Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine functionalizedFe3O4 nanoparticles as novel recyclable magnetic nanocatalysts for Ullmann coupling reaction

Article abstract of DOI:10.1002/aoc.5708

In this study, Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine functionalized Fe₃O₄ magnetic nanoparticles [(Pd-APM-PSi-Fe₃O₄) and (Pd-BIA-PSi-Fe₃O₄)] was designed and used for the synthesis of di aryl ether by Ulmann cross-coupling reactions. Ulmann reaction performed with mixing of the arylhalides and phenol derivatives in DMF solvent. The prepared catalysts were characterized with various analytical techniques such as FT-IR, XRD, TGA, SEM, TEM, EDX, ICP and VSM. Pd-APM-PSi-Fe₃O₄ and Pd-BIA-PSi-Fe₃O₄ catalysts demonstrated good to excellent yields catalytic efficiency for Ulmann reactions in comparison with to commercial palladium catalysts. The catalyst is easily recycled and reused without loss of the catalytic activity. The combined merits of reusable catalyst conditions make the condensation with safe operation, no leaching of pd into environment, low pollution, rapid access to products and simple workup. Also, these novel magnetic nanocatalysts are superior to the industry standard Pd in every relevant aspect. They feature a way higher initial activity, a much more convenient separation, better recycling, and less contamination of the products. Last but not least, they can be very easily prepared from commercially available Fe₃O₄ nanoparticles using standard laboratory equipment.

Full text of DOI:10.1002/aoc.5708

Received: 31 December 2019
DOI: 10.1002/aoc.5708
Revised: 8 March 2020
Accepted: 10 March 2020
F U L L P A P E R
Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-
2-amine functionalizedFe3O4 nanoparticles as novel
recyclable magnetic nanocatalysts for Ullmann coupling
reaction
Jin Chen1 | Linfang Dai1 | Jiayu Li1 | Majid Mohammadnia2
1Business School, Central South
In this study, Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-
2-amine functionalized Fe3O4 magnetic nanoparticles [(Pd-APM-PSi-Fe3O4)
and (Pd-BIA-PSi-Fe3O4)] was designed and used for the synthesis of di aryl
ether by Ulmann cross-coupling reactions. Ulmann reaction performed with
mixing of the arylhalides and phenol derivatives in DMF solvent. The prepared
catalysts were characterized with various analytical techniques such as FT-IR,
XRD, TGA, SEM, TEM, EDX, ICP and VSM. Pd-APM-PSi-Fe3O4 and Pd-BIA-
PSi-Fe3O4 catalysts demonstrated good to excellent yields catalytic efficiency
for Ulmann reactions in comparison with to commercial palladium catalysts.
The catalyst is easily recycled and reused without loss of the catalytic activity.
The combined merits of reusable catalyst conditions make the condensation
with safe operation, no leaching of pd into environment, low pollution, rapid
access to products and simple workup. Also, these novel magnetic
nanocatalysts are superior to the industry standard Pd in every relevant aspect.
They feature a way higher initial activity, a much more convenient separation,
better recycling, and less contamination of the products. Last but not least,
they can be very easily prepared from commercially available Fe3O4
nanoparticles using standard laboratory equipment.
University, Changsha City, Hunan
Province, 410000, China
2Young Researcher and Elite Club,
Department of Chemistry, Bojnord
Branch, Islamic Azad University,
Bojnourd, Iran
Correspondence
Jin Chen, Business School, Central South
University, Changsha City, Hunan
Province, 410000, China.
Email: tsyshengye@126.com
K E Y W O R D S
1H-benzo[d ]imidazol-2-amine, 2-Aminopyrimidine, magnetic, Nanocatalyst, palladium
nanoparticles
1 | INTRODUCTION
Cheap and economical catalyst to prepare the
corresponding symmetrical biaryl.[3,4] and nowadays N-,
The Ullmann reaction or Ullmann coupling for the first
time has reported in 1901. It is a coupling reaction
between aryl halides and copper that is named after
Fritz Ullmann.[1,2] In other words, this reaction has
attracted recently high interest from the industry and
used by chemists to produce a C-C bond between two
aromatic nuclei in the presence of copper powder as a
O-, S-, P- and C-aryl bonds formation are easily accessi-
ble through these processes in many bioactive organic
compounds.[5]
For first time, aryl iodides were used in coupling reac-
tions that were broaded by copper at high temperature
conditions.[6,7] After that, progressions in the Ullmann
coupling reactions have permitted the application of aryl
Appl Organomet Chem. 2020;e5708.
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© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5708

