NaY Zeolite Functionalized by Sulfamic Acid/Cu(OAc)2 as a Novel and Reusable Heterogeneous Hybrid Catalyst in Efficient Synthesis of Bis, Tris, and Tetrakis(indolyl)methanes, 3,4-Dihydropyrimidin-2(1H)-ones, and 2-Aryl-1H-benzothiazoles

Article abstract of DOI:10.1002/jccs.201700035

An efficient acid-catalyzed synthesis of some bis, tris, and tetrakis(indolyl)methanes, 3,4-dihydropyrimidin-2(1H)-ones, and 2-aryl-1H-benzothiazoles is reported using NaY zeolite functionalized by sulfamic acid/Cu(OAc)₂ (NaY zeolite-NHSO₃

Full text of DOI:10.1002/jccs.201700035

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
NaY Zeolite Functionalized by Sulfamic Acid/Cu(OAc)2 as a Novel and Reusable
Heterogeneous Hybrid Catalyst in Efficient Synthesis of Bis, Tris, and Tetrakis(indolyl)
methanes, 3,4-Dihydropyrimidin-2(1H)-ones, and 2-Aryl-1H-benzothiazoles
*
Samira Kazemi , Akbar Mobinikhaledi and Mojgan Zendehdel
Faculty of Science, Department of Chemistry, Arak University, Arak 38156-8-8349, Iran
(Received: January 27, 2017; Accepted: March 23, 2017; DOI: 10.1002/jccs.201700035)
An efficient acid-catalyzed synthesis of some bis, tris, and tetrakis(indolyl)methanes, 3,4-dihydro-
pyrimidin-2(1H)-ones, and 2-aryl-1H-benzothiazoles is reported using NaY zeolite functionalized
by sulfamic acid/Cu(OAc)2 (NaY zeolite-NHSO3H/Cu(OAc)2) in excellent yield. The heterogene-
ous catalyst has a simple work-up procedure and could be recycled and reused for six reaction
cycles.
Keywords: Bis(indolyl)methane; Tris(indolyl)methane; Tetrakis(indolyl)methane; Heterogeneous
catalyst; 3,4-Dihydropyrimidin-2(1H)-ones; 2-Aryl-1H-benzothiazoles; NaY zeolite
functionalized by sulfamic acid/Cu(OAc)2.
INTRODUCTION
Owing to the unique pharmacological properties of
anti-inflammatory, antitumor, antiviral, and antifungal
agents.17 In the last few decades, these compounds have
also found applications as calcium channel blockers, anti-
hypertensive agents, α1a-antagonists, and neuropeptide Y
(NDY) antagonists used for the treatment of prostatic
hyperplasia.17,18 The synthesis of 3,4-dihydropyrimidin-2
(1H)-ones was first reported by Biginelli (1893) by a sim-
ple one-pot condensation of a β-keto ester, an aldehyde,
and urea under strongly acidic conditions. However, this
protocol often suffers from low yields of the more
demanding products in the case of aliphatic and certain
substituted aromatic aldehydes. Owing to the extensive
biological and pharmacological applications of 3,4-dihy-
dropyrimidin-2(1H)-ones, many improved routes have
been continuously reported for the synthesis of these com-
pounds either by the classical one-pot Biginelli approach19
or through the development of novel multistep proce-
dures.20 In recent years, a variety of catalytic methods for
promoting the Biginelli reaction have been developed
employing various metal salts as Lewis acid catalysts
including LiBr,21a NiCl2ꢀ6H2O,21b FeCl3ꢀ6H2O,21b
CuCl2ꢀ2H2O,21c CeCl3ꢀ7H2O,21d Mn(OAc)3ꢀ2H2O,21e
indole derivatives,1 there is always a growing need for
new synthetic methods in this field. Vibrindole A, which
is a naturally occurring bisindolylmethane, exhibits
important biological activity.2 Bis(indolyl)methane and
tris(indolyl)methane scaffolds, which are mostly present
in natural products,3 exhibit a broad range of biological
activities including prevention of bladder cancer
growth,4 renal cell carcinoma growth,5 colon cancer,6
and breast cancer.7 Also, the oxidized forms of
bis(indolyl)methane and tris(indolyl)methane are
applied as dyes8 and calorimetric sensors.9 These various
notable uses of bis(indolyl)methane and tris(indolyl)
methane have encouraged researchers to find efficient
methods for the synthesis of indole derivatives. The gen-
eral method for the synthesis of bis(indolyl)methane
includes the reaction of aldehydes or ketones with
indoles in the presence of protic10 or Lewis acids,11
which is analogous to the acid-catalyzed Ehrich test.12
Numerous catalysts such as Montmorillonite K-10,
ZrCl4, ion-exchange resin, TBBDA, Ph3CCl,13 iodine,14
zeolites,15 and silica sulfuric acid (SSA)16 have been
found to promote these reactions.
