Full text of DOI:10.1016/j.jorganchem.2018.05.002

Accepted Manuscript
Synthesis of pyridopyrimidinones by N-heterocyclic carbene palladium(II) supported
on KCC-1 in aqueous solution
Seyed Mohsen Sadeghzadeh, Rahele Zhiani
PII:
S0022-328X(18)30306-1
10.1016/j.jorganchem.2018.05.002
JOM 20435
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 24 March 2018
Revised Date: 30 April 2018
Accepted Date: 4 May 2018
Please cite this article as: S.M. Sadeghzadeh, R. Zhiani, Synthesis of pyridopyrimidinones by N-
heterocyclic carbene palladium(II) supported on KCC-1 in aqueous solution, Journal of Organometallic
Chemistry (2018), doi: 10.1016/j.jorganchem.2018.05.002.
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ACCEPTED MANUSCRIPT
Synthesis of pyridopyrimidinones by N-heterocyclic carbene
palladium(II) supported on KCC-1 in aqueous solution
Seyed Mohsen Sadeghzadeh*,a,b, Rahele Zhiania,b
aYoung Researchers and Elite Club, Neyshabur Branch, Islamic Azad university, P.O. Box 97175-613, Neyshabur, Iran
bNew Materials Technology and Processing Research Center, Department of Chemistry, Neyshabur Branch, Islamic Azad
University, Neyshabur, Iran
Abstract
New N, N'-substituted imidazolium salts and their corresponding diiodopyridinepalladium(II) complexes were successfully
synthesized and supported on KCC-1 (KCC-1/Pd-NHC-Py) has been developed for synthesis of pyridopyrimidinones,
providing excellent yields of the corresponding products with remarkable chemoselectivity. This morphology ultimately
leads to higher catalytic activity for the KCC-1-supported nanoparticles. The KCC-1/Pd-NHC-Py NPs were thoroughly
characterized by using TEM, FESEM, TGA, and BET. We supported a drug on the surface of a silica and used as a catalyst
for synthesis another drug.
Keywords: Nano catalyst; Pyridopyrimidinone; One-pot synthesis; Green chemistry; KCC-1
Introduction
Fused N-heterocycles are among the most widely used chemicals owing to its medicinal, [1] agrochemical, [2] and material
properties. [3, 4] The 2H-pyridopyrimidinone scaffold is an important class of nitrogen heterocycles. Many synthetic
pyridopyrimidinones have occupied privileged position in drug development due to their unprecedented biological activities.
This scaffold is an integral part of marketed drugs for the treatment of Schizophrenia [5] and asthma. [6] Many of these
molecules have been reported as anticancer, [7] antimalarial, [8, 9] and anticoccidial [10] agents. Some of the them have also
been recognized as aldose reductase inhibitors, [11] estrogen-related receptors (ERRs) agonists, [12] G protein signaling
(RGS) protein regulators, [13] HIV integrase inhibitors,[14] efflux pump inhibitors,[15] etc.[16] Pyridopyrimidinone
scaffold is also a key constituent of numerous natural products possessing wide range of biological activities including
antitumor, anti-influenza, oxidative burst inhibitory, lipid droplet synthesis inhibition, and anti-obesity properties. [17-20]
Recently, much attention has been paid to the development of N-heterocyclic carbene metal complexes and remarkable
advances have been made especially on their applications as organometallic catalysts. This was attributed to the ability of N-
heterocyclic carbene ligands to provide highly active and stable metal complexes for various catalytic applications. The
highly sigma donating property of NHC ligands prevents the formation of inactive palladium black during the catalytic
reactions. [21-27] Along a similar theme, PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation), a
term recently coined and demonstrated by Organ and coworkers,[28-31] also resulted in highly active catalysts for various
Pd-mediated C–C cross-coupling reactions. [32-34]
Recently, Polshettiwar et al. [35] reported a novel fibrous nanosilica (KCC-1) material, which has special center-radial pore
structures with their pore sizes gradually increasing from the center to the surface. KCC-1 material showed high specific
surface area due to the pores in the fibers, and the accessibility of the active sites was significantly increased as a result of
the special structure. [36-40] Additionally, the 3D architectures generated hierarchical pore structure with macropores can
also improve the mass transfer of the reactant. [41-43] The KCC-1-based sorbents may have several advantages over
conventional silica-based sorbents, including (i) high catalyst loading, (ii) minimum reduction in surface area after
functionalization and (iii) more accessibility of the catalyst sites to enhance the reaction, due to the fibrous structure and
highly accessible surface area of KCC-1. Given our continued interest in nanocatalysis and catalyst development for organic
reactions, [44-51] we reported the preparation and characterization of palladium (II) complex supported by KCC-1
nanoparticles. In addition, we described its utility for investigate the one-pot synthesis of pyridopyrimidinones, which could
be easily separated from the reaction mixture for reuse (Scheme 1).
