Synthesis, characterization, and application of Cu2O and NiO nanoparticles supported on natural nanozeolite clinoptilolite as a heterogeneous catalyst for the synthesis of pyrano[3,2-b]pyrans and pyrano[3,2-c]pyridones

Article abstract of DOI:10.1039/c4ra10537k

In this research, Cu₂O and NiO nanoparticles supported on natural nanozeolite clinoptilolite (CP) was found to be a recoverable catalyst system for synthesis of pyrano-[3,2-c]pyridone and pyrano[3,2-b]pyran derivatives in aqueous media. The nan

Full text of DOI:10.1039/c4ra10537k

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Page 1 ofJ8ournal Name
►
ARTICLE TYPE
Synthesis, characterization and application of Cu2O and NiO
nanoparticles supported onto natural nanozeolite clinoptilolite as
heterogeneous catalyst for the synthesis of pyrano[3,2-b]pyrans and
pyrano[3,2-c]pyridones
5
Seyed Meysam Baghbanian*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
In this research, the synthesis of Cu2O and NiO nanoparticles supported onto natural nanozeolite
Clinoptilolite (CP) were found to be a recoverable catalyst system for the synthesis of pyrano-[3,2-
10 c]pyridone and pyrano[3,2-b]pyran derivatives in aqueous media. The nanocatalysts were characterized
by various techniques such as XRD, BET, SEM, TEM, TEM-EDS and XPS analyses. TEM study reveals
that Cu2O and NiO nanoparticles have particle size less than 10 nm. XRD and XPS characterizations
show that the existence forms of Cu2O or NiO on the surface of natural nanozeolite CP. The easy
recovery of the catalyst and high yield of the products make the protocol attractive and economic.
15 Furthermore, the nanocatalysts could be recycled and reused several times without significant loss of their
catalytic activities.
Pyranopyridone derivatives have been found to possess a wide
1. Introduction
spectrum of biological actions such as antibacterial,3 antifungal
and antialgal,4 anti-inflammatory,5 antileishmanial,6 platelet
aggregation,7 and nitric oxide production.8 Furthermore, several
50 pyranopyridone including alkaloids exhibit cancer cell growth
inhibitory activity and are investigated as potent anticancer
agents.9 Pyranopyran derivatives also are an important class of
structural pattern of many natural and synthetic compounds
which have a high activity profile due to their wide range of
55 biological activities such as anticancer,10 anti-tuberculosis,11 anti-
HIV,12 calcium channel antagonist activity,13 antifungal,14
Zeolite Clinoptilolite (CP) is microporous aluminosilicates that
are [SiO4]4- and [AlO4]4- tetrahedral that link together to form a
20 three dimensional structure of well-defined pores and channels, a
negative charge is associated with each Al atom. The general
formula for the composition of CP is Mx/n[(AlO2)x(SiO2)y]·mH2O
where M is represents cations of n valence that balance the
negative charges on the framework. The aluminium in the zeolite
25 framework has a substantial negative charge that is balanced by
exchangeable cations such as Na+ or K+. These cations can be
easily exchanged by simply stirring the zeolite in an aqueous
solution containing the desired cation that due to their unique
properties, CP can be employed as catalyst for the synthesis of
30 organic compounds.1 Therefore, the investigation on the use of
“CP” as a reliable catalyst support seems to be worth mentioning.
So, we considered the applicability of this valuable multipurpose
compound as a support of metal catalyst due to its great
characteristics including high and adjustable acidity, well defined
35 pore structures with channels and cavities of molecular
dimensions and high ion exchange capabilities.2
antimicrobial,15
antiproliferative,16
antidiabetic,17
anti-
inflammatory and antiviral.18 On the other hand,
pyranopyranones are also known for their biological properties
60 including antioxidant and cytotoxic activities.19 Therefore, the
synthesis of pyrano-[3,2-c]pyridone and pyrano[3,2-b]pyran
skeletons are of enormous importance in organic synthesis.
In recent years, efficient methods have been developed for the
synthesis of pyrano-[3,2-c]pyridone and pyrano[3,2-b]pyran
65 derivatives with the aim of preparing of a new series of a fused
heterocyclic systems exhibiting high levels of biologically
activity using a range of different catalysts.3-18,20 Although these
methods are effective, but most of them still have some
drawbacks resulting in significant limits on their synthetic
70 applications such as most of the catalyst are synthetic and require
laborious, time-consuming, high reaction temperatures, use of
toxic solvents and moderate yields. Thus, development of a
simple, eco-benign, low cost protocol, using neutral and reusable
catalyst for one-pot synthesis of pyrano-[3,2-c]pyridone and
aDepartment of Chemistry, Ayatollah Amoli Branch, Islamic Azad
University, P.O. Box 678, Amol, Iran;
40 E-mail:
S.M.Baghbanian@iauamol.ac.i†Electronic
Supplementary
Information Electronic supplementary information (ESI) available: See
DOI: 10.1039/b000000x
45
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

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pyrano[3,2-b]pyran derivatives still remains as an attractive goal
The N2 adsorption-desorption isotherms for nano CP, AT-Nano
CP, nano Cu2O-CP and nano NiO-CP were measured and the
for researchers. In this work, in continuation of our investigations
into the development of new catalysts,21 we describe here 55 specific surface area (S), the total pore and micropore volumes
synthesis, characterization and application of Cu2O and NiO
nanoparticles supported onto nanozeolite CP as a heterogeneous
catalyst in the synthesis of pyrano-[3,2-c]pyridone and
pyrano[3,2-b]pyran derivatives in aqueous media.
