Fe3O4/SO3H@zeolite-Y as a novel multi-functional and magnetic nanocatalyst for clean and soft synthesis of imidazole and perimidine derivatives

Article abstract of DOI:10.1039/c9ra02910a

In this study, SO₃H@zeolite-Y was synthesized by the reaction of chlorosulfonic acid with zeolite-NaY under solvent-free conditions, which was then supported by Fe₃O₄ nanoparticles to give SO₃H@zeolite-Y (Fe₃O₄/SO₃H@zeolite-Y) magnetic nanoparticles. Several techniques were used to evaluate the physical and chemical characterizations of the zeolitic nanostructures. Fe₃O₄-loaded sulfonated zeolite was applied as a novel multi-functional zeolite catalyst for the synthesis of imidazole and perimidine derivatives. This efficient methodology has some advantages such as good to excellent yield, high purity of products, reusability of nanocatalyst, simple reaction conditions, environmental friendliness and an economical chemical procedure from the viewpoint of green chemistry.

Full text of DOI:10.1039/c9ra02910a

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Fe3O4/SO3H@zeolite-Y as a novel multi-functional
and magnetic nanocatalyst for clean and soft
synthesis of imidazole and perimidine derivatives
Cite this: RSC Adv., 2019, 9, 19333
*
Mehdi Kalhor
and Zohre Zarnegar
In this study, SO3H@zeolite-Y was synthesized by the reaction of chlorosulfonic acid with zeolite-NaY
under solvent-free conditions, which was then supported by Fe3O4 nanoparticles to give SO3H@zeolite-
Y (Fe3O4/SO3H@zeolite-Y) magnetic nanoparticles. Several techniques were used to evaluate the
physical and chemical characterizations of the zeolitic nanostructures. Fe3O4-loaded sulfonated zeolite
was applied as a novel multi-functional zeolite catalyst for the synthesis of imidazole and perimidine
derivatives. This efficient methodology has some advantages such as good to excellent yield, high purity
of products, reusability of nanocatalyst, simple reaction conditions, environmental friendliness and an
economical chemical procedure from the viewpoint of green chemistry.
Received 17th April 2019
Accepted 3rd June 2019
DOI: 10.1039/c9ra02910a
rsc.li/rsc-advances
solvents and low yield reactions.20,21 Thus, the development of
suitable and fantastic methods is still desirable for the
1. Introduction
synthesis of perimidines and highly substituted imidazoles
especially by using highly active, robust, stable, and green
catalysts.
Nitrogen-containing heterocyclic compounds including imid-
azole and perimidine have attracted signicant interest over the
past decade due to their widespread applications.1–3 They are
predominantly used as antimicrobial, antiulcer, anti-
inammatory, antifungal, antitumor, antibiotic, anti-
thrombotic, and therapeutic agents.4–6 Some of the imidazole
and perimidine molecules with biological activities are pre-
sented in Fig. 1.7–9
Imidazole was rst reported in 1858 by Heinrich Debus via
cyclocondensation of glyoxal, formaldehyde, and ammonia.10
Various synthetic methods have already reported the synthesis
of substituted imidazoles by varying the functional groups on
reactants. The tri-substituted imidazoles have been synthesized
via multicomponent reaction using 1,2-dicarbonyl compounds,
different aldehydes, and a nitrogen source in the presence of
acidic catalysts.11–18 Although these reported catalytic methods
are very useful and effective in some aspects, they may have
some limitations and difficulties such as strongly acidic
conditions, occurrence of side reactions, long reaction time,
and require harsh reaction conditions, and complex work-up
and purication.
Recently, magnetic separations have been introduced as
optional approach for recovering and reusing catalysts in
chemical catalytic procedures. Magnetic nanocatalysts are
heterogeneous catalytic systems with advantages of simple
recovery and reuse aer completion of reactions. Among the
various types of magnetic catalysts, the sulfonic acid function-
alized heterogeneous catalyst based on the magnetic systems
show excellent catalytic activities, high stability, easy prepara-
tion and reusability, enhanced selectivity, operational
simplicity, and more economically viable processes. In this
context, different types of magnetic SO3H-bearing organic and
inorganic compounds used in catalytic reactions such as
sulfonic acid magnetic graphene oxide for synthesis of inda-
zolophthalazinetriones,22 Fe3O4@MCM-48–SO3H for the
synthesis of benzo[f]chromeno[2,3-d]pyrimidinones,23 Fe3O4@-
PEG400-SO3H and its use in Paal–Knorr reaction,24 Fe3O4@-
SiO2–SO3H for the synthesis of amidoalkyl naphthols,25 cobalt
ferrite chitosan sulfonic acid magnetic nanoparticle for one-pot,
four-component synthesis of 2H-indazolo[2,1-b]phthalazine-
triones,26 SO3H-functionalized magnetic-titania nanoparticles
for the synthesis of benzimidazoquinazolinones and poly-
hydroquinolines,27 and etc.28 To the best of our knowledge, there
is no report for the application of magnetic SO3H-
functionalized zeolite in chemical organic reactions.
