Application of sulfonic acid functionalized SBA-15 as a new nanoporous acid catalyst in the green one-pot synthesis of spirooxindole-4H-pyrans

Article abstract of DOI:10.1002/jhet.1746

Sulfonic acid functionalized SBA-15 (SBA-Pr-SO₃H) as a new nanoporous solid acid catalyst was applied in the green one-pot synthesis of spirooxindole-4H-pyrans via condensation of isatins, malononitrile or methyl cyanoacetate or ethyl cyanoacetate, and 4-hydroxycoumarin in water solvent. SBA-Pr-SO₃H was proved to be an efficient heterogeneous nanoporous solid acid catalyst with a pore size of 6 nmthat could be easily handled and removed from the reaction mixture by simple filtration and can be recovered and reused for several times without any loss of activity. The significant merits of present methodology are its simplicity, short reaction time, good yields, and environmentally benign mild reaction condition as water was used as a green solvent.

Full text of DOI:10.1002/jhet.1746

Month 2014 Application of Sulfonic Acid Functionalized SBA-15 as a New Nanoporous
Acid Catalyst in the Green One-Pot Synthesis of Spirooxindole-4H-pyrans
a
a
b
b
*
Negar Lashgari, Ghodsi Mohammadi Ziarani, Alireza Badiei, and Mansoureh Zarezadeh-Mehrizi
aDepartment of Chemistry, Alzahra University, P.O. Box 1993891176, Iran
bSchool of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6455, Iran
*
E-mail: gmziarani@hotmail.com
Received February 18, 2012
DOI 10.1002/jhet.1746
Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
Sulfonic acid functionalized SBA-15 (SBA-Pr-SO3H) as a new nanoporous solid acid catalyst was applied in
the green one-pot synthesis of spirooxindole-4H-pyrans via condensation of isatins, malononitrile or methyl
cyanoacetate or ethyl cyanoacetate, and 4-hydroxycoumarin in water solvent. SBA-Pr-SO3H was proved to
be an efficient heterogeneous nanoporous solid acid catalyst with a pore size of 6 nm that could be easily handled
and removed from the reaction mixture by simple filtration and can be recovered and reused for several times
without any loss of activity. The significant merits of present methodology are its simplicity, short reaction time,
good yields, and environmentally benign mild reaction condition as water was used as a green solvent.
J. Heterocyclic Chem., 00, 00 (2014).
INTRODUCTION
The spirooxindole ring system is one of the most impor-
tant spirocycles found in a variety of natural products [15].
It is also the central structural framework of bioactive
molecules [16].
In continuation of our studies toward using nanoporous
solid acid catalysts in organic reactions [17–20], in this arti-
cle, we investigate the catalytical activity of SBA-Pr-SO3H
as a highly efficient heterogeneous acid catalyst and an active
nanoreactor in the synthesis of spirooxindole-4H-pyrans.
In recent times, many research efforts have been focused on
the preparation and the application of new solid acid catalysts
such as ordered mesoporous materials. Their environmental
compatibility, reusability, high selectivity, operational sim-
plicity, and ease of isolation of the products have led to poten-
tial application of these materials in different fields such as
catalysis [1], separation [2,3], sensor design [4], and
nanoscience [5]. The SBA-15 is a new nanoporous silica with
hexagonal structure, large pore size, high surface area, great
pore wall thickness, and high thermal stability that makes it
a unique inorganic solid support. SBA-15 functionalized with
organic and inorganic moieties exhibits efficient catalytic
activity in a variety of organic transformations [6]. Integration
of acidic functional groups (e.g., -SO3H) into SBA-15 has
been investigated to make promising solid acids [7]. Applica-
tions of these nanocatalysts in organic synthesis and one-pot
reactions in green conditions have great importance.
The 4H-pyran derivatives are found to possess various
biological and pharmacological properties, such as antibac-
terial [8], antiviral [9], and diuretic activities [10]. They
have been identified as potent and specific IKCa channel
blockers [11] and inhibitors of influenza virus sialidase
[12]. Moreover, they can be used as cognitive enhancers
for the treatment of neurodegenerative diseases [13]. Some
of 2-amino-4H-pyrans can be employed as photoactive
materials [14].
