CsOH/γ-Al2O3: A heterogeneous reusable basic catalyst for one-pot synthesis of 2-amino-4,6-diaryl pyrimidines

Article abstract of DOI:10.1039/c5nj03565a

A new strategy for a one-pot synthesis of 2-amino-4, 6-diaryl pyrimidines using CsOH/γ-Al₂O₃ as a heterogeneous, reusable basic catalyst is presented. The developed synthetic protocol for pyrimidines is a one-pot three-component reac

Full text of DOI:10.1039/c5nj03565a

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CsOH /γ-Al2O3: A heterogeneous reusable basic catalyst for one
pot synthesis of 2-amino-4, 6-diaryl pyrimidines
Amey Nimkar, M. M. V. Ramana*, Rahul Betkar, Prasanna Ranade and Balaji Mundhe
Received 00th January 20xx,
Accepted 00th January 20xx
A new strategy for one pot synthesis of 2-amino-4, 6-diaryl pyrimidines using CsOH/γ-Al2O3 as a heterogeneous, reusable
basic catalyst is presented. The developed synthetic protocol for pyrimidines is one pot three component reaction of
acetophenones, aromatic aldehydes and guanidine hydrochloride in ethanol. The characterization of the catalyst CsOH/γ-
Al2O3 was performed by using FT-IR, XRD, TG-DTA, SEM, BET surface area and CO2-TPD analysis techniques. The analytical
data proves that the catalyst has excellent reusability and also indicates its good thermal stability.
DOI: 10.1039/x0xx00000x
www.rsc.org/
protocol in synthetic chemistry.21-23 One pot reactions are
always in limelight due to less reaction time, lessened amount
of waste generated and high reaction rates. Application of
1. Introduction
Pyrimidines are important structural motif of various drug
molecules as they exhibit diversified biological activities.
Pyrimidine derivatives serve as antineoplastic,1 antibacterial,2
anti HIV,3 antibiotics,4 antifungals,5 antituberculars.6
Pyrimidine bases like thymine, cytosine, and uracil are
essential building blocks of nucleic acids. Many of the
established drugs containing pyrimidine nucleus are reported
in literature namely 5-Fluorouracil as anticancer,7 Idoxuridine
as antiviral,8 Zidovudine as anti HIV,9 Trimethoprim as
antibacterial.10 Along with their direct application to human
beings, certain pyrimidines are used as herbicides11 and plant
growth regulators.12 Beyond their applications in the biological
world, pyrimidines are widely employed in material chemistry
due to their liquid crystalline property.13 Also some pyrimidine
derivatives show selective ion sensing property,14
optoelectronic property,15 and efficient Dye sensitized solar
cells.16
catalyst in organic transformation is a key step towards an
efficient synthesis of target molecule.24 Use of heterogeneous
catalytic media improves the isolation of product along with
reusability of the catalyst.25, 26 Hence, we have designed a new
protocol for the synthesis of 2-amino-4, 6- diaryl pyrimidines
from aromatic aldehydes, acetophenones and guanidine
hydrochloride using heterogeneous basic catalyst CsOH/γ-
Al2O3 (Scheme 1
)
Scheme 1- Modified synthetic route to afford 2-amino-4, 6-
diaryl pyrimidines.
Due to their importance, huge amount of work has been done
for the synthesis of pyrimidines. 2-amino-4, 6-diaryl
pyrimidines have been synthesized from chalcones,17 β-
diketones,18 flavones19 using different bases like K2CO3, KOH,
NaOH and also via microwave irradiation.20 Usually pyrimidine
synthesis encounters long reaction time, low product yield,
multistep synthesis. Therefore, there is scope to develop a
rapid and green procedure for the synthesis of 2-amino-4, 6-
diaryl pyrimidines.