(Vtot and Vmic), the specific surface area (SBET) and the average
pore diameter (D) were calculated using the Brunauer-Emmett-
Teller (BET) method (supporting information). Using the Barrett-
Joyner-Halenda (BJH) method, the mesopore surface area SBJH
60 and the mesopore volume VBJH were calculated for nano CP, AT-
Nano CP, nano Cu2O-CP and nano NiO-CP and summarized in
Table 1. According to the Brunauer, Deming, Derning and Teller
(BDDT) classification, characteristic of mesoporous solids,22 All
the materials displayed typical type IV with an H3 hysteresis loop
65 at P/Po ∼ 0.984. The nano CP with average pore diameters
∼12.20 nm contained a specific surface area of 49.7 m2.g-1 and a
specific pore volume of 0.15 cm3.g-1. Increase in the specific
surface area from 49.7 m2.g-1 to 55.6 m2.g-1 and a slight decrease
in the specific pore volume from 0.15 cm3.g-1 to 0.11 cm3.g-1 are
70 observed after the activation of nano CP might be due to the
leaching of Al from sites of the zeolite matrix and decationation
during acid activation. The BJH curves of nitrogen desorption
display descent distribution of pore volume in the mesoporous
section (1-100 nm). The pore diameter from 1.64 nm to 1.21 nm
75 and the pore volume from 0.15 cm3.g-1 to 0.1 cm3.g-1 decreased
after the activation of nano CP. According to the analysis of the
data listed in Table 1, the specific surface area and pore volume
were decreased after encapsulation of nano Cu2O or NiO in the
cavity of AT-Nano CP can be due to clogging of some pores by
80 nano Cu2O or NiO. Since that a sudden change has not occurred
in the specific pore volume and surface area of AT-Nano CP
upon introducing nano Cu2O-CP or nano NiO-CP further
approves that pores of AT-Nano CP are not clogged by nano
Cu2O-CP or nano NiO-CP larger than the pore size of AT-Nano
85 CP. Accordingly, from the obtained results one could just
conclude that nano Cu2O-CP or nano NiO-CP were grafted on the
pores of AT-Nano CP.
5
2. Results and discussion
The nanozeolite CP was prepared according to a simple method
10 developed recently by our group.21a Initially the nanozeolite
clinoptilolite was converted to the homoionic Na+-exchanged
form by stirring in 2 M NaCl solution and subsequently activated
with 4 M sulfuric acid. The activated nanozeolite CP was
designated as AT-Nano CP. AT-Nano CP was taken into a round
15 bottom flask and an aqueous solution of MCl2 (M= Cu and Ni)
was added under vigorous stirring condition to afforded Cu and
Ni exchanged AT-nano CP. Finally, the M-containing products
were carried out by heating under air to give Cu2O and NiO
nanoparticles into pores of AT-Nano CP. The nano catalysts were
20 characterized by XRD, BET, SEM, TEM, TEM-EDS and XPS.
XRD pattern of AT-Nano CP (Fig. 1a) shows peaks at 2θ = 22.0°,
27.96° and 35.92° which agrees with the natural zeolite of
clinoptilolite (JCPDS 00-025-1349). This revealed that the
surface modification of AT-Nano CP do not lead to their phase
25 change. X-ray diffraction of nano Cu2O-CP (Fig. 1b) contains the
above peaks together with an obvious diffusion peak at 42.4°,
62.5° and 73.6°could be corresponding to the (200), (220) and
(311) planes of Cu2O crystal with a cubic phase (JCDS 78–2076)
and the pattern of nano NiO-CP (Fig. 1c) also consist of two
30 characteristic diffraction peaks appear at 45.4° and 63.5°, which
correspond to the (200) and (220) planes of NiO crystal with a
cubic phase (JCPDS, No. 71-1179). These new peaks, observed
in the XRD patterns of nano Cu2O-CP and NiO-CP may be due to
encapsulation of nano Cu2O or NiO in the cavity of nanozeolite
35 CP. Further, a little change occurred in the relative peak
intensities of nanozeolite upon introducing nano Cu2O-CP or
nano NiO-CP. These observations indicate that the crystallinity of
the nanozeolite has not undergone any significant change during
the process of encapsulation. The average crystallite size for nano
40 Cu2O and nano NiO were calculated based on the strongest
intensity of (220) peak using the Debye-Scherrer’s formula D =
0.89λ/(βcosθ); where D is the grain size, β is the angular line
Table 1. Surface properties of different nanozeolite based
90 support/catalysts
Specific surface
Pore volume
[cm3·g-1]
Pore diameter
[nm]
Sample
area
[m2·g-1]
SBET
SBJH Vtot(BET) V(BJH) Dav
D(BJH)
Nano CP
AT- Nano CP 55.63 39.52
Nano Cu2O-CP 47.4 38.41
49.70 45.68
0.15
0.11
0.09
0.08
0.15
0.1
0.11
0.12
12.19
8.05
10.07
8.88
1.64
1.21
1.63
1.26
Nano NiO-CP
49.1 35.47
width of half-maximum intensity in radians,
θ is Bragg
diffraction angle and λ is the X-ray wavelength used. The average
The structural and morphological characterization of nano CP,
AT-Nano CP, nano Cu2O-CP and nano NiO-CP were performed
using SEM (Fig. 3). Comparison of the SEM images of nano CP
95 (Fig. 3a), AT-Nano CP (Fig. 3b), nano Cu2O-CP (Fig. 3c) and
nano NiO-CP (Fig. 3d) shows that the morphological features are
not changed significantly such as the spherical or ellipsoidal
shape and non-aggregation characteristics. SEM image of nano
Cu2O-CP and nano NiO-CP also showed that the average particle
100 size was found in the range of 35-85 nm.
45 size is found to be below 10 nm.