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CHEN ET AL.
bromides or chlorides in the presence of catalysts such as
Cu and Pd.[8,9]
In the course of an study targeted towards the attain-
ment of more eco-friendly protocols, in following of our
research on synthesis of heterocyclic compounds in the
presence of MNP catalyst,[32–34] here in it has afforded to
preparation of diaryl ether derivatives using Ullmann
coupling reaction via O-arylation reactions from aryl
halide (1 mmol), phenol derivative (1 mmol) and 0.1 g of
K2CO3 in DMF (7 mL) in the presence of Pd based on
2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine
functionalizedFe3O4 nanoparticles [(Pd-APM-PSi-Fe3O4)
and (Pd-BIA-PSi-Fe3O4)] as a new recoverable magnetic
nanocatalyst (Scheme 1).
Rawal et al. have worked the synthesis of Ullmann
coupling aryl halides by palladium complexes as cata-
lyst.[10] Recently, the catalysts based on Pd/N for
Ullmann coupling reactions with many reducing agents
like
diaminoglyoxime,[11]
amidoxime[12]
and
triethylamine[13] have been especially developed. At all of
these catalysts purification of products is challenging
problem.[14] Also, Veisi et al. have reported palladium
nanoparticles supported on chitosan as efficient catalyst
with no applying reducing agent for the Ullmann reduc-
tive coupling.[15]
Diaryl ethers and its derivatives form an important
and significant class of organic compounds and key moie-
ties during the polymer and life sciences industries in
many biologically active natural products. The total syn-
thesis of several natural cyclopeptides, such as vancomy-
cin and anti-HIV agents like chloropeptin, which contain
this substructure, has captured substantial attention and
interest. Traditional route to prepration of diaryl ethers is
of Pd- or Cu-catalyzed Ullmann coupled with aryl halides
and phenols to form C–O bond.[16–18] In spite of the
excellent efficiency of the Pd-catalyzed Ullmann coupled,
the use of expensive palladium and elaborate
phosphorated ligands would limit its using to large- or
industrial-scale production.[19]
In recent year substantial efforts have been performed
to the development of new methods for the synthesis of
diarylethers under relatively mild conditions. Principal
progress has been done in modifying the Cu-catalyzed
Ullmann coupling reaction by applying several special
ligands and heterogeneous reusable catalysts with easy
recovery.[20–23]
In past decade, magnetic nanoparticles (MNPs) are
widely used as supports of depositing metal nanoparticles
as heterogeneous recoverable catalysts for Ullmann reac-
tion because of their extraordinary structure and attrac-
tive propeties such as superparamagnetic, high surface
energy, high chemical activity, low Curie temperature,
high magnetic sensitivity, and large surface-to-volume
ratio. Suitable surface coating and improving some effi-
cient protection strategies to remain the stability of mag-
netic MNPs is very significant.[24] In fact, surface
functionalized MNPs have been greatly used in biotech-
nology and catalysis.[25] These days, the design of novel
magnetically separable plans has catcher a major deal of
interests as an attractive choice to improve the effective
separation of heterogeneous catalysts from products by
an external magnet.[26,27]
2 | RESULTS AND DISCUSSION
2.1 | Characterization of the prepared
Pd-APM-PSI-Fe3O4 and Pd-BIA-PSi-Fe3O4
nanoparticles
2.1.1 | Fourier transforms infrared (FT-
IR) analysis
The FT-IR spectra of Fe3O4, Fe3O4– ClPSi, APM-PSi-
Fe3O4 and BIA-PSi-Fe3O4, Pd-APM-PSi-Fe3O4 and Pd-
BIA-PSi-Fe3O4 are shown in Figure 1. The adsorption
bands at 586 and 447 cm−1 were assigned to Fe-O
stretching band and 3427 cm−1 corresponded to broad
OH groups on magnetic surface of MNPs. In addition, In
the FT-IR spectrum of Fe3O4– ClPSi, adsorption bands at
1037 cm−1 that is attributed to the Si-O groups. In the
FT-IR spectrum of APM-PSi-Fe3O4 and BIA-PSi-Fe3O4,
new bands were discerned at 1622 and 1410 cm−1 due to
the C=N and C-H (Aromatic) stretching vibration bands,
respectively. The characteristic bands at 2860 and
2919 cm−1 are allotted to the symmetric and asymmetric
stretching of C–H bond in 2-Aminopyrimidine,1H-
benzo[d]imidazol-2-amine and propyl group unit of
Fe3O4– ClPSi, APM-PSi-Fe3O4 and BIA-PSi-Fe3O4 mag-
netic nanoparticle. These bands proved that
2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine
have been successfully reacted with amino present in the
structure of APM-PSi-Fe3O4 and BIA-PSi-Fe3O4. The N-H
stretching peak of the amide group in APM-PSi-Fe3O4
and BIA-PSi-Fe3O4 has emerged at 3372 cm−1. In addi-
tion to, in the FT-IR spectrum of Pd-APM-PSi-Fe3O4 and
Pd-BIA-PSi-Fe3O4O4, the intensity of the adsorption band
at 629 cm−1that is assigned to the bending vibration of
C–H in pyridine heterocyclic ring is reduced after forma-
tion of APM-PSi-Fe3O4 and BIA-PSi-Fe3O4 complex with
Pd. Hence, the obtained data from FT-IR spectroscopy
can be verified the existence of the nonomagnetic parti-
cle, heterocyclic moiety and Pd in the structure of Pd-
Excellent biocompability and biodegradability as well
as good magnetic qualities can be displayed for functional
many organic compounds coated on MNPs.[28–31]

