Magnetic core–shell nanoparticles containing I3- as a novel catalyst for the facial synthesis of imidazole derivatives in solvent-free conditions

Article abstract of DOI:10.13005/ojc/340341

A novel Fe₃O₄@SiO₂@(CH₂)₃N+Me₃I₃- magnetite nanoparticle was prepared and utilized in the synthetic conversion of aldehydes to imidazole derivatives in solvent-free conditions. T

Full text of DOI:10.13005/ojc/340341

ISSN: 0970-020 X
CODEN: OJCHEG
018, Vol. 34, No.(3):
Pg. 1504-1512
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
2
www.orientjchem.org
Magnetic core–shell Nanoparticles Containing I - as a Novel
3
Catalyst for the Facial Synthesis of Imidazole Derivatives in
Solvent-free Conditions
2
1
2
ESMAIL KORANI , KEIꢀAN GHODRATI * and MANꢁARbANO ASNAASHARI
1
Department of Chemistry, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
2
Department of Chemistry, North Tehran Branch, Islamic Azad University, Tehran, Iran.
*
Corresponding author E-mail: kghodrati@yahoo.com
http://dx.doi.org/10.13005/ojc/340341
(Received: May 30, 2017; Accepted: January 06, 2018)
AbSTRACT
A novel Fe O @SiO @(CH ) N+Me I - magnetite nanoparticle was prepared and utilized
3
4
2
2
3
3 3
in the synthetic conversion of aldehydes to imidazole derivatives in solvent-free conditions. These
functionalized magnetic core–shell nanoparticles (MNPs) were characterized by Standard technique
such asTEM, SEM, EDX, FT-IR, XRD, andVSM.The work up of reaction was very simple containing
only a magnetic decantation. This novel catalyst could be separated easily and recycled several
times without any significant decreasing of catalytic activity.
Key Words: Fe O @SiO @(CH ) N+Me I -, Magnetic separation, Magnetic core-shell,
3
4
2
2
3
3 3
Imidazoles, Solvent-free.
INTRODUCTION
In the past quarter of the century,
of catalysts and products over the reaction and
process steps.The magnetic nano particles can omit
2
or improve many of these drawbacks .According the
nanoparticle catalysts have attracted chemists
attention because of their unique properties both in
the reaction and workup. However, according their
simple separation, in addition of their nano size
advantages, their application have been developed
advantages of using magnetic nano particles, some
of them have been introduced in organic chemistry
3-15
and catalyst fields
.
Imidazoles and their derivatives are a
big class in organic chemistry. They have been
introduced and utilized for many years because
1
more and more . In the other hand, most catalysts
such as nano particles have some drawbacks in
usual separation methods, for instance, filtration or
centrifugation. These general methods lead to loss
1
of their unique biological activity . Imidazoles
were usually produced by the reaction between a
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4