50
Fig. 1. XRD patterns of (a) AT-Nano CP, (b) nano Cu2O-CP and (c) nano
NiO-CP

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35 confirmed by energy-dispersive X-ray spectroscopy on a TEM
(TEM-EDS). The results reveal presence of C, O, Al, Si and Cu
in nano Cu2O-CP (Fig. 4c) and C, O, Al, Si and Ni in nano NiO-
CP (Fig. 4d).
40
5
45
10
15
20
50
Fig 3. SEM images of (a) Nano CP, (b) AT-Nano CP and (c) Cu2O-CP
and (d) nano NiO-CP
25 The morphology and size of Cu2O-CP (Fig. 4a) and nano NiO-CP
(Fig. 4b) were investigated by transmission electron microscopy
(TEM). The pictures show that the average particle size of Cu2O
and NiO is below 10 nm. As shown in Fig. 4a and b, the anchored
crystal Cu2O and NiO nanoparticles distributed evenly on the
30 nanozeolite CP without obvious aggregations and particles can
deposit on the pores of these nanozeolite. The results from the
TEM studies are in general in agreement with the results obtained
from X-ray diffraction measurements. The Cu2O and NiO
nanoparticles deposition on the AT-Nano CP was further
Fig 4. TEM images of (a) Nano Cu2O-CP and (b) Nano NiO-CP. TEM-
EDS data of (c) Nano Cu2O-CP (d) Nano NiO-CP.
The surface properties of nano Cu2O-CP and nano NiO-CP
55 were analyzed using XPS. The peaks at 931.9 and 952.3 eV
corresponding to Cu 2p3/2 and Cu 2p1/2 are clearly observed in

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Fig. 5a. the Cu 2p3/2 peak can be assigned to Cu2O in accordance 40 reaction time (Table 2, entry 1). The results show that all of nano
with data in the literature.23 Fig. 5b shows the core level spectra
for the Ni 2p peak over the binding energy ranges from 850-885
eV. The Ni 2p XPS spectrum shows two edges of Ni 2p3/2 (from
about 855 eV to 865 eV) and Ni 2p1/2 (from about 868 eV to 885
eV), which confirms the presence of the corresponding elements
for the NiO nano metal shell. The Ni 2p1/2 (872.1 eV) and Ni 2p3/2
(854.3 eV) peaks were assigned to the Ni(II) ions in NiO.24 The
splitting separation between these two main peaks, namely, 17.8
catalysts could promote the reaction, but nano Cu2O-CP catalyst
is significantly more effective than other catalysts in the synthesis
of pyrano-[3,2-c]pyridone 4a and it provides better results with
high yields.
5
45
Table 2. Optimization of reaction conditions for the synthesis of pyrano-
[3,2-c]pyridone 4a a
Amount of the
catalyst [g]
Yield
[%]b
Entry Solvent
Catalyst
10 eV, indicated the well-defined symmetry of Ni(II) ion in oxide
form.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
EtOH
DMF
-
-
tracec
40
55
70
50
65
80
65
88
92
92
85
65
45
50
Nano NiO
Nano Cu2O
AT-Nano CP
0.01
0.01
0.01
0.004
0.008
0.01
0.004
0.008
0.01
0.02
0.01
0.01
0.01
0.01
Nano NiO-CP
Nano NiO-CP
Nano NiO-CP
Nano Cu2O-CP
Nano Cu2O-CP
Nano Cu2O-CP
Nano Cu2O-CP
Nano Cu2O-CP
Nano Cu2O-CP
15
Toluene Nano Cu2O-CP
CH2Cl2
Nano Cu2O-CP
a Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol), 4-
hydroxy-1,6-dimethylpyridin-2(1H)-one (1 mmol) and solvent (5 mL)
b
50 after 1h at room temperature. Isolated yields. cAfter 2h at room
temperature
In order to optimize the reaction conditions, the catalytic
efficiency was studied with various amounts of nano Cu2O-CP in
the model reaction (Table 2, entries 8-10). The results reveal that
55 0.01 g of nanocatalyst provided the best effects in terms of
economy of catalyst charge and purity of products (Table 2, entry
10). Moreover, higher amounts of the catalyst (0.02 gr) did not
improve the yield and the reaction time (Table 2, entry 11). The
model reaction was also performed in other solvents such as
60 EtOH, DMF, toluene, CH2Cl2 and instead of H2O (Table 2,
entries 12-15). Changing the solvent showed no further increase
in the yield under optimized conditions. Therefore, the best
results were obtained from the reaction of these components in
water (5 mL) in the presence of 0.01 g of Nano Cu2O-CP at room
65 temperature affording the pyrano-[3,2-c]pyridone 4a in a 92%
yield (Table 2, entry 10).
20
Fig. 5. XPS spectrum of (a) Cu 2p spectral peaks of Nano Cu2O-CP and
(b) Ni 2p spectral peaks of Nano NiO-CP
These nanocatalysts were then explored as a heterogeneous
25 catalyst for the synthesis of pyrano-[3,2-c]pyridones and of
pyrano[3,2-b]pyrans derivatives via three-component reaction.
In order to find the best reaction conditions for the synthesis of
pyrano-[3,2-c]pyridones, the reaction of 4-hydroxy-1,6-
dimethylpyridin-2(1H)-one 1 (1 mmol) with benzaldehyde 2 (1
30 mmol) and malononitrile 3 (1 mmol) was chosen as a model
reaction in water at room temperature (Scheme 1).
