Catalytic Performance of Hydrophobic Sulfonated Nanocatalysts CMK-5-SO3H and SBA-15-Ph-PrSO3H for Ecofriendly Synthesis of 2-Substituted Benzimidazoles in Water

Article abstract of DOI:10.1055/s-0035-1561354

The hydrophobicity of environmentally benign organosulfonic acid-functionalized silica (SBA-15-Ph-PrSO₃H) and sulfonic acid-based nanoporous carbon (CMK-5-SO₃H) was assessed in relation to the green synthesis of 2-substituted benzimidazoles from aldehydes and benzene-1,2-diamine in open air in an aqueous medium. The results are rationalized in terms of the inclusion of the substrates inside hydrophobic cavities of the catalysts. Furthermore, the more hydrophobic and more water-resistant catalyst CMK-5-SO₃H showed superior catalytic activity. Their excellent yields, their use of water as a green solvent, and their recyclability and environmentally friendly nature makes these catalysts important alternatives to classical acid catalysts.

Full text of DOI:10.1055/s-0035-1561354

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Georg Thieme Verlag Stuttgart · New York
2016, 27, A–D
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Synlett
D. Zareyee et al.
Letter
Catalytic Performance of Hydrophobic Sulfonated Nanocatalysts
CMK-5-SO H and SBA-15-Ph-PrSO H for Ecofriendly Synthesis of
3
3
2-Substituted Benzimidazoles in Water
Daryoush Zareyee*
Sakineh Rostamian Tuyehdarvary
Leila Allahgholipour
Zinatossadat Hossaini
Mohammad A. Khalilzadeh
Department of Chemistry, Qaemshahr Branch, Islamic Azad
University, Qaemshahr, Iran
zareyeee@gmail.com
Received: 20.11.2015
Accepted after revision: 11.01.2016
Published online: 05.02.2016
es have been made in this area, some of the methods suffer
from such disadvantages as the use of hazardous organic
solvents or harsh reaction conditions, low yields, and labo-
rious workups. Therefore, the development of efficient, re-
cyclable, and environmentally benign catalysts for these
transformations with nonpolluting reagents and solvents is
desirable.
DOI: 10.1055/s-0035-1561354; Art ID: st-2015-d0900-l
Abstract The hydrophobicity of environmentally benign organosul-
fonic acid-functionalized silica (SBA-15-Ph-PrSO H) and sulfonic acid-
based nanoporous carbon (CMK-5-SO H) was assessed in relation to the
green synthesis of 2-substituted benzimidazoles from aldehydes and
benzene-1,2-diamine in open air in an aqueous medium. The results
are rationalized in terms of the inclusion of the substrates inside hydro-
phobic cavities of the catalysts. Furthermore, the more hydrophobic
3
3
Water-mediated organic synthesis9,27–33 has recently be-
come an important area for research to meet environmental
34,35
demands.
In fact, with tightened regulatory pressures
and more water-resistant catalyst CMK-5-SO H showed superior cata-
3
focusing on organic solvents, the search for alternatives is
gaining in importance. In this respect, the development of
water-tolerant catalysts has become an area of intensive re-
search. However, in many reactions catalyzed by solid sul-
fonic acids, water is co-adsorbed on the surface of the cata-
lyst, resulting in poisoning of the surface and the produc-
tion of a more hydrophilic environment, thereby reducing
the activity of the catalyst. From this viewpoint, the use of
hydrophobic solid acids in the presence of water has at-
tracted considerable attention as a means of developing en-
vironmentally benign reaction conditions and media for or-
lytic activity. Their excellent yields, their use of water as a green solvent,
and their recyclability and environmentally friendly nature makes these
catalysts important alternatives to classical acid catalysts.
