1,3,5-Tris(2-hydroxyethyl)isocyanurate functionalized graphene oxide: A novel and efficient nanocatalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1: H)-ones

Article abstract of DOI:10.1039/c7nj00632b

In this research, the preparation, characterization and catalytic application of a novel 1,3,5-tris(2-hydroxyethyl)isocyanurate functionalized graphene oxide (GO-THEIC) nanomaterial are described. The GO/THEIC nanomaterial was characterized by Fourier tra

Full text of DOI:10.1039/c7nj00632b

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
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ARTICLE
1,3,5-Tris(2-hydroxyethyl) isocyanurate functionalized graphene
oxide: a novel and efficient nanocatalyst for the one-pot synthesis
of 3,4-dihydropyrimidin-2(1H)-ones
Received 00th January 20xx,
Accepted 00th January 20xx
Mohammad G. Dekamin*†, Fatemeh Mehdipoor and Amene Yaghoubi
DOI: 10.1039/x0xx00000x
In this research, the preparation, characterization and catalytic application of a novel 1,3,5-tris(2-hydroxyethyl) isocyanurate
functionalized graphene oxide (GO-THEIC) nanomaterial is described. The GO/THEIC nanomaterial was characterized by
Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy
(EDS) and thermal gravimetric analysis (TGA) technique. The catalytic application of the GO-THEIC nanocatalyst was then
investigated in the Biginelli condensation of different aldehydes with alkylacetoacetates and urea or thiourea under solvent-
free conditions and at a moderate temperature. Moreover, the significant advantages of this procedure are the stability and
reusability of the catalyst, low loading of the catalyst, avoiding the use of toxic transition metals, short reaction times, high to
excellent yields, easy separation and purification of the products.
www.rsc.org/
[cmmim][BF4],8c D-xylonic acid,8d ErCl3.6H2O,8e bioglycerol-
based sulfonic acid functionalized carbon,8f imidazol-1-yl-acetic
acid,8g SiO2-CuCl2,8h HClO4-SiO2,9a silica-bonded S-sulfonic
Introduction
Multicomponent reactions (MCRs) have emerged as an
important research area in organic and medicinal chemistry.
MCR strategies improve atom economy and offer diversity and
acid (SBSSA),9b bentonite/PS-SO3H,9c MCM-41-R-SO3H,9d
Fe3O4/PAA-SO3H,9e
-sulfonic acid poly(4-vinylpyridinium)
N
chloride,9f PEG-SANM nanocomposite,9g phosphomolybdic
acid nanoparticles on imidazole functionalized Fe3O4@SiO2.9h
Although each of these methods has its advantages but some of
them suffer from disadvantages such as expensive and moisture
sensitive reagents, strongly acidic conditions, use of harmful
organic solvents, harsh reaction conditions, long reaction times,
tedious work-up procedure, unsatisfactory yields, non-
recoverability of the catalyst and environmental pollution.
efficiency in the synthesis of complex molecules especially
heterocyclic compounds in a fast and often experimentally
simple procedures. In such reactions, three or more reactants
come together in a single reaction vessel to form new products
that have portions of all the components. From environmental
and economic viewpoints, MCRs are well known as valuable
tools for the preparation of structurally diverse drug-like
compounds. In this respect, dihydropyrimidinones (DHPMs) and
their derivatives have attracted considerable interest because of
their wide spectra of significant biological activities and
pharmacological properties such as antihypertensive acting as as
Recently, nanoscience has emerged as a new and interesting
science among chemistry, material, physics, medicinal, biology,
mechanic and other sciences due to its novel, extensive and
unique applications in various fields. Today, nanoscience
appears to be essential and important as an active research area
in the field of catalysis of various reactions, especially in organic
chemistry. For comprehending the importance of this science in
the catalytic field, we have introduced a green nanocomposite
that has remarkable properties such as thermal stability,
mechanical strength and a wide surface. More recently, graphene
has been known as a popular material attracting attention in the
fields of chemistry, physics, and materials science because of its
proper functional groups for more manipulation and optimal
thermal, mechanical and electronic properties.10
calcium
channel
modulators,
antiviral,
antimitotic,
anticarcinogenic, adrenergic receptor antagonists, antibacterials,
mitotic Kinesin inhibitors and others, as reviewed elsewhere.1-5
Because of their importance and wide range of applications,
different types of methods have been reported for the preparation
of DHPMs which among them the Biginelli reaction is the most
important one.6 Literature survey shows that various
homogeneous or heterogeneous catalytic systems using different
energy inputs including classical heating, ultrasound irradiation
or grinding under ball-milling conditions have been reported for
the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives.