21f
21g
21h
21i
21j
21k
ZrCl4, InCl3, InBr3, ZnCl2, CdCl2, LiClO4
,
21l
and Bi(NO3)3.
Dihydropyrimidinones and their derivatives are of
remarkable biological and pharmacological importance as
Compounds containing benzothiazoles rings have
been widely used in the pharmaceutical industry.17,22
*Corresponding author. Email: samira.kazemy@gmail.com
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Kazemi et al.
Benzothiazole derivatives are broadly established in
bioorganic and medicinal chemistry and have applica-
tions in drug discovery and development. They have
been applied for the treatment of autoimmune and
inflammatory diseases23 and in the prevention of
epilepsy,24 amyotrophic lateral sclerosis,25 analgesim,26
tuberculosis,27 viral infections,28 and cancer.29 Also,
benzothiazole derivatives are employed in industrial
chemistry as antioxidants30 and vulcanization accele-
tors.31 Therefore, due to the importance of these hetero-
cyclic compounds for the synthesis of benzothiazoles,
various methodologies have been described.29,32 From
the various reports, the most popular method usually
involves the oxidative condensation of 2-aminothio phe-
nols with carboxylic acids28,33 or aldehydes.34 Unfortu-
nately, most of the previously reported procedures have
many disadvantages and limitations such as high reac-
tion temperature, severe reaction requirements, long
reactions times, requirement for excess of reagents, tedi-
ous work-up procedures, low yields, use of costly toxic
or air-sensitive catalysts, and so on.35 Consequently,
there is still a need to develop simple, mild, rapid, and
inexpensive procedures for the synthesis of these
heterocycles.
Recently, significant factors such as reusability,
yield of products, simple recovery, cost of catalysts,
short reaction times, and green chemistry have led to
the use solid acid catalysts. Furthermore, applying het-
erogeneous catalysts such as zeolites have some benefits
such as nontoxicity and environmental friendliness,
suitable acidity, thermal stability, and shape selectivity,
which affect the efficiency of reactions, work-up, and
purity of the products.36–38 So, with the aim of develop-
ing a more efficient synthetic process, we now report
the synthesis of some bis(indolyl)methane, tris(indolyl)
methane, and tetrakis(indolyl)methane derivatives using
NaY zeolite functionalized by sulfamic acid/Cu(OAc)2
(NaY zeolite-NHSO3H/Cu(OAc)2) as a heterogeneous
catalyst under mild conditions (Schemes 1 and 2). Also,
this heterogeneous catalyst was used successfully for
catalyzing the Biginelii reaction (Scheme 3). Finally,
Scheme
derivatives.
1. Synthesis
of
bis(indolyl)methane
Scheme
derivatives.
2. Synthesis
of
tris(indolyl)methane
Scheme 3. Synthesis of 3,4-dihydropyrimidin-2
(1H)-ones.
several 2-aryl-1H-benzothiazoles were synthesized in
high yields at room temperature in the presence of this
catalyst (Scheme 4).
RESULTS AND DISCUSSION
Characterization of NaY zeolite-NHSO3H/Cu(OAc)2
The NaY zeolite-NHSO3H/Cu(OAc)2 catalyst was
characterized by Fourier transform infrared (FT-IR)
spectroscopy, scanning electron microscopy (SEM),
energy-dispersive X-ray (EDX), thermogravimetric
analysis (TGA), and X-ray diffraction (XRD). The FT-
IR spectra of NaY zeolite, NaY zeolite-NH2, NaY
zeolite-NHSO3H, and NaY zeolite-NHSO3H/Cu(OAc)2
are shown in Figure 1(a)–(d), respectively. The FT-IR
spectra of all hybrid materials indicate an intense band
at ~1049 cm−1 attributable to the asymmetric stretching
of the Al–O–Si chain of the zeolite. The symmetric
stretching and bending frequency bands of the Al–O–Si
Scheme 4. Synthesis of 2-aryl-1H-benzothiazoles.