Key words benzimidazoles, heterogeneous catalysis, sulfonic acids,
hydrophobicity, cyclizations
As nitrogen-containing heterocyclic compounds, ben-
zimidazole and its derivatives have received extensive at-
tention in medicinal chemistry and show a wide spectrum
1–3
of pharmacological activities. They exhibit significant ac-
4
36–45
tivity against several viruses, including HIV, herpes sim-
ganic reactions, with excellent efficiency.
5
6
7
plex virus (HSV-1), influenza, and hepatitis C. Further-
more, these compounds can act as ligands for transition
We have recently described the use of the heteroge-
4
4–48
neous sulfonic acid nanoreactors SBA-15-Ph-PrSO H
3
8
49–51
metals in modeling biological systems. Because of the im-
and CMK-5-SO H
for a range of organic transforma-
3
portance of benzimidazoles from the industrial, pharmaco-
logical and synthetic viewpoints, several strategies have
been developed for the preparation of these compounds.
Generally, the condensation of o-phenylenediamines with
carboxylic acids or their derivatives has been used to syn-
thesize benzimidazoles, but harsh dehydrating conditions
tions. Here, we disclose the use of both these hydrophobic
solid-acid catalysts in the synthesis of benzimidazoles in
water at room temperature. Because of our continued inter-
est in applying hydrophobic catalysts to organic transfor-
mations in aqueous media,4
8,51
we explored the use of SBA-
15-Ph-PrSO H and CMK-5-SO H as efficient catalysts for the
3
3
9–12
are usually required.
However, the simplest and most ef-
rapid synthesis of benzimidazoles, because of the nontoxic
nature, ease of handling, and recyclability of these catalysts
(Figure 1).52
fective method for synthesizing benzimidazole is the con-
densation/aromatization reaction of an aldehyde with an
13–26
arylenediamine.
However, although pioneering advanc-
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D. Zareyee et al.
Letter
ine the effect of the hydrophobicity of the surface phenyl
groups on the catalytic performance of the sulfonic acid
functionality, we tested SBA-15-PrSO H, a catalyst lacking
3
hydrophobic phenyl groups, in the model reaction in water.
SBA-15-PrSO H exhibited a lower reactivity (35% isolated
3
yield after 100 minutes). Therefore, the enhancement of
catalytic properties observed with SBA-15-Ph-PrSO H can
3
be attributed to its hydrophobic character. In the absence of
catalyst, the reaction did not yield any product at room
temperature, even after a prolonged reaction time (20 h),
confirming the critical role of the sulfonic acid groups.
To assess whether the aforementioned results could be
generalized to other substrates and to investigate the scope
and versatility of this protocol, we examined structurally
diverse aldehydes in the synthesis of substituted benzimid-
azoles. As shown in Table 1, benzene-1,2-diamine reacted
smoothly with several aldehydes at room temperature in
water to afford a wide range of 2-substituted benzimidaz-
ole derivatives in good to excellent yields. Aldehydes bear-
ing either electron-donating or electron-withdrawing sub-
stituents gave the corresponding benzimidazoles in good to
excellent yields (Table 1, entries 1–16). The electronic na-
ture of the substituents on the aromatic ring shows no
marked effects on the conversion. In all cases, the reaction
proceeded efficiently at room temperature in water with-
out the formation of any byproducts. During the reaction,
functionalities such as methoxy, chloro, bromo and alkyl
present in the substrates were unaffected.
Figure 1 Synthesis of benzimidazoles in aqueous media using SBA-15-
Ph-PrSO H as a hydrophobic catalyst
3
Thermogravimetric analysis of SBA-15-Ph-PrSO H (Fig-
3
ure 2) showed an initial mass loss due to desorption of wa-
ter below 100 °C. This was followed by a second mass loss,
starting at 240 °C, corresponding to the loss of the covalent-
ly bound organic material.