The acid strength and acid distribution of AT-nano CP, Nano
Cu2O-CP and Nano NiO-CP measured by amine titration method
70 (n-butylamine titration) using Hammett indicators are listed in
Table 3. The limits of the H0 of samples were recognized by
observing the colour of the adsorbed form of the Hammett
indicators. The total acid amount for AT-nano CP, Nano Cu2O-
CP and NiO-CP were obtained 2.4, 2.9 and 2.7 mmol/g,
75 respectively. Measurements of surface acidity by amine titration
method showed to the increase number of Lewis acid sites by the
presence of Cu2O and NiO. These results can explains better
performance of Nano Cu2O-CP than other mesoporous materials
in the synthesis of pyrano-[3,2-c]pyridone 4a (Table 2, entries 4-
80 10) . Higher activity of Nano Cu2O-CP compared with alone AT-
nano CP and Nano NiO-CP was explain by presence of stronger
acid sites connected to zeolite.
NH2
CN
O
OH
H
O
Nano catalyst
NC
CN
Water, r.t
H3C
N
O
H3C
N
O
Me
4a
Me
1
3
2
Scheme
1 The model reaction for the synthesis of pyrano-[3,2-
35 c]pyridone 4a
The reaction was carried out in the present of nano Cu2O-CP,
nano NiO-CP, AT-Nano CP, CuO and NiO nanoparticles, and the
results are presented in Table 2. In the absence of catalyst, only a
trace amount of desired product was obtained even after in longer

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Table 3 Acid distribution of AT-nano CP, Cu2O-CP and NiO-CP
catalysts
optimal reaction conditions and the results are summarized in
Table 5. Results demonstrate that all substituted benzaldehydes
containing electron-donating or electron-withdrawing substituents
in the aromatic ring were reacted with malononitrile to provide
35 the corresponding products 6 in good to excellent yields under
optimized reaction conditions.
Acid amount (mmol/g)
H0 ≤ +2.8 H0 ≤ +3.3 H0 ≤ +4.8 H0 ≤ +6.8 Total
Catalyst
AT-Nano CP
0.9
0
0.7
0.9
0.8
0.8
0.9
0.9
2.4
2.9
2.7
Nano Cu2O-CP 0.9
Nano NiO-CP 0.9
0.2
0.1
Table 5 Synthesis of pyrano[3,2-b]pyrans 6 catalyzed by Nano Cu2O-CPa
Encouraged by the remarkable results, and in order to show
generality and scope of this new protocol, a variety of pyrano-
[3,2-c]pyridone derivatives were synthesized from the three-
component reaction of pyridin-2-ones 1a or 1b (1mmol),
aromatic aldehydes 2 (1mmol), and malononitrile 3 (1 mmol) in
the presence of nano Cu2O-CP (0.01 gr) in aqueous medium at
R
5
Nano Cu2O-CP
(0.008 g)
O
2
O
O
CN
HO
HO
NC
CN
R
H
Water, r.t
OH
O
NH2
O
5
O
6
3
Cl
10 room temperature. The results have been summarized in Table 4.
According to the results, the substrates with electron-withdrawing
gave better yields than with electron-donating groups. To develop
this reaction into a more general method, other pyridin-2-one
substrates, 4-hydroxy-6-methylpyridin-2(1H)-one 1b were also
15 tried (Table 4). They all gave the corresponding products in good
to excellent yields.
Cl
O
O
CN
O
O
CN
O
O
CN
HO
HO
HO
O
NH2
O
NH2
O
NH2
6a, (92%)
6b, (90%)
6c, (85%)
Cl
F
Br
Cl
Table 4 Synthesis of pyrano[3,2-c]pyridones 4 and 5 catalyzed by Nano
O
CN
O
CN
O
CN
HO
HO
HO
Cu2O-CPa
O
NH2
O
NH2
CH3
O
O
NH2
NH2
O
O
CN
6e, (90%)
OH
N
O
6d, (85%)
6f, (92%)
O
Nano Cu2O-CP
R
R
H
NC
CN
Water, r.t
S
O
O
N
O
H3C
O
H3C
X
1
X
4 or 5
O
CN
O
CN
CN
HO
HO
HO
3
2
(1a): X= Me
(1b): X= H
O
O
NH2
O
NH2
O
NH2
20
O
O
a
6g, (92%)
6i, (85%)
6h, (85%)
40
NH2
NH2
NH2
Reaction conditions: kojic acid 5 (1 mmol), aromatic aldehydes 2 (1
mmol), malononitrile 3 (1 mmol), Nano Cu2O-CP (0.01 gr) in 5 mL of
water for 1h at room temperature.
CN
CN
CN
O
N
O
O
N
H3C
O
Cl
H3C
H3C
H3C
N
O
H3C
O
Br
The recyclability of the catalyst for reactions was investigated.
CH3
, (95%)
CH3
CH3
, (90 %)
4b
4c
4a
, (92%)
45 The catalyst was recovered by filtration technique after each
experiment and washed with hot distilled water (2 mL) and
ethanol (2 mL) twice. The recovered catalyst was dried in an
oven and reused successively several times (up to 8 uses) without
any significant loss of activity (Fig. 6). The strong interaction of
50 Cu2O nanoparticles with the zeolite surface could be the reason
for the repetitive use of the catalyst in a greater number of
catalytic runs with high efficiency.
NH2
NH2
NH2
CN
CN
CN
O
O
O
OMe
H3C
N
O
OMe
N
O
Me
H3C
N
O
NO2
CH3
OMe
CH3
, (90%)
CH3
, (95%)
4d
4f
, (85%)
4e
NH2
NH2
NH2
CN
CN
CN
O
O
O
N
O
H3C
N
O
Cl
H3C
N
H
O
OMe
H
H
5b
, (90 %)
5a
, (85 %)
5c
. (80 %)
a
Reaction conditions: pyridin-2-ones 1a or b (1 mmol), aldehyde 2 (1
mmol), malononitrile 3 (1 mmol), Nano Cu2O-CP (0.01 gr) in 5 mL of
water for 1h at room temperature.