2
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Synthesis of Some Heterocycles by a Novel Catalyst
Fig. 1. FT-IR spectra of NaY zeolite (a), NaY
zeolite-NH2 (b), NaY zeolite-NHSO3H (c), and NaY
zeolite-NHSO3H/Cu(OAc)2 (d).
framework of the zeolite appear at 765 and 455 cm−1
,
respectively.39 The out-of-plane bending and stretching
of the O–H group appear at 785 and 3400–3500 cm−1
,
respectively. The peak appearing at 1150 is assigned to
the S = O stretching vibration, which confirms the pres-
ence of the SO3H group (Figure 1(c) and (d)). The sym-
metric and asymmetric stretching vibration modes of
amine group are observed at 3200–3400 cm−1 (Figure 1
(b)–(d)). The weak band at 2900 cm−1 can be attributed
to the C–H stretching vibration (Figure 1(d)).
Fig. 3. EDX spectra of NaY zeolite-NHSO3H
(a)
and
NaY
zeolite-NHSO3H/Cu
The microstructure of the catalyst was investigated
using SEM. The SEM image of NaY zeolite-NHSO3H/
Cu(OAc)2 in Figure 2(b) shows particles with a mean
diameter of ~300 nm and nearly spherical shape, which
indicates no change in the particle’s size and shape
when compared to those for NaY zeolite-NHSO3H in
Figure 2(a).
(OAc)2 (b).
The EDX analysis of NaY zeolite-NHSO3H/Cu
(OAc)2 clearly reveals the presence of Cu as well as
other expected main elements including N, Al, Si, O,
C, Na, and S (Figure 3(b)). The lower intensity of Na
in comparison with that for NaY zeolite-NHSO3H
(Figure 3(a)) demonstrates the exchange of Na+ as a
monovalent cation by the divalent cation Cu2+ in zeo-
lite’s pores without any change in the zeolite
structure.
(a)
(b)
Thermal analysis was used to monitor the decom-
position profile of NaY zeolite-NHSO3H/Cu(OAc)2
(Figure 4). It shows a weight loss of 12% up to 350ꢁC
in first stage due to the adsorbed water in the catalyst.
The second-stage weight loss of 11% was observed in
the temperature range of ~350–430ꢁC, which is due to
the organic moiety. The weight loss above 450ꢁC is
attributed to zeolite decomposition.
Fig. 2. SEM images of NaY zeolite-NHSO3H
(a)
and
NaY
zeolite-NHSO3H/Cu
(OAc)2 (b).
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Kazemi et al.
(OAc)2; therefore, bis(indolyl)methane was obtained in
lower yield and over longer reaction times (Table 1,
entry 13). To prove the generality of this protocol, the
reaction was then extended to a variety of aldehydes
and ketones with indole, whose results are summarized
in Table 2. As the results show, both electron-
withdrawing (Table 2, entries 5, 6, 10, 11, and 12) and
electron-releasing groups (Table 2, entries 2, 3, 4, 8,
and 9) tolerate this condensation. In regard to the sug-
gested mechanism in Scheme 5, in the first condensation
of indole, the activity of aldehyde for nucleophilic
attack is important. As is known, the electron-
withdrawing substituents accelerate this step. So, the
electron-withdrawing groups drive the reaction faster
than electron-releasing substituents (Table 2, entries
5, 6, 10, 1,1 and 12). Also, it was observed that ortho
substituents (Table 2, entries 4, 5, 9, and 10) make the
reaction slower than para substituents (Table 2, entries
3, 6, 8, and 12) probably due to steric effects. Also, glu-
taraldehyde as an aliphatic dialdehyde, terphetalde-
hyde, and isophthalaldehyde were converted to the
corresponding tetrakis(indolyl)methanes in notable
yields (Table 2, entries 13–15). In addition, the effi-
ciency of the catalyst was tested for the condensation of
indole with some α, β-unsaturated ketones, and it was
observed that NaY zeolite-NHSO3H/Cu(OAc)2 was
also effective and usable for the one-pot condensation
of 3 mol of indole with α, β-unsaturated ketones
(Table 2, entries 16–18). As expected from the sug-
gested mechanism in Scheme 6, the reaction times for α,
β-unsaturated ketones are quite long because of the low
activity caused by conjugation. In this case, the reaction
could be accelerated by electron-withdrawing groups in
the alkene section of the molecule. Additionally, some
ketones including cyclic aliphatic ketone, acyclic ali-
phatic ketone, and acethophenone as an aromatic
ketone proceeded the reaction to provide the corre-
sponding products following this methodology. Gener-
ally, it was found that ketones reacted very slowly and
resulted in lower yields than aldehydes (Table 2, entries
19–22). Finally, isatin reacted to afford the correspond-
ing bis(indolyl)methane only in one carbonyl.