Perimidines or 1H-benzo[d,e]quinazolines as saturated N-
heterocycles are valuable molecules in the pharmaceutical
industry, agriculture, and synthetic chemistry. Perimidine
derivatives are usually prepared through condensation reaction
of
1,8-diaminonaphthalene
with
various
carbonyl
compounds.19–21 However, most of reported methods suffers
Over the past decade, the use of zeolites as heterogeneous
catalysts or ideal supports for homogeneous catalysts have been
employed for some catalytic processes due to their attractive
properties such as high surface area, nanoporous crystalline
from long reaction times, cumbersome work-up procedures,
Department of Chemistry, University of Payame Noor, P. O. Box 19395-4697, Tehran,
Iran. E-mail: mekalhor@gmail.com; Fax: +98 2537179170; Tel: +98 2537179170
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Fig. 1 Some of the imidazoles and perimidines with medicinal properties and biological activities.
structure, less or no corrosion, high thermostability, persis-
Fig. 2 shows the SEM images of the zeolite-NaY, SO3-
tence in all organic solvents, no waste or disposal problems, H@zeolite-Y and Fe3O4/SO3H@zeolite-Y. In Fig. 2a, it is obvious
easy set-up of continuous processes, etc.29,30 Although various that the zeolite-NaY has a crystalline structure. As Fig. 2b shows,
SO3H-activated zeolites used for catalytic reactions,31 direct the structure of SO3H@zeolite-Y is similar to that of the pristine
methanol fuel cell application,32 and as temperature tolerant zeolite with a rougher surface. Moreover, it can be observed
proton conducting material,33 but there is no example of the use from Fig. 2c that the surface of magnetic zeolite is rough aer
of magnetic SO3H-modied zeolite-NaY in order to design effi- being coated with Fe3O4. Fig. 2d clearly shows, the Fe3O4
cient a heterogeneous catalyst for the synthesis of N-containing nanoparticles are distributed on the surface of SO3H@zeolite-Y.
heterocycles.
The above mention results indicate that zeolite was successfully
In the present research, an eco-friendly and simple synthetic coated with magnetic particles.
method have been developed for the preparation of the imidazole
The composition of Fe3O4/SO3H@zeolite-Y was analyzed by
and perimidine heterocycles by using of Fe3O4 magnetic nano- energy dispersive X-rays (EDX) and the results are presented in
particles supported on zeolosulforic acid (Fe3O4/SO3H@zeolite-Y) Fig. 3. Elemental analysis results conrm the Fe element in the
nanocomposite as a magnetic solid acid catalyst (Scheme 1).
modied zeolite structure.
The XRD determination was carried out to acquire crystalline
structural information on Fe3O4/SO3H@zeolite-Y. The XRD
patterns of magnetic zeolite supported SO3H is shown in Fig. 4.
The main peaks at 2q values of 30.56ꢀ, 35.96ꢀ, 43.66ꢀ, 53.94ꢀ,
57.59ꢀ, 63.20ꢀ and 74.97ꢀ are belong to crystal indexes of (220),
(331), (400), (422), (511), (440) and (533), respectively. The ob-
tained results are consistent with standard XRD data of Fe3O4
(JCPDS no. 01-1111), indicating that Fe3O4 has been success-
fully made. According to Scherrer's equation, the equivalent
particle size could be calculated as about 10 nm.
2. Results and discussion
2.1. Characterization of nanocatalyst
As shown in Scheme 2, zeolite-NaY was functionalized with
SO3H groups, which has an affinity with positive ferrous and
ferric ions. Aer the addition of ammonium hydroxide solution,
Fe3O4 nanoparticles were formed on the surface of SO3-
H@zeolite-Y. A systematic study was carried out for the char-
acterization of the synthesized Fe3O4/SO3H@zeolite-Y.
Scheme 1 The synthetic pathway of imidazole and perimidine heterocycles using Fe3O4/SO3H@zeolite-Y.
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Scheme 2 Simplified schematic representation of the preparation of Fe3O4/SO3H@zeolite-Y.
A comparison is made between, FT-IR spectra of zeolite-NaY, 3459 cmꢁ1 region is related to the O–H stretching of hydrogen
SO3H@zeolite-Y and Fe3O4 zeolitic structures. In the spectrum bonded internal silanol groups and hydroxyl stretching of
of zeolite-NaY, in Fig. 5a, the broad absorption band in water, while the peak at 1636 cmꢁ1 corresponds to the O–H
Fig. 2 FESEM photographs of (a) zeolite-NaY, (b) SO3H@zeolite-Y, (c) and (d) Fe3O4/SO3H@zeolite-Y.
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Fig. 3 The EDX spectrum of Fe3O4/SO3H@zeolite-Y.
group bending mode of water. Moreover, the absorption bands bond. The bands at 945 and 798 cmꢁ1 maybe assigned to the
1021 and 792 cmꢁ1 are attributed to the symmetric and asym- S–O bond. The band at 455 cmꢁ1 is attributed to the bending
metric stretching vibrations of the Si–O–Si groups, respectively. vibrations of Si–O–Si or Al–O–Si groups for the modied zeolite-
In FT-IR spectrum of SO3H@zeolite (Fig. 5b), the broad band at NaY. FT-IR spectrum of Fe3O4/SO3H@zeolite-Y in Fig. 5c,
3420 cmꢁ1 is related to the stretching vibrations of O–H groups. reveals the presence of all adsorption band corresponding to
There is an adsorption band at 1635 cmꢁ1 for OH bending SO3H@zeolite. Further, the existence of peak at 576 cmꢁ1
vibration belonging to physically adsorbed H2O. The absorption corresponds to the stretching vibrations of Fe–O groups indi-
band around 1087 cmꢁ1 is related to the Si–O stretching cates that magnetic Fe3O4 nanoparticles is supported on
vibration and the asymmetric and symmetric stretching of S]O sulfonated zeolite.