OH
O
N
O
+
R
R
OMe
N
N
NH2
Scheme 1 Synthesis of pyridopyrimidinones in the presence of KCC-1/Pd-NHC-Py NPs.
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Experimental
Materials and methods
Chemical materials were purchased from Fluka and Merck in high purity. Melting points were determined in open capillaries
using an Electrothermal 9100 apparatus and are uncorrected. FTIR spectra were recorded on a VERTEX 70 spectrometer
(Bruker) in the transmission modein spectroscopic grade KBr pellets for all the powders. The particle size and structure of
nano particle was observed by using a Philips CM10 transmission electron microscope operating at 100 kV. Powder X-ray
diffraction data were obtained using Bruker D8 Advance model with Cu ka radition. The thermogravimetric analysis (TGA)
1
was carried out on a NETZSCH STA449F3 at a heating rate of 10 °C min−1 under nitrogen. H and 13C NMR spectra were
recorded on a BRUKER DRX-300 AVANCE spectrometer at 300.13 and 75.46 MHz, BRUKER DRX-400 AVANCE
spectrometer at 400.22 and 100.63 MHz, respectively. Elemental analyses for C, H, and N were performed using a Heraeus
CHN–O-Rapid analyzer. The purity determination of the products and reaction monitoring were accomplished by TLC on
silica gel polygram SILG/UV 254 plates. Mass spectra were recorded on Shimadzu GCMS-QP5050 Mass Spectrometer.
General procedure for the preparation of KCC-1 NPs
TEOS (2.5 g) was dissolved in a solution of cyclohexane (30 mL) and 1-pentanol (1.5 mL). A stirred solution of
cetylpyridinium bromide (CPB 1 g) and urea (0.6 g) in water (30 mL) was then added. The resulting mixture was continually
stirred for 45 min at room temperature and then placed in a teflon-sealed hydrothermal reactor and heated 120 °C for 5 h.
The silica formed was isolated by centrifugation, washed with deionized water and acetone, and dried in a drying oven. This
material was then calcined at 550 °C for 5 h in air.
General procedure for the preparation of KCC-1/3-iodopropylsilane NPs
KCC-1 NPs (2 mmol) and THF (20 mL) were mixed together in a beaker, and then NaH (20 mmol) was dispersed in to the
mixture by ultrasonication. 3-iodopropylsilane (22 mmol) was added drop-wise at room temperature and stirred for another
o
16 h at 60 C. The resultant products were collected and washed with ethanol and deionized water in sequence, and then
dried under vacuum at 60 oC for 2 h for further use.
General procedure for the preparation of 5-(4-methoxyphenyl)-1-methyl-1H-imidazole
5-Bromo-1-methyl-1H-imidazole (0.50 mmol), Pd(PPh3)2Cl2 (0.025 mmol, 5.0 mol%), K2CO3 (1.0 mmol), DMF (2.0 mL),
distilled water (2.0 mL) and the (4-methoxyphenyl)boronic acid (0.60 mmol), were added in a 10 mL round bottom flask.
o
The mixture was stirred at 90 C for 24 h. After completion of the reaction, the mixture was cooled down to room
temperature and extracted 3 times with ethyl acetate. The combined ethyl acetate extract was dried using anhydrous MgSO4.
The solvent was removed under reduced pressure and the product was purified by silica gel column chromatography using
hexane-ethyl acetate (1:1) followed by 7 % methanol in ethyl acetate as an eluent.
General procedure for the preparation of KCC-1/N-Heterocyclic carbene
5-(4-Methoxyphenyl)-1-methyl-1H-imidazole (0.50 mmol) and KCC-1/3-iodopropylsilane (200 mg) were added into a 10
mL round bottom flask. The mixture was stirred at 100 oC for 48 hours. The mixture was cooled down to room temperature.
Diethyl ether (5 mL) was added and stirred for 15 minutes. The ether was decanted. The product was washed several times
with ether. The pure product was dried under vacuum.
