Covalently anchored n-propyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride on SBA-15 as a basic nanocatalyst for the synthesis of pyran heterocyclic compounds

Article abstract of DOI:10.1039/c3ra43443e

In the present study, highly ordered n-propyl-1,4 diazoniabicycle[2.2.2] octane chloride functionalized mesoporous SBA-15, SBA-DABCO, with high surface area and narrow pore-size distribution was synthesized and characterized by TEM, SEM, FT-IR, CHN, TGA,

Full text of DOI:10.1039/c3ra43443e

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Covalently anchored n-propyl-4-aza-1-
azoniabicyclo[2.2.2]octane chloride on SBA-15 as a
basic nanocatalyst for the synthesis of pyran
heterocyclic compounds
Cite this: RSC Adv., 2014, 4, 4403
*
Jamal Davarpanah and Ali Reza Kiasat
In the present study, highly ordered n-propyl-1,4 diazoniabicycle[2.2.2]octane chloride functionalized
mesoporous SBA-15, SBA-DABCO, with high surface area and narrow pore-size distribution was
synthesized and characterized by TEM, SEM, FT-IR, CHN, TGA, XRD and BET. The organic-modified SBA-
15 has hexagonal crystallographic order, pore diameter up to 54.2 A˚, and the content of DABCO groups
up to 1.38 mmol gꢀ1. The catalyst shows an environmentally benign character, which can be easily
prepared, stored and recovered without obvious significant loss of activity. The synthesized basic
organocatalyst provides a green and useful method for the one-pot synthesis of pyran annulated
heterocyclic compounds, and especially spirooxindole pyran compounds in aqueous media. The
significant features of the present protocol are simple, environmentally benign, high yields, no
chromatographic separation and recyclability of the catalyst.
Received 6th July 2013
Accepted 25th October 2013
DOI: 10.1039/c3ra43443e
www.rsc.org/advances
Besides, SBA-15 has abundant surface silanol groups, a well-
organized array of straight channels, high surface area, open
pore structure and narrow pore size distribution.8–10 These
1. Introduction
In recent years, ionic liquids have attracted signicant attention
as being an environmentally-friendly reaction media for their
unique properties of high thermal and chemical stability,
negligible vapor pressure, and selective dissolvability.1 But the
high cost and difficulty in recycling limited their further appli-
cations to the industrial scale. To solve this problem, supporting
or immobilizing became general concepts applied to hetero-
genized ILs, which is recognized as a green approach in their
catalytic applications.2,3 Silica is usually used as an ionic liquid
carrier due to its easy availability and low cost.4,5 However, the
wide-range pore distribution, irregular pore shape, low pore
volume and low specic surface area of silica oen leads to low
graing amount of ionic liquids, high mass-transfer resistance
and poor catalytic activities. To elevate the graing amount of
ionic liquids, the preparation and application of mesoporous
materials for such applications have become an intensively
studied hotspot in heterogeneous catalysis.
advantageous characteristics made SBA-15 an attractive solid
support in the eld of catalysis and functional materials.1,11–13
The regular arrangement of uniform pores over all the porous
structure is likely to ensure good accessibility to the active
centers of functional groups attached to the surface and to
impart fast mass transport rates. In addition, the big pore size of
SBA-15 is advantageous to reaction substance transports inside
pore channels and to further the process of the reaction.14
One-pot multicomponent reactions (MCRs) that convert
more than two educts directly into their products, have gained
considerable attention due to the atom economy and powerful
bond forming efficiency in combinatorial and medicinal
chemistry.15 In recent years, development of such multicom-
ponent coupling reaction strategies in aqueous medium has
been of considerable interest, as they provide simple and rapid
access to a large variety of organic scaffolds through a sustain-
able path.16 Pyran derivatives are of considerable interest in
industry as well as in academia owing to their promising
biological activity such as anticoagulant, anticancer, diuretic,
spasmolytic and anti-anaphylactin agents.15,16 Although a few
methods with distinct advantages have been recently reported
by using various catalysts, at the same time they suffer from
certain drawbacks such as extended reaction times, unsatis-
factory yields, high costs, harsh reaction conditions, toxic
solvents and use of stoichiometric amounts of catalyst, as well
as using environmentally toxic catalysts. Additionally the main
At the beginning of the 1990s, ordered mesoporous materials
were discovered to reduce diffusion constraints encountered in
microporous materials.6 Among these kinds of materials, mes-
oporous silicate materials such as SBA-15 have gained an
increased attention owing to their interesting properties that
include tunable pore sizes, stabilities and shape selectivity.7
Chemistry Department, College of Science, Shahid Chamran University, Ahvaz,
61357-4-3169, Iran. E-mail: akiasat@scu.ac.ir; Fax: (+98) 611-3331746; Tel: (+98)
611-3331746
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drawback of almost existing methods is that the catalysts are ethanol). Finally, the material was ltered, washed several times
decomposed under aqueous work-up conditions and their with water and ethanol, and dried at 50 ꢁC.