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1505
carbonyl group and 1,2-diamine in the presence
of a special reagent or forced reaction condition
and.....Therefore, introducing a new safe and green
reagents are desirable.
2.
The using of numbers of reagents and catalysts
indicating the importance of these compounds in
organic synthesis. However, the majority of these
reagents and catalysts suffer from some drawback
such as low yields of the products, tedious work
up, toxic reagents, high cost, long reaction time
In continue with our research about nano
16
catalyst , we report herein the synthesis of novel
magnetically triiodide catalyst and its application to
the synthesis of imidazole derivatives.The synthetic
steps are summarized in scheme 1.
Scheme 1. Synthetic steps of Fe O @SiO @(CH ) N+Me I - magnetic catalyst
3
4
2
2
3
3 3
The preparation of first magnetite particles
was dispersed in DMF (50 mL) by the ultrasonic
treatment for 30 min., MeI (2 mL) and K CO was
as a magnetic core was performed by reaction
2
3
between ferrous and ferric chloride with NH OH. An
added to the mixture under vigorous stirring for
6 hours.An external magnet was used to separation
of Fe O @SiO @(CH ) N+Me I- from the solution.
4
inert layer of SiO was coated around previous core.
2
The outer surface modification was made through the
grafting of amino propylsilane, conversion of amine
group to fourth ammonium group and finally, adding
the triiodide anion to nano particle surface.Moreover,
this magnetic catalyst was characterized by known
appropriate technique such as SEM, TEM, EDX,
XRD, FT-IR and VSM. Finally, the produced catalyst
was used as a novel catalyst for the synthesis of
imidazole derivatives.
3
4
2
2
3
3
Then the produced nano particles washed with
water several times and dried in air. Afterward, this
nano particle was dispersed in ethanol (20 ml) by
ultrasonic treatment and a solution of I in ethanol
2
was added to dispersed solution and was stirred for
one day.The resulting dark violet nano catalyst was
collected by an external magnet and washed with
5 mL ethanol.
General procedure
ExꢂERIMENTAL
Asolutionofsubstrate(1mmol),arylaldehyde
(
1 mmol), and Fe O @SiO @(CH ) N+Me I - MNPs
3 4 2 2 3 3 3
ꢂreparation of catalyst
(
0.007 gr) was heated at 100 °C under magnetic
Preparation of magnetic nanoparticles
stirring for the requested reaction time. The
complication of reaction was demonstrate by TLC.
The EtOH (10 mL) was added and the reined nano
particles was collected by an external magnet. The
mixture was poured into ice-water (30 mL) and the
pure heterocyclic product was filtered, washed with
ice-water, and dried.
(
Fe O ), silica-coated MNPs (Fe O @SiO ) and
3 4 3 4 2
amino propyl modified silica-coated magnetic
nanoparticles (Fe O @SiO @APTES)
3
4
2
ꢂreparation of triiodide modified nanoparticle
Fe O @SiO @(CH ) N+Me I -)
(
3
4
2
2
3
3 3
The Fe O @SiO @APTES (100 mg)
3
4
2

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1506
RESULTS AND DISCUSSION
The TEM observation indicates all prepared nano
particles have almost spherical core–shell structure
Characterization of magnetic nanoparticle
TEM analysis
The size and morphology of the prepared
novel catalyst were characterized by TEM (Fig. 1).
(
Fig. 1). The size of magnetic core is less than
0 nm and the diameter of all layers a shell are
around 30 nm.
2
(
a)
(ꢃ)
Fig. 1.TEM images of (a) Fe O @SiO (ꢃ) Fe O @SiO @(CH ) N +Me I -.
3
4
2
3
4
2
2
3
3 3
SEM analysis
but whenTEOS coatedThe Fe O the average sizes
3 4
The Scanning Microscope Electronic (SE)
images indicate size and morphology of prepared
nano particles (Fig. 2). According this data, all
nano particles have a spherical shape with a large
surface area. These images show that Fe O is
increase to 20 nm (Fig. 2b). Furthermore, the SEM
observation of Fe O @SiO @APTES determined
3
4
2
a recognizable layers on Fe O magnetic core
3
4
(Fig. 2c). Finally, Fig. 2d shows the structure of
Fe O @SiO @(CH ) N+Me I - as core shell structure
3
4
3
4
2
2
3
3 3
spherically with nano dimensions less than 15 nm,
with average size of particles less than 50 nm.
(
a)
(ꢃ)
(c)
(
d)
Fig. 2. SEM images of prepared nano particles: (a) Fe O (ꢃ) Fe O @ SiO
2
(e)
3
4
4
3
4
(
c) Fe O @ SiO @ NH (d) Fe O @ SiO @ N(CH ) I- (d) Fe O @ SiO @ N(CH ) I -
3 4 2 2 3 4 2 3 2 3 2 3 2 3