Fig. 4. TG-DTA curve of NaY zeolite-NHSO3H/
Cu(OAc)2.
Figure 5 illustrates the XRD pattern of NaY
zeolite-NHSO3H (Figure 5(a)) and NaY zeolite-
NHSO3H/Cu(OAc)2 (Figure 5(b)), which indicate no
changes in the general structure and morphology of
NaY zeolite during the immobilization procedures.
Synthesis of bis, tris, and tetrakis(indolyl)methanes using
NaY zeolite-NHSO3H/Cu(OAc)2
To evaluate the synthetic potential of this method,
the condensation of indole (2 mmol, 0.234 g) with benz-
aldehyde (1 mmol, 0.1 mL) in the presence of different
amounts of NaY zeolite-NHSO3H/Cu(OAc)2 and in
several solvents was studied as a model reaction. Con-
sidering the obtained results in terms of yields and reac-
tion times (Table 1), MeCN was found to be the best
solvent, and the optimal amount of the catalyst was
0.02 g (Table 1, entry 3). It is notable that NaY zeolite-
NHSO3H had lower catalytic effect than NaY/Cu
Finally, in order to demonstrate the efficiency of
this technique, it was compared with some reported
methods (Table 3). As this table shows, the proposed
method clearly gives improved yields and shorter reac-
tion times. Also, the reusability of the catalyst makes
Fig. 5. XRD pattern of NaY zeolite-NHSO3H
(a)
and
NaY
zeolite-NHSO3H/Cu
(OAc)2 (b).
4
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Synthesis of Some Heterocycles by a Novel Catalyst
Table 1. Optimization of the reaction parameters for synthesis of 3,30-(phenylmethylene)bis(1H-indole)
Entrya
Catalyst
Amount of catalyst (g)
Solvent
Time (min)
Yield (%)b
1
2
3
4
5
6
7
8
No catalyst
NaY zeolite
—
MeCN
MeCN
MeCN
DMF
CHCl3
Ethyl acetate
Toluene
EtOH
24 (h)
200
40
Trace
30
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.01
0.025
0.03
0.02
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H/Cu(OAc)2
NaY zeolite-NHSO3H
98
85
40
70
35
85
15
50
60
240
100
300
60
200
100
35
9
H2O
10
11
12
13
MeCN
MeCN
MeCN
MeCN
94
88
65
35
200
a Conditions: indole (2 mmol), benzaldehyde (1 mmol), solvent 4 mL, room temperature.
b Isolated yields.
the protocol less contaminative and nearly green. In
addition, since the catalyst is heterogeneous, the work-
up procedure is easy, and chromatography or other
complex purification methods are not necessary.
According to the obtained results, it seems that NaY
zeolite also helps the catalytic effect of sulfonic acid
group and accelerates the reaction.
On the basis of the above results, to investigate
the scope and generality of this method, the process
was extended to other aliphatic (Table 4, entries 10, 11,
and 13), aromatic (Table 4, entries 1–9), and hetero-
aromatic (Table 4, entry 12) aldehydes that tolerate
both electron-withdrawing and electron-donating sub-
stituents. It was observed that although the aliphatic
aldehydes generally reacted more slowly than aromatic
aldehydes, the catalyst was effective for all aldehydes.
The mechanism for the Biginelli reaction in acidic con-
ditions has been proposed by Kappe.18
Synthesis of 3,4-dihydropyrimidin-2(1H)-ones using NaY
zeolite-NHSO3H/Cu(OAc)2
In order to show the merit of the present work in
comparison with some reported procedures, we com-
pare the results of the synthesis of 3,4-dihydropyrimi-
din-2(1H)-ones (Table 4, entry1) in the presence of
NaY zeolite-NHSO3H/Cu(OAc)2 with some other con-
ditions (Table 5).