25 In following to further explore the potential of this protocol, we
also examined three component reactions using another reactant,
kojic acid 5 instead of pyridin-2-ones 1a,b under similar reaction
conditions (Table 5). Under these conditions, a variety of
substituted aromatic aldehydes were applied for the synthesis of
30 pyrano[3,2-b]pyran derivatives using of nano Cu2O-CP under the
55 Fig. 6 The reusability of nano Cu2O-CP separable catalyst

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In the present study, a reproducible synthetic procedure has been 55 flask mixture was refluxed for 1 h. After cooling, the supernatant
developed to prepare Cu2O and NiO nanoparticles into the
nanopores of modified nanozeolite clinoptilolite. The presence of
nano NiO and Cu2O in the nanozeolite has a significant influence
on the acidity of the clinoptilolite skeleton leading to an increase
was discarded and the activated nanozeolite clinoptilolite was
repeatedly washed with deionized water (250 mL) until the
solution became neutral and finally dried in oven at 80 °C
overnight to obtain the white solid product. The activated
5
in the number of Lewis acid sites. The results indicate that nano 60 nanozeolite clinoptilolite was designated as AT-Nano CP.
Cu2O-CP could be considered as catalyst for the synthesis of
pyrano-[3,2-c]pyridone and pyrano[3,2-b]pyran derivatives in
4.3.2. Preparation of Cu and Ni oxide nanoparticles on the
surface of AT-Nano CP
good to excellent yields. These nanocatalysts are thermally stable,
One gram of AT-Nano CP was taken into a 100 mL round bottom
10 inexpensive, and easy to prepare. In addition, it could be easily
separated from the reaction mixture and reused for several times
without any significant loss of its activity.
flask and 100 cm3 of 25 mmol L-1 MCl2 (M= Cu and Ni) was
65 added slowly under vigorous stirring condition. The resulting
mixture was stirred for 24 h at room temperature, and the M-
containing product was then recovered by filtration. The
suspension was filtered off, washed with water and dried at 80
°C. Dehydration of the M-containing products was carried out by
70 heating under air. The obtained Cu and Ni exchanged AT-nano
CP were heated at a heating rate of 10 °C min-1 to 550 °C and
then were isothermally heated for 60 min. The influence of Cu2O
and NiO loading on AT-Nano CP was studied using the same
experimental conditions. According to atomic absorption results
75 of copper and nickel determination, their Cu2O and NiO contents
were 200 and 95 mg Cu2O and NiO per gram of the catalyst,
respectively.
4. Experimental Section
4.1. Materials
15 All reagents were prepared from analytical reagent grade
chemicals unless specified otherwise and purchased from Merck
Company. The raw zeolite material was an Iranian commercial
Clinoptilolite (Afrandtooska Company) obtained from deposits in
the region of Semnan (ca. 1 $ per kg).
20 4.2. Instrumentation
The X-ray powder diffraction (XRD) of the catalyst was carried
out on a Philips PW 1830 X-ray diffractometer with Cu Kα
source (λ=1.5418 Å) in a range of Bragg’s angle (10-90°) at room
temperature. N2 sorption measurement was performed using
25 Belsorp mini II at 273 K. Prior to the measurements, all the
samples were degassed at 393 K in a vacuum line overnight. The
specific surface area and pore volume were calculated with the
Brunauer-Emmett-Teller (BET) method, and the pore size
distribution was expected with desorption branch based on the
30 Barrett-Joyneer-Halenda (BJH) model. Scanning electron
microscope (SEM) pictures were taken using KYKY-EM3200
microscope (acceleration voltage 26 kV). Transmission electron
microscopy (TEM) experiments were conducted on a JEOL-2100
microscope operated at 150 KV. The TEM model Samples are
35 sonicated by mixing with 95% ethanol for 30 min, and
subsequently dropped onto copper grids coated with carbon film,
and dried thoroughly in an electronic drying cabinet at a
temperature of 25 °C and relative humidity 45%. The chemical
composition and crystallinity analysis of the samples are
40 characterized using an energy-dispersive X-ray spectrometer
(EDS, INCA) operated at 150 KV. X-ray photoelectron spectra
(XPS) were recorded on a BESTEC GmbH-8025 spectrometer
using an Mg Kα (hν = 1253.6 eV) and Al Kα (hν = 1486.6 eV) X-
4.3.3. General procedure for the synthesis of pyrano-[3,2-
c]pyridone and pyrano[3,2-b]pyran derivatives
80 A mixture of 4-hydroxy-1,6-dimethylpyridin-2(1H)-one or 5-
hydroxy-2-(hydroxymethyl)-4H-pyran-4-one or 4-hydroxy-6-
methylpyridin-2(1H)-one (1 mmol), aldehyde (1 mmol),
malononitrile (1 mmol), and catalyst (0.01 g) in 5 mL of water
was stirred at room temperature for 1 h (Table 3 and 4). After this
85 time, the catalyst was removed by filtration, washed with ethanol
(2 mL), dried in vacuum and reused. The filtrate was evaporated
under reduced pressure to give the desired product and
recrystallized from hot ethanol to afford pure products. The
products were characterized by 1H and 13C NMR.
90 4.4. Spectral data of the synthesized compounds
4.4.1.
2-Amino-5,6-dihydro-6,7-dimethyl-5-oxo-4-phenyl-4H-
pyrano[3,2-c]pyridine-3-carbonitrile (4a). Mp 250-252 °C. 1H
NMR (400 MHz, DMSO-d6) δ: 2.38 (s, 3H, CH3), 3.35 (s, 3H,
CH3), 4.42 (s, 1H, CH), 6.12 (s, 1H, CH), 7.09 (s, 2H, NH2),
95 7.15-7.21 (m, 3H, ArH), 7.27-7.30 (m, 2H, ArH). 13C NMR (100
MHz, DMSO-d6) δ: 21.6, 31.3, 37.5, 58.2, 98.2, 105.0, 120.1,
125.1, 128.2, 128.9, 146.3, 149.5, 155.2, 160.4, 162.7.