Cesium hydroxide has been frequently employed as a basic
catalyst for various chemical transformations.27 The main
disadvantage of using CsOH alone is the reusability of catalyst
and hygroscopic nature. Alumina also served as a basic catalyst
in various organic reactions.28 Some initial experiments were
carried out using alumina as a heterogeneous catalyst but
there was no formation of product. Recently we have
developed CsOH/γ-Al2O3 as a basic catalytic system for the
synthesis of 4H-pyran derivatives.29 CsOH/γ-Al2O3 catalytic
system has not been reported for the synthesis of 2-amino-4,
6-diaryl pyrimidines.
In the past decade, one pot reactions have been the zest of
chemists and now are practiced as one of the most important
Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (E),
Mumbai-400 098, India
+91-22-26543358, Fax No.: +91-22-26528547
2. Experimental
2.1. Chemicals and instruments
ramanammv@yahoo.com
Unless otherwise stated, all reagents were purchased from
Sigma Aldrich (India) and used without purification. All melting
† Footnotes relaꢀng to the ꢀtle and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [FT-IR, 1H, 13C and MS spectra
of the selected compounds]. See DOI: 10.1039/x0xx00000x
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points were recorded on centrofix syndicate MP apparatus and When the catalyst was calcined at 400oC, product formation
are uncorrected. 1H NMR (300 MHz) and 13C NMR (75 MHz) was observed with good yield both in fresh cycle and recycle of
spectra were recorded on Bruker AVANCE spectrometer
(Bruker BioSpin AG, Fällanden, Switzerland; 300 MHz) using Table 1 Optimization of catalytic activity.
Cl
DMSO-d6/CDCl3 as solvent and TMS as an internal standard.
Chemical shifts (δ) were expressed in terms of ppm. Infrared
experiments were performed using Frontier Perkin Elmer IR
spectrometer. XRD analysis of the catalyst was performed
using Shimadzu Maxima 7000 S X-ray Diffractometer. Perkin
Elmer Pyris Diamond Thermogravimetric Analyzer was used
for TG-DTA studies. The analysis was carried out under inert
atmosphere (N2) with temperature control of 10oC min-1.
Scanning Electron Microscopy (SEM) analysis was carried out
using FEI-Inspect 450 FEGSEM. Surfer Autosorb-1,
Thermofisher Scientific was used for BET surface area analysis
of the catalyst.
O
CH3
O
H
1. Catalyst,
RT / 1 h
+
N
N
2.Guanidine hydrochloride
Reflux / 4 h
NH2
Cl
Entry
Reaction conditiona
Yielda
(%)
1
2
3
4
Ethanol
-
CsOH in Ethanol
Alumina in Ethanol
70
-
2.2. Preparation of CsOH/γ-Al2O3 catalyst
CsOH (1.0g) and γ-Al2O3 (2.0g) were stirred in 20.0 ml
methanol for 2.0 hours at room temperature. Methanol was
recovered under reduced pressure and the solid mass was
dried at 100oC followed by calcination at 400oC for 4 hours.
The obtained solid mass was crushed in to fine powder with
the help of mortar and pestle.
CsOH/γ-alumina in
ethanol without
65
calcination at 400oC
5
CsOH/γ-alumina in
ethanol with
80
calcination at 400oC
2.3. General procedure for pyrimidine synthesis
CsOH/γ-Al2O3 (10mol%) was added to the mixture of aromatic
aldehyde (1 mmol) and acetophenone (1 mmol) in 30.0 ml
ethanol. The reaction mixture was stirred at room
temperature for 1 hour. After the completion of reaction (TLC
control for formation of chalcone), guanidine hydrochloride (1
mmol) was added and refluxed for 4 hours. Catalyst was then
filtered and reaction mixture poured in to ice cold water (30
ml). Crude solid product was collected by filtration and
recrystallized from ethanol to afford pure product (3a-3h).
a Isolated yield
Table 2 Optimization of amount of CsOH/γ-Al2O3 catalyst
loaded.
