Synthesis of spirooxindole derivatives catalyzed by GN/SO3H nanocomposite as a heterogeneous solid acid

Article abstract of DOI:10.1007/s11164-018-3535-5

In this study, we synthesized a GN/SO₃H solid acid nanocomposite by immobilization of chlorosulfonic acid onto the surface of g-C₃N₄. The nanocomposite was characterized by different techniques (transmission electron micro

Full text of DOI:10.1007/s11164-018-3535-5

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Synthesis of spirooxindole derivatives catalyzed by GN/
SO3H nanocomposite as a heterogeneous solid acid
Ali Allahresani1 Bahare Taheri1 M. A. Nasseri1
•
•
Received: 11 May 2018 / Accepted: 12 July 2018
Ó Springer Nature B.V. 2018
Abstract
In this study, we synthesized a GN/SO3H solid acid nanocomposite by immobi-
lization of chlorosulfonic acid onto the surface of g-C3N4 . The nanocomposite was
characterized by different techniques (transmission electron microscopy, Fourier
transform infrared spectroscopy, thermal gravimetric analysis, atomic absorption
spectroscopy, X-ray diffraction, and energy dispersive X-ray spectrometer). The
GN/SO3H nanocomposite was then applied to the synthesis of spirooxindole
derivatives via multicomponent reaction of isatins, 1,3-dicarbonyl compounds, and
malononitrile at reflux conditions in an ethanol/water solvent (1:1). The heteroge-
neous nanocomposite showed high catalytic activity in one-pot; the multi-compo-
nent reaction of malononitrile, isatins, and 1,3-dicarbonyl compounds under reflux
conditions and the corresponding spirooxindole derivatives were synthesized in
good to excellent yields (70–95%). We found that the nanocomposite can be easily
recovered and reused for several times with a minimal decrease of its catalytic
performance.
Keywords Graphitic carbon-nitride Á Heterocyclic compounds Á Spirooxindole
derivatives Á Heterogeneous solid acid
Introduction
Sulfuric acid as a homogeneous Bronsted acid is a liquid acid which is widely used
as a catalyst for the synthesis of chemical compounds in different industries. Despite
high catalytic efficiency, atom and energy-inefficiency, tedious workup, equipment
corrosion, environmental pollution due to the production of large-scale sulfate
wastes and neutralization of this catalyst are some drawbacks of using sulfuric acid
&
Ali Allahresani
a_allahresani@birjand.ac.ir; rasaniali@gmail.com
1
Department of Chemistry, Faculty of Sciences, University of Birjand,
P.O. Box 97175-615, Birjand, Iran
123