CHEN ET AL.
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SCHEME 1 Ullmann coupling reaction with Pd-
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 as nano magnetic
catalyst
FIGURE 1 The FTIR spectra of Fe3O4,
Fe3O4– ClPSi, APM-PSi-Fe3O4 and BIA-PSi-
Fe3O4, Pd-APM-PSI-Fe3O4 and Pd-BIA-PSi-
Fe3O4 [Colour figure can be viewed at
wileyonlinelibrary.com]
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 nanoparticle
(Figure 1).
crystal, in which the crystalline structure makes a beam
of incident X-rays to diffract into many special direc-
tions.[35] Powder X-ray diffraction patterns of three sam-
ples Fe3O4, Pd-APM-PSI-Fe3O4 and Pd-BIA-PSi-Fe3O4
are displayed in Figure 2. As it can be seen in Figure 2,
the peaks at 2θ = 40.0ꢀ, 46ꢀ and 68ꢀ allotted to the (111),
(200) and (220) were assigned to Palladium. Also
2θ = 30.2ꢀ, 35.30ꢀ, 43. 3ꢀ, 53.65ꢀ, 57.3ꢀ, and 62.8ꢀ peaks
2.1.2 | X-ray diffraction (XRD) analysis
X-ray diffraction (XRD) is the experimental method
determining the atomic and molecular structure of a
FIGURE 2 XRD spectra of nanoparticles
containing the Fe3O4, Pd-APM-PSi-Fe3O4 and
Pd-BIA-PSi-Fe3O4 [Colour figure can be viewed
at wileyonlinelibrary.com]