Cl
O
CH3
O
H
1.CsOH-γ Al2O3
Ethanol
RT / 1 h
+
N
N
3. Results and discussion
2.Guanidine hydrochloride
Reflux / 4 h
A set of experiments was performed to determine the active
catalytic component of the CsOH/γ-Al2O3 catalytic system. The
reaction of acetophenone (1 mmol), 4-chlrobenzaldehyde (1
mmol) and guanidine hydrochloride (1 mmol) in one pot was
carried out using only ethanol as a solvent. No product
formation was observed in this case. (Table 1, Entry 1)
Similarly, reactions were carried out using CsOH in ethanol
and alumina in ethanol. Product formation was observed in
case of CsOH in ethanol, but no regeneration of the catalyst
as all the CsOH gets dissolved in ethanol. (Table 1, Entry 2)
Alumina in ethanol did not lead to formation of product.
NH2
Cl
Entry
mol % of catalyst
Yielda
(%)
1
2
3
4
5
5
58
80
75
75
72
10
15
20
25
(
Table 1, Entry 3) Thus alumina is not the active component of
the catalyst and is used as a support. A set of reactions were
carried out with CsOH/γ-Al2O3 catalyst, with and without
calcination at 400oC. In the case of catalyst without
calcination, product formation was observed in the first cycle
of the reaction, due to the basicity provided by CsOH. However
when the catalyst was recovered and reused in second cycle
there was traces of the product. This is due to the loss of CsOH
during the recovery of the catalyst (washing with ethanol), as
CsOH is adsorbed on the surface of alumina. (Table 1, Entry 4)
a Isolated yield
the catalyst. (Table 1, Entry 5) The above experiment clearly
supports the requirement of the calcination of the catalyst as
the active component cesium hydroxide is well incorporated
into alumina support.
2 | J. Name., 2012, 00, 1-3
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Optimization of reaction condition was carried out on the basis Table 4 Synthesis of 2-amino-4, 6-diaryl pyrimidine derivatives
of the amount of catalyst loaded. Ranging from 5 mol% to 25 using CsOH/γ-Al2O3
mol% of catalyst, a set of reactions was performed using
R1
R2
O
CH3
O
H
acetophenone, 4-chloro benzaldehyde and guanidine
hydrochloride in ethanol. Yield of the reaction was poor at the
low amount of the catalyst loading. (Table 2, entry 1) However
at higher loading of catalyst (10 mol %), yield increases up to
80%. (Table 2, entry 2) There was not much alteration in the
yield, after further increase in concentration of the catalyst.
Literature survey indicates that the maximum dispersion of the
catalyst particles is obtained at particular fixed
concentration.30 Beyond this concentration, catalyst particles
get agglomerated and do not participate in the reaction.
Agglomeration of the catalyst will certainly decrease the
surface area required for catalytic organic transformation.31,32
Thus for CsOH/γ-Al2O3, maximum dispersion of the catalyst
and catalytic activity was obtained at 10 mol% concentration.
Similarly different solvents were screened for the pyrimidine
synthesis, out of which ethanol gave the best results. The
results from Table 2 show that, efficiency of the reaction
mainly depends on the amount of catalyst loaded. Various
basic catalytic systems were also screened to select the most
superior catalyst. Among these catalysts, CsOH/γ-Al2O3
catalytic system proved to be superior in terms of yield than
1.CsOH-γ Al2O3,
Ethanol
RT / 1 h
+
N
N
2.Guanidine hydrochloride
Reflux / 4 h
R2
R1
NH2
2a-2h
3a-3h
1a-1h
Entry
3a
R1
H
R2
Yieldb
(%)
M.P
(0C)
H
75
11833,34
3b
3c
4-Cl
3-Cl
4-F
H
80
72
74
80
72
72
80
16033,34
11833,34
13233,34
12833,34
15233,34
15433,34
188
H
3d
3e
H
4-CH3
4-OCH3
4-F
H
H
3f
other heterogeneous basic catalysts. (Table 3
)
3g
4-Br
Table 3 Effect of different catalysts on the reaction
3h
4-Br
Ferrocene
Cl
O
CH3
O
H
a
1. Catalyst, Ethanol
RT / 1 h
Reaction conditions: aldehydes (1 mmol), acetophenones (1
+
mmol), guanidine hydrochloride (1 mmol), 10 mol % CsOH/γ-
Al2O3, ethanol (25 ml).