In order to study the efficiency of NaY zeolite-
NHSO3H/Cu(OAc)2 in the condensation reactions, sev-
eral 3,4-dihydropyrimidin-2(1H)-ones were prepared in
the presence of NaY zeolite-NHSO3H/Cu(OAc)2 as the
heterogeneous catalyst. For optimization of the reaction
conditions, the reaction of benzaldehyde with ethylace-
toacetate and urea as the model reaction was examined
by employing solvent-free conditions under various cat-
alyst molar ratios and reaction times. The experimental
results indicated that the highest yield of the reaction
product (97%) was obtained when NaY zeolite-
NHSO3H/Cu(OAc)2 (0.01 g/mol) was employed under
solvent-free conditions at 60ꢁC heating.
Synthesis of 2-aryl-1H-benzothiazoles using NaY zeolite-
NHSO3H/Cu(OAc)2
The catalytic effect of NaY zeolite-NHSO3H/Cu
(OAc)2 was also established by catalyzing the synthesis
of deferent benzothiazoles via one-pot cyclocondensa-
tion of 2-aminothiophenoles with aromatic aldehydes
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Kazemi et al.
Table 2. Synthesis of bis(indolyl)methanes, tris(indolyl)methanes, and tetrakis(indolyl)methanes
Entrya
1
Substrate
PhCHO
Product
Time (min)
40
Yield (%)b
98
Refs
40
2
3
4
4-Me-PhCHO
4-MeO-PhCHO
2-MeO-PhCHO
45
90
95
94
90
40
16
40
110
5
2-Cl-PhCHO
50
91
41
6
7
4-Cl-PhCHO
40
80
97
91
16
40
2,4-diCl-PhCHO
8
9
4-OH-PhCHO
2-OH-PhCHO
80
90
92
90
40
16
10
11
2-NO2-PhCHO
3-NO2-PhCHO
4-NO2-PhCHO
32
35
92
93
40
40
12
25
400
50
96
89
95
94
40
13c
14c
15c
New
42
60
43
16d
17d
300
240
91
94
New
New
18d
360
90
New
19
20
360
300
64
90
43
43
6
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Synthesis of Some Heterocycles by a Novel Catalyst
Table 2. Continued
Entrya
21
Substrate
Product
Time (min)
300
Yield (%)b
Refs
43
92
75
22
23
360
50
43
43
96
a Conditions: indole (2 mmol, 0.234 g), aldehyde (1 mmol), catalyst (0.02 g), MeCN (4 mL), rt.
b Isolated yields.
c Conditions: indole (4 mmol, 0.468 g), aldehyde (1 mmol), catalyst (0.04 g), MeCN (4 mL), rt.
d Conditions: indole (3 mmol, 0.351 g), chalcone (1 mmol), catalyst (0.03 g), MeCN (4 mL), rt.
Scheme 5. Suggested mechanism for synthesis of bis(indolyl)methane.
(Scheme 4). At first, reaction conditions were optimized
for the condensation of 2-aminothiophenole and benz-
aldehyde as the model reaction. The best yields and
reaction times were obtained under solvent-free condi-
good purity (Table 6). The possible mechanism for this
condensation in the presence of Lewis acid35a and zeoli-
te35b has been reported previously.
Scheme 6. Suggested mechanism for the synthesis of tris(indolyl)methane.
tions using 0.01 g/mol of catalyst at 40ꢁC. Aldehydes
with both electron-withdrawing and electron-releasing
groups participated in this reaction, and 2-aryl-1H-
benzothiazoles were obtained in excellent yields and
Catalyst recovery
To check the reusability of the catalyst, after the
completion of the reaction of indole with benzaldehyde
under the optimal reaction conditions, the filtered
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Kazemi et al.