Some recent examples are ZrOCl2-8H2O,7a trichloroisocyanuric
Graphene oxide (GO) is a derivative of graphene but it have
differing properties. Sheets of GO possess numerous oxygen-
containing functional groups: hydroxyl and carboxyl groups are
located around the edges, whereas carbonyl and epoxide groups
are in the center. The existence of various types of hydrophilic
groups allows GO to be easily exfoliated when it is in the wet
7b
acid (TCCA), Yb(OTf)3,7c Cu(OTf)2,7d Bi(OTf)2,7e different
types of ionic liquids such as [Hmi]Tfa,8a [Cbmim]Cl,8b
Pharmaceutical and Biologically‐Active Compounds Research Laboratory,
Department of Chemistry, Iran University of Science and Technology, Tehran,
16846‐13114, Iran.
* mdekamin@iust.ac.ir
† Dr. Mohammad G. Dekamin (Associate Professor, IUST).
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New J Chem., 2017, 00, 1‐10 | 1
information available should be included here]. See DOI: 10.1039/x0xx00000x
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New J Chem.
state. These active groups can be used to induce chemical
reactions and provide GO with additional functional groups after
the modification, thereby increasing the flexibility and diversity
of GO applications. For example, GO layers can be intercalated
or cross-linked with primary aliphatic amines, alcohols amino
acids, diaminoalkanes, boronates, acyl chloride, and isocyanates,
or they can be covalently linked with polymers through
esterification.10,11 To the best of our knowledge, there is no report
on the use of 1,3,5-tris(2-hydroxyethyl) isocyanurate (THEIC) for
the cross-linking and modifications of GO sheets. The
heteroaromatic isocyanurate ring of THEIC have three flexible and
nonpolar alkyl arms and is well known for its binding ability to
transition metals. Furthermore, it is thermally very stable and is used
Scheme 1. One-pot three-component synthesis of 3,4-dihydropyrimidin-
2(1
isocyanurate functionalized graphene oxide nanomaterial (GO-THEIC,
).
H)-ones (thiones) catalyzed by 1,3,5-tris (2-hydroxyethyl)
1
to enhance the physical properties of a wide variety of polyurethanes, Results and discussion
polyureas and polyesters as coating materials in commercial
The 1,3,5-tris (2-hydroxyethyl) isocyanurate functionalized
graphene oxide (GO-THEIC) nanomaterial ( ) was prepared by
the reaction of GO and Ac2O and subsequent addition of a proper
amount of THEIC to the obtained mixture under sonication. Indeed,
Ac2O accelerates formation of ester functional groups at edges
of GO sheets and ether functional groups at center parts of GO
systems.12 These unique properties as well as other significant
properties associated with GO make 1,3,5-tris (2-hydroxyethyl)
isocyanurate functionalized graphene oxide (GO-THEIC, 1, Fig. 1) a
promising nanomaterial, catalyst or support depending on the used
conditions compared to other GO-modified materials.
1
sheets (Fig. 1). GO-THEIC (1) was then characterized with some
As part of our interest in developing new eco-friendly,
efficient and green methodologies and explore application of
isocyanurate functionalized materials in different fields12d,f as
well as MCRs,13 we wish herein to report catalytic activity of the
spectroscopic and techniques such as Fourier transform infrared
(FTIR) spectroscopy, scanning electron microscopy (SEM),
energy dispersive X-ray spectroscopy (EDX) and thermal
gravimetric analysis (TGA).
GO-THEIC (
highly effective heterogeneous nanocatalyst for the one-pot
three-component synthesis of 3,4-dihydropyrimidin-2-(1 )-one
derivatives under solvent-free conditions (Scheme ).