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CHEN ET AL.
corresponding to the (220), (311), (400), (422), (511), and
(440) was obtained because of the cubic spinel structure
of Fe3O4 NPs. Therefore, according to the results
extracted from XRD spectra it can be confirmed the pres-
ence of the Palladium on organic group moiety in the
nanoparticles containing Pd-APM-PSi-Fe3O4 and Pd-BIA-
PSi-Fe3O4.
10 ꢀC min−1 within a temperature range of 0–800 ꢀC
(Figures 5 and 6). It can be estimated the composition
ratio of the catalyst from the residual mass percentage.
As displayed in Figure 5, the first weight loss stage at
ꢀ
almost 100 C (0.2%) was allotted to the vaporization of
adsorbed water molecules. The second weight loss at
100–450 ꢀC (6.9%) can be assigned to loss of Pd and
2-Aminopyrimidine group. The final weight loss at 450 to
750 ꢀC (2.1%) has contributed to propyl group. According
to the obtained results, the good grafting of Pd-APM-PSi
on the Fe3O4 nanoparticles is proved.
2.1.3 | Energy dispersive x-ray (EDX)
Energy Dispersive X-Ray Analysis (EDX), referred to as
EDS or EDAX, is an x-ray technique used to identify the
elemental composition of materials.[36] Figure 3 and 4
shows EDX analysis of Pd-APM-PSi-Fe3O4 and Pd-BIA-
PSi-Fe3O4. The results displayed that Pd-APM-PSi-Fe3O4
and Pd-BIA-PSi-Fe3O4 are composed of C, O and Pd. This
revealed the existence of Pd in the prepared catalyst.
Also, the TGA spectrum of Pd-BIA-PSi-Fe3O4 is
shown in Figure 6. As it can be seen in Figure 3, the first
weight loss stage at almost 100 C (0.25%) was assigned
ꢀ
to the vaporization of adsorbed water molecules. The sec-
ꢀ
ond weight loss at 100–450 C (7.22%) can be assigned to
loss of Pd and 1H-benzo[d]imidazol-2-amine group. The
ꢀ
final weight loss at 450 to 800 C (2.15%) has contributed
to propyl group. According to these results, the good
grafting of Pd-BIA-PSi on the Fe3O4 nanoparticles is
confirmed.
2.1.4 | ICP-AES analysis
The ICP-AES analysis displays the similar palladium con-
centration on the Pd-APM-PSi-Fe3O4 and Pd-BIA-PSi-
Fe3O4 as catalyst. Also, the absence of palladium metal in
the reaction solvent, exhibiting no metal leaching into
the reaction mixture. The inductively coupled plasma–
atomic emission spectroscopy (ICP-AES) analysis is
played the weight percentage of the Pd to be 7% and 9%
in Pd-APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 NPs.
2.1.6 | Transmission electron
microscope (TEM)
Morphology of synthesized catalysts of Pd-APM-PSi-
Fe3O4 and Pd-BIA-PSi-Fe3O4 nanoparticles were studied
by TEM that displayed in Figures 7 and 8. Particles have
spherical morphology from Figures 7 and 8. According to
TEM images, the average particle size is evaluated about
14 nm in Pd-APM-PSi-Fe3O4 nanoparticles and about
19 nm in Pd-BIA-PSi-Fe3O4 nanoparticles, which is in a
good agreement with the crystallite size evaluated from
XRD at 11.5 nm and 18.5. As indicated in Figures 7 and
8, a fundamentally core–shell structure (dark colored
core for Pd and Fe3O4 nanoparticles and light-colored
shell for organic group) was concluded. This is a
2.1.5 | Thermogravimetric analysis
(TGA)
The thermal behavior of Pd-APM-PSi-Fe3O4 and Pd-BIA-
PSi-Fe3O4 was investigated by thermo-gravimetric analy-
sis (TGA) under an air atmosphere with a heating rate of
FIGURE 3 EDX spectrum of Pd-APM-PSi-
Fe3O4 [Colour figure can be viewed at
wileyonlinelibrary.com]

CHEN ET AL.
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FIGURE 4 EDX spectrum of d Pd-BIA-PSi-
Fe3O4Fig 3 EDX spectrum of Pd-APM-PSi-
Fe3O4 [Colour figure can be viewed at
wileyonlinelibrary.com]
FIGURE 5 TGA diagram of Pd-APM-PSi-
Fe3O4 [Colour figure can be viewed at
wileyonlinelibrary.com]
presentation of almost single crystalline character of Pd-
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 nanoparticles.
Fe3O4 displayed a sphere-like structure. It was appraised
to have individual crystallite sizes ranging 20 and 40 nm.
2.1.7 | Scanning electron microscope
(SEM)
2.1.8 | Magnetic properties of the
catalyst
The scanning electron microscope (SEM) uses a focused
beam of high-energy electrons to create a variety of sig-
nals at the surface of solid materials. The signals that
derive from electron-sample interactions exhibit informa-
tion about the sample including the size distribution, par-
ticle shape, external surface morphology and
fundamental physical properties, chemical composition,
and crystalline structure (Figures 9 and 10).
A vibrating sample magnetometer (VSM)was employed
for determining the magnetic properties of the Fe3O4,
Fe3O4– ClPSi, APM-PSi-Fe3O4 and BIA-PSi-Fe3O4, Pd-
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 at 300
K
(Figure 11 and 12). The magnetization curves for these
nanoparticles display no hysteresis in their magnetiza-
tions. As it can be observed in Figure 11, the saturation
magnetization values for Fe3O4, Fe3O4– ClPSi, APM-PSi-
Fe3O4 and Pd-APM-PSi-Fe3O4 were 80.1, 69.2, 54.5 and
42.6 emu g−1, respectively. Also, as displayed in
Figure 12, the saturation magnetization values for
In Figures 9 and 10, the SEM images of the Pd-APM-
PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 nanoparticle are shown.
The SEM images of Pd-APM-PSi-Fe3O4 and Pd-BIA-PSi-