Fig. 4 XRD pattern of Fe3O4/SO3H@zeolite-Y.
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Fig. 5 FTIR spectra of (a) zeolite-NaY, (b) SO3H@zeolite-Y and (c) Fe3O4/SO3H@zeolite-Y.
Nitrogen adsorption–desorption isotherm analysis and BJH decreased relative to SO3H@zeolite-Y (284.84 nm). These results
pore size distributions were carried out to evaluate the surface conrm successful supporting of Fe3O4 in the pores of SO3H
and structure properties of Fe3O4/SO3H@zeolite-Y. As shown in functionalized zeolite-NaY.36 The Fe3O4/SO3H@zeolite-Y has
Fig. 6, the N2 adsorption–desorption isotherm of Fe3O4/SO3- a higher pore volume (6.77 nm) in comparison with sulfonated
H@zeolite-Y displays an H1-type hysteresis loop and BJH pore zeolite-Y (2.35 nm), which might be due to the presence of
distribution curve of type IV which is in agreement with typical magnetic nanoparticles through the zeolite cavities.
mesostructure. Also, by looking at its hysteresis type, it can be
The magnetization curve of magnetic SO3H@zeolite nano-
seen that Fe3O4/SO3H@zeolite-Y has slits (layer and layer with composites is shown in Fig. 7. The saturation magnetization is
high pores) structure and the initial nanostructure aer the found to be 21.30 emu gꢁ1. With this saturation magnetization
functionalize is still retained,35 The structure data of all these values, it could be rapidly separated from its liquid dispersions
materials are summarized in Table 1. The BET surface area under a magnetic eld. These results indicate that Fe3O4/SO3-
(205.68 m2 gꢁ1) and average pore diameter (6.7767 nm) were H@zeolite-Y exhibits enough magnetic response to meet the
recorded for Fe3O4/SO3H@zeolite-Y. The BET surface area is need of magnetic separation.
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Fig. 6 (a) Nitrogen adsorption–desorption isotherm and (b) BJH pore size distributions of Fe3O4/SO3H@zeolite-Y.
Table 1 Porosimetery values for zeolite-NaY and its modified structures
SBETa (m2 gꢁ1
)
VBJHb (cm3 gꢁ1
)
DBJH (nm)
DAapd (nm)
c
Samples
Zeolite-NaY
SO3H@zeolite-Y
Fe3O4/SO3H@zeolite-Y
619.66
284.84
205.56
0.0667
0.0532
0.0348
4.84
5.15
2.42
2.2358
2.3517
6.7767
a
c
Specic surface area. b Pore volume. Pore size (calculated from the adsorption branch). d Adsorption average pore diameter (4V/A) by BET.
were evaluated in EtOH solvent. The obtained results were listed
in Table 2. The best quantity of the Fe3O4/SO3H@zeolite-Y for
the preparation of tri-substituted imidazoles was 0.02 g (Table
2, entry 3). By increasing the amount of the nanocatalyst the
reaction yield decreased (Table 2, entries 4 and 5). In the next
step, the catalytic reaction was carried out in the various
solvents like EtOH, MeOH, CH3CN, H2O, EtOH : H2O (1 : 1),
DMSO, and CH2Cl2 under reux conditions (Table 2, entries 3
and 6–11). The best yield was obtained in EtOH solvent. The
2.2. The catalytic activity of Fe3O4/SO3H@zeolite-Y in the
synthesis of imidazole and perimidine derivatives
At rst, the catalytic ability of Fe3O4/SO3H@zeolite-Y has been
investigated for the synthesis of various substituted imidazoles.
To optimize the reaction conditions for the synthesis of 2,4,5-
triarylsubstituted imidazoles, the reaction of the benzaldehyde
(1 mmol), benzil (1 mmol) and ammonium acetate (2 mmol)
was considered as a model reaction. To nd the optimized
nanocatalyst ratio, different amounts of the magnetic zeolite
Fig. 7 Field-dependent magnetization curve measured at room temperature for Fe3O4/SO3H@zeolite-Y.