1) nanomaterial as a novel, green, reusable and
H
THEIC
1
100
90
80
70
GO/THEIC
60
50
40
30
20
10
0
GO
4000 3600 3200 2800 2400 2000 1600 1200 800 400
Wavelength(cm‐1
)
Fig. 2. FTIR spectra of the GO sheets (down), 1,3,5-tris(2-
hydroxyethyl) isocyanurate THEIC, up) and 1,3,5-tris(2-
hydroxyethyl) isocyanurate (GO-THEIC) nanomaterial ( , middle).
(
1
The FT-IR spectra of the GO/THEIC, THEIC and GO are
compared in Fig. 2. In the FTIR spectrum of GO, characteristic
bands appeared at 1730, 1631, 1220, 1051 and 831 cm-1 are
attributed to the C=O, C=C, C–OH, and C–O–C bonds of epoxy
vibration, respectively. Moreover, THEIC showed signals at
1679, 1461, 1056 cm-1 which are assigned to the stretching
vibration of the C=O, C–O bonds, C-N bonds, respectively. Also,
the observed characteristic bands at 2972-2885 and 3485-3255
cm-1 cm-1 are attributed to the stretching vibration of the C-H and
O-H bonds of THEIC. Indeed, IR spectrum of GO/THEIC
Fig. 1. A schematic structure of the 1,3,5-tris (2-hydroxyethyl)
isocyanurate functionalized graphene oxide (GO-THEIC) nanomaterial
(1).
2 | New J Chem., 2017, 00, 1‐10
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nanomaterial (1) shows that the characteristic epoxy signal at
831 cm-1 of GO has been disappeared. On the other hand, the
appearance of the characteristic bands of ester and alkyl
functional groups at 1461 cm-1, 2885-2972 cm-1 and reduction in
peak intensity of the band corresponding to carboxylic acid
(2400-3400 cm-1) confirms functionalization of GO by THEIC
(
Fig.s 1, 2.).12d,14,15a Furthermore, energy-dispersive X-ray
(EDX) analysis of this nanomaterial indicated the presence of
carbon, oxygen and nitrogen elements in its composition. These
findings, especially presence of nitrogen in the composition of
the GO-THEIC nanomaterial
(
1
)
confirms successful
incorporation of expected THEIC in the material network (Fig.
3).
Fig. 3. Energy dispersive spectroscopy (EDX) pattern of the 1,3,5-tris(2-
hydroxyethyl) isocyanurate (GO-THEIC) nanomaterial (1).
Fig. 4.
S
canning electron microscopy (SEM) images of 1,3,5-tris(2-
hydroxyethyl) isocyanurate (GO-THEIC) nanomaterial (1).
On the other hand, the morphology of the GO-THEIC
nanomaterial
(1) was evaluated using scanning electron
microscopy (SEM). It is noteworthy that SEM images of GO
typically present a wrinkled sheet-like structure.14,15a However,
upon functionalization with THEIC, the SEM images of GO-
THEIC show a much rougher surface and greater thickness,
which implies that many THEIC molecules have been grafted on
the surface of the GO sheets (Fig. 4).
100
80
60
40
20
0
The thermal stability of the GO/THEIC nanomaterial (1) was
also investigated using thermogravimetric analysis (TGA)
technique (Fig. 5.). A slight weight loss of the GO-THEIC
nanomaterial (1) up to 100 °C is mostly due to the evaporation
0
200
400
600
800
1000
of adsorbed water molecules by O-containing functional groups
of the GO sheets. The first major weight loss between 180 to 300
°C is attributed to the decomposition of oxygen-containing
groups from the GO surface, yielding CO, CO2, and steam. In
addition, weight loss between 300 and 500 ˚C is related to
removal of the isocyanurate ring located in the GO/THEIC
nanomaterial (1) framework.12 Finally,, weight loss between 500 to
760 ˚C is attributed the graphitic carbon burning off produced by
Temperature (°C)
Fig. 5. Thermal gravimetric analysis of the 1,3,5-tris(2-hydroxyethyl)
isocyanurate (GO-THEIC) nanomaterial (1).
To show the e
as a catalyst, for the synthesis of 3,4-dihydropyrimidin-2(1
ones derivatives ( ), the reaction of 4-chlorobenzaldehyde (2a, 1
mmol), urea ( , 1.5 mmol) and ethyl acetoacetate ( , 1 mmol)
was investigated as the model reaction. The reaction conditions
were optimized with regard to appropriate catalyst loading,
different solvents and temperature. The results are summarized
ffi
ciency of the GO/THEIC nanomaterial (
1
),
12d,15
H
)-
due to reduction of the GO platelet.11c,
These observation
5
apparently demonstrates not only grafting of the thermally stable
isocyanurate ring to the texture of GO sheets but also the
existence of π–π stacking interactions between the heteraromatic
isocyanurate ring of THEIC and GO which cause to form more
stacked structure.