recoveries are oen impossible.17 Thus, to overcome these
drawbacks the development of simple and highly efficient 2.3. Synthesis of 1,4-diazabicyclo[2.2.2]octane-SBA (SBA-
methodologies remains desired.
DABCO)
Considering these facts and as a part of our ongoing interest
in the synthesis of biologically relevant heterocyclic
compounds,18–21 we attempted to design an inorganic–organic
hybrid basic nanocatalyst by supporting DABCO, a type of
spindle-shaped molecule with two nitrogen atoms located at
both tips, on highly ordered functionalized mesoporous SBA-15.
This provides a basic organocatalyst with high surface area,
high accessibility of catalyst, and no leaching of active species in
the reaction media. The catalytic ability of this heterogeneous
basic organocatalyst is studied for the one-pot synthesis of
pyran annulated heterocyclic compounds in water.
SBA-Cl (10.0 g) was added to a ask containing 100 mL of
anhydrous toluene and an excess of DABCO (1 g, 9 mmol). The
reaction mixture was reuxed with stirring for 24 h. Then, the
reaction mixture was cooled to room temperature, transferred
to a vacuum glass lter, and washed with toluene. The SBA
chemically bonded with DABCO (SBA-DABCO) was dried at
ꢁ
50 C for 8 h.
2.4. Typical procedure for the preparation of spirooxindoles
and pyran annulated heterocyclic compounds
A mixture of b-diketone (1 mmol), malononitrile (1 mmol), isa-
tin or aldehyde (1 mmol) and SBA-DABCO (0.125 g) was heated
at 80 ꢁC minimum in water for 10–50 min. Aer complete
consumption of aromatic aldehyde as judged by TLC (using
n-hexane-ethylacetate as eluent), the reaction mixture was
ltered for separation of solid product and catalyst from water.
The remaining solid was washed with warm ethanol (3 ꢂ 5 mL)
for separation of the product from the catalyst. Finally, the
product was puried by recrystallization in hot EtOH. The
desired pure product(s) was characterized by comparison of
their physical data with those of known spirooxindoles and
pyran annulated heterocyclic compounds.
2. Experimental
2.1. General
For the direct synthesis of chloro-functionalized SBA-15, tet-
raethylorthosilicate (TEOS) was used as
a silica source,
3-chloropropyltrimethoxysilane (CPTMS) was used as a chlor-
opropyl group source and Pluronic P123 triblock copolymer
(EO20PO70EO20, MW 5800) was used as a structure-directing
agent; all were supplied by Aldrich. Other chemical materials
were purchased from Fluka and Merck companies and used
without further purication. Products were characterized by
comparison of their physical data, IR and 1H-NMR and 13C-
NMR spectra with known samples. NMR spectra were recorded
on a Bruker Advance DPX 400 MHz instrument spectrometer
using TMS as an internal standard. IR spectra were recorded on
a BOMEM MB-Series 1998 FT-IR spectrometer.