A. Allahresani et al.
[1–3]. The design and production of active and stable heterogeneous solid sulfonic
acids is a key to solving these problems. Some metal oxide nanomaterials and
organic compounds are used for the construction of these desired solid acids, but
such materials are usually expensive and have been shown to possess many fewer
sulfuric acid active sites. Recently, an attractive field has opened by the use of
carbon nanomaterials for the immobilization of -SO3H [4–7]. Carbon nitride as a
new type of carbon nanomaterial; A 2-D graphene-like nanosheet can be a good
candidate for the immobilization of organic and inorganic compounds developing
various type of nanocomposites with a different type of active sites. These
nanocomposites have special thermal and chemical stability as well as multiple
applications, especially in the field of photocatalysis. Recently, several papers report
the application of g-C3N4 and related compounds as catalysts in the oxidation of
alcohols, amines, and alkenes with oxygen under visible light, conversion of
carbohydrates into furanics products and the synthesis of biodiesel [8–12].
This compound has other important uses in the fields of material science, optics
and electronics. Moreover, many metal and metal oxides, as well as organic
compounds, have been supported onto the surface of g-C3N4;such metal and metal
oxides and the catalytic activity of corresponding nanocomposites have been
investigated in many fields, especially in the field of environmental pollution
[13–21].
On a different note, heterocyclic compounds are valuable intermediates for the
synthesis of medicinal drugs. The synthesis of oxindole derivatives as an important
type of heterocyclic compounds is still a challenge in the field of organic chemistry
and industrial science. Oxindole derivatives possess good biological and pharma-
ceutical activities [22, 23]. Therefore, the synthesis of these compounds is highly
desirable for medicinal industries. Thus, in continuation of our attempt to develop
novel and benign environmental synthetic protocols [24, 25], herein, we synthesized
GN/SO3H by immobilization of chlorosulfonic acid onto the surface of g-C3N4 and
apply the corresponding nanocomposite to the synthesis of spirooxindole derivatives
via multicomponent reaction of isatins, 1,3-dicarbonyl compounds, and malonon-
itrile at reflux conditions in solvent (ethanol/water: 1:1) (Scheme 1).
Experimental methods
Materials
All chemical materials were purchased from Merck Company. The thermal
gravimetric analysis (TGA), XRD, Fourier transform infrared spectroscopy (FT-IR),
energy dispersive X-ray spectrometer (EDX), and transmission electron microscopy
(TEM) were done using a Perkin-Elmer Diamond TG/DTA thermal analyzer, a
Bruker D8-Advance X-ray diffractometer, a Perkin Elmer FT-IR spectrometer
(Spectrum 2), a JEOL JSM-6360 scanning electron microscope and a Philips CM10
1
instrument, respectively. H and 13C-NMR spectra were also recorded by a Bruker
DPX-250 MHZ Advance NMR instrument.
123

Synthesis of spirooxindole derivatives catalyzed by…
Scheme 1 The synthesis of spirooxindole derivatives catalyzed by GN/SO3H nanocomposite
Synthesis of the g-C3N4 nanosheet
10 grams of melamine were added to an alumina crucible with a cover and the
contents of the crucible were heated in a muffle furnace at air atmosphere at a rate of
2.5 °C/min to 550 °C and kept for 4 h at this temperature. After the time completed,
g-C3N4 (yellow powder) was collected and stored for further use [24].
Synthesis of GN/SO3H nanocomposite
1 g of g-C3N4 was dispersed in dichloromethane (20 mL) for 30 min. Then, a
solution of 4 mL of chlorosulfonic acid in 10 mL dichloromethane was added
dropwise to the solution and stirred for an appropriated time. After that, the GN/
SO3H was separated, washed and dried in an Oven at 80 °C for 8 h.
General procedure for the synthesis of Spirooxindole derivatives
GN/SO3H (80 mg) was added to the 3 mL of EtOH/water (1:1) and dispersed for
30 min. Then, malononitrile (1 mmol), isatin (1 mmol), and dimedone (1 mmol)
were added to the mixture and the mixture was heated to reflux and kept at this
temperature for an appropriate time. After the time of reaction was completed, water
was separated by centrifuging followed by extracting the crude product by ethyl
acetate. The solvent was dried using Na2SO4 and removed from the reaction by
evaporation with a rotary evaporator. Finally, the crude product was recrystallized
in hot ethanol to achieve the pure product. The GN/SO3H nanocomposite was
washed and reused several times.
123