4.4.2. 2-Amino-4-(4-chlorophenyl)-5,6-dihydro-6,7-dimethyl-5-
oxo-4H-pyrano[3,2-c]pyridine-3-carbonitrile (4b). Mp 253-256
100 °C. 1H NMR (400 MHz, DMSO-d6) δ: 2.35 (s, 3H, CH3), 3.31 (s,
3H, CH3), 4.32 (s, 1H, CH), 6.02 (s, 1H, CH), 7.03 (s, 2H, NH2),
1
ray source. H, 13C NMR spectra were recorded on a BRUKER
45 DRX-400 AVANCE spectrometer.
4.3. Catalyst preparation
7.14 (d, 2H, J = 8.3 Hz, ArH), 7.35 (d, 2H, J = 8.3 Hz, ArH). 13
C
4.3.1. Preparation of AT-Nano CP
NMR (100 MHz, DMSO-d6) δ: 21.1, 31.3, 37.4, 57.8, 98.2,
The nanozeolite clinoptilolite was converted to the homoionic
Na+-exchanged form by stirring in 2 mol L-1 of NaCl solution for
50 about 24 h at 25 °C, and then the Na+-nanozeolite clinoptilolite
was filtrated and washed with distilled water (50 mL) two times.
The Na+-nanozeolite was dried in an oven at 100 °C. The Na+-
nanozeolite clinoptilolite (5 g) was taken into a 250 mL round
bottom flask and 100 mL 4 M sulfuric acid was added to it. The
105.5, 120.4, 128.8, 129.5, 131.4, 144.3, 148.4, 155.1, 160.4,
105 161.4.
4.4.3. 2-Amino-4-(4-bromophenyl)-5,6-dihydro-6,7-dimethyl-5-
oxo-4H-pyrano[3,2-c]pyridine-3-carbonitrile (4c). Mp 256-257
°C. 1H NMR (400 MHz, DMSO-d6) δ: 2.33 (s, 3H, CH3), 3.32 (s,
3H, CH3), 4.35 (s, 1H, CH), 6.09 (s, 1H, CH), 7.09 (s, 2H, NH2),
110 7.15 (d, 2H, J = 8.3 Hz, ArH), 7.49 (d, 2H, J = 8.3 Hz, ArH). 13
C

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RSC Advances
NMR (100 MHz, DMSO-d6) δ: 21.5, 30.9, 37.2, 57.4, 97.2,
105.3, 119.9, 120.1, 130.6, 132.4, 144.5, 148.4, 155.2, 159.6, 60 °C. H NMR (400 MHz, DMSO-d6): δ = 4.12 (dd, 1H, J = 16.5
4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile (6b). Mp 195-197
1
161.8.
Hz, J = 6.3 Hz, CHaliph), 4.22 (dd, 1H, J = 16.5 Hz, J = 6.3 Hz,
CHaliph), 4.65 (s, 1H, CHvinyl), 5.55 (t, 1H, J = 6.3 Hz, OH), 6.32
(s, 1H, CHaliph), 6.77 (s, 2H, NH2), 7.20 (d, 2H, J = 8.3 Hz,
CHarom), 7.33 (d, 2H, J = 8.3 Hz, CHarom); 13C NMR (100 MHz,
4.4.4. 2-Amino-4-(4-methylphenyl)-5,6-dihydro-6,7-dimethyl-5-
oxo-4H-pyrano[3,2-c]pyridine-3-carbonitrile (4d). Mp 250-253
°C. 1H NMR (400 MHz, DMSO-d6) δ: 2.20 (s, 3H, CH3), 2.35 (s,
5
3H, CH3), 3.33 (s, 3H, CH3), 4.34 (s, 1H, CH), 6.07 (s, 1H, CH), 65 DMSO-d6): δ = 40.5, 55.9, 59.7, 111.5, 119.2, 129.1, 129.5,
6.98 (s, 2H, NH2), 7.05 (d, 2H, J = 8.3 Hz, ArH), 7.12 (d, 2H, J =
8.3 Hz, ArH). 13C NMR (100 MHz, DMSO-d6) δ: 21.6, 22.2,
134.1, 136.8, 139.2, 148.5, 159.9, 169.3, 170.4.
4.4.12. 2-Amino-4-(2-chlorophenyl)-6-(hydroxymethyl)-8-oxo-
10 30.7, 37.1, 58.4, 97.3, 106.1, 120.5, 128.1, 129.3, 136.2, 142.3,
147.8, 156.0, 159.4, 161.2.
4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile (6c). Mp 212-215
°C. 1H NMR (400 MHz, DMSO-d6) δ = 4.18 (dd, 1H, J = 16.5, J =
4.4.5.
2-Amino-5,6-dihydro-6,7-dimethyl-4-(4-nitrophenyl)-5- 70 6.3 Hz, CHaliph), 4.54 (dd, 1H, J = 16.5, J = 6.3 Hz, CHaliph), 5.21 (t,
oxo-4H-pyrano[3,2-c]pyridine-3-carbonitrile (4e). Mp 242-244
°C. 1H NMR (400 MHz, DMSO-d6) δ: 2.37 (s, 3H, CH3), 3.35 (s,
15 3H, CH3), 4.58 (s, 1H, CH), 6.12 (s, 1H, CH), 7.13 (br s, 2H,
NH2), 7.52 (d, 2H, J = 8.6 Hz, ArH), 8.20 (d, 2H, J = 8.6 Hz,
1H, J= 6.3 Hz, OH), 5.77 (s, 1H, CHvinyl), 6.39 (s, 1H, CHaliph), 7.09
(s, 2H, NH2), 7.25-7.59 (m, 4H, CHarom); 13C NMR (100 MHz,
DMSO-d6) δ =40.1, 54.7, 59.5,111.5, 118.9, 128.3,129.8, 130.5,
131.2, 131.9, 136.7, 137.5, 148.3, 159.6, 167.8, 169.2, 196.1.
