
3
well as the yield for this reaction increased with increasing the percentage weight of
chlorosulfonic acid. However, maximum yield (98%) for synthesis of 2-(4-chlorophenyl)-1H-
benzo[d]imidazole was achieved with only (3%) of loading on the AlOOH surface to promote
the reaction. For find optimize amount of BNPs'SA, the reaction was carried out by varying
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amount of the catalyst. The less amount of catalyst gave a low yield even after a prolonged
reaction time, and the more amount of catalyst could not cause the obvious increase the yield
of product but the reaction time is shorten (Table 1 Entry 1-4). These results indicate that
different scale of acidic contents is required for this conversion. In addition to, the reaction was
investigation in absent, present of BNPs'SA, nano boehmite, and boehmite, but the low yield
and prolonged reaction time was detected in the absence of catalyst similar to nano boehmite
and boehmite (table 1, entry 5-8)
The effects of different temperatures on rate of reaction to synthesis of 2-(4-chlorophenyl)-1H-
benzo[d]imidazole were studied (Table 1, entry 9-12). At room temperature, the reaction has
long time and low yield, and the catalytic activity was increased with increase in temperature
up to 100°C. Therefore, the reaction was kept at 60°C temperature (giving short reaction time
and high yield).
Certainly, solvent plays a critical role in the reactions; therefore, in this research, we decided to
evaluate the effect of solvent and find the optimum reaction temperature, the model reaction
was performed under different reaction conditions. The results collected in (Table 1, entry 13-
19) show that 60°C and solvent-free conditions were the optimum reaction conditions for
synthesis of benzimidazoles derivatives.
The best result was obtained by carrying out the reaction with (mol):1(mol): 0.1(mL): 0.015(mg)
1, 2-phenylendiamine/aryl aldehyde/H
2
O
2
/ BNPs'SA. In the next step, various aromatic
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aldehydes containing both electron-releasing and electron-donating groups were examined
(Table 2) [41-44]. The suggested mechanism of the BNPs'SA catalyzed is shown in (Scheme 2).
In order to see the reusability of the catalysts, the reaction of o-phenylenediamine (1 mmol), 4-
chlorobenzaldehyde (1 mmol), and H (30%, 0.1 mL) in the presence of 0.015 g of catalyst at
0°C was investigated, After the completion of the reaction, the catalyst was filtered, so
2
O
2
6
washed thoroughly first with hot ethanol. The catalyst was dried at 110°C and subjected to
fresh reaction. The reaction was repeated four times without significant loss of activity or
selectivity. Thus, the average chemical yield for 5 consecutive runs was 95%, which clearly
demonstrates the practical recyclability of the BNPs'SA (Fig. 4). FT'IR spectra of BNPs'SA after
1,3 and 5 catalytic cycles are presented in Fig. 5. These spectra look quite similar and this
definitely indicates that the active component catalyst did not loss from the solid catalyst.
Conclusions
In summary, in this paper, a novel and easy method for the synthesis of BNPs'SA was reported
and morphological investigation by XRD, SEM, TEM and FT-IR. We also reported an efficient
method for the preparation of 2-aryl-1H-benzimidazoles using BNPs'SA as a recyclable solid acid
catalyst under solvent-free conditions with short reaction time and produce the corresponding
products in good to excellent yields. The novel heterogeneous nanocatalyst was efficiently
applicable to a wide variety of aromatic aldehydes bearing different types of substituents,
affording the desired products in excellent yields.
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Acknowledgments
We are thankful to the Islamic Azad University branch of Kermanshah for the partial support for
this work.
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Table 1. Optimum conditions for the preparation of 2-(4-chlorophenyl)-1H-benzo[d]imidazol
a
Entry
Solvent
Catalyst Weigh (g) Catalyst
H
2
O
2
Temp.