A. Allahresani et al.
Selected spectral data
2-Amino-20,5-dioxo-5,6,7,8-tetrahydrospiro-[chromene-4,30-indoline]-3-carbonitrile
1
White solid, M.p. [ 250 °C. H-NMR (250 MHz, DMSO-d6), ppm: 1.92 (2H, t,
CH2), 2.15 (2H, m, CH2), 2.67 (2H, t, CH2), 6.67 (1H, d, ArH), 6.91 (1H, t, ArH),
7.13 (1H, d, ArH), 7.23 (1H, t, ArH), 7.37 (2H, s, NH2), 10.67 (1H, s, NH). 13C-
NMR (62.9 MHz, DMSO-d6), ppm: 19.86, 26.88, 36.41, 46.95, 57.65, 109.20,
111.93, 117.47, 121.86, 123.38, 128.57, 134.65, 142.2, 158.71, 166.14, 178.25,
195.14. IR/cm-1: 3356 (N–H), 3295 (N–H), 3170 (C–H, sp2), 2953 (C–H, sp3),
2205 (CN), 1715 (C=O), 1652 (N–C=O), 1474 (C–H, Ar).
2-Amino-7,7-dimethyl-20,5-dioxo-5,6,7,8-tetrahydrospiro [chromene-4,30-indoline]-3-
1
carbonitrile White solid, M.p. [ 250 °C. H-NMR (250 MHz, DMSO-d6) ppm:
0.97 (6H, s, 2CH3), 2.14 (2H, s, CH2), 2.42 (2H, s, CH2), 6.72-7.25 (4H, ArH, 2H,
NH2, m), 10.37 (1H, s, NH). 13C-NMR (62.9 MHz, DMSO-d6) ppm: 27.45, 28.06,
32.32, 47.27, 50.44, 57.90, 109.77, 111.24, 117.73, 122.42, 123.41, 128.55, 134.80,
142.40, 152.0, 159.35, 164.52, 178.45, 195.37. IR/cm-1: 3374 (N–H), 3318 (NH),
3142 (C–H, sp2), 2924 (C–H, sp3), 2190 (CN), 1720 (C=O), 1657 (N–C=O), 1603
(C–H, Ar), 1472 (C–H, Ar).
2-Amino-10-benzyl-7,7-dimethyl-20,5-dioxo-5,6,7,8-tetrahydrospiro [chromene-4,30-
indoline]-3-carbonitrile White solid, M.p. [ 250 °C. 1H-NMR (250 MHz,
DMSO-d6) ppm: 1.08 (3H, s, CH3), 1.05 (3H, s, CH3) 2.12–2.26 (2H, m, CH2),
2.54 (2H, s, CH2), 4.96 (2H, s, CH2-Ar), 6.73 (1H, d, ArH), 6.85 (1H, t, ArH),
7.11–7.18 (2H, m, ArH), 7.20–7.33 (3H, m, ArH), 7.41 (2H, s, NH2), 7.53 (2H, d,
ArH). 13C-NMR (62.9 MHz, DMSO-d6) ppm: 27.44, 28.17, 32.44, 43.72, 47.05,
50.35, 57.50, 109.33, 111.0, 117.95, 123.03, 123.45, 127.55, 127.63, 128.74,
128.84, 134, 136.65, 143.03, 159.42, 165.03, 177.23, 195. IR/cm-1: 3324 (N–H),
3298 (NH), 3144 (C–H, sp2), 2923 (C–H, sp3), 2195 (CN), 1715 (C=O), 1660 (N–
C=O), 1600 (C–H, Ar), 1465 (C–H, Ar).
2-Amino-200,5-dioxo-5,6-dihydro-spiro[pyrano[3,2-c]quinoline-4,30-indoline]-3-car-
bonitrile White solid, M.p.[ 250 °C. 1H-NMR (250 MHz, DMSO-d6), ppm: 6.82
(1H, d, ArH), 6.94 (1H, t, ArH), 7.22 (1H, d, ArH), 7.32 (1H, d, ArH), 7.40 (1H, t,
ArH), 7.45 (1H, t, ArH), 7.51 (1H, d, ArH), 7.52 (2H, s, NH2), 7.97 (1H, d, ArH),
10.70 (1H, s, NH). 13C-NMR (62.9 MHz, DMSO-d6), ppm: 57.52, 70.21, 101.92,
109.90, 112.93, 117.0, 117.44, 122.55, 123.21, 124.55, 125.40, 129.30, 133.55,
134.17, 142.71, 152.43, 155.50, 155.75, 158.93, 177.40. IR/cm-1: 3414 (NH), 3264
(N–H), 3145 (C–H, sp2), 2942 (C–H, sp3), 2205 (CN), 1715 (C=O), 1678 (N–C=O),
1602 (C–H, Ar), 1470 (C–H, Ar).
Results and discussion
To synthesize GN/SO3H heterogeneous solid acid nanocomposite, at first, g-C3N4
was thermally synthesized and dispersed in dichloromethane and chlorosulfonic
acid was added dropwise to the mixture and stirred for a definite time. Then, the
123