ArH); 13C NMR (100 MHz, DMSO-d6) δ: 21.2, 31.2, 37.5, 57.3, 75 4.4.13.
2-Amino-4-(2,4-dichlorophenyl)-6-(hydroxymethyl)-8-
97.6, 105. 2, 120.6, 124. 5, 130.2, 147.6, 149.2, 152.2, 156.3,
159.5, 161.7.
oxo-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile (6d). Mp 240-
241 °C. H NMR (400 MHz, DMSO-d6) δ = 4.13 (dd, 1H, J =
1
20 4.4.6. 2-Amino-6,7-dimethyl-5-oxo-4-(3,4,5-trimethoxyphenyl)-
5,6-dihydro-4H-pyrano[3,2-c]pyridine-3-carbonitrile (4f). Mp
16.5, J = 6.3 Hz, CHaliph), 4.32 (dd, 1H, J= 16.5, J = 6.3 Hz,
CHaliph), 5.52 (t, 1H, J = 6.3 Hz, OH), 5.89 (s, 1H, CHvinyl), 6.45 (s,
259-262 °C. 1HNMR (400 MHz, DMSO-d6) δ: 2.32 (s, 3H, CH3), 80 1H, CHaliph), 7.49 (s, 2H, NH2), 7.50 (d, 1H, J = 8.3 Hz, CHarom),
3.36 (s, 3H), 3.62 (s, 3H, CH3), 3.73 (s, 6H, 2CH3), 4.45 (s, 1H,
CH), 6.09 (s, 1H, CH), 6.75 (s, 2H, NH2), 7.05 (s, 2H, ArH); 13C
25 NMR (100 MHz, DMSO-d6) δ: 21.2, 31.4, 37.5, 56.7, 58.6, 61.3,
97.1, 104.8, 106.5, 121.2, 138.3, 141.2, 148.6, 153.5, 155.8,
159.7, 161.6.
7.92 (d, 1H, J = 2.5 Hz, CHarom), 7.95 (dd, 1H, J = 8.3, J = 2.5 Hz,
CHarom); 13C NMR (100 MHz, DMSO-d6) δ = 39.7, 55.3, 59.4,
117.5, 119.1, 128.4, 129.4, 129.7, 130.6, 131.9, 136.5, 138.2,
149.1, 159.9, 169.1, 170.2, 192.3.
85 4.4.14.
2-Amino-4-(3-bromophenyl)-6-(hydroxymethyl)-8-oxo-
4.4.7.
2-Amino-5,6-dihydro-7-methyl-5-oxo-4-phenyl-4H-
4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile (6e). Mp 244-245
°C. 1H NMR (400MHz, DMSO-d6) δ =4.18 (dd, 1H, J = 16.5, J =
6.3 Hz, CHaliph), 4.35 (dd, 1H, J = 16.5, J = 6.3 Hz, CHaliph), 5.78
(t, 1H, J = 6.3 Hz, OH), 5.84 (s, 1H, CHvinyl), 6.73 (s, 1H, CHaliph),
pyrano[3,2-c]pyridine-3-carbonitrile (5a). Mp 279-282 °C. 1H
30 NMR (400 MHz, DMSO-d6) δ: 2.13 (s, 3H, CH3), 4.29 (s, 1H,
CH), 5.84 (s, 1H, CH), 7.03 (s, 2H, NH2), 7.16-7.22 (m, 3H,
ArH), 7.28-7.32 (m, 2H, ArH), 11.47 (s, 1H, NH). 13C NMR (100 90 7.24 (s, 2H, NH2), 7.48-7.83 (m, 4H, CHarom); 13CNMR(100 MHz,
MHz, DMSO-d6) δ: 19.4, 37.5, 58.2, 96.3, 106.2, 121.4, 127.1,
127.7, 128.5, 145.4, 147.2, 157.4, 159.1, 161.9.
DMSO-d6) δ = 38.9, 55.1, 59.5, 112.9, 119.5, 123.1, 127.1,
131.5, 130.7, 135.6, 137.1, 143.3, 145.4, 159.5, 168.3, 169.6,
195.2.
35 4.4.8. 2-Amino-4-(4-chlorophenyl)-5,6-dihydro-7-methyl-5-oxo-
4H-pyrano[3,2-c]pyridine-3-carbonitrile (5b). Mp 245-247 °C.
4.4.15.
2-Amino-4-(4-fluorophenyl)-6-(hydroxymethyl)-8-oxo-
1H NMR (400 MHz, DMSO-d6) δ: 2.16 (s, 3H, CH3), 4.35 (s, 1H, 95 4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile (6f). Mp 249–252
CH), 5.87 (s, 1H, CH), 7.07 (s, 2H, NH2), 7.18 (d, 2H, J = 8.3 Hz,
ArH), 7.36 (d, 2H, J = 8.3 Hz, ArH), 11.47 (s, 1H, NH). 13C
40 NMR (100 MHz, DMSO-d6) δ: 18.7, 36.4, 56.4, 96.3, 106.7,
120.4, 129.2, 129.8, 131.7, 144.8, 147.5, 157.3, 159.5, 161.7.