Having established the advantages of SBA-15-Ph-Pr-
SO H as a hydrophobic catalyst, we continued to examine
3
the efficacy of the carbonaceous solid sulfonic acid CMK-5-
SO H for the synthesis of benzimidazoles in water. When
3
the same reaction of benzene-1,2-diamine and benzalde-
hyde in water was carried out in the presence of 2 mol% of
CMK-5-SO H, the reaction was complete within 45 minutes
3
and the product was isolated in 96% yield. We then set out
to determine the scope and variability of this new catalyst
and, in each case, we observed that the time required for
the condensation was reduced considerably and the yield of
the products was consistently excellent (Table 1).52
Figure 2 Thermogravimetric analysis of SBA-15-Ph-PrSO H
3
FT-IR spectroscopy provided clear evidence for func-
tionalization of the catalysts by the organosulfonic acids. In
The acid capacities of SBA-15-Ph-PrSO H and CMK-5-
SO H were determined by titration with aqueous NaOH
3
3
SBA-15-Ph-PrSO H, the bands characteristic of the silica
solution. SBA-15-Ph-PrSO H or CMK-5-SO H (50 mg) was
3
3
3
−1
matrix were observed at 484 cm (SiO , tetrahedron vibra-
dispersed in 2 M aqueous NaCl (15 mL) and stirred at room
temperature overnight. The dispersion was then titrated
potentiometrically with 0.1 M NaOH. The loading of sulfon-
ic acid groups immobilized on the surface of SBA-15-Ph-Pr-
SO H (1.61 mmol/g) was almost twice that on CMK-5-SO H
4
−1
tion), 797 cm (Si–O–Si, symmetric vibration), and 1092
cm (strong band; Si–O–Si, asymmetric vibration). C=C,
−1
methylene, and SO –H stretching bands were also observed
3
−1
at 1631, 2926, and 3430 cm , respectively. These indicate
that the phenyl and propylsulfonic acid groups were an-
chored in the pore channels of the mesoporous SBA-15.
We began our studies by treating benzene-1,2-diamine
and benzaldehyde with a catalytic amount of SBA-15-Ph-
3
3
(0.87 mmol/g). However, we used 2 mol% of SBA-15-Ph-Pr-
SO H or CMK-5-SO H for the synthesis of the benzimidaz-
3
3
ole derivatives. Interestingly, we observed that by using
CMK-5-SO H, the time required for the condensation was
3
PrSO H (2 mol%) in water at room temperature as a model
reaction. We observed that the reaction was complete in
reduced considerably and the yield of the product improved
markedly. These results support the hypothesis that the hy-
drophobic reactants access the active sites of the catalyst.
3
100 minutes and gave a 90% yield of the product. To exam-
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D. Zareyee et al.
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The hydrophobic environment on the surface of the carbo-
naceous catalyst (CMK-5-SO H) not only improved its resis-
3
tance to water, but also provided easier mass transfer of the
hydrophobic reaction partners. Hence, the reactants initial-
ly adsorb onto the catalyst surface and subsequently react
at the available active sites.
Finally, we conducted experiments to establish the sta-
bility and reusability of the catalysts after the reaction,
through a series of sequential syntheses of 2-phenyl-1H-
benzimidazole from benzaldehyde and benzene-1,2-di-
amine as model substrates. Upon completion of the reac-
tion, the mixture was filtered and washed with warm EtOH
Figure 3 Transmission electron micrographs of recycled CMK-5-SO
left) and SBA-15-Ph-PrSO H (right)
H
3
(
3
oles from aldehydes and benzene-1,2-diamine in an aque-
for reuse. In this manner, recycled catalysts CMK-5-SO H
ous medium in the presence of SBA-15-Ph-PrSO H or CMK-
3
3
and SBA-15-Ph-PrSO H were used in eight and six consecu-
5-SO H as a benign water-tolerant catalyst, with air as the
3
3
tive runs, respectively. Furthermore, the acidity of the cata-
lysts showed no appreciable reduction over the reaction cy-
cles. The uniformity of the highly ordered structures of
CMK-5-SO H and SBA-15-Ph-PrSO H after recovery was
confirmed by transmission electron microscopy (Figure 3).