RESULTS AND DISCUSSION
A green method for the synthesis of spirooxindole-
4H-pyrans was achieved by the one-pot three-component
condensation of isatin 1, malononitrile 2, and 4-hydroxy-
coumarin 3 in the presence of SBA-Pr-SO3H (Scheme 1).
To optimize the reaction conditions, various solvents
such as H2O, EtOH, the mixture of H2O and EtOH (1:1),
and also solvent-free system were studied in the synthesis
of spirooxindole-4H-pyrans. It was found that water is
the most effective solvent for the reaction of isatin,
malononitrile, and 4-hydroxycoumarin in the presence of
SBA-Pr-SO3H (0.02 g) that affords the desired product in
good yield (Table 1). It was reported that in the absence
of the catalyst, the product was obtained in low yield [21].
Therefore, a series of differently substituted spirooxin-
dole-4H-pyrans were successfully prepared, and the results
© 2014 HeteroCorporation

N. Lashgari, G. Mohammadi Ziarani, A. Badiei, and M. Zarezadeh-Mehrizi
Vol 000
Scheme 1
Table 1
The efficiency of various catalysts in the synthesis of 2-
amino-5-oxo-spiro[(30H)-indol-30,4-4(H)-pyrano(3,2-c)chro-
men]-(10H)-20-one-3-carbonitrile 4a as the model of reaction
has been compared in Table 3. The high yield of product and
short reaction time, in contrast with other existing methods,
demonstrated that SBA-Pr-SO3H with distinct features such
as the pore size of 6 nm acts as an efficient nanoreactor in
this reaction. In other words, it was employed as a nanoscale
environment where the reaction takes place easily in its
nanopores (Fig. 1).
The SBA-15 as a new nanoporous silica can be prepared
by using commercially available triblock copolymer Pluro-
nic P126 as a structure directing agent [34]. The sulfonic acid
functionalized SBA-15 was usually synthesized through
direct synthesis or post-grafting [35,36]. A schematic illus-
tration for the preparation of SBA-Pr-SO3H was shown in
Figure 2. First, the calcined SBA-15 silica was functiona-
lized with (3-mercaptopropyl)trimethoxysilane, and then,
the thiol groups were oxidized to sulfonic acid by hydrogen
peroxide. The surface of the catalyst was analyzed by differ-
ent methods such as TGA, BET, and other methods that were
demonstrated that the organic groups (propyl sulfonic acid)
were immobilized into the pores [19].
The optimization of reaction condition in the synthesis of spirooxindole-
4H-pyran 4a.a
Entry
Solvent
EtOH
Time (min)
Yield (%)b
1
2
3
4
15
20
15
60
80
85
90
75
EtOH/H2O
H2O
Neat (130ꢁC)
aReaction conditions: isatin (2 mmol), 4-hydroxycoumarin (2 mmol),
malononitrile (2 mmol), SBA-Pr-SO3H (0.02 g).
bIsolated yield.
are summarized in Table 2. It was demonstrated that lower
reactivities of the cyanoacetates resulted in longer reaction
times than those of malononitrile. The new products are char-
1
acterized by mp, IR, GC–MS, and H NMR spectral data.
Melting points of known products are compared with
reported values in the literature. The acid catalyst can be
reactivated by simple washing subsequently with diluted
acid solution, water and acetone, and then reused without no-
ticeable loss of reactivity.
The proposed mechanism is shown in Scheme 2. After
protonation of carbonyl group of isatin 1 by the solid acid
catalyst, a fast Knoevenagel condensation occurs between 1
and CH-acidic of cyanoacetic ester 2 to afford isatilidene
malononitrile derivatives 10. Then, Michael addition of 10
with 4-hydroxycoumarin 3 followed by cycloaddition of
hydroxyl group to the cyano moiety provides the desired
product 4 (Scheme 2).
The surface area, average pore diameter calculated by
the BET method, and pore volume of SBA-Pr-SO3H
are 440 m2 gꢀ1, 6.0 nm, and 0.660 cm3 gꢀ1, respectively,
which are smaller than those of SBA-15 because of the
immobilization of sulfonosilane groups into the pores
(Table 4).
Table 2
Synthesis of spirooxindole-4H-pyran derivatives in the presence of SBA-Pr-SO3H under reflux conditions.
Entry
R
X
Product
Time (min)
Yield (%)
mp (ꢁC)
mp (Lit.)