(°C)
Time (min)
Yield (%)
mL
Effect of catalyst weight
1
2
3
4
Solvent-free
Solvent-free
Solvent-free
Solvent-free
0.005
0.01
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
0.1
0.1
0.1
0.1
80
80
80
80
30
15
6
95
98
98
98
0.015
0.025
4
Effect of catalyst
-
5
6
7
8
Solvent-free
Solvent-free
Solvent-free
Solvent-free
0.015
0.015
0.015
0.015
-
80
80
80
80
24h
10h
5h
80
95
95
98
AlOOH
0.1
0.1
0.1
Nano AlOOH
BNPs'SA
8
Effect of temperature
9
Solvent-free
Solvent-free
Solvent-free
Solvent-free
0.015
0.015
0.015
0.015
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
0.1
25
50
60
80
60
15
8
95
95
98
98
1
1
1
0
1
2
0.1
0.1
0.1
6
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Effect of solvent
1
1
1
1
1
1
1
3
4
5
6
7
8
9
CH3CN
AcOEt
0.015
0.015
0.015
0.015
0.015
0.015
0.015
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
BNPs'SA
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Refluxed
Refluxed
Refluxed
Refluxed
Refluxed
60
30
30
30
30
30
30
30
90
90
90
90
90
98
90
CH2Cl2
MeOH
EtOH
Solvent-free
H2O
Refluxed
2 2
Effect of H O
2
2
2
0
1
2
Solvent-free
Solvent-free
Solvent-free
0.015
0.015
0.015
BNPs'SA
-
60
60
60
5h
8
95
98
98
BNPs'SA
BNPs'SA
0.1
0.2
8
a
Isolated yield
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Table 2. Synthesis of benzimidazole derivatives.
H
N
NH2
O
BNPs'SA
Ar
+
Ar C H
Solvent- Free, 60 °C
N
NH2
Time
a, b
Entry
R
Yield(% (
References
(
min)
1
2
3
4
5
6
7
8
9
4- Cl
8
95
95
95
94
96
90
95
96
80
93
95
51
52
54
51
53
51
51
56
55
51
51
4-NO
2
15
14
8
3-NO2
2-Cl
4-F
9
4- MeO
4-Me
4- OH
10
9
12
10
12
11
4- (CH ) N
3
2
1
1
0
1
2-OH
H
a
The products were characterized by comparison of their spectroscopic and physical data with
authentic samples synthesized by reported procedures.
b
Yields refer to pure isolated products.
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020
120
0
31
051
0
02
2
31
251
1
51
220
1
31
171
0
80
5
20
3
5
50
65
8
0
2Ɵ degree
Fig. 1 XRD pattern of nano boehmite
21
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a
b
4
00 04 00 350 09 00 300 10 400 250 10 900 20 02 04 00 150 20 900 10 03 04 00
50 30 900
-
1
Wavenumber (cm )
Fig. 2. FT-IR spectra of a) nano boehmite without sulfonic and, b) BNPs'SA.
22
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a
b
Fig. 3. a) FESEM and, b) TEM images of the BNPs'SA
23
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100
95
90
85
80
75
70
65
60
Fresh
1
2
3
4
5
Run
Fig.4. Recyclability of BNPs'SA for the preparation of 2-(4-chlorophenyl)-1H-benzo[d]imidazole
24
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BNPs'SA Run 1
BNPs'SA Run 3
BNPs'SA Run 5
4
00
900
3500
1400
3000
1900
2500
2400
2000
2900
1500
3400
1000
3900
500
4
000
-
1
Wavenumber (cm )
Fig.5. The comparative FT'IR spectra for BNPs'SA after 1,3 and 5 catalytic recyclability
25
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H
N
NH2
BNPs'SA
R
H
+
Solvent- Free, 60 °C
R
N
NH2
O
Scheme. 1 The condensation reaction for preparation of 2-aryl-1H-benzimidazoles
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NH2
N
NH2
R
H
+
R
NH2
O
AlOOH
AlOOH
SO3
NH2
H
N
H
H
N
H2O2
C
N
R
N
N
H
R
R
Scheme. 2 A possible pathway for synthesis of benzimidazoles derivatives
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