In summary, we have developed an efficient and green
methodology for synthesizing 2-substituted benzimidaz-
oxidant. The higher yields of the target products and the
better performance of CMK-5-SO H can be attributed to its
3
greater hydrophobicity. Both catalysts can be readily recov-
ered and recycled; they possess appreciable hydrolytic sta-
bility in the presence of water and they retain their acidity
over multiple reaction cycles.
3
3
Table 1 Synthesis of 2-Substituted Benzimidazoles by Using Catalytic Amounts of SBA-15-Ph-PrSO H or CMK-5-SO H in Water at Room Temperature
3
3
SBA-15-Ph-PrSO3H (2 mol%), H2O, r.t.
O
NH2
NH2
or
N
+
R
R
H
CMK-5-SO3H (2 mol%), H2O, r.t.
N
H
R = aryl or alkyl
SBA-15-Ph-PrSO
3
H (2 mol%)
3
CMK-5-SO H (2 mol%)
a
a
Entry
R
Time (min)
Yield (%)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
Ph
100
100
90
90
90
88
86
89
91
94
89
91
86
75
82
88
92
80
81
45
50
50
50
45
45
45
50
40
45
60
60
70
30
80
90
96
90
91
90
93
90
92
92
94
89
87
89
87
91
86
87
4-Tol
6 4
4-MeOC H
2-ClC
4-ClC
6
H
4
120
90
6
H
4
3-BrC
4-BrC
6
6
H
4
4
110
120
120
120
120
120
110
130
100
140
140
H
2-HOC
3-HOC
4-HOC
6
6
6
H
H
H
4
4
4
1
1
1
1
1
1
0
1
2-O
4-O
2
NC
NC
6
H
H
4
2
2
6
4
3
1-naphthyl
4
2-thienyl
5
Pr
Et
16
a
Isolated yield.
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D. Zareyee et al.
Letter
Acknowledgment
(28) Pawar, S. S.; Dekhane, D. V.; Shingare, M. S.; Thore, S. N. Chin.
Chem. Lett. 2008, 19, 1055.
The authors acknowledge the support for this work provided by the
Islamic Azad University of Qaemshahr Research Councils.
(
29) Ghosh, P.; Mandal, A. Catal. Commun. 2011, 12, 744.
30) Dhakshinamoorthy, A.; Kanagaraj, K.; Pitchumani, K. Tetrahe-
dron Lett. 2011, 52, 69.
(
(
(
31) Sun, P. P.; Hu, Z. X. J. Heterocycl. Chem. 2006, 43, 773.
32) Varala, R.; Enugala, R.; Kotra, V.; Adapa, S. R. Chem. Pharm. Bull.
References
2
007, 55, 1254.
(
1) Brown, K. L. Chem. Rev. 2005, 105, 2075.
(
(
(
33) Salehi, P.; Dabiri, M.; Zolfigol, M. A.; Otokesh, S.; Baghbanzadeh,
(2) Sondhi, S. M.; Singh, N.; Kumar, A.; Lozach, O.; Meijer, L. Bioorg.
Med. Chem. 2006, 14, 3758.
M. Tetrahedron Lett. 2006, 47, 2557.
34) Li, C. J.; Chang, T. H. Organic Reactions in Aqueous Media; Wiley:
New York, 1997.
(3) Tebbe, M. J.; Spitzer, W. A.; Victor, F.; Miller, S. C.; Lee, C. C.;
Sattelberg, T. R. Sr.; McKinney, E.; Tang, J. C. J. Med. Chem. 1997,
35) Organic Synthesis in Water; Grieco, P. A., Ed.; Blackie Academic
40, 3937.
&
Professional: London, 1998.