Table 3. Comparing this method with some reported methodologies for the synthesis of 3,30-(phenylmethylene)bis(1H-indole)
Entry
Catalyst
Conditions
Time (min)
Yield (%)
Refs
1
2
3
4
5
6
7
NaY zeolite-NHSO3H/Cu(OAc)2
Secondary amine/ionic liquids
Silica sulfuric acid
Prolinium Triflate
Nano-SiO2
rt
M. W
rt
rt
80ꢁC/Ultrasonic
50ꢁC
40ꢁC
40
5
98
95
92
92
93
90
91
This work
40
16
41
44
45
46
42
300
60
57
60
1,3-Dibromo-5,5-dimethylhydantoin
n-Dodecylbenzene sulfonic acid
Table 4. Preparation of 3,4-dihydropyrimidin-2(1H)-onesa
Mp (ꢁC)
Entry
R
Reaction time (min)
Yield (%)b
Found
Reported (Ref )
1
2
3
4
5
6
7
8
C6H5
4-F-C6H4
15
12
17
20
25
35
60
20
55
70
75
40
100
97
94
91
90
92
88
93
98
89
92
91
85
60
205–207
181–182
223–225
220–223
201–203
225–228
249–251
211–213
250–252
182–184
120–123
219–221
181–183
204–20647a
182–18447a
227–22947a
222–22447a
205–20747a
227–22947a
249–25021b
215–21647b
247–24821k
182–18447c
120–12347c
215–21721g
180–18147b
3-NO2−C6H4
2-Cl-C6H4
4-MeO-C6H4
4-HO-C6H4
2,4-Cl2−C6H3
4-Me-C6H4
1-Naphthyl
PhCH2CH2
n-C7H15
9
10
11
12
13
Thiophen-2-yl
C2H5
a Conditions : ethylacetoactate (1.5 mmol), aldehyde (1 mmol), urea (1 mmol), catalyst (0.01 g), solvent-free, 60ꢁC.
b Isolated yield.
Table 5. Comparison of different methods for the synthesis of ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-
carboxylate
Entry
Catalyst
Time (min)
Solvent
Yield (%)
Temperature (ꢁC)
Refs
1
2
3
4
5
6
7
8
NaY zeolite-NHSO3H/Cu(OAc)2
CuCl2.2H2O
LaCl3 ꢀ 7H2O:HCl
HCl
Concentrated HCl
LiBr
Mn(OAc)3.2H2O
ZrCl4
InBr3
InCl3.4H2O
BiONO3
H3PMo12O40
p-TsOH
Silica sulfuric acid
Ersorb-4
KSF
15
60
None
None
97
96
95
78
79
92
96
90
98
94
96
80
91
91
93
82
60
100
Reflux
Reflux
rt
Reflux
Reflux
Reflux
Reflux
Reflux
40–50
reflux
reflux
Reflux
80
This work
17f
300
1080
4320
180
120
240
420
420
90
300
150
360
480
2880
EtOH
EtOH
MeOH
CH3CN
CH3CN
EtOH
EtOH
EtOH
CH3CN
AcOH
EtOH
EtOH
EtOH
None
21b
21b
18a
21a
21e
21f
9
21g
21g
21l
47d
47e
47a
47f
47g
10
11
12
13
14
15
16
130
8
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J. Chin. Chem. Soc. 2017

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Synthesis of Some Heterocycles by a Novel Catalyst
Table 6. Preparation 2-aryl-1H-benzothiazoles under optimized conditionsa
Mp (ꢁC)
Product
Ar
Time (min)
Yield (%)b
Found
Reported (Refs)
1
2
3
4
5
6
7
8
C6H5
20
18
30
30
35
25
19
90
95
97
92
88
87
90
94
88
113–115
230–232
156–158
123–126
170–172
85–87
112–11448
232–23535b
154–15835b
120–12248
169–17235b
84–8648
4-NO2C6H4
2,4-Cl2C6H4
4-MeOC6H4
4-(CH3)2NC6H4
2-ClC6H4
4-ClC6H4
3-NO2C6H4
118–120
181–182
118–11948
182–18448
a Conditions: 2-aminothiophenol (1 mmol), aldehyde (1 mmol), catalyst (0.01 g), solvent-free, 40ꢁC.
b Isolated yield.
catalyst was washed with chloroform, dried at 60ꢁC for
1 h, and reused for the model reaction (Table 2, entry
1). It was found that catalyst could be recycled for at
least six reaction cycles without notable changes in its
catalytic activity (Figure 6). Also after six runs, the FT-
IR spectrum of the recovered catalyst displayed no
obvious change in its structure in comparison to that of
the fresh catalyst (Figure 7).