The purity determination of the products and reaction
monitoring were accomplished by TLC on silica gel PolyGram
SILG/UV 254 plates. The particle morphology was examined by
SEM (Philips XL30 scanning electron microscope) and TEM
(Zeiss-EM10C-80 kV). Nitrogen adsorption measurements were
conducted at 77.4 K on a Micrometrics ASAP-2020 sorption-
meter. The specic surface area and the pore size distribution
were calculated by the Brunauer–Emmett–Teller (BET) method
and Barrett–Joyner–Halenda (BJH) model, respectively.
2.5. Selected spectral data
2-Amino-5-oxo-7,7-dimethyl-spiro[(4H)-5,6,7,8-tetrahydrochro-
mene-4,30-(30H)-indol]-(10H)-20-one-3-carbonitrile (3a): 1H NMR
(DMSO-d6, 400 MHz): d ¼ 1.04 (s, 6H), 2.09 (d, 1H, J ¼ 16 Hz),
2.14 (d, 1H, J ¼ 16 Hz), 2.51 (d, 2H, J ¼ 3.4 Hz), 6.81 (1H, d, J ¼
8.0 Hz), 6.92 (1H, t, J ¼ 7.8 Hz), 7.01 (1H, d, J ¼ 7.8 Hz), 7.21 (1H,
t, J ¼ 8.0 Hz), 7.33 (2H, br s), 10.43 (s, 1H). 13C NMR (DMSO-d6,
100.6 MHz): d ¼ 28.1, 28.5, 32.3, 48.1, 49.9, 57.9, 110.0, 111.2,
117.8, 122.0, 124.1, 127.8, 134.8, 144.1, 157.3, 164.3, 179.2,
196.3. IR (KBr) (vmax, cmꢀ1): 561, 750, 1056, 1222, 1354, 1471,
1606, 1657, 1683, 1723, 2190, 2963, 3145, 3315, 3378.
2-Amino-5-oxo-7-methyl-spiro[(30H)-indol-30,4-4(H)-pyrano-
(4,3-b)pyran]-(10H)-20-one-3-carbonitrile (3b): 1H NMR (DMSO-
d6, 400 MHz): d ¼ 2.29 (3H, s), 6.40 (1H, s), 6.83 (1H, d, J ¼ 7.6
Hz), 6.92 (1H, t, J ¼ 7.6 Hz), 7.13 (1H, d, J ¼ 7.4 Hz), 7.17 (1H, t, J
¼ 7.8 Hz), 7.52 (2H, br s), 10.62 (1H, s). 13C NMR (DMSO-d6,
100.6 MHz): d ¼ 19.9, 47.6, 57.6, 98.5, 98.9, 110.2, 118.2, 122.5,
2.2. Synthesis of chloropropyl-graed SBA-15 (SBA-Cl)
Chloropropyl-graed SBA-15 (SBA-Cl) was prepared according to 124.3, 129.2, 133.6, 142.6, 160.2, 160.3, 160.8, 165.1, 178.3. IR
the reported method.22 Pluronic 123 (4 g) was dissolved in 125 g (KBr) (vmax, cmꢀ1): 495, 752, 1228, 1360, 1477, 1586, 1614, 1646,
of 2.0 M HCl solution at room temperature. Aer TEOS (8.41 g, 1674, 1729, 2204, 2883, 3097, 3212, 3380, 3524.