(
4) Roth, M.; Morningstar, M. L.; Boyer, P. L.; Hughes, S. H.;
Buckheit, R. W. Jr.; Michejda, C. J. J. Med. Chem. 1997, 40, 4199.
5) Migawa, M. T.; Girardet, J.-L.; Walker, J. A. II.; Koszalka, G. W.;
Chamberlain, S. D.; Drach, J. C.; Townsend, L. B. J. Med. Chem.
(
(
36) Mbaraka, I. K.; Shanks, B. H. J. Catal. 2005, 229, 365.
37) Melero, J. A.; Bautista, L. F.; Morales, G.; Iglesias, J.; Briones, D.
Energy Fuels 2009, 23, 539.
38) Liu, F. J.; Meng, X. J.; Zhang, Y. L.; Ren, L. M.; Nawaz, F.; Xiao, F.-S.
J. Catal. 2010, 271, 52.
(
(
1998, 41, 1242.
(6) Hisano, T.; Ichikawa, M.; Tsumoto, K.; Tsaki, M. Chem. Pharm.
Bull. 1982, 30, 2996.
(
39) Kassaee, M. Z.; Masrouri, H.; Movahedi, F. Appl. Catal., A 2011,
395, 28.
(
7) Laplante, S. R.; Jakalian, A.; Aubry, N.; Bousquet, Y.; Ferland, J.
M.; Gillard, J.; Lefebvre, S.; Poirier, M.; Tsantrizos, Y. S.; Kukolj,
G.; Beaulieu, P. L. Angew. Chem. Int. Ed. 2004, 43, 4306.
8) Fekner, T.; Gallucci, J.; Chan, M. K. J. Am. Chem. Soc. 2004, 126,
(
(
40) Mondal, J.; Sen, T.; Bhaumik, A. Dalton Trans. 2012, 41, 6173.
41) Morales, G.; Athens, G.; Chmelka, B. F.; van Grieken, R.; Melero,
J. A. J. Catal. 2008, 254, 205.
(
(
(
42) Mobaraki, A.; Movassagh, B.; Karimi, B. Appl. Catal., A 2014, 472,
223.
123.
9) Dudd, L. M.; Venardou, E.; Garcia-Verdugo, E.; Licence, P.; Blake,
(
43) Karimi, B.; Mobaraki, A.; Mirzaei, H. M.; Zareyee, D.; Vali, H.
ChemCatChem 2014, 6, 212.
44) Karimi, B.; Zareyee, D. Org. Lett. 2008, 10, 3989.
45) Karimi, B.; Zareyee, D. J. Mater. Chem. 2009, 19, 8665.
46) Zareyee, D.; Razaghi Ghadikolaee, A.; Khalilzadeh, M. A. Can. J.
Chem. 2012, 90, 464.
A. J.; Wilson, C.; Poliakoff, M. Green Chem. 2003, 5, 187.
(
(
(
10) Wang, L.; Sheng, J.; Tian, H.; Qian, C. Synth. Commun. 2004, 34,
265.
11) VanVliet, D. S.; Gillespie, P.; Scicinski, J. J. Tetrahedron Lett. 2005,
6, 6741.
12) Keri, R. S.; Hosamani, K. M.; Seetharama Reddy, H. R.;
Shingalapur, R. V. Catal. Lett. 2009, 131, 552.
13) Lu, J.; Yang, B.; Bai, Y. Synth. Commun. 2002, 32, 3703.
14) Gogoi, P.; Konwar, D. Tetrahedron Lett. 2006, 47, 79.
15) Das, B.; Holla, H.; Srinivas, Y. Tetrahedron Lett. 2007, 48, 61.
16) Zhang, Z.-H.; Yin, L.; Wang, Y.-M. Catal. Commun. 2007, 8, 1126.
17) Srinivas, U.; Srinivas, Ch.; Narender, P.; Rao, V. J. Palaniappan S.
Catal. Commun. 2007, 8, 107.