N
N
2. Guanidine hydrochloride
Reflux / 4 h
b Isolated yield.
NH2
Cl
Entry
Catalyst
Yielda
(%)
synthesized. (Table 4) The reaction was carried out at a
temperature of 80oC in ethanol using different aromatic
aldehydes, acetophenones, and guanidine hydrochloride in the
presence of CsOH/γ-Al2O3 catalytic system. Conventionally the
reaction between acetophenone and aromatic aldehyde is
carried out to afford chalcone which then condenses with
guanidine hydrochloride to give 2-amino-4, 6-diaryl
pyrimidines. The advantages of the current one pot synthetic
protocol is high yield, short reaction time, mild reaction
conditions and the need for separating the intermediate
chalcone is avoided.
(10 mol %)
1
2
3
4
5
KOH/ γ-Al2O3
KF/ γ-Al2O3
65
50
60
55
80
Cs2CO3/ γ-Al2O3
CsF/ γ-Al2O3
CsOH/γ-Al2O3
Table 5 Recyclability of CsOH/γ-Al2O3 Catalyst
Product
a Isolated yield
No. of cycle
Yielda
(%)
1
2
3
4
5
80
Molar composition of the catalyst was optimized by using
CsOH and Al2O3 in 1:1 and 1:2 ratios respectively.
When experiment was carried out at equimolar concentration
of CsOH and alumina, hygroscopic nature of the catalyst was
not diminished. Whereas at 1:2 molar composition of CsOH
and alumina, the catalyst becomes non-hygroscopic, which is
attributed to complete reactivity of CsOH with alumina.
80
78
76
76
3b
Once the reaction conditions were optimized, a series of 2-
amino-4, 6-diaryl pyrimidine derivatives (3a-3h) were
a Isolated yield
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1H, 13C NMR and IR spectra of the pyrimidine derivatives (3a- catalyst. (Fig. Supp. info. S-20) EDAX spectrum of the catalyst
3h) were consistent with the data reported in the literature.33, clearly indicates the presence of cesium, aluminium and
34
Reusability is one of the major aspect of using
heterogeneous catalytic media. Catalyst was separated by
simple filtration, washed with ethanol and dried at 400oC for
80
80
60
one hour. Recycled catalyst was loaded successively up to 5
60
cycles without affecting its activity (Table 5).
40
After the synthesis of pyrimidine derivatives in good yields,
40
a. alumina
b. CsOH
20
characterization of the catalyst was performed by using
various analytical and spectroscopic methods. In the FT-IR
spectrum of CsOH/γ-Al2O3 catalyst calcined at 400oC, along
with the CsOH and Al2O3 characteristic bands, new frequency
bands were observed which are assigned as follows. Broad
band at 3400 cm-1 attributed to (-OH) group of water
physisorbed on surface of γ-Al2O3. Cs-O bending vibrations
were observed at 1350-1480 cm-1. The bands at 850-880 cm-1
20
1000
2000
3000
80
4000
1000
2000
3000
4000
60
40
20
0
c. CsOH
ꢀ Al O
ꢀꢀ
2 3
after calcination
at 400oC
and 910 cm-1 were assigned to Al-O-Cs bonding. (Fig.1
)
1000
2000
3000
4000
Figure 2a and Figure 2b shows XRD pattern for γ-Al2O3 and
CsOH/γ-Al2O3 catalyst after calcination at 400oC respectively.
In Figure 2a, characteristic signals were obtained for γ-Al2O3 at
2θ = 32o, 37o, 43o, 46o, 67o. The diffraction peaks of γ-Al2O3 are Fig.1 FT-IR spectra of (a) γ-Al2O3, (b) CsOH, (c) CsOH/ γ-Al2O3
in good agreement with International Centre for Diffraction catalyst after calcination at 4000C.
Wavenumber (cm-1)
Data Powder Diffraction file (PDF) 29-0063. Along with parent
400
peaks of alumina, new diffraction peaks in XRD pattern of
catalyst mainly attributed to formation of new phase Cs2O
during calcination of catalyst. XRD pattern for catalyst were
obtained at 2θ = 19o, 23o, 26o, 29o, 33o, 37o, 49o, 51o, 64o, 67o
(a)
300
200
100
0
Alumina
(Fig. 2b). It was observed that the signals obtained for catalyst
were almost similar to that of Cs2O with slight shift in values
and broadening of peaks (International Centre for Diffraction
Data Powder Diffraction file (PDF) 00-009-0104). This shift in
signals of catalyst compared with Cs2O signals is due to
presence of Alumina. Intensity peaks of alumina in the catalyst
were also found lower due to presence of cesium hydroxide.
Thus we can conclude that, after calcination, insitu formed
Cs2O is well incorporated in crystal structure of γ-Al2O3. XRD
pattern of the catalyst after the 5th cycle of reuse shows
unaltered diffraction pattern as that of fresh catalyst CsOH/γ-
(b)
fresh catalyst
1st cycle
Al2O3 after calcination at 400oC. (Fig. 2b
)
5th cycle
TG-DTA experiments were performed using Perkin Elmer Pyris
Diamond Thermogravimetric Analyzer under inert reaction
atmosphere (N2) with temperature control of 100C min-1.
25
50
75
2 Theta (θ)
Figure 3 shows the TG-DTA curves of the catalytic system Fig.2 XRD patterns of (a) γ-Al2O3 and (b) CsOH/ γ-Al2O3 calcined
CsOH/γ-Al2O3 after calcination at 400oC. First and second at 4000C i. fresh catalyst ii. 1st cycle iii. 5th cycle of reuse.
endotherms at 100oC and 250oC were assigned to the loss of
110
15
10
5
physisorbed and chemisorbed water respectively. The third
weight loss at 750oC is due to volatilization of Cs2O.35,36 The
results from TG-DTA curves indicate the wide operating range
of temperatures for the catalytic system and are in accordance
with our previous investigations.29
100
90
80
70
60
CsOH/γ−Al O
2 3
0
Figure 4a illustrates the SEM micrograph of γ-Al2O3. Alumina
exhibits thick plate like morphology similar to flower shaped
structure. Figure 4b reveals the surface morphology of the
catalyst before reaction. Visual observations from Fig.4
provide primary information about the incorporation of the
cesium hydroxide on alumina which was strongly supported by
-5
-10
0
200 400 600 800 1000
o
Temperature( C)
Energy Dispersive X-ray analysis (EDAX) spectrum of the Fig.3 TG-DTA analysis of CsOH/ γ-Al2O3 catalyst
4 | J. Name., 2012, 00, 1-3
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oxygen. Thus, Fig. 4b shows the composite nature of catalyst
unlike alumina. Fig. 4c and Fig. 4d represents the surface
morphology of the reused catalyst after 1st and 5th cycle
respectively. The EDAX spectrum for the same shows no
alterations in the composition of the catalyst. (Fig. Supp. info.
S-20
)
Fig.5 N2 adsorption-desorption isotherm of CsOH/ γ-Al2O3
catalyst.
Fig. 6 BJH pore size distribution curve of CsOH/ γ-Al2O3 catalyst
Fig.4 SEM images of (a) γ-Al2O3 (b) CsOH/ γ-Al2O3 before
reaction (c) CsOH/ γ-Al2O3 after 1st recycle reaction (d) CsOH/
γ-Al2O3 after 5st recycle reaction.
400
300
200
100
0
BET surface area analysis of the catalyst was performed at
liquid nitrogen temperature (78 K). Powdered catalyst sample
(0.5 g) was placed in sample holder and allowed to degas for 2
hours at 150oC to remove contaminant gases and water
vapors. Then the sample was analyzed for surface area
properties and specific surface area of sample was calculated
using BET adsorption equation. Figure 5 relates to a nitrogen
sorption isotherm of CsOH/γ-Al2O3 catalyst.
0
200
400
600
800
1000
Temperature / °C
Catalyst exhibits type IV adsorption pattern. In the low
pressure range (P/P0
<
0.4), adsorption and desorption Fig. 7 CO2-TPD analysis of the catalyst CsOH/γ-Al2O3
isotherm nearly superimpose each other and at higher
pressure (P/P0 > 0.7) isotherm increases. Type IV adsorption Table 6 BET experimental results of the catalyst CsOH/γ-Al2O3.
Constant
C
Monolayer
adsorption
BET
surface
Avg.radius
size
pattern indicates that initially nitrogen gas is chemisorbed on
surface of the catalyst. After complete formation of monolayer
of N2 on catalytic surface, physisorption is initiated. At lower
pressure chemisorption is preferred over physisorption.
volume(cm3/g)
area (m2/g)
(Ao)
47.043
6.7563
29.3965
21.5644
Type IV isotherm shows small hysteresis loop like structure,
indicating the presence of very small mesopore volume. The
hysteresis effect and the slope of the plateau increased to
yield Type IV isotherm with a significant increase in the
nitrogen uptake through the entire pressure range indicating
the presence of mesopores. Using the multiplot BET equation,
specific surface area of the catalyst was calculated, which
CsOH/γ-Al2O3. According to BET theory, Monolayer adsorption
suggests the chemisorption between surface of the catalyst
and the adsorbate while further upcoming layers indicate the
physisorption between catalyst and the adsorbate. BJH
desorption pore size distribution curve of the catalyst was
used to calculate maximum pore size distribution which is 10-
50 Ao (mesopores) radius (Fig. 6).
comes out to be 29.39 m2/g. Figure (Supp. info
. S-21) shows
the multipoint BET plot of the CsOH/γ-Al2O3 catalyst. Table 6
represents the BET experimental results of the catalyst
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Fig. 7 depicts the TPD profile of CO2 adsorbed on CsOH/γ-Al2O3
catalyst. In the lower temperature region, the catalyst has a 2. S. N. Pandeya, D. Shriram, G. Nath and E. D. Clercq,
small to moderate amount of CO2 desorption at 100-300oC and
Farmaco, 1999, 54, 624.
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Husseiny, Med. Chem. Res., 2013, 22, 3943.
the presence of basic sites on the catalyst. The TPD plot of
adsorbed CO2 for γ-alumina shows the presence of weak basic
Hwang, Y. Ko and I. Choi, Bioorg. Med. Chem. Lett., 2014,
24, 5473.
sites at relatively lower temperatures.37 Presence of cesium 4. O. Moukha-chafiq and R. C. Reynolds, ACS. Comb. Sci., 2014,
hydroxide shows the broad desorption signal at higher
16, 232.
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transformation.
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The plausible mechanism of reaction is shown in Scheme 2.
7. D. B. Longley, D. P. Harkin and P. G. Johnston, Nat. Rev.
Cancer, 2003, 3, 330-338.
H2N
Ar
NH2
H
Ar
Ar
H
8. G. Smolin, M. Okumoto, S. Feiler and D. Condon, Am. J.
Ophthalmol., 1981, 91, 220-225.
Ar
O
HN
Aldol condensation
O
H
O
9. C. E. Mackewicz, A. Landay, H. Hollander and J. A. Levy, Clin.
Immunol. Immunopathol., 1994, 73, 80-87.
10 L. F. Kuyper, J. M. Garvey, D. P. Baccanari, J. N. Champness,
D. K. Stammers and C. R. Beddell, Bioorg. Med. Chem.,
1996, 4, 593-602.
NH2
NH
Ar
NH
Cs
Cs
N
Ar
O
Cs2O
-H2O
N
HN
Ar
H
11. M. G. Hoffmann, U. Doeller, M. Bruenjes, H. Dietrich, E.
Gatzweiler, D. Schmutzler and C. H. Rosinger, WO
2014086738 A1, 2014.
OH
Ar
Ar
N
NH
Cs
Cs
12. A. Cansev, H Guelen, Z. M. Kesici, S. Ergin and M. Cansev,
WO 2014129996 A1, 2014.
H
O
-Cs2O
Ring Closure
NH
13. S. M. Kelly, J. Funfschilling and A. Villiger, Liquid Crystals,
1994, 16, 813.
Ar
14. H. A. Zamani, M. R. Ganjali and N. Seifi, Collect. Czech.
Chem. Commun., 2007, 72, 1189.
Ar
N
NH2
Ar
N
NH2
[O]
15. G. Huges, C. Wang, A. S. Batsanov, M. Fern, S. Frank, M. R.
Bryce, I. F. Perepichka, A. P. Monkman and B. P. Lyons, Org.
Biomol. Chem., 2003, 1, 3069.
N
N
Ar
Ar
16. L. Lin, C. Tsai, K. Wong, T. Huang, C. Wu, S. Chou, F. Lin, S.
Chen and A. Tsai, J. Mat. Chem., 2011, 21, 5950.
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Scheme 2 Plausible mechanism to afford 2, 4-diaryl pyrimidine
using CsOH/ γ-Al2O3 catalyst
4. Conclusions
In conclusion, the developed one pot synthetic approach for 2-
18. S. Goswami, S. Jana, S. Dey and A. K. Adak, Aust. J. Chem.,
2007, 60, 120.
amino-4, 6- diaryl pyrimidine has several advantages 19. R. Giridhar, R. Tamboli, R. Ramajayam, D. Prajapati, and M.
compared to methods reported in the literature. It involves Yadav, Eur. J. Med. Chem., 2012, 50, 428.
one pot process, short reaction time, high yields along with 20. S. P. Meenakshisundaram, M. Gopalakrishnan, S.
reusability of heterogeneous catalyst. Detailed studies of the Nagarajan and N. Sarathi, Catal. Commun., 2007, 8, 713.
catalyst for its characterization and properties has been 21. K. R. Senwar, P. Sharma, S. Nekkanti, M. Sathish, A. Kamal,
accomplished utilizing FTIR, XRD, TG-DTA, SEM, EDAX, BET
surface area analysis and CO2-TPD analysis techniques.
B. Sridhar and N. Shankaraiah, New J. Chem., 2015, 39,
3973.
Structural features of the catalyst remain unaltered after the 22. Y. He, S. Guo, X. Fan, C. Guo and X. Zhang, Tetrahedron lett.
reaction and reusability was studied up to 5 cycles. Thus, the 2014, 55, 4747.
developed one pot synthetic protocol is simple, green and 23. T. K. Khatab, K. A. M. El-Bayouki and W. M. Basyouni,
highly efficient.
Tetrahedron lett., 2014, 55, 6039.
24. R. M. Kamble and V. K. Singh, Tetrahedron lett., 2001, 42,
Acknowledgement
We acknowledge the financial support from Department of 25. C. S. Radatz, L. A. Soares, E. R. Vieira, D. Alves, D.
7525.
Chemistry, University of Mumbai and UGC, New Delhi, India.
Russowsky and P. H. Schneider, New J. Chem., 2014, 38,
1410.
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Graphical Abstract
CsOH /γ-Al2O3: A heterogeneous reusable basic catalyst for one pot synthesis of 2-amino-4, 6-
diaryl pyrimidines.
Amey Nimkar, M. M. V. Ramana*, Rahul Betkar, Prasanna Ranade and Balaji Mundhe.
Pyrimidine derivatives were synthesized in one pot using a novel heterogeneous reusable
catalyst and complete characterization of catalyst was performed.