40.41 mmol) was added, the resultant solution was equilibrated
2-Amino-5-oxo-spiro[(30H)-indol-30,4-4(H)-pyrano(3,2-c)chro-
at 40 C for prehydrolysis, and then CPTMS (1.3 g, 6.5 mmol) men]-(10H)-20-one-3-carbonitrile (3c): 1H NMR (DMSO-d6, 400
was slowly added into the solution. The resulting mixture was MHz): d ¼ 6.91 (1H, d, J ¼ 7.4 Hz), 6.96 (1H, t, J ¼ 7.8 Hz), 7.25
stirred at 40 ꢁC for 20 h and reacted at 95 ꢁC under static (2H, t, J ¼ 7.8 Hz), 7.50 (1H, d, J ¼ 8.6 Hz), 7.55 (1H, t, J ¼ 7.8
conditions for 24 h. The solid product was recovered by ltration Hz), 7.64 (2H, br s), 7.78 (1H, t, J ¼ 7.8 Hz), 7.96 (1H, d, J ¼ 7.8
and dried at room-temperature overnight. The template was Hz), 10.62 (1H, s). 13C NMR (DMSO-d6, 100.6 MHz): d ¼ 50.0,
removed from the as synthesized material by reuxing in 95% 57.9, 102.1, 110.2, 113.0, 117.3, 117.5, 122.7, 123.2, 123.9, 125.2,
ethanol for 48 h (1.5 g of as-synthesized material per 400 mL of 130.1, 134.2, 135.2, 142.2, 151.2, 157.3, 158.4, 160.1, 178.1. IR
ꢁ
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(KBr) (vmax, cmꢀ1): 572, 761, 942, 1100, 1220, 1309, 1390, 1476,
1620, 1679, 1700, 1725, 2200, 2982, 3110, 3280, 3445.
SBA-DABCO solid base catalyst by a two-step chemical
modication.
4H-Naphtho[1,2-b]pyran-3-carbonitrile-2-amino-4-phenyl
The FT-IR spectra of SBA-Cl and SBA-DABCO are shown in
1
(Table 4, entry 1): H NMR (DMSO-d6, 400 MHz): d ¼ 4.96 (1H, Fig. 1. In both materials, the typical Si–O–Si bands around
s), 6.21 (2H, br s), 7.18 (1H, d, J ¼ 8.2 Hz), 7.16–7.41 (5H, m), 1220, 1070, 801 and 473 cmꢀ1 associated with the formation
7.58–7.72 (3H, m), 7.92 (1H, d, J ¼ 8.2 Hz), 8.4 (1H, d, J ¼ 8.2 Hz). of a condensed silica network are present, but weak peaks
13C NMR (DMSO-d6, 100.6 MHz): d ¼ 59.2, 119.1, 119.6, associated with noncondensed Si–OH groups in the range of
120.9123.1, 125.0, 126.1, 126.7, 126.9, 127.0, 127.5, 128.1, 128.9, 940–960 cmꢀ1 were also present. The absorbance peak of the
133.9, 143.1, 146.1, 158.9. IR (KBr) (vmax, cmꢀ1): 560, 740, 931, C–N with the wavelength of 1000–1200 cmꢀ1 cannot generally
1120, 1230, 1310, 1395, 1480, 1590, 1670, 2200, 3340, 3450.
be resolved due to its overlap with the absorbance of the Si–O–
4H-Naphtho[1,2-b]pyran-3-carbonitrile-2-amino-4-(4-chloro- Si stretch in the same range and that of Si–CH2–R stretch in
phenyl) (Table 4, entry 4): 1H NMR (DMSO-d6, 400 MHz): the range 1200–1250 cmꢀ1. The weak bands located at 2950 to
d ¼ 5.32 (1H, s), 6.89 (2H, s), 7.22 (2H, d, J ¼ 7.6 Hz), 7.38 (2H, d, 2830 cmꢀ1 correspond to C–H asymmetric and symmetric
J ¼ 7.6 Hz), 7.50-7.62 (3H, m), 7.89 (1H, d, J ¼ 7.8 Hz), 8.25 (1H, stretching vibration modes, respectively. The strong peak
d, J ¼ 8.0 Hz). 13C NMR (DMSO-d6, 100.6 MHz): d ¼ 55.1, 118.6, around 1630 cmꢀ1 is mainly from the bending vibration of
120.1, 120.6, 123.2, 125.1, 126.4, 127.3, 127.5, 128.6, 129.2, adsorbed H2O.23 FT-IR spectrum of Amine-SBA-15 exhibited
131.0, 132.3, 134.2, 144.3, 146.2, 161.3. IR (KBr) (vmax, cmꢀ1): two bands at 2975 cmꢀ1 and 1465 cmꢀ1, assigned to the C–H
750, 807, 1105, 1185, 1379, 1405, 1574, 1603, 1637, 1663, 2201, stretching vibration and C–N bending vibration of the tertiary
3195, 3318, 3478.