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1507
x-ray diffraction
XRD pattern of pure magnetic nano catalyst
are showed in Fig 3. The most intense peak shows
the average sizes of nano particles according
Debye–Scherrer’s formula D = 0.9λ/β cosθ,
(1.542 Å);β= the angular line width of half-maximum
1
9, 20
intensity; θ= Bragg’s angle in degree)
. Based
on this data averages sizes of synthesized nano
particles are less than 50 nm that confirm the SEM
and TEM data.
(D= the average crystalline size;λ= X-ray wavelength
Fig. 3. xRD patterns of Fe O @SiO @(CH ) N+Me I -
3
4
2
2
3
3 3
-
1 21
EDS analysis
bond showed a significant signal in 585 cm
. It
Duo to EDS patterns, clearly show the
is noticeable that Si-OH and Si-O-Si groups were
−1
presence of N, C, O, Si, Fe and I (Fig. 4). The
presence of Fe indicate iron oxide in nano articles.
The higher intensity signals of Si and O, in addition,
confirmed by bands at 804, 951 and 1086 cm .The
stretching vibration of -OH group was confirmed by
−1
a broad band at 3300 - 3500 cm (Fig. 5b). The
−
1
shows the grafting of SiO layer to magnetic core.
significant bands at 2965 and 2850 cm belong
to the stretching vibration of C-H bond of propyl
amine group of APTES, which prove the successful
grafting of this on silica layer.Furthermore, a band at
2
The signal of C proves the presence of this element
in the structure of nano particle. Likewise, the N and
I signal demonstrate the alkylated ammonium group
and triiodide anion respectively.
−
1
1440 cm belong to the tertiary amine group.
Overall, these results confirm that this novel nano
particles successfully prepared.
Magnetic properties
The magnetization curve of Fe O , silica
3
4
coated Fe O and Fe O @SiO @(CH ) N+Me I - are
3
4
3
4
2
2
3
3 3
presented in Fig. 6a-c.This kind of characterization
would be called vibrating sample magnetometer
(
VSM). As can be seen from the diagrams, the
magnetization of bare Fe O MNPs is about 60.0
3
4
2
3
emu/g at room temperature . When the layers
were added, the saturation magnetization would
be decrease more and more. In fact, the saturation
magnetization of Fe O @SiO @(CH ) N+Me I -
+
-
3
4
2
2
3
3 3
Fig. 4. EDx patterns Fe O @SiO @(CH ) N Me I
3 3
3
4
2
2
3
would be around 40 emu/g, which is lower than the
bare one. Decrease of the saturation magnetization
result from the creation of a silica shell around the
Fe O core.
FTIR spectrosocpy
In the Fig. 5a-cthe FT-IR spectra of all
prepared nano particles are showed. The Fe-O
3
4

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1508
(a)
(b)
(
c)
Fig. 5. FT-IR spectra: (a) Fe O @ SiO MNꢂs; (ꢃ) AꢂTES coated Fe O MNꢂs and (c) Fe O @SiO (CH ) N+Me I -.
3
4
2
3
4
3
4
2
2
3
3 3

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1509
Fig. 6. ꢀSM of prepared nano particles at room temperature of (a) Fe O MNꢂs; (ꢃ) Fe O @SiO MNꢂs; and
3
4
3
4
2
(
c) Fe O @SiO @(CH ) N+Me I -
3 4 2 2 3 3 3
Optimization of nano catalyst for imidazole
synthesis
The imidazoles preparation reaction was
performed in the both solvent and solvent free
conditions. As regard the first, a verity of different
solvents were utilized for this conversion, such
as diethyl ether, ethanol, dichloromethane, THF,
toluene, acetonitrile, and DMF. Although, very low
yield of products were obtained in the presence of
DMF as solvent, but no one performed a noticeable
yields. As can be seen from the Table 1 only solvent
free condition is the best case for this reaction.
Likewise, the catalyst amount's effect was explored
on reaction time and yieldsTable 2).Although, in the
absence of this catalyst no products were found, but
there are two basic trends in the presence of different
amount of catalyst. The yield of products went up
by increasing the catalyst amount from 0.025 to
The reaction process is simple and fast and
proceeded in excellent yields of products.At the first
step, the conversion reaction carried out in different
protic and aprotic solvents and the product yields
compared to solvent free condition (Table 1).
Taꢃle 1: Effect of different solvent on product
yield for the synthesis of 2-(4-chlorophenyl)-
1
H- ꢃenzimidazole
Entry
Solvent a
Time(min.)/Yield(%)
1
2
3
4
5
6
7
8
9
CH CH OH
60/ trace
60/ trace
60/ trace
60/ trace
60/ trace
60/ trace
60/14
60/36
60/72
15/94
3
2
CH CH OCH CH
3
2
2
3
CH Cl2
2
0
.07 g. But with higher amount of catalyst the yield
of products were leveled off.
THF
Toluene
Taꢃle 2: catalyst amounts effect on the
preparation of 2-(4-chlorophenyl)-1H-
ꢃenzimidazole
CH CN
3
DMF
b
None
c
Entry
Catalyst(g)
Time(min)/ Yield(%)
None
d
1
0
None
1
2
3
4
5
0.025
0.05
0.07
0.10
-
15/29
15/85
15/94
15/94
15/ -
The reactions were carried out with 4-chloro
benzaldehyde (1mmol), orth-phenylene diamine
(
1mmol), and nano catalyst (0.07 g). a) reflux
o
condition, b) in solvent- free condition at 50 C, c) in
solvent- free condition at 75 C, d) in solvent- free
condition at 100 C
Reaction of 4-chloro benzaldehyde (1mmol),
1,2- diamino benzene (1mmol), and catalyst in
o
o
o
solvent- free conditions at 100 C.