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CHEN ET AL.
FIGURE 6 TGA diagram of Pd-BIA-PSi-
Fe3O4 [Colour figure can be viewed at
wileyonlinelibrary.com]
their response to an external magnetic field and reserved
its activity even after several cycles.
2.2 | Catalytic application of the Pd-
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 as
nanocatalyst
To find optimum conditions, the reaction of iodobenzene
and phenol for the synthesis of diphenyl ether in the
presence of the catalyst was performed as a model reac-
tion. The reaction was carried out with different amounts
of the Pd-BIA-PSi-Fe3O4 (5, 7, and 10 mol%) as nano cat-
alyst in several temperatures at various solvent. As can
be seen in Table 1, the optimum reaction conditions are
the Pd-BIA-PSi-Fe3O4 (7 mol%) in 7 ml DMF at 70 ꢀC.
In following of investigation, application of Pd-BIA-
PSi-Fe3O4, as nanocatalyst in the synthesis of diphenyl
FIGURE 7 TEM micrographs of Pd-APM-PSi-Fe3O4
nanoparticles
Fe3O4– ClPSi, BIA-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 were
80.1, 69.2, 50.0 and 41.7 emu g−1, respectively.
A low decrease of the saturation magnetization of Pd-
APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 observed due to
the connection of Pd on the surface of APM-PSi-Fe3O4
and BIA-PSi-Fe3O4 nanoparticles. In the other words,
these differences are because of the different coating
layers and their thicknesses on the surface of MNPs.
The result high values of saturation magnetization
Pd-APM-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 nanoparticles
can easily be separated and recycled from the products by
FIGURE 8 TEM micrographs of Pd-BIA-PSi-Fe3O4
nanoparticles

CHEN ET AL.
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PSi-Fe3O4 Pd-BIA-PSi-Fe3O4 are resembling to Pd-BIA-
PSi-Fe3O4 in the reactions.
2.3 | Comparing superiority of Pd-APM-
PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4
nanocatalysts over some previously
reported protocols
Finally, to exhibit the approachability of this work and
the activity of prepared catalyst for the synthesis of
diaryl ethers and its derivatives were compared with
some other reported heterogeneous catalysts in the lit-
erature in Table 3. The results expose that the reac-
tions in the presence of Pd-APM-PSi-Fe3O4 and Pd-
BIA-PSi-Fe3O4 as nanocatalysts were performed in
short times and high yields relative with simple work-
up procedure which makes it a applicable method for
the preparation of these compounds in comparison
with the other reported results in the literature
(Table 3).
FIGURE 9 The SEM images of Pd-APM-PSi-Fe3O4
nanoparticles [Colour figure can be viewed at wileyonlinelibrary.
com]
The most significant advantage of heterogeneous solid
catalyst in all of organic reactions is its recoverability and
reusability. Hence, the recoverability and reusability pre-
pared catalyst were studied using the selected model
reaction of iodobenzene and phenol in DMF (Table 2,
entry 1). After the com-platoon of the reaction, the
desired reaction mixture was cooled to room tempera-
ture. After that, the catalyst was recovered by an external
magnet and washed with deionized water and ethanol
and dried for the next experiment. According to the
results, the catalyst has the proper activity, reusability,
and stability in the reaction media and reused five times
without any loss of its activity (Figure 13, 14 and 15). In
the absence of the catalyst, the reaction under the similar
reaction conditions provided no product.
FIGURE 10 The SEM images of Pd-BIA-PSi-Fe3O4
nanoparticles [Colour figure can be viewed at wileyonlinelibrary.
com]
ether was studied. According to the results, the best
results obtained with choosing the amount of catalyst Pd-
APM-PSI-Fe3O4 (10 mol%) in 7 ml DMF at 70 ꢀC.
3 | EXPERIMENTAL
3.1 | Chemicals and apparatus
To investigate the scope and limitations of Pd-APM-
PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4 as catalyst a variety of
phenols reacted with various substituted phenyl halides
under the optimum reaction conditions and the results
are reported in Table 2. It was concluded that chloroben-
zene tolerated the reaction conditions and obtained the
corresponding product in excellent efficiency. The turn-
over number indicates the maximum use that can be
made of a catalyst for a unique reaction under defined
conditions by a number of molecular reactions or reac-
tion cycles occurring at the reactive center up to the
decay of activity. It also seen that the results of Pd-APM-
All reagents were purchased from Merck and Aldrich
and used without further purification. The X-ray powder
diffraction (XRD) of the desired catalyst was carried out
on a Philips PW 1830 X-ray diffractometer with CuKα
source (λ = 1.5418 Å) inꢀ a range of Bragg's angle
(10–80ꢀ) at temperature 25 C. Fourier transform infra-
red (FT-IR) spectrum was performed using a FT-IR
spectrometer (Vector 22- Bruker) in the range of
400–4000 cm−1 at room temperature. Scanning electron
microscopy (SEM) analysis was recorded using VEGA//
TESCAN KYKY-EM 3200 microscope (acceleration