Conclusion
In conclusion, NaY zeolite-NHSO3H/Cu(OAc)2
was found to be a mild, efficient, and reusable solid
acid catalyst for the reaction of indoles with aldehydes
to furnish bis(indolyl)methanes, tris(indolyl)methanes,
and tetrakis(indolyl)methanes at room temperature.
Also, the syntheses of 3,4-dihydropyrimidin-2(1H)-ones
and 2-aryl-1H-benzothiazoles were carried out success-
fully in the presence of NaY zeolite-NHSO3H/Cu
(OAc)2. The reusability of this heterogeneous organic/
Fig. 7. FT-IR spectra of fresh catalyst and the six
times reused catalyst.
inorganic hybrid catalyst makes this method nearly
green and environmentally friendly. High yields, rather
short reaction times, mild conditions, easy work-up,
good purity, and low-cost procedure are advantages of
this method.
EXPERIMENTAL
All chemicals used were purchased from Merck
and Fluka. Melting points were determined on an
electro-thermal digital melting point apparatus. The
catalyst was characterized by an atomic absorption
instrument (Varian SpectrAA 200), an X-Ray diffrac-
tometer (Philips 8440) at room temperature using Cu
Kα radiation, an FT-IR spectrometer (Galaxy series
FT-IR 5000), and a TGA-DSC apparatus (Rheometric
scientific STA-1500). NMR spectra were recorded on a
Bruker (300 MHz) spectrometer, and the chemical
shifts (ppm) were referenced to the internal standard
Fig. 6. Catalytic efficiency of the recycled catalyst.
J. Chin. Chem. Soc. 2017
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9

Article
Kazemi et al.
Scheme 7. Step-by-step synthesis of NaY zeolite-NHSO3H/Cu(OAc)2.
tetramethylsilane (TMS). Microanalyses were per-
formed by an elemental analyzer (Elemental, Vario EL
III) at Arak University. The Microanalyses results
agreed favorably with the calculated values. Reactions
were monitored by thin-layer chromatography using sil-
ica gel-coated aluminum sheets F254 (Merck).
General procedure for the synthesis of tris(indolyl)
methanes
To a mixture of indole (3 mmol, 0.351 g) and
α,β-unsaturated ketone (1 mmol) in 1,4-dioxane
(4 mL), NaY zeolite-NHSO3H/Cu(OAc)2 (0.03 g) was
added and stirred for an appropriate time at room tem-
perature. The work-up stage was similar to that
reported for the preparation of bis(indolyl)methanes.
Spectral data for the new compounds are as
follows:
1,1,5,5-Tetra(1H-indol-3-yl)pentane (13, Table 2):
Mp: 115–117ꢁC. IR (cm−1): 3410, 3053, 2924, 2852,
1616, 1456, 1415, 1336, 1276, 1244, 1091, 1010,
744, 491, 424. 1HNMR (δ (ppm), CDCl3): 0.92 (m,
2 H), 1.36 (m, 4 H), 4.68 (m, 2 H), 6.58–8.20 (m, 25 H).
13C NMR (δ (ppm), CDCl3):25.50, 32.90, 36.01,
102.60, 110.37, 111.05, 111.26, 111.49, 114.88, 117.63,
118.12, 119.10, 119.53, 119.81, 120.73, 121.70, 121.98,
122.42, 123.69, 124.17, 126.11, 126.56, 127.83, 135.75,
136.53, 137.17, 138.79, 140.08. Elemental analysis:
Calculated: C, 83.43; H, 6.06; N: 10.52. Obtained: C,
84.05; H, 6.23; N, 9.72.
General procedure for the synthesis of NaY zeolite-
NHSO3H/Cu(OAc)2 catalyst
To a mixture of NaY zeolite in toluene (20 mL),
trimethoxysilyl propylamine (2 mL) was added and stir-
red for 24 h under reflux conditions. Then zeolite was
separated by filtration and dried at 60ꢁC. For sulfona-
tion, chlorosulfonic acid (2 mL) and triethylamine
(0.2 mL) were added to a mixture of functionalized zeo-
lite (1 g) in toluene (20 mL) and stirred under reflux
conditions for 24 h. Finally, the precipitate was fil-
trated, washed with water, and dried at 60ꢁC as the
NaY-SA compound. A pH analysis of NaY-SA for
loading of SO3H showed 1 mmol/g. In the next step,
NaY-SA (1 g) was reacted with 100 mL of a 0.001 M
solution of Cu(OAc)2 in toluene for 24 h at room tem-
perature. After sonication (2 × 3 min), the NaY zeolite-
NHSO3H/Cu(OAc)2 product was filtered and dried at
60ꢁC (Scheme 7). Then the loading of copper in NaY
zeolite-NHSO3H/Cu(OAc)2 was determined to be 2%
by atomic absorption spectroscopy.