3
4
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in Table 1. It was observed that a moderate yield of the desired enol tautomers 4’ as the nucleophilic component required for Michael
product, ethyl 4-(4-chlorophenyl)-6-methyl-2-oxo-1,2,3,4- addition to the activated intermediate (III) and formation of open-
tetrahydropyrimidine-5-carboxylate (5a), was obtained in the chain ureides (IV). Finally, the intermediate (IV) undergoes
presence of 15 mg loading of the catalyst
conditions (Table , entry 1). On the other hand, the use of same of GO-THEIC nanomaterial (1) to afford the desired 3,4-
loading of the catalyst
in EtOH under reflux conditions dihydropyrimidin-2(1H)-one derivatives.16 Furthermore, the ability of
1 under ultrasonic intramolecular cyclization and subsequent dehydration in the presence
1
1
improved the yield of desired product 5a compared to sonication numerous distributed hydroxyl groups on the surface of GO-THEIC
or other solvents (entries 2-4). Interestingly, when the model nanomaterial (1) to activate carbonyl components of the reaction by
reaction was studied under same catalyst loading and solvent- hydrogen bonding may also be considered as a complementary part of
free conditions at 80 °C the yield of the desired product 5a was its observed catalytic activity.12d,13a,c,h,i,j
increased significantly (entry 5). Further investigation of the
effect of temperature under solvent-free conditions on the yield Table 1. Optimization of the three‐component reaction 4‐
of desired product 5a indicated that lower yields obtained in chlorobenzaldehyde (2a), urea (3) and ethyl acetoacetate (4) under different
longer reaction times at temperatures lower than 80 °C (entries conditionsa
6,7). Moreover, by reducing of the amount of catalyst to 10 mg
catalyst loading, lower yield of the desired product 5a was
obtained under similar conditions at 80 °C (entry 8). In contrast,
increasing of the amount of catalyst to 20 mg catalyst loading
had no significant influence on yield of the desired product (entry
9). Additionally, the desired product 5a was obtained in very low
yield using ball-milling technique in the presence of same
catalyst loading under solvent-free conditions or catalyst-free
conditions at 80 °C (entries 10,11). On the other hand, lower
yields of the desired product 5a was abtained under similar
conditions when GO or 1,3,5-tris(2-hydroxyethyl) isocyanurate
were examined as catalysts (entries 12,13).
Catalyst
loading/m
g
Temp.
(°C)
Time
(min)
Entry
Solvent
Yieldb (%)
15
15
15
15
15
15
15
10
20
15
-
EtOH
r.t
120
110
150
180
40
50
65
31
10
95
76
12
83
94
15
21
70
59
1c
2
Encouraged by these results, the catalytic activity of
EtOH
Reflux
Reflux
Reflux
80
GO/THEIC nanomaterial
synthesis of different 3,4-dihydropyrimidin-2(1
1
was further investigated for the
)-ones
H2O
H
3
derivatives (5a-v) under the optimized conditions (15 mg
GO/THEIC loading, solvent-free conditions at 80 °C). Indeed,
both aromatic carbocyclic or heterocyclic aldehydes 2a-v
involved in the Biginelli MCR to afford corresponding products
CH2Cl2
4
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
5
70
60
5a-v. The results are summarized in Table 2. As it can be seen,
6
good to excellent yields of the desired products 5a-v were
obtained under the optimized reaction conditions within short
reaction times in all studied cases. The GO/THEIC nanomaterial
45
60
7
80
40
8
1
was simply isolated from the reaction mixture during
crystallization of the products and recovered for the next runs.
Furthermore, thiophene-2-carbaldehyde 5m which is
80
40
9
(
)
r.t
90
10d
11
12e
13f
susceptible to polymerization under acidic conditions survived
under optimized reaction conditions to afford the corresponding
product 5m in good yield.