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CHEN ET AL.
FIGURE 11 Room temperature
magnetization curves of Fe3O4, Fe3O4– ClPSi,
APM-PSi-Fe3O4 and Pd-APM-PSIFe3O4
nanoparticle [Colour figure can be viewed at
wileyonlinelibrary.com]
FIGURE 12 Room temperature
magnetization curves of Fe3O4 , Fe3O4– ClPSi,
BIA-PSi-Fe3O4 and Pd-BIA-PSi-Fe3O4
nanoparticle [Colour figure can be viewed at
wileyonlinelibrary.com]
TABLE 1
Optimization conditions for preparation of diphenyl ether in the presence of Pd-BIA-PSi-Fe3O4 as magnetic nanocatalyst
Amount of the
catalyst (mol%)
Entry
Solvent
CH3OH
DMF
Temperature (ꢀC)
Time (hr)
Yield(%)a
TON
6.5
8.0
4.5
6.0
9.9
----
8
TOF (h−1
0.72
2.66
0.5
)
1
10
10
10
10
10
10
5
60
110
100
70
9
3
65
80
2
3
H2O
9
45
4
CH3CN
DMSO
DMF
6
60
1
5
140
25
1.5
10
4
99
6.6
6
Trace
40
-----
2
7
DMF
50
8
7
DMF
50
4
55
7.8
6.0
16
1.95
1.5
9
10
5
DMF
50
4
60
10
11
12
DMF
70
2
80
8
7
DMF
70
1.5
1.5
98
14
9.33
6.6
10
DMF
70
99
9.9
aYields refer to isolated product.

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TABLE 3
Comparison the results of Pd-APM-PSI-Fe3O4 and Pd-BIA-PSi-Fe3O4 with other catalysts in the Ullman reaction
Entry
Catalyst
Conditions
Time
45 min
4 hr
Yield (%)a [Ref]
1
2
3
4
5
6
7
8
9
CNC-BIA-Pd (0.2%mol)
KF/CP (0.62 g),
K2CO3,,DMSO, 80 ꢀC
DMSO, 110–115 ꢀC
K3PO4, DMF, 100 ꢀC
Chxn-Py-Al, MeCN, 110 ꢀC
K2CO3(2.0 eq), DMSO
K3PO4, toluene, 100 ꢀC
Cs2CO3, DMSO, 120 ꢀC
K2CO3, DMF, 70 ꢀC
K2CO3, DMF, 70 ꢀC
90 [16]
96 [42]
80 [43]
80 [44]
76 [45]
90 [46]
93 [47]
Copper(I)-Bipyridyl (0.5–5 mol%),
Cs2CO3(2 mmol), Cu2O(5 mol%),
GO-Pd17SE15 (1.0 mol % Pd),
Pd (OAc)2 (2.0 eq)
48 hr
36 hr
3 hr
10 hr
12 hr
1.5 hr
1.5 hr
Cu/RGO-Fe3O4 nanocoposite
Pd-APM-PSI-Fe3O4 (7 mol %)
Pd-BIA-PSi-Fe3O4 (10 mol %)
98 (Present work)
97 (Present work)
aYields refer to isolated pure products.
spectra were evaluated in DMSO-d6 as a solvent. Mag-
netic measurements were performed using a vibration
sample magnetometer (VSM, MDK, and Model 7400)
analysis. The metal loading was discerned by induc-
tively coupled plasma-atomic emission spectrometer
(ICP-AES). Melting points were estimated on an Elec-
trothermal 9100 apparatus.
FIGURE 13 Image shows that Pd-APM-PSI-Fe3O4 or Pd-
BIA-PSi-Fe3O4magnetic nanocatalysts can be separated by using
magnetic field. A reaction mixture in the absence (right) or
presence of a magnetic field (left) [Colour figure can be viewed at
wileyonlinelibrary.com]
3.2 | General procedure
3.2.1 | Preparation of the magnetic Fe3O4
nanoparticles (MNPs)
FIGURE 14 The reusability of Pd-APM-
PSI-Fe3O4 as catalyst [Colour figure can be
viewed at wileyonlinelibrary.com]
voltage 26 kV). The spectrum of elemental analysis of
catalyst was examined by energy dispersive X-ray
(EDX), VEGA3 XUM/TESCAN). Thermogravimetric
analysis (TGA) was performed on a Stanton Red craft
STA-780 (London, UK). NMR spectra were recorded
with a Bruker DRX-400 AVANCE (Merck and Aldrich)
To prepare of magnetic Fe3O4 nanoparticles (MNPs),
first, FeCl3.6H2O (4.865 g, 0.018 mol) and FeCl2·4H2O
(1.789 g, 0.0089 mol) were added to 100 ml deionized
water and after that, sonicated to dissolve all of salts
completely. Afterwards, 10 ml of 25% NH4OH (10 ml)
was added rapidly into the reaction mixture in one part
under N2 atmosphere at room temperature followed by
1
instrument (300.1 MHz for H, 75.4 MHz for 13C). The