Synthesis of spirooxindole derivatives catalyzed by…
corresponding GN/SO3H nanocomposite was characterized by several techniques
including TGA, TEM, XRD, and FT-IR.
Characterizations of catalyst
The IR Spectra of g-C3N4 and GN/SO3H are shown in Fig. 1. The broad peaks
ranging from 3000 to 3450 cm-1 are assigned to the stretching vibration of the N–H
bond. Heterocyclic C=N stretching vibration bond appeared at 1648 cm-1. The
vibration of C–N bond of tri-triazine showed vibration bonds at 1235, 1320, 1405,
and 1545 cm-1. In addition, the peak centered at 807 cm-1 is assigned to the out-
of-plane vibration of the triazine cycle. A new broad peak which ranges from 1050
to 1100 and 500 cm-1 belongs to S=O and confirmed that -SO3H is supported onto
the surface of g-C3N4 (Fig. 1b).
Figure 2, shows the XRD patterns of g-C3N4 and GN/SO3H. In the XRD patterns
of g-C3N4, the peaks at 13.1° and 27.4° are assigned to (100) and (002) (according
to JCPDS 087-1526). These peaks show in-plane repeated units, an interlayer
stacking peak, and the hexagonal phase of the nanosheet of g-C3N4, respectively
(Fig. 2a). In Fig. 2b, despite the presence of -SO3H, g-C3N4 still has a crystalline
nature.
Figure 3a, b show the TEM images of g-C3N4 and GN/SO3H, respectively. The
TEM image of pure g-C3N4 nanosheets shows the agglomeration of the lamellar
structure (Fig. 3a). Figure 3b shows the TEM image of GN/SO3H, which
demonstrate the presence of –SO3H on the surface of g-C3N4 nanosheets.
The thermal stability of g-C3N4 and GN/SO3H were investigated (Fig. 4). Both
samples have an initial weight loss of about 2–3% at a temperature range of about
100 °C, which belongs to the removal of absorbed water. The pure g-C3N4 is
stable up to 550 °C and the sublimation or decomposition of g- C3N4 nanosheets
Fig. 1 FT-IR spectra of g-C3N4 (a) and Gn/SO3H (b)
123

A. Allahresani et al.
Fig. 2 XRD pattern of g-C3N4
(a) and GN/SO3H (b)
Fig. 3 TEM images of g-C3N4
(a) and GN/SO3H (b)
123

Synthesis of spirooxindole derivatives catalyzed by…
Fig. 4 TGA images of g-C3N4 (a) and GN/SO3H (b)
was started by increasing the temperature from 550 °C and completed at 600 °C
(Fig. 4a). In the GN/SO3H, the decomposition temperature increased to 650 °C,
confirming that -SO3H has tight contact with g-C3N4 (Fig. 4b).
The EDX analysis was used for the distribution of elements in GN/SO3H (Fig. 5).
It was found that the percentage of C, N, O, and S are 31.37, 62.53, 5.58, and 0.52,
respectively. The presence of S and O atoms confirm the successful synthesis of the
composite.
Fig. 5 The EDX pattern of GN/SO3H
123