80
100
40
15
15
80
A probable mechanistic pathway for the formation of 3,4-
dihydropyrimidin-2(1H)-one derivatives 5 catalyzed by GO-THEIC
nanomaterial (1) is outlined in Scheme 2. According to the
mechanism, it can be proposed that GO-THEIC nanomaterial (1) can
mainly activate the carbonyl group of aldehydes 2 via COOH groups
on its surface to facilitate nucleophilic addition of urea or thiourea (3)
on the carbonyl group to afford intermediate (I) and followed by rapid
dehydration and formation of imine (III) in the third step.
Simultaneously, the catalyst can activate carbonyl group of alkyl
acetoacetates 4 to form proper concentrations of their corresponding
80
40
a Reaction conditions: 4-Chlorobenzaldehyde (2a, 1 mmol), ethyl acetoacetate (3, 1
mmol) and urea (4, 1.5 mmol) in the presence of GO-THEIC nanomaterial (1) under
different conditions. b Isolated yields. c Under ultrasonic condition. d The reaction was
performed under Ball-milling Conditions. eGO was used as catalyst. f1,3,5-tris(2-
hydroxyethyl) isocyanurate was used as catalyst.
4 | New J Chem., 2017, 00, 1‐10
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ARTICLE
Table 2. One-pot three-componet synthesis of 3,4-dihydropyrimidin-2(1
H
)-ones derivatives
5
from aldehydes
2, ethyl or methyl acetoacetate (
3)
and urea/thiourea ( ) catalyzed by GO-THEIC nanomaterial (
4
1
) under the optimized conditionsa
Entry
Aldehyde
R1
X
Product
Time (min)
Yieldb,c(%)
M.p (°C)
Found / Reported
213-215 / 213-21517
180-182 / 180-18218
215-218 / 214-21519
218-221 / 219-22120
184-187 / 184-18521
181-184 / 180-18222
199 / 20023
1
2
4-ClC6H4
4-FC6H4
Et
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
40
35
50
60
35
90
70
50
45
50
40
50
30
60
40
50
70
40
35
45
40
40
95
80
85
77
70
82
72
75
91
85
84
94
80
80
90
89
91
80
81
87
82
85
5a
5b
5c
5d
5e
5f
Et
Et
3
4-BrC6H4
4
2-ClC6H4
Et
5
3-BrC6H4
Et
6
4-CNC6H4
4-NO2C6H4
2-NO2C6H4
4-MeC6H4
4-MeOC6H4
2-MeOC6H4
4-OHC6H4
2-Thienyl
2-ClC6H4
Et
7
Et
5g
5h
5i
8
Et
237 / 234-23624
9
Et
212-215 / 213-21525
195-197 / 194-19626
255-258 / 257-25927
231/5-233 / 233-23528
213-215 / 212-21429
256-259 / 255-25730
198-200 / 198-20031
187-190 / 189-19132
246-248 / 247-24933
278-280 / 280-28334
162-164 / 16535
10
11
12
13
14
15
16
17
18
19
20
21
22
Et
5j
Et
5k
5l
Et
Et
5m
5n
5o
5p
5q
5r
5s
Me
Me
Me
Me
Me
Et
4-MeC6H4
4-MeOC6H4
4-OHC6H4
2-MeOC6H4
2-ClC6H4
4-MeC6H4
2-MeOC6H4
4-ClC6H4
Et
S
173-175 / 176-17836
187-189 / 189-19037
176-179 / 180-18338
5t
Et
S
5u
5v
Me
S
a Reaction conditions: 4-Chlorobenzaldehyde (2a, 1 mmol), ethyl or methyl acetoacetate (3, 1 mmol) and urea/thiourea (4, 1.5 mmol) in the presence of 15 mg of the catalyst (1) under
solvent-free conditions at 80
C. b Isolated Yields.
̊
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O
O
Ar
Ar
O
NH
H
H2O
+
(2)
COOH
N
H
X
(5)
H
+
(1)
O
COO-
Ar
H
Ar
O
H
X
O
NH
H2N
NH2
(V)
X
N
H
(3)
H2O+
COO-
COOH
H
X
NH2
H
O
N
H
Ar
(I)
O
Ar
X
O
COOH
NH
COO-
H
NH2
O
X
(IV)
NH2
O
H2N
N
H
N
X
Ar
H
H
(II)
H
(III)
H2O
Ar
O
H
HOOC
O
O
O
O
O
(4)
COOH
=
GO-THEIC (1)
Scheme 2. Proposed mechanism for the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives 5 catalyzed by GO-THEIC nanomaterial (1).