amine group, respectively. These two peaks are not observed
1H-Naphtho[2,1-b]pyran-2-carbonitrile-3-amino-1-(4-chloro- in the spectrum of the Cl-SBA-15.24 The broad band around
phenyl) (Table 4, entry 13): 1H NMR (DMSO-d6, 400 MHz): 3450 cmꢀ1 is due to the stretching vibration of SiO–H bond
d ¼ 5.01 (1H, s), 7.15 (1H, d, J ¼ 8.4 Hz), 7.25 (2H, s), 7.35 (2H, d, and the HO–H vibration of a water molecule adsorbed on the
J ¼ 8.4 Hz), 7.41 (2H, d, J ¼ 8.2 Hz), 7.45–7.62 (3H, m), 7.83 (1H, silica surface. The band around 1635 cmꢀ1 is also due to the
d, J ¼ 8.0 Hz), 8.33 (1H, d, J ¼ 8.2 Hz). 13C NMR (DMSO-d6, 100.6 bending vibration of water molecules bound to the silica
MHz): d ¼ 63.1, 113.2, 114.5, 115.2, 116.8, 124.0, 125.3, 128.1, matrix. SBA-Cl shows a peak at 644 cmꢀ1 assigned to the C–Cl
128.5, 128.8, 129.2, 129.4, 130.3, 131.0, 132.3, 132.5, 148.0, vibration. This peak is not observed for the SBA-DABCO
158.2, 158.8. IR (KBr) (vmax, cmꢀ1): 560, 740, 931, 1120, 1230, spectrum.
1310, 1395, 1480, 1590, 1670, 2200, 3340, 3450.
The quantity of functionalized organic groups, determined
from CHN elemental analysis, is presented in Table 1. The
amount of DABCO is 1.38 mmol per gram in SBA-DABCO, that is
91% of propylchloride group in SBA-Cl.
3. Results and discussions
The morphological features of SBA-DABCO were studied
by TEM and SEM (Fig. 2 and 3). From the TEM image, the
hexagonal pore structure and orderly pore arrangement
could be clearly observed and conrmed the long-range,
three dimensional, mesoporous ordering in this organo-
catalyst. Long-range order and mesoporous structure arrays
were not disturbed signicantly aer DABCO graing. The
SEM image of catalyst also indicated a uniform particle size
with hexagonal shape.
Thermal stability of samples was investigated by thermal
gravimetric analysis-derivative thermogravimetric analysis
(TGA-DTG) in which the observed weight loss was associated
with the loss of the organic components attached to the silica
Well-ordered mesoporous chloro-functionalized SBA-15 was
rst synthesized by the direct incorporation of chloropropyl
groups through co-condensation of TEOS and CPTMS
precursors in the presence of a Pluronic P123 triblock copol-
ymer as a supramolecular template to direct the organization
of polymerizing silica. DABCO was then graed onto the
surface of the mesoporous silica by a simple nucleophilic
substitution reaction. Scheme 1 shows the schematic repre-
sentation of the synthetic pathway for the synthesis of
Scheme 1 Synthesis of DABCO-functionalized SBA-15.
Fig. 1 FT-IR spectra of SBA-Cl and SBA-DABCO.
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Table 1 Elemental analysis data of SBA-Cl and SBA-DABCO
Materials
C (W%)
H (W%)
N (W%)
SBA-Cl
SBA-DABCO
13.21
16.36
2.12
3.38
0.09
3.86
Fig. 2 TEM image of SBA-DABCO.
Fig. 3 SEM image of SBA-DABCO.
Fig. 5 Pore size distributions of SBA-Cl (a), SBA-DABCO (c) and
nitrogen adsorption–desorption isotherms of SBA-Cl (b), SBA-
DABCO (d).
Fig.