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1510
Taꢃle 3: Synthesis of some heterocyclic compounds using Fe O @SiO @(CH ) N+Me I -
3
4
2
2
3
3 3
Entry
Ar
X
Product
Time (min.)/ Yield (%)
m.p.
Reported
Observed
1
2
3
4
5
6
C H4
NH
NH
NH
NH
NH
NH
17/92
13/90
15/92
13/88
17/94
20/90
290-292 290-293[27]
220-222 223-226[28]
263-264 264-265[27]
264-265 265-267[29]
288-290 288-291[30]
321-323 322-323[27]
6
4-OMeC H4
6
4-MeC H4
6
4-OHC H4
6
4-ClC H4
6
4-NO C H
4
2
6
In general, all data show significantly that
the best reaction condition is the solvent free at
00 °C in the presence of 0.07g of periodate
magnetic nano catalyst.
1
The results of condition's optimization
were used in the reaction of a variety of aldehyde
derivatives with 1,2-diamino benzene to synthesis
of some heterocyclic compounds (Table 3).
Synthesis of imidazole, thiazole and pirimidine
derivatives using Fe O @SiO (CH ) N+Me I -
3
4
2
2
3
3 3
As can be seen from the Table 3, there are
1
5 examples for catalytic conversion of aldehyde to
Fig. 7. Reusaꢃility of catalyst in
the corresponding heterocyclic compounds using this
novel catalyst containing I -.The yields are excellent
CONCLUSION
3
and the procedure is very simple.Likewise, the work
up is easy too. The catalyst is readily separated by
only using an external magnet.
In this manuscript, we herein report a
novel magnetic nano catalyst containing periodide
(
Fe O @SiO @(CH ) N+Me I -) as a green, efficient
3 4 2 2 3 3 3
Catalyst recovery and its staꢃility
and recoverable nano catalyst.The separation of this
catalyst from reaction mixture is very simple too. It
could be isolated using an external magnet vessel.
The imidazole, thiazole, and pirimidine derivatives
could be easily prepared using this novel nano
catalyst in excellent yields.
The reaction of 4-chlorobenzaldehyde
and o-phenylene diamine in the presence of the
catalytic amount of Fe O @SiO @(CH ) N+Me I -
3
4
2
2
3
3 3
was performed for demonstrate recoverability of this
catalyst.The catalyst was recycle and reused for five
times without any losing of its activity. In fact, this
unique nano catalyst could be recycled and reused
times and times (Fig. 7). On the other hands, the
catalyst shows very good shelf life too. This novel
catalyst last for months. So, it can be stored for
months without significant decline in its activity.
ACKNOWLEDGMENT
Financial support from the Islamic Azad
University of Kermanshah and north Tehran are
gratefully acknowledged.

GHODRATI et al., Orient. J. Chem., Vol. 34(3), 1504-1512 (2018)
1511
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