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Table 2 Optimizing the model reaction conditions for the synthesis of imidazole 4aa
Entry
Catalyst (g)
Solvent
Temperature (ꢀC)
Time (min)
Yieldb (%)
1
2
3
4
5
6
7
8
0.005
0.010
0.020
0.030
0.040
0.020
0.020
0.020
0.020
0.020
0.020
0.020
0.020
0.020
EtOH
EtOH
EtOH
EtOH
80
80
80
80
80
65
120
80
100
100
40
50
60
70
80
80
80
90
60
45
45
45
60
60
60
90
90
90
90
60
45
120
55
240
70
82
98
95
93
90
85
55
20
35
58
60
75
92
15
90
50
EtOH
MeOH
DMSO
CH3CN
H2O
EtOH : H2O (1 : 1)
CH2Cl2
EtOH
EtOH
EtOH
EtOH
EtOH
9
10
11
12
13
14
15
16
17
Zeolite-NaY (0.02)
SO3H@zeolite-Y (0.02)
—
EtOH
a
b
Reaction conditions: benzil (1 mmol), benzaldehyde (1 mmol), ammonium acetate (2 mmol) and catalyst in solvent. Isolated yield.
same reaction in the presence of 0.02 g of zeolitic catalyst was was obtained in high yield within 45 min (Table 1, entry 3). A
carried out at different temperatures to assess the effect of further increase in temperature and time did not improve the
temperature on the reaction yield. The yield increased as the product yield (Table 2, entry 12). Although SO3H@zeolite-Y
ꢀ
reaction temperature was raised. At 80 C, the desired product showed a good catalytic effect for this reaction (Table 2, entry
Table 3 Synthesis of 2,4,5-trisubstituted imidazoles catalyzed by Fe3O4/SO3H@zeolite-Ya
Entry
R
Product
Time (min)
Yieldb (%)
mprep/mplit. (ꢀC)
1
2
3
4
5
6
7
8
H
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
45
65
20
45
65
45
35
60
65
50
50
35
30
45
98
97
85
93
97
98
97
95
95
98
98
97
98
96
270–272 (271–273)11
226–228 (226–227)37
268–270 (267–268)11
215–217 (215–217)11
200–202 (209–211)38
214–216 (214–216)11
259–261 (259–260)11
226–228 (230–231)11
168–170 (196–199)37
254–256 (194–197)37
168–170 (175–178)37
260–262 (260–262)11
301–303 (302–303)11
231–233 (230–232)11
2-NO2
3-NO2
3-OH, 4-OMe
2-OMe
3,4-OMe
3-OH
4-OMe
2-Cl
2,3-Cl
2,4-Cl
4-Cl
9
10
11
12
13
14
3-Br
4-Me
a
Reaction conditions: benzil (1 mmol), aldehyde (1 mmol), ammonium acetate (2 mmol) and Fe3O4/SO3H@zeolite-Y (0.020 g) in EtOH at 80 ꢀC.
Isolated yield.
b
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Scheme 3 The suggested mechanism of tri-substituted imidazoles synthesis.
16), but centrifugation had required in order to separate the
The scope and generality of the synthesis of 2,4,5-triaryl
nanocatalyst. Modern catalytic methods offer a great potential substituted imidazoles were studied by using various aromatic
for future developments in the synthesis of heterogeneous aldehydes bearing both electron-withdrawing and electron-
catalysts based on magnetic nanomaterials. Magnetic separa- donating groups. As the results clearly show (Table 3), this
tion is a simpler, faster, and cleaner way to recover the catalyst. organic transformation in the presence of the zeolitic nano-
The presence of magnetite nanoparticles also improved cata- composite provided the corresponding products in high yields
lytic effect and decreased slightly at reaction time. Therefore, and appropriate reaction times (Table 3, 4a–n).
the Fe3O4/SO3H@zeolite-Y was chosen was chosen to improve
A plausible mechanism for the formation of 2,4,5-triaryl-1H-
the catalytic path. Also, this condensation was performed under imidazoles in the presence of Fe3O4/SO3H@zeolite-Y catalyst is
catalyst-free conditions. The yield of the product was 50% aer shown in Scheme 3. Fe3O4/SO3H@zeolite-Y as heterogeneous
4 h (Table 2, entry 17). Therefore, the presence of the nano- multi-functional nanocatalyst facilitates this cyclocondensation
catalyst was necessary for a shorter time and higher efficiency. due to the existence of both Lewis acid (Fe3O4) and Brønsted
Table 4 Optimizing the model reaction conditions for the synthesis of perimidine 6da
Entry
Catalyst (g)
Solvent
Temperature (ꢀC)
Time (min)
Yieldb (%)
1
2
3
4
5
6
7
8
0.0047
0.008
0.016
0.008
0.008
0.008
0.008
0.008
EtOH
EtOH
EtOH
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
4
4
4
4
4
10
15
18
10
120
8
81
98
70
80
75
63
51
46
81
20
89
10
MeOH
DMSO
CH3CN
CH2Cl2
H2O
EtOH : H2O (1 : 1)
EtOH
EtOH
9
0.008
10
11
12
Zeolite-Y (0.008)
SO3H@zeolite-Y (0.008)
—
EtOH
120
a
Reaction conditions: benaldehyde (1 mmol), 1,8-diaminonaphthalene (1 mmol), catalyst, in solvent at 25 ꢀC. b Isolated yield.