4 Thermal gravimetric analysis-derivative thermogravimetric
analysis (TGA-DTG) of (a) SBA-Cl and (b) SBA-DABCO.
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Table 2 Specific surface area (SBET), diameter pore and total pore
volume
pore to a smaller diameter and decreased the surface area and
pore volume.
Over the years, the fast assembly of molecular diversity
utilizing multicomponent reactions (MCRs) has received a
great deal of interest. MCRs are dened as one-pot processes
where three or more substrates combine either simultaneously
(so called tandem or domino reactions), or through a sequen-
tial addition procedure that does not require any change of
solvent. MCRs are gaining more and more importance espe-
cially in the total synthesis of natural products, and medicinal
heterocyclic compounds, because of their simplicity, higher
yield of products, and lower reaction times.27,28 The applica-
tions of heterocyclic compounds in our life are undeniable.
Tetrahydrobenzo[b]pyrans and dihydropyrano[c]chromenes
have recently attracted much attention as an important class of
heterocycles due to their biological and pharmacological
properties, such as diuretic, anti-cancer, anticoagulant, and
anti-anaphylactic activities.29 Aminochromene derivatives
exhibit a wide spectrum of biological activities including anti-
cancer, antimicrobial agents, photoactive materials, and are
also utilized in the synthesis of the blood anticoagulant
warfarin and tacrine analogs.30
BET surface area
Diameter
(nm)
Pore volume
Sample
(m2 gꢀ1
)
(cm3 gꢀ1
)
SBA-Cl
SBA-DABCO
753
290
9.72
5.42
1.25
0.70
gel. TGA-DTG curves for SBA-Cl and SBA-DABCO were shown
in Fig. 4. The sample of SBA-Cl shows two and SBA-DABCO
shows three distinct steps of weight loss in the combined TG-
DTG curves. The curves show that the rst weight loss occurs
before 200 ꢁC, which can be attributed completely to the loss
of adsorbed water molecules. TGA of the samples demon-
strated highꢁthermal stability, with decomposition starting at
around 300 C under a nitrogen atmosphere. The secondary
weight losses at about 380 ꢁC and 480 ꢁC come from the
decomposition of organic substances in SBA-DABCO
composites. The decomposition is complete at about 650–
700 C to form the constituent inorganic oxides.25
ꢁ
The mesoporous nature of the synthesized samples were
studied by N2 adsorption–desorption isotherms (Fig. 5).
Nitrogen adsorption–desorption isotherms of the SBA-Cl and
SBA-DABCO in Fig. 5 exhibit the typical IV adsorption (accord-
ing to the IUPAC classication).26 Both the isotherms present a
sharp adsorption step in the P/P0, which implies that the
materials possess a large pore size with narrow distributions.
This was further conrmed by the pore size distributions
calculated by the Barrett–Joyner–Halenda (BJH) method from
the adsorption branches. The characteristic data on the
samples are summarized in Table 2. From Table 2, we can see
that the introduction of DABCO to mesoporous silica shied the
Scheme 3 Synthesis of spiro[(2-amino-3-cyano-5-oxo-5,6,7,8,tet-
rahydro-4H-chromene)-4,30-oxindoles] by reaction of isatin
(1 mmol), dimedone (1 mmol) and malononitrile (1 mmol) in water.
Scheme 2 Preparation of pyran annulated heterocyclic compounds and spirooxindole pyran compounds in water, catalyzed by SBA-
DABCO.
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Table 3 The one-pot three component reaction of isatin (1 mmol),
dimedone (1 mmol), and malononitrile (1 mmol) in water
herein we report the synthetic applicability of SBA-DABCO as a
base catalyst for rapid and efficient preparation of pyran
annulated heterocyclic compounds and spirooxindole pyran
Entry
Solvent
Catalyst (g)
T (ꢁC)
Yield (%)
derivatives in water through
(Scheme 2).
a multicomponent reaction
1
2
3
4
5
6
7
8
—
H2O
—
H2O
EtOH
EtOH–H2O
CH2Cl2
H2O
H2O
H2O
—
—
0.1
0.1
0.1
0.1
0.1
0.05
0.125
0.125
0.125
0.125
100
Reux
100
Reux
Reux
Reux
Reux
Reux
Reux
80
10
20
35
73
70
70
35
66
85
85
75
68
The catalytic performance of this novel basic organocatalyst
has been systematically studied in the rapid and efficient
preparation of pyran annulated heterocyclic compounds and
spirooxindole pyran derivatives in water through a multicom-
ponent reaction (Scheme 2).