General procedure for the preparation of KCC-1/Pd-NHC-Py
N-Heterocyclic carbene ligand precursor (100 mg), palladium(II) iodide (0.50 mmol), potassium carbonate (2.0 mmol) and
pyridine (5.0 mL) were added into a 15 mL round bottom flask. The reaction mixture was stirred at 90 oC for 24 h. The crude
product was cooled down to room temperature and diluted with 5 mL dichloromethane. After filtering it, the residue was
washed with ethanol again and air-dried at room temperature. Finally, a fine powder was ground out of the resulted complex
to be later used as a catalyst.
General procedure for synthesis of pyridopyrimidinones
A mixture of 2-aminopyridine derivative (1.0 mmol) and Baylis-Hillman adducts (1.0 mmol), and KCC-1/Pd-NHC-Py NPs
(1 mg) was stirred heating under reflux in TFA (3 mL) for 1 h. The catalyst was separated by filtration. Evaporation of the
solvent of the filtrate under reduced pressure gave the crude products. The pure products were isolated by chromatography
on silica gel eluted with petroleum ether:EtOAc (3:1).
Results and discussion
The KCC-1 coreeshell was synthesized by a simple method and then functionalized by the N-heterocyclic carbene
palladium(II), according to scheme 2. The synthesized KCC-1/Pd-NHC-Py NPs was then characterized by different methods
such as TEM, SEM, TGA, and BET (Scheme 2).
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OH
N
+
H3CO
B
OH
N
Br
CH3
N
N
CH3
H3CO
O
O
O
O
O
O
I
N
N
I
CH3
H3CO
EtO
EtO Si
EtO
PdI2
+
I
O
N
O
O
KCC-1
I
N
N
Pd N
I
CH3
H3CO
Scheme 2 Schematic illustration of the synthesis for KCC-1/Pd-NHC-Py NPs.
The morphology and structure of the KCC-1 and KCC-1/Pd-NHC-Py NPs are further characterized by FESEM and TEM.
Figure 1a shows an FESEM image of highly textured KCC-1 samples, where the samples have spheres of uniform size with
diameters of ~300 nm and a wrinkled radial structure. TEM image of KCC-1 shows that wrinkled fibers (with thicknesses of
~8.5 nm) grow out from the center of the spheres and are arranged radially in three dimensions (Figure 1b). Also, the
overlapping of the wrinkled radial structure forms cone-shaped open pores. The FESEM and TEM image shows that the
entire sphere is solid and composed of fibers. Furthermore, this open hierarchical channel structure and fibers are more
easily for the mass transfer of reactants and increase the accessibility of active sites. The FESEM and TEM images of KCC-
1/Pd-NHC-Py NPs showed that after modification the morphology of KCC-1 is not change (Figures 1c and 1d).
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Figure 1 FESEM images of KCC-1 NPs (a); TEM images of KCC-1 NPs (b); FESEM images of KCC-1/Pd-NHC-Py NPs (c); TEM images
of KCC-1/Pd-NHC-Py NPs (d).
It was very important to us that the catalyst was stable. The mechanical stability of KCC-1/Pd-NHC-Py NPs was examined
using FESEM. The morphology of KCC-1/Pd-NHC-Py NPs remains unaffected even after mechanical compression up to
200 MPa pressure (Figure 2a). Also, we conducted a series of experiments to study the effect of microwave irradiation
stabilities on the morphology of KCC-1/Pd-NHC-Py NPs ratios were varied, which isn't affected at power to 650 W (Figure
2b). KCC-1/Pd-NHC-Py NPs also possesses high solvothermal stability, and the structures remained unchanged even after
heating in boiling DMSO for 60 h (Figure 2c). The FESEM analysis of KCC-1/Pd-NHC-Py NPs at 1000 oC showed that it is
thermally stable with no visible changes in the morphology and size of the particles (Figure 2d). We did not observe any
coagulation of the particles even after severe thermal treatment. This is an interesting perspective, as thermal stability is the
significant condition for catalysts operating in highly exothermic media. That way, as-synthesized high-surface-area KCC-
1/Pd-NHC-Py NPs have considerable thermal, mechanical, microwave irradiation, and solvothermal stabilities which are
necessary attributes for good catalytic support.