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Table 5 Synthesis of dihydroperimidine catalyzed by Fe3O4/SO3H@zeolite-Ya
Entry
R
Product
Time (min)
Yieldb (%)
mprep/mplit. (ꢀC)
15
16
17
18
19
20
21
22
23
24
25
26
27
H
6a
6b
6c
6d
6e
6f
6g
6h
6i
4
4
4
3
4
5
5
4
6
4
4
4
6
98
98
90
98
90
89
90
95
89
95
98
95
88
104–106 (104–106)20
180–192 (192–194)20
200–202(183–185)39
224–226 (201–202)20
160–162 (161–163)20
214–216 (205–207)20
180–182 (192–193)40
148–150 (165–166)20
204–206 (168–169)20
144–146 (145–146)20
171–173 (173–174)20
130–132 (131–133)21b
340–342 (350)20
2-NO2
3-NO2
4-NO2
4-OMe
3,4-OMe
2-OH
2-OH, 5-Br
2-OH, 4-OMe
3-Cl
6j
6k
6l
4-Cl
2,3-Cl
5-NO2
c
6m
a
Reaction conditions: aldehyde (1 mmol), 1,8-diaminonaphthalene (1 mmol), Fe3O4/SO3H@zeolite-Y (0.008 g), in EtOH at 25 ꢀC. b Isolated yield.
5-Nitrofuran-2-yl.
c
acidic (SO3H) sites. On the basis of the literature and substrates diamine intermediate (A). Condensation of diamine with benzil
chemistry, the SO3H Brønsted acid supported on Fe3O4 Lewis (3) followed by cyclization, dehydration, and then rearrange-
acid polarizes the carbonyl group of aldehyde. Then, hydroxyl- ment through the imino intermediate (B) yielded the
amine intermediate (1a) is formed by condensation reaction of substituted imidazole product (4).11
an aromatic aldehyde (1) and NH3 (2), which is then dehydrated
In another synthesis procedure, the catalytic performance of
to imine (2a). The addition of the second mole of NH3 produces Fe3O4/SO3H@zeolite-Y was investigated for the synthesis of
Scheme 4 The possible reaction mechanism for the synthesis of 2-aryl perimidines in the presence of Fe3O4/SO3H@zeolite-Y.
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aqueous solutions more effective and simple (as a signicant
advantage in comparison with the SO3H@zeolite-Y catalyst).
The catalyst free reaction has no good results for the synthesis
of 2-substituted 2,3-dihydro-1H-perimidines (Table 4, entry 12).
To extend the scope of this study, the above optimized
conditions, were employed for a cyclocondensation reaction
between
a variety of aromatic aldehydes and 1,8-dia-
minonaphthalene over the Fe3O4/SO3H@zeolite-Y catalyst
(Table 5, 6a–m). Based on these results, both electron-donating
and electron-withdrawing groups proceed smoothly with very
good efficiency to form the desired products in high yields
within the very short time.
Fig.
8 Examination of Fe3O4/SO3H@zeolite-Y reusability in the
synthesis of imidazoles and perimidines.
A possible mechanism (Scheme 4) is proposed for the
synthesis of 2-aryl perimidines which is consistent with the
literature.21 The nucleophilic attack of diamino aromatic ring to
Fe3O4/SO3H@zeolite-Y-activated aldehyde generated the imine
intermediate with the removal of H2O molecule. Subsequently,
nucleophilic attack of the second amino group to nanocatalyst-
activated imine intermediate is followed by cyclization process
to give the desired product.
The reusability and recyclability of Fe3O4/SO3H@zeolite-Y
catalyst was investigated in the model reactions for the prepa-
ration of tri-substituted imidazoles and 2-aryl perimidines
(Fig. 8). In both of these reactions, the nanocatalyst was easily
recycled at least ve times without signicant loss of activity. In
this regard, aer completion of the reaction, the catalyst was
separated by an external magnet, washed with ethyl acetate and
dried at 50 ꢀC to be ready for the subsequent runs. The FTIR and
dihydroperimidine derivatives (Table 4, entries 1–12). In order
to optimize the reaction conditions, some parameters such as
solvent, catalyst amount, and temperature, were probed for the
condensation of benzaldehyde with 1,8-diaminonaphthalene as
a model reaction in the presence of Fe3O4/SO3H@zeolite-Y. The
optimum reaction conditions were found to be use of 0.008 g of
Fe3O4/SO3H@zeolite-Y in the EtOH solvent at 4 min with 98%
yield (Table 4, entry 2). It can be concluded that the nano-size
and large surface area of the support makes the heterogenized
SO3H catalyst readily available for substrates. Further, the
catalytic performance of Fe3O4 (as a Lewis acid) supported on
the zeolite for the reaction is attributed to the large surface area
of the nanocatalyst and support, which facilitate the appro-
priate interaction of the reactant and product molecules.
Moreover, this technique makes catalyst separation from
Fig. 9 FTIR spectra of (a) fresh and (b) recovered Fe3O4/SO3H@zeolite-Y.
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Fig. 10 XRD pattern of recovered Fe3O4/SO3H@zeolite-Y.