1
2
3
4
5
6
7
8
9
H
Cl
Br
H
Cl
Br
H
CN
CN
CN
COOMe
COOMe
COOMe
COOEt
COOEt
COOEt
4a
4b
4c
4d
4e
4f
4g
4h
4i
15
20
20
20
20
35
30
30
35
90
85
78
75
78
75
83
91
84
304–306
>300
>300
279–280
287–288
296–298
257–260
280–282
285–286
303 [21]
>300 [22]
>300 [23]
275–277 [24]
New
New
251–253 [23]
New
Cl
Br
New
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014 Spirooxindole-4H-pyrans Synthesis Using SBA-Pr-SO3H as a Nanoporous Acid Catalyst
Scheme 2
Figure 3 illustrates the SEM and TEM images of
SBA-Pr-SO3H. SEM image (Fig. 3, left) shows uniform
particles about 1 mm. The same morphology was observed
for SBA-15. It can be concluded that morphology of solid
was saved without change during the surface modifica-
tions. On the other hand, the TEM image (Fig. 3, right)
reveals the parallel channels, which resemble the pores’
configuration of SBA-15. This indicates that the pore of
SBA-Pr-SO3H was not collapsed during the two-step
reactions.
was suggested that SBA-15 functionalized with Brönsted
sulfonic sites shows the favorable acidity, and it would
activate the substrate molecules and then act as a nanoreactor
in a way to obtain the product in excellent yield.
EXPERIMENTAL
General. The chemicals employed in this work were obtained
from Merck Company and were used with no purifications. IR
spectra were recorded from KBr disk using a FTIR Bruker Tensor
27 instrument. Melting points were measured by using the
capillary tube method with an electro thermal 9200 apparatus. The
1H NMR (500MHz) was run on a Bruker DPX, 500 MHz using
TMS as an internal standard (DMSO-d6 solution). GC–MS
analysis was performed on a GC–MS model: 5973 network mass
selective detector, Gc 6890 Agilent. Nitrogen adsorption and
desorption isotherms were measured at ꢀ196ꢁC using a Japan
Belsorb II system after the samples were vacuum dried at 150ꢁC
overnight. Surface areas were calculated by the BET method, and
pore sizes were calculated by the Barrett–Joyner–Halenda method.
SEM analysis was performed on a Philips XL-30 field emission
CONCLUSIONS
In summary, we have successfully demonstrated that the
nano acid catalyst of SBA-Pr-SO3H efficiently catalyzes
the one-pot three-component synthesis of spirooxindole-
4H-pyrans in aqueous media. Environmentally friendly
conditions, short reaction times, good yields, and simple
work-up procedures are some advantages of this method. It
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

N. Lashgari, G. Mohammadi Ziarani, A. Badiei, and M. Zarezadeh-Mehrizi
Vol 000
Table 3
Comparison of efficiency of various catalysts in synthesis of 2-amino-5-oxo-spiro[(30H)-indol-30,4-4(H)-pyrano(3,2-c)chromen]-(10H)-20-one-3-carboni-
trile 4a.
Entry
Catalyst
Solvent
Condition
Time
Yield (%)
Year
Ref.
1
2
3
4
5
6
7
8
Piperidine
Neutral alumina
Et3N
EtOH
—
EtOH
—
Stir (RT)
MW
Heating
MW
Reflux
Heating
Reflux
Heating
Heating
Heating
Heating
Heating
Heating
Stir (RT)
Reflux
2 h
86
94
92
92
72
88
95
88
94
92
92
91
93
86
90
88
90
1989
2003
2005
2007
2007
2007
2008
2009
2010
2010
2010
2010
2010
2010
2011
2011
[25]
[26]
[27]
[28]
[28]
[24]
[29]
[30]
[23]
[31]
[22]
[32]
[21]
[21]
[33]
[33]
3 min
10 min
3.5 min
1.5 h
3 h
5 min
8 h
15 min
1 h
InCl3/SiO2
InCl3
CH3CN
H2O
EtOH
H2O
H2O
H2O
H2O
PEG
H2O
H2O
H2O
—
TEBAa
NEt3
b-CDb
9
L-proline
EDDAc
Sodium stearate
—
10
11
12
13
14
15
16
17
3 h
90 min
2 h
Alum
Alum
15 h
TBABd
40 min
60 min
15 min
TBAB
SBA-Pr-SO3H
Heating
Reflux
H2O
This Work
aTEBA, triethylbenzylammonium chloride.
bb-CD, b-cyclodexrin.
cEDDA, ethylenediamine diacetate.
dTBAB, tetrabutylammonium bromide.