A. Allahresani et al.
Catalytic activity
A control experiment consisted of 1 mmol of isatin, malononitrile and 1,3-
cyclohexadione, confirming that in the absence of the catalyst only a trace amount
of the corresponding product was detected (Table 1, entry 1). An additional
experiment containing 1 mmol of isatin, malononitrile and 1, 3-cyclohexadione in
the presence of g-C3N4 was conducted and the same results were obtained (Table 1,
entry 8). The mixture was then heated at reflux conditions for 1 h and the reaction
was not progressed. Then, a model reaction consisting of 1 mmol of isatin,
malononitrile and 1, 3-cyclohexadione was selected for the catalytic activity of GN/
SO3H. Catalyst in the amount of 0.04 g was dispersed in ethanol/water (1:1) and
1 mmol of each reactant was added to the mixture and heated at room temperature
for 80 min; the prepared product was obtained in 20% yield. This model reaction
was repeated at reflux conditions for the mentioned time and 58% product was
isolated (Table 1, entry 2). These results showed that GN/SO3H was essential for
the progress of the reaction at reflux conditions. Then, the effect of the amount of
catalyst was investigated on the yield of the reaction at reflux conditions and the
results showed that 0.08 g of catalyst is the optimum condition for the model
reaction (Table 1, entry 5). Further increase in the amount of catalyst did not show a
considerable increase in the yields nor decrease the time of the reaction (Table 1,
entries 6 and 7). Due to the important effect of solvent on the progress of the
reactions, the progress of the reaction was investigated using different nonpolar,
medium and high polar solvents; the mixture of ethanol and water (1:1) was chosen
as the best solvent in terms of the yield and time of the model reaction (Table 2,
Entry 10).
After the reaction parameters were conditioned, the generality of the method for
the production of spirooxindoles was investigated. Three types of ketone consisting
of 1,3-cyclohexadione, dimedone and aldehyde derivatives, as well as 1,
4-hydroxycoumarin, were reacted with isatin and malononitrile; the results are
Table 1 The effect of different
amount of GN/SO3H
Entry
GN/SO3H (g)
Time (min)
Yielda
1
2
3
4
5
6
7
8b
–
80
80
50
40
40
40
40
80
Trace
58
0.04
0.06
0.07
0.08
0.1
90
90
95
97
0.11
0.1
98
Trace
Isatin (1.0 mmol), malononitrile (1 mmol), 1,3-cyclohexadione
(1 mmol), ethanol/water (1:1) (3 mL). Reflux conditions
aIsolated yields
bg-C3N4 as catalyst
123

Synthesis of spirooxindole derivatives catalyzed by…
Table 2 The effect of solvent
on the yield of spirooxindoles
Entry
Solvent (3 mL)
Time (min)
Yield (%)
1
2
n-Hexane
CH2Cl2
THF
120
55
50
50
60
60
60
60
60
40
18
47
60
40
75
61
77
75
49
95
3
4
CHCl3
5
CH3CN
EtOAc
6
7
MeOH
8
EtOH
9
H2O
10
EtOH/water (1:1)
Isatin (1.0 mmol), 1,3-cyclohexadione (1 mmol), malononitrile
(1 mmol), GN/SO3H (0.08 g). Reflux conditions
displayed in Table 3. Also, the effect of isatin derivatives was investigated. When
1,3-cyclohexadione and malononitrile were reacted with different types of isatins,
the results showed the substituent groups of the benzene ring of isatin (electron-
neutral, electron-rich or electron-poor groups) have no considerable effect on the
yield of the reaction, and the desired products were produced in high yields
(Table 3, entries 1–9, 90–98%). By using dimedone instead of 1,3-cyclohexadione,
the progress of the reaction was slightly increased (Table 3, entries 10–13). In the
case of 4-hydroxycoumarin as a substrate, the reactions were proceeded more
slowly and lower yields were observed, which may be due to the lower activity of
carbonyl group of 4-hydroxycoumarin (Table 3, entries 14–22). The effect of
benzaldehyde derivatives was also investigated in the reactions; the results showed
that the yields and times of the reactions were emphasized, and longer times with
lower yields were observed (Table 3, entries 23–27). The efficiency of the catalyst
was compared with those reported in the literature [26–33]. As can be seen in
Table 4, this catalyst showed good catalytic activity and excellent yields (95%) in
shorter times compared to most of the reported works (Table 4, entries 1–5).
In addition, a reasonable mechanism for preparation of spirooxindole derivatives
was introduced (Scheme 2). GN/SO3H can activate the carbonyl group of isatin, and
after that malononitrile, nucleophilic attack to activated carbon generate interme-
diate 2. This intermediate generates intermediate 3 via elimination by Konevenagel
condensation; after addition of dimedone to this intermediate the corresponding
product was synthesized [34].
Reusability of the catalyst is important for industries. Therefore, after each
experiment, the nanocomposite was separated and applied for another reaction and,
as the results showed, no considerable decrease in the yields were observed even
after 10 cycles, which confirms the stability and efficiency of the catalyst (Fig. 6).
123