Table 6 Comparison of the catalytic efficiency of Fe3O4/SO3H@zeolite-Y with other catalysts for the synthesis of imidazoles (entries 1–8) and
perimidines (entries 9–16) for their model reactions (1 mmol from the raw materials)
Entry
Catalyst/conditions
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
Fe3O4g-C3N4 (0.02 g), EtOH, 78 ꢀ
C
2
2
95 (ref. 41)
95 (ref. 42)
95 (ref. 43)
90 (ref. 44)
93 (ref. 37)
77 (ref. 45)
90 (ref. 46)
98 (this work)
81 (ref. 20)
70 (ref. 47)
80 (ref. 48)
88 (ref. 49)
93 (ref. 50)
95 (ref. 21)
83 (ref. 51)
98 (this work)
Fe3O4@chitosan (0.05 g), EtOH, reux
Benzethonium chloride (10 mole%), EtOH : H2O, 70 ꢀ
C
0.75
1
0.25
0.13
2
0.75
0.42
45–50
0.22
24
Sodium dodecyl-sulfate (0.02 g), H2O, 80 ꢀ
C
Fe3O4@SiO2$HM$SO3H (0.04 g), solvent-free, 110 ꢀC
Fe3O4@SiO2$HM$SO3H (0.060 g), solvent-free, MWI
Sulfamic acid-Fe3O4 NPs (0.1 g), EtOH, reux
Fe3O4/SO3H@zeolite-Y (0.02 g), EtOH, 80 ꢀ
CuY-zeolite (0.002 g), EtOH, rt
NaY zeolite (0.2 g), EtOH, rt
C
9
10
11
12
13
14
15
16
FePO4 (10 mol%), EtOH, rt
Ytterbium(III) triuoromethanesulfonate (0.1 equiv.), MeCN, rt
Fe3O4/SiO2/(CH2)3N+Me3Br3 (0.007), solvent-free, 80 ꢀ
Nano-g-Al2O3/SbCl5 (0.1 g), solvent-free, rt
Cu(NO3)2 (5 mole%), 2H2O, EtOH, rt
C
12
ꢁ
0.25
0.17
0.07
Fe3O4/SO3H@zeolite-Y (0.008 g), EtOH, rt
a
Isolated yield.
XRD data of the recycled catalyst shows no change in its
structure (Fig. 9 and 10).
3. Conclusions
Also, to show the advantages of using Fe3O4/SO3H@zeolite-Y
nanocatalyst in the synthesis of 2,4,5-triaryl-1H-imidazoles
(Table 4, entries 1–8) and 2,3-dihydro-1H-perimidines (Table 4,
entries 9–16), this catalytic method was compared with litera-
ture resulted in reports of using various catalysts for the model
reactions. As shown in Table 6, in the presence of this new
magnetic nanocomposite [with Lewis acid (Fe3O4) and
Brønsted–Lowry acid (SO3H)], the results were better than other
catalysts.
In conclusion, magnetic SO3H@zeolite-Y nanocomposite sup-
ported nano Fe3O4 was successfully synthesized and used for
the synthesis of 2,4,5-trisubstituted imidazoles and 2-aryl peri-
midines under mild conditions. The most interesting features
of the present method are simple preparation, the use of non-
toxic nature of the nanocatalyst, easy separation of the cata-
lyst aer reaction, and substantial improvements in the reac-
tion time and yield. The nanocatalyst was readily recycled by an
external permanent magnet and could be reused ve times
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without any signicant loss of its performance. Further appli- spectroscopic data with those of the authentic samples. Char-
cations of multi-functional nanocatalysts based on the zeolie- acterization data for some of the imidazole compounds are
NaY to other green reactions are currently under investigation. given below.
2-(3-Nitrophenyl)-4,5-diphenyl-1H-imidazole (4c). FTIR (KBr)
n (cmꢁ1): 3434 (N–H), 1627 (C]C), 1524 (C]N), 14.89 (N]O),
4. Experimental
4.1. Chemicals and apparatus
1
1348 (N–O); H NMR (DMSO-d6, 400 MHz) d (ppm): 7.14–7.16
(m, 5H, Ar–H), 7.38–7.44 (m, 5H, Ar–H), 7.47 (d, 1H, 3J ¼ 7.6 Hz,
3
Ar–H), 8.00 (d, 1H, J ¼ 7.6 Hz, Ar–H), 8.46 (d, 1H, 3J ¼ 7.6 Hz,
All chemicals were purchased from the Merck and Fluka
Ar–H), 8.48 (d, 1H, 3J ¼ 7.6 Hz, Ar–H), 8.91 (s, 1H, Ar–H), 9.8 (s,
Chemical Companies. The products were identied by
1H, N–H).
comparing the physical data with those of known samples or by
their spectral data. FT-IR spectra were obtained with KBr disc on
a galaxy series FT-IR 5000 spectrometer. 1H NMR and 13C NMR
spectra were recorded with a Bruker DRX-400 spectrometer at
400 and 100 MHz respectively. The surface morphology of
zeolite and modied structures were analyzed by eld emission
scanning electron microscopy (FESEM) (EVO LS 10, Zeiss, Carl
Zeiss, Germany). The magnetic measurement of samples was
carried out in a vibrating sample magnetometer (VSM) (4 inch,
NDKF, Kashan, Iran) at room temperature. Diffuse reectance
spectra were acquired on an X-ray photoelectron spectrometer
(Escalab 250Xi). Nitrogen adsorption aꢀnd desorption isotherms
(BET analysis) were measured at 196 C by a Japan Belsorb II
system aer the samples were vacuum dried at 150 ꢀC
overnight.