CHEN ET AL.
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FIGURE 15 The recycling of Pd-
BIA-PSi-Fe3O4 as nanocatalyst [Colour
figure can be viewed at
wileyonlinelibrary.com]
stirring about 25 min with magnetic stirrer. The black
precipitate was washed with deionized water for four
times (Scheme 2).
product of 2-Aminopyrimidine and 1H-benzo[d]
imidazol-2–amine coated iron oxide nanoparticles
(Scheme 4).
3.2.2 | Preparation of 3-chloropropyl
trimethoxy silane functionalizedFe3O4
nanoparticles (Fe3O4– ClPSi)
3.2.4 | Preparation of Pd-APM-PSi-Fe3O4
and Pd-BIA-PSi-Fe3O4 nanoparticles
To prepare of Pd-APM-PSI-Fe3O4 and Pd-BIA-PSi-
Fe3O4 nanoparticles, first, Pd (OAc)2 (0.5 mmol,
0.11 g) and BIA-PSi-Fe3O4 or APM-PSi-Fe3O4
(0.25 mmol, 0.06 g) were dissolved in ethanol (10 ml)
in a 25 mlr round-bottom flask under nitrogen atmo-
sphere. Then, the mixture was stirred at 60 ꢀC for
24 hr. After the complete reaction, the (Pd-APM-PSI-
Fe3O4), (Pd-BIA-PSi-Fe3O4) nanoparticles ware sepa-
rated by a magnetic, washed with deionized water and
ethanol several times and then dried in an oven for
overnight (Scheme 5).
First, 1.5 g of the obtained magnetic Fe3O4 nanoparticles
(MNPs) in the preceding step were added to 100 ml of
ethanol and placed in the supersonic apparatus for
25 min. Then 2.5 ml of 3-chloropropyl trimethoxy silane
was added to it in reflux condition and stirred for 3.5 hr
with mechanical stirrer. The obtained precipitate was fil-
tered off with an external magnet and washeꢀd twice with
ethanol and finally overnight at oven at 85 C to obtain
3-chloropropyl triethoxy silane nanoparticles coated with
3-chloropropyl triethoxy silane (Scheme 3).
3.2.3 | Preparation of APM-PSi-Fe3O4
and BIA-PSi-Fe3O4 nanoparticles
3.2.5 | General procedure for the
synthesis of diaryl ethers via Ullmann
coupling reaction using Pd-APM-PSi-Fe3O4
and Pd-BIA-PSi-Fe3O4 as the magnetic
nanocatalyst
Here, 1.5 g of obtained Fe3O4 nanoparticles were added
to 150 ml of ethanol and placed in the supersonic appara-
tus for 30 min. Then 1 g of 2-Aminopyrimidine or 1H-
benzo [d] imidazol-2-amine was added under reflux con-
ditions and stirred vigorously with mechanical stirrer for
8 hr. The obtained precipitate was filtered off with an
external magnet and rinsed with ethanol several times
and placed in the oven for 24 hr to dry and obtained the
To prepare diaryl ethers using Ullmann coupling reaction
via O-arylation reactions from aryl halide (1 mmol), phe-
nol derivative (1 mmol) and 0.1 g of K2CO3 in DMF
(7 mL) were placed into a round bottom flask containing
SCHEME 2 Preparation of magnetic Fe3O4 nanoparticles
SCHEME 3 Preparation of Fe3O4– ClPSi magnetic
(MNPs). [Colour figure can be viewed at wileyonlinelibrary.com]
nanoparticles (MNPs)