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Figure 2 FESEM images of KCC-1/Pd-NHC-Py NPs after mechanical compression at pressures of 200 Mpa (a); after microwave irradiation
at power to 650 W (b); after heating in boiling DMSO for 60 h (c); after calcination at 1000 oC/6 h (d).
o
The thermal behavior of KCC-1/Pd-NHC-Py NPs is shown in figure 3. The weight loss below 150 C was ascribed to the
elimination of the physisorbed and chemisorbed solvent on the surface of the KCC-1/Pd-NHC-Py material. In the second
stage (180–350 oC), weight loss is about 33.1 wt%, which can be attributed to the organic group derivatives.
100
95
90
85
80
75
70
65
60
0
200
400
600
800
T/oC
Figure 3 TGA diagram of KCC-1/Pd-NHC-Py NPs.
The N2 adsorption–desorption isotherms of KCC-1/Pd-NHC-Py NPs showed characteristic type IV curve (Figure 4), which
isconsistent with literature reports on standard fibrous silica spheres. As for KCC-1, the BET surface area, total pore volume,
and BJH pore diameter are obtained as 439 m2/g, 1.49 cm3/g, and 14.78 nm respectively, whereas the corresponding
parameters of KCC-1/Pd-NHC-Py NPs have decreased to 372 m2/g, 1.05 cm3/g, and 13.03 nm. The nitrogen sorption
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analysis of KCC-1/Pd-NHC-Py NPs also confirms a regular and uniform mesostructure with a decrease in surface area, pore
diameter and pore volume parameters in comparison with that of pristine KCC-1. With the functionalization by Pd-NHC-Py-
Si, the corresponding pore volumes are drastically reduced. This could be ascribed to increased loading with the sensing
probe, which occupies a large volume inside the silica spheres (Figure 4 and Table 1).
1800
1600
1400
1200
1000
800
600
400
200
0
0
0.2
0.4
0.6
0.8
1
Relative pressure (P/Po)
Figure 4 Adsorption–desorption isotherms of KCC-1/Pd-NHC-Py NPs.
Table 1 Structural parameters of KCC-1 and KCC-1/Pd-NHC-Py NPs materials determined from nitrogen sorption experiments.
Catalysts
KCC-1
SBET (m2 g-1)
439
Va (cm3 g-1)
1.49
DBJH (nm)
14.78
KCC-1/Pd-NHC-Py
372
1.05
13.03
To optimize reaction conditions for the KCC-1/Pd-NHC-Py NPs catalyst system, the effects of various reaction parameters
were investigated . We examined the effect of solvent on the synthesis of pyridopyrimidinone using the KCC-1/Pd-NHC-Py
NPs at heating under reflux (Table 2). Solvent does affect on catalysts performance. n-Hexane, benzene, CCl4, or
cyclohexane, an non-polar solvent, gave pyridopyrimidinone a lower yield (Table 2, entry 13-16). Also, i-PrOH, MeOH,
EtOH, and H2O, protic polar solvents, gave also pyridopyrimidinone in low yields (Table 2, entry 17-20). The reaction was
do better in aprotic polar solvent. CH3CN, THF, CH2Cl2, DMF, Toluene, Dioxane, CHCl3, EtOAc, and DMSO gave
pyridopyrimidinone in average yields (Table 2, entries 4-12). In this study, it was found that THF is a more efficient (Table
2, entry 4) over other solvents. A solvent that stabilizes one of two competing transition states that control the selectivity
should enhance the selectivity of the product obtained via the stabilized transition state. We also investigated the crucial role
of temperature in the synthesis of pyridopyrimidinone in the presence of KCC-1/Pd-NHC-Py NPs as a catalyst. Results
clearly indicated that the catalytic activity is sensitive to reaction temperature. The best temperature for this reaction was at
reflux (Table 2, entry 1-4).
Table 2 The effect of solvent and temperature for synthesis of pyridopyrimidinone.a
Entry
1
2
Solvent
THF
THF
Temp. (◦C)
r.t.
Yield (%)b
-
40
31
85
97
41
33
39
27
41
25
3
THF
50
4
5
6
7
8
9
10
THF
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
DMSO
Dioxane
CH3CN
CH2Cl2
EtOAc
DMF
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11
12
13
14
15
16
17
18
19
20
21
Toluene
CHCl3
n-Hexane
Benzene
CCl4
Cyclohexane
H2O
EtOH
i-PrOH
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
100
18
36
18
9
17
12
26
24
35
22
-
MeOH
solvent-free
a Reaction conditions: 2-aminopyridine (1 mmol), 2-(hydroxymethyl) acrylate (1 mmol), solvent (10 mL), and catalyst (1 mg), 1 h.
b GC yields [%].