2-(3-Hydroxy, 4-methoxyphenyl)-4,5-diphenyl-1H-imidazole
(4d). FTIR (KBr) n (cmꢁ1): 3530 (N–H), 1594 (C]C), 1499 (C]N);
1H NMR (DMSO-d6, 400 MHz) d (ppm): 2.77 (s, 3H, CH3), 6.75 (d,
3
1H, J ¼ 8.4 Hz, Ar–H), 7.14–716 (m, 6H, Ar–H), 7.35–7.39 (m,
5H, Ar–H), 7.49 (s, 1H, Ar–H), 7.53 (s, 1H, OH), 7.8 (s, 1H, N–H).
2-(3-Hydroxyphenyl)-4,5-diphenyl-1H-imidazole (4g). FTIR
(KBr) n (cmꢁ1): 3373 (N–H), 1590 (C]C), 1479 (C]N); 1H NMR
(DMSO-d6, 400 MHz) d (ppm): 6.98 (t, 2H, 3J ¼ 8 Hz, Ar–H), 7.06–
7.10 (m, 4H, Ar–H), 7.11–7.16 (m, 5H, Ar–H), 7.41–7.43 (m, 4H,
Ar–H), 7.46 (s, 1H, OH), 8.8 (s, 1H, N–H).
2-(3-Bromophenyl)-4,5-diphenyl-1H-imidazole (4m). FTIR
(KBr) n (cmꢁ1): 3432 (N–H), 1599 (C]C), 1455 (C]N); 1H NMR
(DMSO-d6, 400 MHz) d (ppm): 7.34–7.35 (m, 7H, Ar–H), 7.51–
7.56 (m, 5H, Ar–H), 7.89 (s, 1H, Ar–H), 8.13 (s, 1H, Ar–H), 9.9 (s,
1H, N–H).
2-(4-Methylphenyl)-4,5-diphenyl-1H-imidazole (4n). FTIR
(KBr) n (cmꢁ1): 3431 (N–H), 1601 (C]C), 1497 (C]N); 1H NMR
(DMSO-d6, 400 MHz) d (ppm): 2.30 (s, 3H, CH3), 7.14–7.20 (d,
4.2. Synthesis of Fe3O4/SO3H@zeolite-Y
For preparation of SO3H@zeolite-Y, a 500 mL ask was equip-
ped with a constant pressure dropping funnel containing 3 mL
of ClSO3H. Then, 1.5 g of zeolite-NaY was charged into the ask
and ClSO3H was added dropwise manner to zeolite-NaY over
a period of 30 min. at 0 ꢀC. Aer the addition was complete, the
mixture was stirred for 45 min. Aerwards, the mixture was
washed with CH2Cl2 and H2O under sonication and dried at
50 ꢀC. In continue, nano magnetic zeolosulforic acid (NMSZ)
3
3H, J ¼ 7.2 Hz, Ar–H), 7.21–7.30 (m, 5H, Ar–H), 7.49–7.50 (m,
3
4H, Ar–H), 7.92 (d, 2H, J ¼ 7.2 Hz, Ar–H), 10.0 (s, 1H, N–H).
4.4. General procedure for the preparation of 2-substituted
2,3-dihydro-1H-perimidines
A mixture of aldehyde (1 mmol), 1,8-diaminonaphthalene
(1 mmol, 0.158 g), Fe3O4/SO3H@zeolite-Y (0.008 g), in EtOH was
was prepared by
a chemical co-precipitation process as
described by Mesdaghinia et al.34 FeCl2$4H2O (2.3 mmol, 0.45 g)
and FeCl3$6H2O (4.6 mmol, 1.23 g) precursors (1 : 2, molar
ratio) were dissolved in 25 mL of water and 1 g of SO3H@zeolite-
Y were dispersed in this aqueous solution under N2 atmosphere
bubbling for 1 h. Then, 20 mL of ammonium hydroxide (25%)
ꢀ
stirred at 25 C. Aer completion of the reaction, (TLC moni-
toring using hexane and ethyl acetate, 3 : 1), the nanocatalyst
was separated by magnetic eld. A mixture of ice and water was
added to the ltrate and the precipitate product was obtained by
ltration and washed thoroughly with water–ethanol mixture.
The product was puried by recrystallization in ethanol–water
and identied by physical and spectroscopic techniques.
Characterization data for some of the compounds are given
below.
ꢀ
was added to the mixture. The mixture was stirred at 90 C for
30 minutes. The black precipitate was extracted by an external
magnet and washed with HCl solution (0.1 M), double-distilled
ꢀ
water and dried at 70 C in vacuum oven to obtain the Fe3O4/
SO3H@zeolite-Y nanocomposite.