any substrates and washed by EtOH, EtOAc and n-hexane,
Recyclability is another important aspect of this active, respectively. The obtained balck powder was then dried in an
efficient and eco-friendly heterogeneous catalyst. In this part of oven and reused in subsequent runs (Fig. 5). As can be seen in
our study, it has been presented that the GO-THEIC (1) could be Fig. 5b, the IR spectrum of the recovered catalyst after four times
recovered and reused at least four times in the subsequent runs for is completely similar to that of the fresh catalyst. These results
the model reaction using the same recovered catalyst without a demonstrate that the nature of the GO-THEIC (
significant loss of its catalytic activity. Indeed, after completion remains relatively undamaged after each run.
of the reaction, the catalyst was separated from the products or
1), as the catalyst,
95
93
90
90
87
1
2
3
4
5
Run
(a)
(b)
Fig. 5. Reusability of GO-THEIC for the synthesis of 5a (a); FT-IR spectra of the fresh GO-THEIC (1) and the recycled GO-THEIC after five
runs.
6 | New J Chem., 2017, 00, 1‐10
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In order to demonstrate the merits of this newly developed for the synthesis of dihydropyrimidin-2(1H)-one derivatives is indeed
protocol, it has been compared with some of the recent published superior to many of previously published procedures in terms of
procedures. The results are summarized in Table 4. Data in Table 4 product yield, catalyst loading, elimination of toxic metals, reaction
clearly show that the catalytic activity and efficiency of GO-THEIC time and reaction temperature.
Table 4. Comparative synthesis of compounds 5a using the reported methods versus the present method
Temp (°C)
110
Time (min)
60
Yield (%)
88
Reference
Entry
1
Catalyst
SBSSA
Catalyst loading
50 mg
Solvent
AcOH
39
Phytic acid
ZAF-16/16
10 mol%
20 mg
Solvent-free
Ethylene glycol
Solvent-free
Solvent-free
Solvent-free
EtOH
100
140
210
300
66
86
67
89
88
85
92
72
82
84
97
95
40
2
3
41
Bi2Mn2O7
14 mg
104
42
4
PISA
10 mol%
0.5 mol%
50 mg
120
180
180
300
270
120
480
120
40
43
5
β-Cyclodextrin
Poly(SIL)
100
44
6
80
45
7
Cellulose sulfonic acid
PTA@MIL-101
PANF-PAMSA
Graphite
50 mg
H2O
Reflux
100
46
8
0.6 mol%
5 mol%
100 mg
15 mg
Solvent-free
EtOH
47
48
9
Reflux
70
10
11
12
Solvent-free
Solvent-free
49
GO-THEIC
80
This Work
a Obtained results for the synthesis of compound 5a.
known compounds and were identified by comparison of their
physical and spectroscopic and analytical data with the authentic
samples.
Experimental
General
General procedure for the preparation of GO-THEIC (1)
100 mg GO and 200 mg of Ac2O were added into a 50 mL
round bottom flask charged with 10 mL deionized water. The
mixture was ultrasonically mixed for 1.5 h. Then, 300 mg of 1,3,5-
tris(2-hydroxyethyl) isocyanurate (THEIC) was added into a
mixture and again put under ultrasonic for 2.5 h. Next, the
obtained suspension was separated using centrifuge (12000 rpm)
for 20-30 minutes.and then 20 mL of HCl 9.6 M was added into
the abovementioned suspension. The resulting mixture was
allowed to stand at 80 °C for 1 h. The resulting solid was isolated
by using centrifuge, washed completely with deionized water to
remove excess of HCl or THEIC. Finally, the balck solid was
dried at 50 °C for 24 h under air.