3,30-(3-(1H-Indol-2-yl)-1,3-diphenylpropane-1,1-
diyl)bis(1H-indole) (16, Table 2): Mp: 140–142ꢁC. IR
(cm−1): 3408, 3053, 2928, 2850, 1608, 1508, 1454, 1415,
1
1336, 1217, 1167, 1093, 1008, 744, 459, 422. H NMR
(δ (ppm), CDCl3): 2.90–2.97 (d, 2 H), 4.29 (m, 1 H),
6.57–8.05 (m, 28 H). 13C NMR (δ (ppm), CDCl3):
29.67, 38.84, 42.22, 98.61, 119.25, 111.05, 121.61,
121.87, 122.12, 123.14, 125.16, 127.60, 128.11, 128.61,
128.96, 129.53, 131.58, 132.15, 135.45, 135.78, 139.16,
14.12, 145.50. Elemental analysis: Calculated: C,
86.47; H, 5.77; N, 7.76. Obtained: C, 87.11; H,
5.67; N: 7.22.
General procedure for the synthesis of bis(indolyl)
methanes
To a mixture of indole (2 mmol, 0.234 g) and
aldehyde (1 mmol) in acetonitrile (4 mL), NaY zeolite-
NHSO3H/Cu(OAc)2 (0.02 g) was added and stirred for
an appropriate time at room temperature. After com-
pletion of the reaction as monitored by TLC (n-hexane/
EtOAc; 8:2), the NaY zeolite-NHSO3H/Cu(OAc)2 cata-
lyst was filtered and the organic layer evaporated under
reduced pressure to give the pure product.
3,30-(3-(1H-Indol-2-yl)-3-(4-nitrophenyl)-1-phenyl-
propane-1,1-diyl)bis(1H-indole) (17, Table 2): Mp:
127–129ꢁC. IR (cm−1): 3327, 3053, 2924, 2854, 1662,
10
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Synthesis of Some Heterocycles by a Novel Catalyst
1595, 1514, 1454, 1415, 1338, 1215, 1095, 1012,
846, 742, 686, 422, 223; H NMR (δ (ppm), CDCl3):
under reduced pressure to give the pure product. For
further purification, the products were recrystallized
from ethanol 96%. All the products were characterized
1
2.02 (m, 2 H), 4.17–4.26 (d, 1 H), 6.96–8.32 (m, 27 H);
13C NMR (δ (ppm), CDCl3): 31.10, 40.26, 63.34,
109.42, 111.64, 116.70, 117.95, 120.51, 123.36, 123.99,
125.27, 127.17, 127.78, 130.98, 133.53, 134.47, 140.49,
141.13, 142.37, 144.93, 161.43, 165.20. Elemental anal-
ysis: Calculated: C, 79.84; H, 5.15; N, 9.55.
Obtained: C, 78.56; H, 5.31; N, 9.87.
1
by their IR, H, and 13C NMR spectral data, and their
melting points were compared with literature values
(Table 6).35b,48
ACKNOWLEDGMENT
We thank Arak University for the scientific and
instrumental support.
3,30-(3-(1H-Indol-2-yl)-3-(4-methoxyphenyl)-1-phe-
nylpropane-1,1-diyl)bis(1H-indole) (18, Table 2): Mp:
114–116ꢁC. IR (Cm−1): 3404, 3059, 2920, 2850, 1656,
1595, 1510, 1456, 1421, 1338, 1294, 1251, 1217, , 1172,
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benzothiazoles
To a mixture of 2-aminothiophenol (1 mmol) and
aldehydes (1 mmol) was added NaY zeolite-NHSO3H/
Cu(OAc)2 (0.01 g) and heated at 40ꢁC for an appropri-
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Article
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