2-(2-Nitrophenyl)-2,3-dihydro-1H-perimidine (6b). FT-IR
(KBr, nmax): 3357, 3230 (N–H), 2921 (C–H), 1518, 1333 (NO2),
4.3. General procedure for the synthesis of 2,4,5-triaryl
substituted imidazoles
1601, 1414, 1347 (C]C), 1165, 1125, 1031 (C–N), 826, 758 cmꢁ1
;
1H NMR (300 MHz, DMSO-d6): dH 8.03 (d, J ¼ 8.11 Hz, 1H, H–Ar),
A mixture of benzil (1 mmol, 0.210 g), aldehyde (1 mmol), 7.88 (d, J ¼ 7.92 Hz, 1H, H–Ar), 7.75–7.64 (m, 2H, H–Ar), 7.18 (t, J
ammonium acetate (2 mmol, 0.154 g) and Fe3O4/SO3H@zeolite- ¼ 8.10 Hz, 2H, H–Ar), 7.03 (d, J ¼ 8.25 Hz, 2H, H–Ar), 6.82 (br,
Y (0.020 g) in EtOH was stirred at 80 ꢀC. Aer completion of the 2H, NH), 6.53 (d, J ¼ 7.5 Hz, 2H, H–Ar), 5.82 (s, 1H, N–CH–
reaction (TLC monitoring using n-hexane and ethyl acetate, N) ppm; 13C NMR (75 MHz, DMSO-d6): d ¼ 149.3, 142.5, 136.9,
9 : 1), the nanocatalyst was separated by magnetic decantation 134.6, 134.0, 130.4, 130.0, 127.5, 124.4, 116.2, 112.5, 105.2,
and the solvent was evaporated. The crude product was either 61.4 ppm.
recrystallized from aqueous-acetone and air dried. The products
2-(2-Hydroxy-4-methoxyphenyl)-2,3-dihydro-1H-perimidine
were characterized by comparing the results of physical and (6i). FT-IR (KBr, nmax): 3420 (NH, OH), 2916 (C–H), 1600, 1420
19344 | RSC Adv., 2019, 9, 19333–19346
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(C]C), 1257, 1107 (C–O), 1028 (C–N), 811, 759, 418 cmꢁ1; H
NMR (300 MHz, DMSO-d6): dH 9.70 (s, 1H, OH), 7.35 (d, J ¼
8.82 Hz, 1H, H–Ar), 7.22–7.11 (m, 2H, H–Ar), 6.96 (d, J ¼ 8.05 Hz,
2H, H–Ar), 6.52–6.43 (m, 6H, H–Ar and NH), 5.57 (s, 1H, N–CH–
N), 3.70 (s, 3H, OCH3) ppm; 13C NMR (75 MHz, DMSO-d6): dC
160.6, 156.9 (C–O), 143.9, 134.8, 129.8, 127.2, 127.2, 120.0,
115.7, 112.9, 104.9, 101.5, 61.1 (N–C–N), 55.4 (OCH3) ppm.
2-(2,3-Dichlorophenyl)-2,3-dihydro-1H-perimidine (6l). FT-
IR (KBr) (nmax): 3348, 3235 (N–H), 3044 (C–H), 1625, 1600,
1493, 1420, 1403, 1382, 1265 (C]C), 1182, 1161, 1043 (C–N),
M. E. Abdel Rehim, Res. Chem. Intermed., 2012, 38, 1527–
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1
835, 787, 757 (C–Cl), 603 cmꢁ1; H NMR (500 MHz, DMSO-d6):
dH 7.69 (d, J ¼ 8.15 Hz, 2H, H–Ar), 7.45 (t, J ¼ 7.90 Hz, 1H, H–Ar),
7.19 (t, J ¼ 7.78 Hz, 2H, H–Ar), 7.04 (d, J ¼ 8.15 Hz, 2H, H–Ar),
6.83 (s, 2H, NH), 6.52 (d, J ¼ 7.35 Hz, 2H, H–Ar), 7.83 (s, 1H, N–
CH–N) ppm; 13C NMR (125 MHz, DMSO-d6): dC 142.7, 141.8,
134.7, 132.1, 131.1, 130.7, 128.8, 128.6, 127.3, 116.1, 112.5,
105.0, 63.5 (N–CH–N) ppm.
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2-(5-Nitrofuran-2-yl)-2,3-dihydro-1H-perimidine (6m). FT-IR
(KBr, nmax): 3434 (N–H), 1603, 1480 (C]C), 1520, 1360 (–NO2),
1
1020 (C–N), 808, 601 cmꢁ1; H NMR (300 MHz, DMSO-d6): dH
8.25 (d, J ¼ 7.00 Hz, 2H, H–Ar), 7.69 (s, 2H, H–Ar), 7.52–7.27 (m,
6H, H–Ar and 2NH), 5.25 (s, 1H, N–CH–N) ppm; 13C NMR (75
MHz, DMSO-d6): dC 161.3, 150.2, 137.0, 135.5, 130.1, 128.4,
124.4, 119.2, 116.1, 114.6, 69.7 (N–C–N) ppm.
9 (a) N. Xi, Q. Huang and L. Liu, in comprehensive heterocyclic
chemistry III, ed. A. R. Katritzky, C. A. Ramsden, E. F. V.
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Conflicts of interest
There are no conicts to declare.
Acknowledgements
10 H. Debus, Ann. Chem. Pharm., 1858, 107, 199–208.
11 Z. Zarnegar and J. Safari, New J. Chem., 2014, 38, 4555–4565.
12 K. F. Shelke, S. B. Sapkal, S. S. Sonar, B. R. Madje,
B. B. Shingate and M. S. Shingare, Bull. Korean Chem. Soc.,
2009, 30, 1057–1060.
We are thankful to the Payame Noor University for the partial
support of this work.
13 S. D. Jadhave, N. D. Kokare and S. D. Jadhave, J. Heterocycl.
Chem., 2009, 45, 1461–1464.
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