°C. 1H NMR (400 MHz, DMSO-d6) δ = 4.19 (dd, 1H, J= 16.3, J=
6.0 Hz, CHaliph), 4.33 (dd, 1H, J= 16.3, J = 6.0 Hz, CHaliph), 4.78 (t,
1H, J = 6.0 Hz, OH), 5.69 (s, 1H, CHvinyl), 6.44 (s, 1H, CHaliph),
7.20-7.27 (m, 2H, CHarom), 7.30 (s, 2H, NH2), 7.35-7.46 (m, 2H,
4.4.9. 2-Amino-5,6-dihydro-4-(4-methoxyphenyl)-7-methyl-5-oxo- 100 CHarom); 13C NMR (100 MHz, DMSO-d6) δ = 39.5, 56.5, 59.4,
4H-pyrano[3,2-c]pyridine-3-carbonitrile (5c). Mp 224-225 °C.
1H NMR (400 MHz, DMSO-d6) δ: 2.10 (s, 3H, CH3), 3.75 (s, 3H,
45 CH3), 4.35 (s, 1H, CH), 5.92 (s, 1H, CH), 6.98 (d, 2H, J = 8.1 Hz,
ArH), 7.05 (s, 2H, NH2), 7.12 (d, 2H, J = 8.1 Hz, ArH), 11.56 (s,
112.4, 116.5 (d, J = 25.0 Hz, C-F), 119.7, 129.5 (d, J = 9.8 Hz, C-
F), 136.5, 137.5 (d, J = 3.8 Hz, C-F), 149.1, 160.2, 162.4 (d, J =
295.2 Hz, C-F), 168.5, 169.7, 198.6.
4.4.16.
2-Amino-6-(hydroxymethyl)-8-oxo-4-m-tolyl-4,8-
1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 18.6, 35.8, 55.5, 105 dihydropyrano[3,2-b]pyran-3-carbonitrile (6g). Mp 221-222 °C.
58.7, 96.7, 106.9, 114.2, 120.7, 128.7, 137.2, 146.1, 156.8, 158.2,
159.4, 161.9.
1H NMR (400MHz, DMSO-d6) δ = 2.38 (s, 3H, CH3), 4.28 (dd,
1H, J = 16.2, J = 6.2 Hz, CHaliph), 4.26 (dd, 1H, J = 16.2, J = 6.2
Hz, CHaliph), 4.81 (t, 1H, J = 6.2 Hz, OH), 5.72 (s, 1H, CHvinyl),
6.38 (s, 1H, CHaliph), 6.79 (d, 1H, J = 8.0 Hz, CHarom), 7.18 (d, 1H,
50 4.4.10.
2-Amino-6-(hydroxymethyl)-8-oxo-4-phenyl-4,8-
dihydropyrano[3,2-b]pyran-3-carbonitrile (6a). Mp 222-225 °C.
1H NMR (400 MHz, DMSO-d6): δ = 4.15 (dd, 1H, J=16.5, J = 110 J = 8.0 Hz, CHarom), 7.12 (s, 2H, NH2), 7.32 (t, 1H, J =8.0 Hz,
6.3 Hz, CHaliph), 4.26 (dd, 1H, J= 16.5, J = 6.3 Hz, CHaliph), 5.35 (t,
1H, J = 6.3 Hz, OH), 5.65 (s, 1H, CHvinyl), 6.33 (s, 1H, CHaiiph),
55 7.10 (s, 2H, NH2), 7.27-7.52 (m, 5H, CHarom); 13C NMR (100
MHz, DMSO-d6) δ = 40.4, 55.8, 57.5, 111.5, 117.2, 119.2,128.7,
131.0, 132.3, 135.2, 136.5, 148.1, 159.2, 169.4, 169.9, 195.4.
CHarom); 13C NMR (100 MHz, DMSO-d6) δ = 32.9, 55.5, 59.2,
111.4, 119.6, 125.1, 128.1, 128.8, 137.3, 138.3, 141.1, 149.4,
159.2, 167.4, 169.5, 195.6.
4.4.17.
2-Amino-4-(furan-2-yl)-6-(hydroxymethyl)-8-oxo-4,8-
115 dihydropyrano[3,2-b]pyran-3-carbonitrile (6h). Mp 223-225°C.
1H NMR (400 MHz, DMSO-d6) δ = 4.18 (dd, 1H, J=16.5, J = 6.3
4.4.11.
2-Amino-4-(4-chlorophenyl)-6-(hydroxymethyl)-8-oxo-

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Hz, CHaliph), 4.27 (dd, 1H, J = 16.5, J = 6.3 Hz, CHaliph), 4.72 (t,
1H, J= 6.3 Hz, OH), 5.24 (s, 1H, CHvinyl), 6.47 (s, 1H, CHaliPh), 7.21
(s, 2H, NH2), 7.47 (d, 2H, J = 4.8 Hz, CHarom), 7.56-7.67 (m, 2H,
CHarom); 13C NMR (100 MHz, DMSO-d6) δ = 34.5, 55.6, 59.3,
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107.6, 110.7, 112.1, 112.9, 118.5, 142.1, 142.8, 153.4, 159.5, 60 Heterocycl. Compd. 2011, 46, 1354.
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4.4.18. 2-Amino-6-(hydroxymethyl)-8-oxo-4-(thiophen-2-yl)-4,8-
dihydropyrano[3,2-b]pyran-3-carbonitrile (6i). Mp 233-236 °C.
1H NMR (400 MHz, DMSO-d6) δ = 4.22 (dd, 1H, J=16.5, J = 6.3
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Acknowledgements
This research is supported by the Iran National Science
Foundation (INSF) (INSF 92013217) and the Islamic Azad
University, Ayatollah Amoli Branch, Iran.
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