As shown in Figure 5, the amount of catalyst also has a significant effect on the coupling reaction. The reaction rate was
accelerated quickly in the range 0.8–1.0 mg. However, the yield decreased when the amount of catalyst reached 1.8 mg.
Based on these report, it can be inferred that increasing amount of catalyst was propitious to produce pyridopyrimidinone
when the amount of catalyst was less than 1.6 mg. Therefore, the amount of catalyst of 1.0 mg was considered as suitable
condition.
100
90
80
70
60
50
40
30
20
10
0
0
0.2 0.4 0.6
0.8
1
1.2 1.4
1.6 1.8
2
Catalyst (mg)
Figure 5 Effect amount of catalyst on yield of pyridopyrimidinone.
The influence of time on this reaction is exhibited in Figure 6. It is obvious that the pyridopyrimidinone yield increased up to
97 % for 60 min. Whereas further increase in the time don't resulted in a slight decrease in the product yield. Therefore, the
optimal time for the synthesis of pyridopyrimidinone are 60 min.
100
90
80
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
Time (min)
Figure 6 Effect of time on yield of pyridopyrimidinone.
7

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For further investigation the efficiency of the catalyst, different control experiments were performed and the obtained
information is shown in Table 3. Initially, a standard reaction was carried out using KCC-1 showed that any amount of the
desired product was not formed after 1 h of reaction time (Table 3, entries 1). Also, when KCC-1/N-Heterocyclic carbene
was used as the catalyst, a reaction was not observed (Table 3, entries 2). The N-Heterocyclic carbene group could not give
the satisfactory catalytic activity under mild reactions. Based on these disappointing results, we continued the studies to
improve the yield of the product by added the Pd-NHC-Py. Notably, there was not much difference in the reaction yields
when reaction was carried out using KCC-1/Pd-NHC-Py NPs and Pd-NHC-Py catalyst (Table 3, entries 3 and 7), however,
Pd-NHC-Py is not recoverable and reusable for the next runs. These observations show that the reaction cycle is mainly
catalyzed by Pd-NHC-Py on the KCC-1 nanostructure. The nano-sized particles increase the exposed surface area of the
active site of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the
homogeneous catalysts. As a result, KCC-1/Pd-NHC-Py NPs was used in the subsequent investigations because of its high
reactivity, high selectivity and easy separation. Also, the activity and selectivity of nano-catalyst can be manipulated by
tailoring chemical and physical properties like size, shape, composition and morphology. To assess the exact impact of the
presence of KCC-1 in the catalyst, the KCC-1/Pd-NHC-Py NPs compared with MCM-41/Pd-NHC-Py, SBA-15/Pd-NHC-Py,
and nano-SiO2/Pd-NHC-Py. When nano-SiO2/Pd-NHC-Py, MCM-41/Pd-NHC-Py or SBA-15/Pd-NHC-Py was used as the
catalyst, the yield of the desired product was average to good, but the yield for KCC-1/Pd-NHC-Py was excellent. Non-
negligible activity of the silica was attributed to its shape, composition and morphology. Besides, the large space between
fibers can significantly increase the accessibility of the active sites of the KCC-1.That is why, the KCC-1 was more effective
than nano-SiO2, MCM-41, and SBA-15 (Table 3, entries 3-6). As a result, KCC-1 NPs were used in the subsequent
investigations because of its high reactivity, high selectivity and easy separation (Table 3).
Table 3 Influence of different catalysts for synthesis of pyridopyrimidinone.a
Entry
Catalyst
KCC-1
Yield (%)b
1
2
3
4
5
6
7
-
KCC-1/N-Heterocyclic carbene
KCC-1/Pd-NHC-Py
Nano-SiO2/Pd-NHC-Py
MCM-41/Pd-NHC-Py
SBA-15/Pd-NHC-Py
Pd-NHC-Py
-
97
59
89
82
98
aReaction conditions: 2-aminopyridine (1 mmol), 2-(hydroxymethyl) acrylate (1 mmol), TFA (3 mL), and catalyst (1 mg), 1 h.
bIsolated yield.
To examine the scope of the catalytic properties of the catalyst for synthesis of pyridopyrimidinone derivatives, various
types of aminopyridines were reacted with Baylis-Hillman adducts in the presence of a catalytic amount of KCC-1/Pd-NHC-
Py NPs. It was found that all aminopyridines and Baylis-Hillman adducts were suitable for this reaction, giving the desired
products excellent yields (Table 4).