Figure 1. Synthesis of spirooxindole-4H-pyran derivatives using SBA-Pr-SO3H as a nano-reactor.
scanning electron microscope operated at 16 kV, whereas TEM was
carried out on a Tecnai G2F30 at 300 kV. Elemental analysis (C, H,
N) for new compounds were performed using a Thermo Finnigan
Flash EA 1112 instrument.
Preparation of SBA-15. The nanoporous compound SBA-
15 was synthesized according to the method described by Zhao
and coworkers [34,37]. In a typical synthesis batch, commercially
available pluronic P123 triblock copolymer surfactant
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014 Spirooxindole-4H-pyrans Synthesis Using SBA-Pr-SO3H as a Nanoporous Acid Catalyst
Figure 2. Schematic illustration for the preparation of SBA-Pr-SO3H.
acetone. The modified SBA-15-Pr-SO3H was dried and used as
Table 4
nanoporous solid acid catalyst in the following reaction.
Porosimetry values for SBA-15 and functionalized SBA-15.
General procedure for the preparation of spirooxindole-
4H-pyrans 4a–i.
A mixture of isatin (0.29 g, 2 mmol),
Surface area
Pore volume
Pore diameter
(nm)
(cm2 gꢀ1
)
(cm3 gꢀ1
)
malononitrile (0.13 g, 2 mmol), 4-hydroxycoumarin (0.32 g,
2 mmol), and SBA-Pr-SO3H (0.02 g) in refluxing water (5 mL)
was stirred for about 15 min. Upon completion, monitored by
TLC, the generated solid product was filtered from the water
and dissolved in acetonitrile and methanol, which was then
filtered for removing the unsolvable catalyst, and the filtrate was
cooled to afford the pure product 4a. The spectroscopic and
analytical data for selected compounds are presented in the
following part. The catalyst was washed subsequently with
diluted acid solution, distilled water, and then acetone, dried
under vacuum and reused for several times without significant
loss of activity.
SBA-15
SBA-Pr-
SO3H
649
440
0.806
0.660
6.2
6.0
(EO20PO70EO20, Mac = 5800) (4.0g) was dissolved in 30g of water
and 120 g of 2 M HCl solution. Then, TEOS (8.50 g) was added to
reaction mixture that was stirred for 8 h at 40ꢁC. The resulting
mixture was transferred into
autoclave and kept at 100ꢁC for 20 h without stirring. The gel
composition P123 HCl H2O TEOS was
a Teflon-lined stainless steel
Methyl 2-amino-5-oxo-spiro[(30H)-50-chloro-indol-30,4-4(H)-
:
:
:
pyrano(3,2-c)chromen]-(10H)-20-one-3-carbonitrile (4e).
Mp
0.0168:5.854:162.681:1 in molar ratio. After cooling down to
room temperature, the product was filtered, washed with distilled
water, and dried overnight at 60ꢁC in air. The as-synthesized
sample was calcinated at 550ꢁC for 6 h in air atmosphere to
remove the template.
Functionalization of the SBA-15 by organic groups.
Functionalization of the SBA-15 catalyst was schematically
shown in Figure 2. The calcinated SBA-15 (2 g) and (3-
mercaptopropyl)trimethoxysilane (10 mL) in dry toluene
(20 mL) were refluxed for 24 h. The product was filtered and
extracted for 6 h in CH2Cl2 using a soxhlet apparatus and then
dried under vacuum. The solid product was oxidized with H2O2
(40 mL) and one drop of H2SO4 in methanol (20 mL) for 24 h at
RT, and then the mixture was filtered and washed with H2O and
287–288ꢁC; IR (KBr) υmax (cmꢀ1) = 3369, 3307, 3189, 2940,
1
1719, 1661, 1612, 1481, 1353, 1288, 1111, 1027, 989, 762; H
NMR (500 MHz, DMSO-d6) d = 10.56 (s, 1H, NH), 8.44 (s, 2H,
NH2), 8.02 (t, 1H, ArH), 7.72 (t, 1H, ArH), 7.51 (t, 1H, ArH ),
7.43 (d, 1H, ArH), 7.13–7.17 (m, 2H, ArH), 6.75 (d, 1H, ArH),
3.46 (s, 3H, CH3); MS m/z = 424 (M+), 372, 279, 267, 167, 149
(100), 81, 69, 57, 43. Anal.Calcd for C21H13ClN2O6: C, 59.38;
H, 3.08; N, 6.59. Found: C, 59.45; H, 3.14; N, 6.64.