All chemicals were purchased from Merck or Aldrich
companies and were used as received except for benzaldehyde
which a fresh distilled sample was used. Scanning electron
microscopy (SEM) images were obtained using Sigma
instrument of Zeiss Company, Germany. Thermal gravimetric
analysis (TGA) was performed by means of Bahr company STA
504 instrument. FTIR spectra were acquired as KBr pellets on a
Shimadzu FT-IR-8400S spectrometer. Melting points were
determined using an Electrothermal 9100 apparatus and are
uncorrected. 1H NMR (500 MHz) spectra were recorded using a
Bruker DRX-500 Avance spectrometer with CDCl3 or DMSO as
solvent at ambient temperature. Analytical thin layer
chromatography (TLC) for monitoring reactions was carried out
using Merck 0.2 mm silica gel 60 F-254 Al-plates, and EtOAc
and n-hexane (1:2, v/v) as eluents. All the products (5a-v) are
General experimental procedure for the synthesis of 3,4-
dihydropyrimidin-2(1H)-ones derivatives (5a-v) catalysed by GO-
THEIC (1)
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ARTICLE
New J Chem.
4
5
6
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426, 198-204.
In a 5 mL round-bottomed flask, aldehyde (
acetoacetate ( , 1 mmol) and urea or thiourea (
15 mg of the catalyst
stirred at 80 C for times indicated in Table
of the reaction monitored by TLC (eluent: EtOAc : n-hexane),
EtOH (4 mL) was added and the obtained mixture was heated
2
4
, 1 mmol), alkyl
, 1.5 mmol) and
,
3
1
were added. The obtained mixture was
. After completion
2
̊
2
and filtered off to separate the solid catalyst
1. Then, water was
(a) B. Jauk, F. Belaj and C. O. Kappe, J. Chem. Soc., Perkin Trans.
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̊
1, 1999, 307-314; (b) C. O Kappe, Acc. Chem. Res., 2000, 33, 879-
the desired products 5a-v in 80–95% yields based on the starting
aldehyde. The separated catalyst was suspended in EtOH, EtOAc
and n-hexane (1 mL) for 30 min, respectively and finally was
filtered. The obtained black powder was heated in an oven at
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7
8
70 ̊C for 1 h and reused for successive runs.
8
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Conclusions
In summary, 1,3,5-tris(2-hydroxyethyl) isocyanurate
functionalized graphene oxide (GO-THEIC) nanomaterial was
prepared by crosslinking of GO sheets with the flexible and
symmetrical trifunctional alcohol 1,3,5-tris(2-hydroxyethyl)
isocyanurate for the first time and characterized. The GO-
THEIC was shown to be a highly efficient and recyclable
transition metal-free catalyst for the one-pot three-component
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2
synthesis of 3,4-dihydropyrimidin-2(1
different aldehydes, urea and ethyl acetoacetate under solvent-
free conditions. The reaction system was significantly a ected
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Acknowledgements
We are grateful for the financial support from The Research
Council of Iran University of Science and Technology (IUST),
Tehran, Iran (Grant No 160/347). We would also like to
acknowledge the support of Iran Nanotechnology Initiative
Council (INIC), Iran. The authors also wish to thank Dr. Elaheh
Kowsari (Department of Chemistry, Amir Kabir University of
Technology, Tehran, Iran) for helpful discussion.
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New J Chem.
Graphical Abstr
1,3,5-Tris(2-hydroxyethyl) isocyanurate
functionalized graphene oxide: a novel
and efficient nanocatalyst for the one-
pot synthesis of 3,4-dihydropyrimidin-
2(1H)-ones
Mohammad G. Dekamin*, Fatemeh Mehdipoor and Amene
Yaghoubi
In this research, the preparation, characterization and catalytic
application of a novel 1,3,5-tris(2-hydroxyethyl) isocyanurate
functionalized graphene oxide (GO-THEIC) nanomaterial is
described. The GO/THEIC nanomaterial was characterized by
Fourier transform infrared (FTIR) spectroscopy, scanning electron
microscopy (SEM), energy dispersive X-ray spectroscopy (EDS)
and thermal gravimetric analysis (TGA) technique. The catalytic
application of the GO-THEIC nanocatalyst was then investigated
in the Biginelli condensation of different aldehydes with
alkylacetoacetates and urea or thiourea under solvent-free
conditions and at
a moderate temperature. Moreover, the
significant advantages of this procedure are the stability and
reusability of the catalyst, low loading of the catalyst, avoiding the
use of toxic transition metals, short reaction times, high to
excellent yields, easy separation and purification of the products.
10 | New J Chem., 2017, 00, 1‐10
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