Table 4 Synthesis of pyridopyrimidinone derivatives in the presence of KCC-1/Pd-NHC-Py NPs.a
Entry
Aminopyridines
BH adducts
Product
Yield
(%)b
OH
O
O
N
N
O
1
96
OMe
OMe
N
NH2
N
O
OH
F
2
90
N
F
N
NH2
N
N
O
O
O
Cl
Br
I
OH
OH
OH
O
O
O
3
4
5
92
94
91
N
OMe
OMe
OMe
Cl
Br
N
NH2
NH2
N
N
N
N
I
N
NH2
NH2
N
O
H3C
OH
O
6
97
N
OMe
H3C
N
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H3C
N
O
CH3
OH
O
7
95
N
OMe
N
NH2
CH3
OH
O
CH3
8
9
96
98
N
O
OMe
O
N
N
NH2
N
N
O
OH
N
OMe
NH2
N
O
O
O
OH
OH
OH
OH
OH
OH
OH
O
O
O
O
O
O
O
F
10
11
12
13
14
15
16
92
94
95
95
94
95
96
N
OMe
OMe
OMe
OMe
OMe
OMe
OMe
F
N
NH2
N
N
Cl
Br
N
Cl
N
NH2
NH2
N
Br
N
N
O
I
N
I
N
NH2
NH2
N
O
H3C
N
H3C
N
H3
C
N
O
CH3
N
N
NH2
CH3
N
CH3
N
O
N
NH2
a Reaction conditions: aminopyridines (1 mmol), Baylis-Hillman adducts (1 mmol), TFA (3 mL), and catalyst (1 mg), 1 h.
bIsolated yield.
It is important to note that the heterogeneous property of KCC-1/Pd-NHC-Py NPs facilitates its efficient recovery from the
reaction mixture during work-up procedure. The activity of the recycled catalyst was also examined under the optimized
conditions. After the completion of reaction, the catalyst was separated by filtration, washed with methanol and dried at the
pump. The recovered catalyst was reused for ten consecutive cycles without any significant loss in catalytic activity (Figure
7).This lack of reduction in catalyst performance can be attributed to the simple and stability of the catalyst structure. The
lack of any reduced performance of the catalyst could be related to its simple and stable structure. Pd (II) leaching was
studied by inductively coupled plasma mass spectrometry (ICP-MS) analysis of the catalyst, after ten cycles of reactions.
The contents of Pd (II) in catalyst before and after reaction were 4.9 % and 4.7 % respectively, determined by ICP-MS.
These indicate that most of Pd (II) species leaching into solution are recaptured onto the fibers of KCC-1 after completion of
the reaction. It is important to note that the heterogeneous property of KCC-1/Pd-NHC-Py NPs facilitates its efficient
recovery from the reaction mixture after the completion of reaction (Table 5).
9

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100
95
90
85
80
75
70
1
2
3
4
5
6
7
8
9
10
Reuse
Figure 7 The reusability of catalysts for synthesis of pyridopyrimidinone.
Table 5 The loading amount of Pd (II).
Entry
1
2
Catalyst
KCC-1/Pd-NHC-Py
KCC-1/Pd-NHC-Py after ten reuses
wt %
4.9
4.7
Conclusions
In the present study KCC-1/Pd-NHC-Py NPs was synthesized and characterized as an environmentally-friendly nanocatalyst
for the synthesis of pyridopyrimidinones with various electronically diverse substrates. The experimental results displayed
the core-shell structure of the synthesized catalyst with a mean size range of 250-300 nm. In addition, the catalyst was easily
recoverable and reusable. Subsequently, high yields in short reaction times were achieved without the need for a
pyridopyrimidinone catalyst as well as excellent reusability for at least ten times in the corresponding reaction without a
reduction in catalytic activity.
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1
2
3
4
5
6
7
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Highlights
1- An efficient N, N'-substituted imidazolium salts and their corresponding
diiodopyridinepalladium(II) complexes supported on KCC-1 (KCC-1/Pd-
NHC-Py) has been developed.
2- The KCC-1/Pd-NHC-Py NPs were thoroughly characterized by using TEM,
FESEM, TGA, and BET.
3- High catalytic activity and ease of recovery from the reaction mixture by
filtration.