A. Allahresani et al.
Table 3 Preparation of oxindole derivatives
Entry
Product
Substrate 1
Substrate 2
Time (min) Yield (%)
1
40
40
40
95
92
95
2
3
4
5
40
40
90
97
6
7
8
40
40
40
95
95
95
9
40
91
123

Synthesis of spirooxindole derivatives catalyzed by…
Table 3 continued
Entry
Product
Substrate 1
Substrate 2
Time (min) Yield (%)
10
40
95
11
12
40
40
93
91
13
14
40
60
95
85
15
60
86
16
17
60
75
60
88
123

A. Allahresani et al.
Table 3 continued
Entry
Product
Substrate 1
Substrate 2
Time (min) Yield (%)
18
60
60
70
85
85
75
83
89
19
20
21
22
23
60
60
60
120
24
120
90
123

Synthesis of spirooxindole derivatives catalyzed by…
Table 3 continued
Entry
Product
Substrate 1
Substrate 2
Time (min) Yield (%)
25
70
85
90
90
26
27
120
93
Reaction condition: Isatin (1 mmol), malononitrile (1 mmol), dimedone (1 mmol)
Table 4 The comparison of the efficiency of GN/SO3H with different catalysts
Entry
Catalyst
Solvent/T (°C)
Time (min)
Yield (%)
References
1
2
3
4
5
6
7
8
9
Sodium stearate
TEBA
H2O/60 °C
H2O/90 °C
DMSO/60 °C
H2O/60 °C
Urea: CHCl3/80 °C
Ethylene glycole
H2O/ref.
180
120
120
480
240
20
95
88
40
88
88
88
80
80
95
[26]
[27]
AIUM (10 mol%)
B-CD
[28]
[29]
DES (0.5 mL)
Ni NPS
[30]
[31]
SBA-PR-NH2
NET3
5
[32]
EtOH/ref.
30
[33]
GN/SO3H
EtOH/water (1:1), ref.
40
This work
Isatin (1 mmol), malononitrle (1 mmol), dimedone (1 mmol)
Conclusions
In summary, we easily synthesized GN/SO3H nanocomposite by immobilization of
chlorosulfonic acid onto the g-C3N4 and characterized the nanocomposite by FT-IR,
TGA, XRD, EDX, and TEM. To study the catalytic activity of as-prepared
nanocomposite, the reactions of isatin derivatives with malononitrile and different
carbonyl compounds were studied using GN/SO3H via one-pot, three-component
reaction at reflux conditions. The results showed that the products were produced at
123

A. Allahresani et al.
H
CN
=
GN/SO3H
O
O
CN
O
O
N
H
O
N
H
(2)
O
(1)
N
H
O
H
N
O
H
H
N
CN
O
O
C
CN
O
O
NC
NH2
CN
N
H
O
O
N
O
H
(3)
Scheme 2 The reasonable mechanism for the synthesis of spirooxindole derivatives
Fig. 6 The reusability of GN/SO3H for the synthesis of spirooxindole derivatives
excellent yields in a short time. Compared to 1,3-cyclohexadione and dimedone,
4-hydroxycoumarin gave lower yields in a longer time. Finally, this protocol has
some advantageous including easy recovery and reusability and stability of the
catalytic system, with eco-friendly as well as excellent yields.
Acknowledgements The authors are grateful from the University of Birjand for the financial support.
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