(
(
(
4
4
(
47) Zareyee, D.; Moosavi, S. M.; Alaminezhad, A. J. Mol. Catal. A:
Chem. 2013, 378, 227.
48) Zareyee, D.; Alizadeh, H. RSC Adv. 2014, 4, 37941.
49) Zareyee, D.; Ghandali, M. S.; Khalilzadeh, M. A. Catal. Lett. 2011,
(
(
(
(
(
(
(
141, 1521.
(
(
50) Zareyee, D.; Serehneh, M. J. Mol. Catal. A: Chem. 2014, 391, 88.
51) Zareyee, D.; Mirzajanzadeh, E.; Khalilzadeh, M. A. J. Chem. Sci.
(Berlin, Ger.) 2015, 127, 1229.
(
(
18) Shingalapur, R. V.; Hosamani, K. M. Catal. Lett. 2010, 137, 63.
19) Gadekar, L. S.; Arbad, B. R.; Lande, M. K. Chin. Chem. Lett. 2010,
(
52) 2-Substituted Benzimidazoles (Table 1, Entries 1–16);
General Procedure
In a round-bottomed flask, a mixture of benzene-1,2-diamine
21, 1053.
(
20) Jacob, R. G.; Dutra, L. G.; Radatz, C. S.; Mendes, S. R.; Perin, G.;
Lenardão, E. J. Tetrahedron Lett. 2009, 50, 1495.
21) Chari, M. A.; Shobha, D.; Kenawy, E.-R.; Al-Deyab, S. S.; Subba
Reddy, B. V.; Vinu, A. Tetrahedron Lett. 2010, 51, 5195.
22) Ruiz, V. R.; Corma, A.; Sabater, M. J. Tetrahedron 2010, 66, 730.
23) Bachhav, H. M.; Bhagat, S. B.; Telvekar, V. N. Tetrahedron Lett.
011, 52, 5697.
24) Chari, M. A.; Shobha, D.; Sasaki, T. Tetrahedron Lett. 2011, 52,
575.
25) Rathod, S. B.; Lande, M. K.; Arbad, B. R. Bull. Korean Chem. Soc.
010, 31, 2835.
26) Itoh, T.; Nagata, K.; Ishikawa, H.; Ohsawa, A. Heterocycles 2004,
3, 2769.
27) Trivedi, R.; De, S. K.; Gibbs, R. A. J. Mol. Catal. A: Chem. 2006, 245,
(1 mmol) and the appropriate aldehyde (1 mmol) in H O (5 mL)
2
was stirred at r.t. in the presence of SBA-15-Ph-PrSO H (0.012 g,
2
time (Table 1). When the reaction was complete (TLC; hexane–
EtOAc, 4:1), hot EtOH was added, and the mixture was filtered
and concentrated under vacuum to give a crude product that
was purified by crystallization (EtOH).
3
(
mol%) or CMK-5-SO H (0.046 g, 2 mol%) for the appropriate
3
(
(
2
(
(
(
(
2
-Phenyl-1H-benzimidazole (Table 1, Entry 1)
5
53
White solid; Yield: 174 mg (90%); mp 288–291 °C (Lit. 288–
1
2
2
7
90 °C). H NMR (400 MHz, DMSO-d ): δ = 7.19–7.23 (dd, J = 9.4,
6
2
.8 Hz, 2 H), 7.49 (t, J = 7.2 Hz, 1 H), 7.54–7.56 (m, 2 H), 7.57–
.60 (m, 2 H), 8.19 (dd, J = 8.4, 1.2 Hz, 2 H), 12.93 (s, 1 H). 13
C
6
NMR (100 MHz, DMSO-d ): δ = 119.3, 122.3, 126.9, 127.1, 129.4,
6
130.3, 130.6, 151.6.
8.
(
53) Nagawade, R. R.; Shinde, D. B. Chin. Chem. Lett. 2006, 17, 453.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–D