In the preliminary stage of investigation, we focused on a
three-component process for the model reaction of isatin
(1 mmol), dimedone (1 mmol) and malononitrile (1 mmol)
(Scheme 3). Aer some experiments (Table 3), it was found that
the use of 1 equiv. of malononitrile per dimedone and isatin in
the presence of SBA-DABCO (0.125 g) in water at 80 ꢁC were the
best condition.
9
10
11
12
H2O
H2O
60
40
Owing to the widespread applications of the described
compounds, and in continuation of our previous research to
develop green chemistry by using water as a reaction medium,
Under the optimized reaction conditions, a series of
biologically interesting spirooxindole pyran derivatives were
efficiently synthesized (Scheme 4) by means of three-component
Scheme 4 Synthesis of spirooxindole pyran derivatives in water, catalyzed by SBA-DABCO.
Scheme 5 The one-pot three component reaction of aldehyde (1 mmol), malononitrile (1 mmol) and a or b-naphthol (1 mmol) in water at 80 ꢁC,
catalyzed by SBA-DABCO.
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Table 4 The one-pot three component reaction of aldehyde (1 mmol), malononitrile (1 mmol) and a or b-naphthol (1 mmol) in water at 80 ꢁC,
catalyzed by SBA-DABCO
Entry
R
Naphthol
Product
Time (min)
Yield (%)
1
H
20
89
2
3
4
4-Me
4-OMe
4-Cl
30
30
15
85
84
91
5
6
4-NO2
10
20
94
90
2-Cl
7
8
3-Me
3-F
30
15
86
89
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Table 4 (Contd.)
Entry
R
Naphthol
Product
Time (min)
Yield (%)
9
3-Cl
20
25
89
87
10
H
11
12
13
4-Me
4-OMe
4-Cl
35
35
20
84
84
89
14
15
4-NO2
15
25
91
87
2-Cl
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Table 4 (Contd.)
Entry
R
Naphthol
Product
Time (min)
Yield (%)
16
3-Me
30
84
characterized by FT-IR, CHN, SEM, TEM, TGA-DTG, BET and
BJH. The catalytic activity of this base catalyst has been
successfully applied for the one-pot synthesis of pyran annu-
lated heterocyclic compounds, and especially spirooxindole
pyran compounds in water. The promising points for the pre-
sented methodology are clean reaction proles, short reaction
times, simplicity in operation, catalyst with high catalytic
activity and good recycle exploitation.
Acknowledgements
We gratefully acknowledge the support of this work by Shahid
Chamran University Research Council.
Fig. 6 Recyclability of catalyst.
reactions of isatin, malononitrile, and 1,3-dicarbonyl or enol
compounds catalyzed by mentioned basic catalytic system in
water.
To further explore the potential of this protocol for hetero-
cyclic synthesis, we investigated one-pot three-component
reactions involving malononitrile, aromatic aldehydes and a or
b-naphthol compounds. To our delight, under the above opti-
mized conditions, a variety of the desired products 4 and 5 were
obtained in good yields (Scheme 5, Table 4).
The reusability of the catalyst in the reaction of isatin,
dimedone and malononitrile in water at 80 ꢁC was evaluated. In
this procedure, aer completion of each reaction, hot ethanol
was added and the catalyst was ltered. The recovered catalyst
was washed with ethanol, dried and reused (Fig. 6). The results
illustrated in Fig. 6 show that the catalyst can be reused for up to
ten cycles without signicant loss in its activity.
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