14 of 15
CHEN ET AL.
SCHEME 4 Preparation of APM-
PSi-Fe3O4 and BIA-PSi-Fe3O4
magnetic nanoparticles
4 | CONCLUSION
SCHEME 5 Preparation of Pd-APM-PSI-Fe3O4
and Pd-BIA-PSi-Fe3O4 magnetic nanoparticles
Pd-BIA-PSi-Fe3O4 (7 mol%) or Pd-APM-PSi-Fe3O4
(10 mol%) of the catalyst. The obtained mixture was
refluxed at 70 C for 1.5 hr under robust stirring. The
reaction mixture was cooled after the completion of the
reaction and the solvent was removed under the reduced
pressure. Then, the mixture was diluted with CH2Cl2 and
the catalyst was separated by an external magnet. The fil-
trate was vaporized on a rotary evaporator and the crude
product was purified by column chromatography using
ethyl acetate/n-hexane.
In conclusion, it was prepared an organic–inorganic
hybrid recoverable heterogeneous catalyst based on Pd-
2-aminopyrimidine or 1H-benzo[d]imidazol-2-amine
functionalizedFe3O4 nanoparticles (Pd-APM-PSi-Fe3O4
and Pd-BIA-PSi-Fe3O4) and characterized by FT-IR,
XRD, TGA, TEM, SEM, EDX, ICP-AES analysis and VSM
techniques. Prepared Pd-APM-PSi-Fe3O4 and Pd-BIA-
PSi-Fe3O4 nanocatalysts were used for Ullmann coupling
reactions of aryl halide to synthesis of diphenyl ether
compounds in DMF solvent at 70 Cꢀ. As it can be seen
from obtained results, aryles derivatives provide the
desirable products in high to excellent yields. This meth-
odology proposes a general way of developing reusable
and heterogeneous (Pd) metal–ligand catalyst. Also, this
method has advantages such as simple procedure, easy
separation, biocompatibility, high yields of obtained
products and good reversibility.
ꢀ
Selected spectra for two known products are given
below:
3-Nitrophenyl-2,6-dimethoxyphenyl ether (Table 2, entry
10): m.p.: 36–38 ꢀC; 1H NMR (400.13 MHz, DMSO):
δ = 4.11 (s, 6H, OCH3), 6.58–6.66 (m, 3H), 7.16–7.18 (m,
2H), 7.32–7.38 (m, 2H) ppm.; 13C NMR (100.6 MHz,
DMSO): δ = 52.2, 117.8, 117.2, 118.2, 121.2, 124.6, 127.2,
128.9, 132.2, 131.4, 133.2 ppm.
ACKNOWLEDGEMENTS
3-Nitrophenyl-2,6-dimethylphenyl ether (Table 2, entry
11): m.p.: 40–41 ꢀC; 1H NMR (400.13 MHz, DMSO):
δ = 2.11 (s, 6H, CH3), 7.00–7.12 (m, 3H), 7.22–7.25 (m,
3H), 7.36 (s, 1H) ppm.; 13C NMR (100.6 MHz, DMSO):
δ = 22.5, 121.0, 121.0, 124.1, 127.1, 127.5, 128.2, 129.2,
130.2, 131.1, 134.2 ppm.
This research was supported by the Research Council of
the Islamic Azad University in Iran.
ORCID
Majid Mohammadnia https://orcid.org/0000-0001-
8172-8244

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How to cite this article: Chen J, Dai L, Li J,
Mohammadnia M. Pd based on 2-
Aminopyrimidine and 1H-benzo[d]imidazol-2-
amine functionalizedFe3O4 nanoparticles as novel
recyclable magnetic nanocatalysts for Ullmann
coupling reaction. Appl Organomet Chem. 2020;
e5708. https://doi.org/10.1002/aoc.5708