Methyl 2-amino-5-oxo-spiro[(30H)-50-bromo-indol-30,4-4(H)-
pyrano(3,2-c)chromen]-(10H)-20-one-3-carbonitrile (4f).
Mp
296–298ꢁC; IR (KBr) υmax (cmꢀ1) = 3426, 3367, 3306, 3134,
2951, 1700, 1651, 1609, 1478, 1350, 1283, 1114, 1077, 991,
758; 1H NMR (500 MHz, DMSO-d6) d = 10.57 (s, 1H, NH),
8.11 (s, 2H, NH2), 8.03 (m, 1H, ArH), 7.73 (m, 1H, ArH), 7.51
Figure 3. SEM image (left) and TEM image (right) of SBA-Pr-SO3H.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

N. Lashgari, G. Mohammadi Ziarani, A. Badiei, and M. Zarezadeh-Mehrizi
Vol 000
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(t, 1H, ArH ), 7.43 (d, 1H, ArH), 7.27 (t, 2H, ArH), 6.71 (d, 1H,
ArH), 3.78 (s, 3H, CH3); MS m/z = 468 (M+), 310, 267, 177, 149,
119, 91 (100), 69, 57, 43. Anal.Calcd for C21H13BrN2O6: C,
53.75; H, 2.79; N, 5.97. Found: C, 53.73; H, 2.84; N, 6.06.
Ethyl
2-amino-5-oxo-spiro[(30H)-50-chloro-indol-30,4-4(H)-
pyrano (3,2-c) chromen]-(10H)-20-one-3-carbonitrile (4h). Mp
280–282ꢁC; IR (KBr) υmax (cmꢀ1) = 3377, 2972, 2923, 1713,
1
1648, 1612, 1479, 1350, 1281, 1109, 1045, 968, 758; H NMR
(500 MHz, DMSO-d6) d = 10.45 (s, 1H, NH), 8.48 (s, 2H, NH2),
8.03 (m, 1H, ArH), 7.52 (t, 1H, ArH), 7.30 (t, 1H, ArH ), 7.15 (d,
1H, ArH), 6.77–7.07 (m, 2H, ArH), 6.71 (d, 1H, ArH), 3.45 (q,
2H, CH2), 1.85 (t, 3H, CH3); MS m/z = 438 (M+), 368, 310, 279,
257, 239, 177, 149 (100), 83, 69, 57, 43. Anal.Calcd for
C22H15ClN2O6: C, 60.22; H, 3.45; N, 6.38. Found: C, 60.36; H,
3.34; N, 6.17.
Ethyl
2-amino-5-oxo-spiro[(30H)-50-bromo-indol-30,4-4(H)-
pyrano (3,2-c) chromen]-(10H)-20-one-3-carbonitrile (4i).
Mp
285–286ꢁC; IR (KBr) υmax (cmꢀ1) = 3376, 2972, 2924, 2854,
1711, 1646, 1614, 1474, 1354, 1281, 1111, 1076, 969, 757; H
1
NMR (500 MHz, DMSO-d6) d = 10.57 (s, 1H, NH), 8.17 (s, 2H,
NH2), 8.02 (m, 1H, ArH), 7.73 (m, 2H, ArH), 7.51 (t, 1H, ArH ),
7.43 (d, 1H, ArH), 7.30 (t, 1H, ArH), 6.72 (t, 1H, ArH), 3.45 (q,
2H, CH2), 0.85 (t, 3H, CH3); MS m/z = 482 (M+), 432, 399, 239,
177, 149, 91, 71, 58, 43 (100). Anal.Calcd for C22H15BrN2O6: C,
54.68; H, 3.13; N, 5.80. Found: C, 54.45; H, 3.17; N, 5.65.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet