Heterogenized hybrid catalyst of 1-sulfonic acid-3-methyl imidazolium ferric chloride over NaY zeolite for one-pot synthesis of 2-amino-4-arylpyrimidine derivatives: A viable approach

Article abstract of DOI:10.1016/j.apcata.2016.06.015

A new hybrid material of NaY zeolite supported 1-sulfonic acid-3-methyl imidazolium ferric chloride [Msim][FeCl₄] has been developed by modifying the zeolite surface with six different w/w ratios through wet impregnation method. These composite

Full text of DOI:10.1016/j.apcata.2016.06.015

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Applied Catalysis A: General 523 (2016) 321–331
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Heterogenized hybrid catalyst of 1-sulfonic acid-3-methyl
imidazolium ferric chloride over NaY zeolite for one-pot synthesis of
2-amino-4-arylpyrimidine derivatives: A viable approach
Pinky Gogoi, Arup Kumar Dutta, Susmita Saikia, Ruli Borah∗
Department of Chemical Sciences, Tezpur University, Napaam, 784028, Tezpur, Assam, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new hybrid material of NaY zeolite supported 1-sulfonic acid-3-methyl imidazolium ferric chloride
[Msim][FeCl4] has been developed by modifying the zeolite surface with six different w/w ratios through
wet impregnation method. These composites were fully characterized by Powder XRD, FT-IR, Raman, TGA,
SEM, TEM, EDX, BET, ICP-OES and Hammett acid strength measurement methods. The zeolite framework
was found to be remaining preserved up to w/w ratio of 0.2 with some portion of extra framework
Al species (EFAl) while crystallinity of the composites decreased from lower to higher loading. The
overall thermal stability of composite materials increases up to w/w ratio of 0.1 than NaY. The cat-
alytic performance of composite materials were examined for the novel one-pot consecutive formation
of Biginelli- 3,4-dihydropyrimidin-2-(1H)-ones to 2-amino-4-arylpyrimidines. The 0.1 ratio composite
material showed excellent catalytic activity up to ten consecutive cycles in solvent-free medium under
the optimized reaction condition.
Received 12 February 2016
Received in revised form 10 June 2016
Accepted 10 June 2016
Available online 14 June 2016
Keywords:
Heterogenized hybrid catalyst
1-Sulfonic acid-3-methyl imidazolium
ferric chloride salt
NaY zeolite
Extra framework aluminium species
Reusable catalyst
© 2016 Elsevier B.V. All rights reserved.
2-Amino-4-arylpyrimidine
1. Introduction
pounds [14]. Valkenberg et al., also presented three different
approaches for the preparation of novel catalysts of supported ILs
Encapsulation of ionic liquid salt in microporous solids such as
zeolite is an attractive technique for heterogenization, since leach-
ing can be controlled when the salt is confined exclusively in the
zeolite pores [1–3]. Zeolites are among the most efficient support
for ionic liquids owing to their unique properties such as high
surface area, well organized pore channels, good thermal stabil-
ity, environmentally benign nature and high absorption towards
organic compounds. Ionic liquid salts are also characterized by
their low melting point, non-flammability, relatively low viscosi-
ties, high thermal and chemical stability [4]. The presence of acidic
or basic character of ionic liquids makes them more suitable for dual
role in organic synthesis as catalyst and recyclable solvent [5–8].
The combination of the two aforementioned types of materi-
als (zeolites and ionic liquids) could result in composite materials
suitable for various applications such as separation technol-
ogy, catalysis and fuel cell [2,9–13]. For example, DeCastro
et al., developed 1-butyl-3-methyl-imidazolium chloride and AlCl3
immobilized beta type zeolite for the alkylation of aromatic com-
on zeolites and other porous supports for the Friedel–Crafts reac-
tion [15]. Eguizábala et al., utilized ammonium based ionic liquids
immobilized in Y and beta type zeolites by solution methods as
hydrophilic-conducting fillers for proton exchange membrane fuel
cell [16]. The heterogenization process can easily modify the sur-
face of solid support by transferring some properties of IL phase on
to the surface for specific use [17,18]. Such acidic or basic hybrid cat-
alysts can be separated from the product by filtration in any suitable
solvent. This type of composite material allows us to design solid
material possessing uniform and well-dispersed surface topologies
with definite properties and controlled chemical reactivity which
may act as ‘designer surface’. Hybrid zeolite catalysts have advan-
tages compared to the parent ones in terms of their tunable acidity,
hydrophilicity or hydrophobicity and thermal stability.
Pyrimidines are integral part of DNA and RNA, and also have
diverse biological activities like anticancer, anti-inflammatory,
analgesic, anticonvulsant, anthelmintic and anti-allergic agents
[19,20]. 2-Aminopyrimidine unit is the structural motif of several
bioactive natural products and finds extensive applications as drug
like scaffold in medicinal chemistry such as anti-atherosclerotic
Aronixil, anti-histaminic Thonzylamine, anti-anxiolytic Buspirone,
HMG-CoA reductase inhibitor Rosuvastatin and anti-cancer drug
∗
Corresponding author.
E-mail address: ruli@tezu.ernet.in (R. Borah).
http://dx.doi.org/10.1016/j.apcata.2016.06.015
0926-860X/© 2016 Elsevier B.V. All rights reserved.

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P. Gogoi et al. / Applied Catalysis A: General 523 (2016) 321–331
N
N
Cl
N
O
N
O
N
N
N
N
N
NH
O
O
N
N
NH
OH
Buspirone
Aronixil
Thonzylamine
F
N
N
O
N
N
HN
OH OH
OOC
N
N
SO2Me
H2N
N
NH2
N
N
N
N
H
Me
Me
N
Minoxidil
Gleevec
Rosuvastatin (Ca-salt)
Me
Fig. 1. Commercial drugs with pyrimidine/2-aminopyrimidine/2-amino-4-arylpyrimidine moiety.
H2N
O
O
NH
NO2
H3C
X
O
CH3
X
X
N
1
H3CH2COOC
CHO
H3CH2COOC
H3C
NO2
NH
room tempearture/ neat
H3C
N
H
4
O
3mg of
N
NH2
[Msim][FeCl4]/NaY=0.1(Cat.)
2
5
O
Where X=electron withdrawing or donating groups
H2N
NH2
3
Scheme 1. One pot synthesis of 2-amino-4-arylpyrimidine derivatives via in situ formation of DHPMs.
Gleevec (Fig. 1). They are also capable of exhibiting rho-associated
protein kinease-1 inhibitor, glycogen synthase kinease-3 inhibitor
and N-type calcium channel blockers [21–24]. The Biginelli
3,4-dihydropyrimidinones (DHPMs) are the chemical precursors
of multi-functionalized pyrimidines. The preparation of DHPMs
involves a three component reaction of ␤-keto ester, aldehydes
and urea (or thiourea) using a variety of acid catalysts at dif-
ferent conditions (Scheme 1) [25–28]. Several modified methods
have been developed for the Biginelli reaction till date [29–33].
Despite the connecting link with pyrimidines, there has been lack
of efficient methodologies to convert DHPMs to pyrimidines. Few
methodologies are available in literature which achieved this by
dehydrogenation of the DHPMs followed by nucleophilic substitu-
tion at C-2 position [34–36].
In 2007, Matoobi et al., introduced a modified sequential five
steps microwave assisted conversion of DHPMs to 2-amino-4-
aryl pyrimidine derivatives at high temperature in sealed vessel
through isolation of each intermediate involved in S-alkylation,
oxidation and nucleophilic substitution steps [23].
In this context, there is
a scope to develop mild, sim-
pler and more efficient route to construct complex library of
pyrimidine derivatives via in situ conversion of DHPMs to 2-amino-
4-arylpyrimidine derivatives using sequential acid catalyzed
condensation-aromatization reactions according to Scheme 1 from
the three component Biginelli reactions [45–47].
2. Experimental
Puchala et al., first reported the dehydrogenation of DHPMs by
nitric acid with 50–60% of oxidized products [37]. Other meth-
ods include the use of ceric ammonium nitrate, (diacetoxyiodo)
benzene, Mn(OAc)3 and MnO2, tert-butylhydroperoxide in the
oxidative aromatization of 1,4-dihydropyrimidine [38–41]. Quan
et al., reported a simple iodine mediated S N or C N cross-coupling
and oxidative–aromatization of 3,4-dihydropyrimidine-2(1H)-
thione with a secondary amine [42]. Kang et al., also synthesized
C-2 functionalized pyrimidines via Kappe dehydrogenation of the
DHPMs and PyBroP-mediated coupling with nucleophiles at room
temperature for 24 h [43]. Most of the known dehydrogenation
methods suffer from longer reaction time (36–67 h), higher tem-
perature, and lower yields and inefficiency of the oxidizing agents
[34–36]. The inactive nature of DHPMs ring towards various oxidiz-
ing agents makes dehydrogenation a more difficult task [36–44].
2.1. General techniques
All chemicals were purchased from different chemical suppli-
ers and used as received without any further treatment. X-ray
diffraction patterns of the prepared samples were recorded using
a Rigaku (miniflex UK) X-ray diffractometer with CuK␣ radia-
tion (0.15418 nm) operated at 30 kV and 15 mA at a scan speed
of 2◦ min−1 and 2␪ range of 5–70◦. The percent crystallinity of
the samples was calculated from the XRD peaks by using the for-
mula: %Crystallinity = (Intensity of the characteristic XRD peak of
the hybrid catalyst)/(Intensity of the characteristic peak of the
base zeolite). The 1HNMR and 13CNMR were recorded on a JEOL
400 MHz spectrometer (␦ in ppm) in CDCl3 and DMSO-d6 solvents.
Perkin Elmer FT-IR spectrometer was used to take FT-IR spectra. The
Hammett plot of the solid acids was determined on an UV 2550

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323
Fig. 2. Powder XRD spectrum of the parent and modified NaY zeolite sample; (a) NaY, (b) [Msim][FeCl4]/NaY = 0.03, (c) [Msim][FeCl4]/NaY = 0.05, (d) [Msim][FeCl4]/NaY = 0.1,
(e) [Msim][FeCl4]/NaY = 0.2, (f) [Msim][FeCl4]/NaY = 0.5, (g) [Msim][FeCl4]/NaY = 1.
spectrophotometer. The thermogravimetric (TGA) analysis of the
three solid acids was performed on Shimadzu TGA 50 instrument.
All elemental analyses were obtained from PerkinElmer 20 ana-
lyzer. Melting points were recorded on a Buchi-560 apparatus. The
amount of Fe present in the used catalyst composite was deter-
mined with an ICP-OES Perkin Elmer Optima 2100DV instrument.
The laser micro-Raman spectroscopic measurement was conducted
in a Horiba LabRAM HR spectrometer equipped with a He Ne
laser that has an excitation wavelength of 514.5 nm. The BET sur-
face area of the catalysts was measured in Quantachrome Nova
Win apparatus. The scanning electron microscopy (SEM) analyses
were carried out using a JEOL JSM-6390LV SEM, equipped with an
Energy-Dispersive X-ray analyzer.
time. The progress of 2nd step was also tracked with TLC technique
using EtOAc and hexane (1:5) as developing solvent. The work-up
step involved addition of 6 mL of CH2Cl2 to the crude mixture to
separate the unreacted DHPMs and catalyst by filtration from the
solution of crude pyrimidine. The catalyst was recovered as solid
residue on filter paper from the hot solution of DHPMs in ethanol.
The saturation of dichloromethane (DCM) solution of pyrimidine
at 0 ◦C precipitated the unreacted 2,4-dinitro-phenyl hydrazine as
red precipitates. Evaporation of DCM solution yielded the pyrimi-
dine derivatives as solid residue which was further recrystallized
from acetone and methanol solution.
3. Results and discussion
2.2. Synthesis of NaY supported hybrid catalysts of
[Msim][FeCl4](b–g)
3.1. Characterization of the hybrid catalysts
[Msim][FeCl4] ionic solid was prepared through a reported pro-
cedure [5]. The [Msim][FeCl4] loaded NaY zeolite catalysts were
prepared by wet impregnation method. The following steps have
been utilized: (i) the NaY zeolite powder was out gassed at 600 ◦C
for 3 h, (ii) [Msim][FeCl4] and NaY zeolite were mixed well with six
different weight/weight (w/w) ratios (such as 0.03, 0.05, 0.1, 0.2,
0.5 & 1) of ionic solid and NaY zeolite using few drops of distilled
EtOAc to ensure complete mixing, and finally (iii) the mixtures were
heated at 150 ◦C in a vacuum oven for 12 h.
3.1.1. Powder XRD analysis
The powder XRD patterns of NaY and modified zeolite compos-
ites (Fig. 2) support the preservation of zeolite framework up to the
w/w ratio of 0.2. Above that, complete destruction of the framework
occurs which can be attributed for acid induced dealumination of
Y- zeolite at 150 ◦C to maximum amount of extra framework alu-
minium species (EFAl) in presence of higher loaded (0.5 & 1) SO3H
containing [Msim][FeCl4] ionic solid [48–51].
A small peak observed at 2␪ = 45.13◦ for all composites which
becomes prominent for e (0.2), f (0.5) and g (1) composites. Partial
ionic interaction between Fe species and zeolite framework could
also occur during impregnation method and was found to be more
effective beyond [Msim][FeCl4]/NaY = 0.2 ratio. The extra peak cen-
tered at 2␪ = 45.13◦ matches well with the XRD database of FeCl3
(JCPDS card no. 770999) and represents the attachment of [FeCl4]−
species with the surface of zeolite. On modification, the crystallinity
of the zeolite particles decreases and it has a direct correlation with
loading percentages.
2.3. General procedure for the synthesis of
2-amino-4-arylpyrimidine derivatives 5
A mixture of ethyl acetoacetate (1 mmol), aromatic alde-
hyde (1 mmol) and urea (1.5 mmol) was heated in
a two
necked 50 mL round bottom flask at 60 ◦C for 10 min using
3 mg of [Msim][FeCl4]/NaY = 0.1 catalyst. The formation of 3,4-
dihydropyrimidin-2-(1H)-one was confirmed through thin layer
chromatography (TLC) using EtOAc and hexane (1:3) as solvent
system. After completion of the 1st step, 1 mmol of 2,4-dinitro-
phenylhydrazine was added to the crude mixture along with few
drops of dichloromethane and heated at 80 ◦C for the specified
This implies that partial dealumination transforms a portion of
crystalline zeolite into amorphous state along with preservation
of significant fraction of crystalline structure in Fig. 2 up to 0.2 (e)
loading of [Msim][FeCl4] salt [52].

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Fig. 3. FT-IR spectra of the parent as well as modified NaY zeolite samples, where (a) NaY, (b) [Msim][FeCl4]/NaY = 0.03, (c) [Msim][FeCl4]/NaY = 0.05, (d)
[Msim][FeCl4]/NaY = 0.1, (e) [Msim][FeCl4]/NaY = 0.2, (f) [Msim][FeCl4]/NaY = 0.5, (g) [Msim][FeCl4]/NaY = 1.
The relative crystallinity difference between modified samples
and the parent zeolite were compared by taking four high intensity
peaks at 2␪ = 15.3◦, 23.48◦, 26.85◦ and 31.05◦ and an informative
graph is included in the supplementary section along with the table
(see, supporting file, Fig. 1 and Table 1).
the parent framework during preparation of [Msim][FeCl4] loaded
composites with NaY. Furthermore, the identical FT-IR spectra of
four composites (b–e) and NaY(a) represents insufficient dealumi-
nation inside the framework in presence of less amount of acidic
salt [58].
The recorded FT-IR spectra (Fig. 4) of [Msim][FeCl4]/NaY = 0.1
sample after calcination at 250 ◦C, 350 ◦C and 450 ◦C also wit-
nessed complete intactness of characteristic bands of the fresh
0.1(d) composite within 400–1800 cm−1. This observation supports
the thermal stability of this composite with small portion of non-
framework Al species in solid state [59,60]. On the other hand, the
intensity of O H bending peaks gradually reduced at high tem-
perature calcination which indicate the loss of some hydroxyls
associated with the 1641 cm−1 band up to 450 ◦C as included in
supporting information (Fig. 3, Supporting File).
3.1.2. FT-IR analysis
FT-IR spectra of the parent and the modified samples were
recorded and represented in Fig. 3 in the region 400–1800 cm−1
.
The 0.2(e) loaded sample shows optimum dealumination state,
without an appreciable change of basic vibrational frequencies of
NaY zeolite like powder X-ray analysis (Fig. 2) [53]. The sharp band
in the region of 1638–1642 cm−1 for all composites can be con-
sidered for bending vibration of water molecules attached to the
zeolite structure including
C
N
stretching vibration of imida-
zolium cation of ionic salt [5]. The O H stretching vibration at
3459 cm−1 for parent zeolite shifts its position to 3441 cm−1 with
an intense peak for the composite [Msim][FeCl4]/NaY = 1(g) and
this represents the existence of strong hydrogen bonding within
the composite involving O H group [54]. The framework sensitive
double-ring vibration peak at 577 cm−1 of NaY observed around
578–579 cm−1 for the composites of 0.03(b), 0.05(c), 0.1(d) and
0.2(e). The other characteristic frequencies of NaY zeolite, corre-
sponding to bending, symmetrical and asymmetrical stretching
vibrations of TO4 (Si or Al) building units have been displayed at
455–458 cm−1, 721–793 cm−1 and 1019–1143 cm−1 for the above
four composites [55]. The strong S O symmetric and asymmet-
3.1.3. SEM-EDX analysis
Fig. 5 displays the SEM images of NaY zeolite, 0.1(d) and 0.2(e)
[Msim][FeCl4]/NaY composites. Both the size and uniformity of the
particles decrease on modification. Originally the parent NaY zeo-
lite has cube like large particle structure. The change in surface
morphology for the loaded materials depicts the anchoring of ionic
solid on the surface of zeolite as smaller size cube type particles.
They form more aggregation in case of w/w ratio of 0.2 than 0.1.
This may convert the surface of [Msim][FeCl4]/NaY = 0.2 composite
to non-uniform in nature and decreases the number of acidic sites
for catalytic performance.
ric stretching and bending vibrations of ionic salt at 1222 cm−1
,
The EDX spectra of the [Msim][FeCl4]/NaY = 0.1 composite con-
firmed the presence of constituent elements of the ionic solid along
with the zeolite (Fig. 6).
1075 cm−1 and 618 cm−1 are also overlapping with the above fun-
damental vibrations of TO4 unit of NaY zeolite [5]. The characteristic
absorption peaks of the composites almost disappeared for 0.5(f)
and 1(g) [Msim][FeCl4]/NaY samples which can be accounted for
destruction of the parent zeolite framework by rapid acid mediated
dealumination process in these two samples to form large amount
3.1.4. TEM analysis
The
TEM
imaging
was
carried
out
for
the
of non-framework Al species such as Al(OH)2 or AlO+ etc [56,57].
[Msim][FeCl4]/NaY = 0.1 composite zeolite at high resolution
(Fig. 7). These images proved that in the composite the crystallinity
of basic NaY zeolite was preserved as observed in the PXRD pattern
in Fig. 2. No substantial damages were detected on the hexagonal
+
From the above discussion of IR studies, we can assume that the
modified samples have some extra framework species of alumi-
nosilicate and silica gel formed by partial or complete destruction of