A new nano-Fe3O4-supported organocatalyst based on 3,4-dihydroxypyridine: an efficient heterogeneous nanocatalyst for one-pot synthesis of pyrazolo[3,4-b]pyridines and pyrano[2,3-d]pyrimidines

Article abstract of DOI:10.1002/aoc.3534

A simple and practical strategy for the synthesis of a novel nano-Fe₃O₄-supported organocatalyst system based on 3,4-dihydroxypyridine (Fe₃O₄/Py) has been developed. The prepared catalyst was characterized using

Full text of DOI:10.1002/aoc.3534

Full paper
Received: 28 April 2016
Revised: 7 May 2016
Accepted: 12 May 2016
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.3534
A new nano-Fe3O4-supported organocatalyst
based on 3,4-dihydroxypyridine: an efficient
heterogeneous nanocatalyst for one-pot
synthesis of pyrazolo[3,4-b]pyridines
and pyrano[2,3-d]pyrimidines
Mozhgan Pirhayatia, Ali Kakanejadifarda and Hojat Veisib*
A simple and practical strategy for the synthesis of a novel nano-Fe3O4-supported organocatalyst system based on 3,4-
dihydroxypyridine (Fe3O4/Py) has been developed. The prepared catalyst was characterized using Fourier transform infrared
spectroscopy, transmission and scanning electron microscopies, X-ray diffraction, vibrating sample magnetometry and energy-
dispersive X-ray analysis. Accordingly, the Fe3O4/Py nanoparticles show a superparamagnetic property with a saturation
magnetization of 61 emu gꢀ1, indicating potential application in magnetic separation technology. Our experimental results reveal
that the pyridine-functionalized Fe3O4 nanoparticles are an efficient base catalyst for the domino condensation of various
aromatic aldehydes, Meldrum’s acid and 5-methylpyrazol-3-amine under very mild reaction condition and in the presence of
ethanol solvent. Moreover, the synthesized catalyst was used for one-pot, three-component condensation of aromatic aldehydes
with barbituric acid and malononitrile to produce 7-amino-2,4-dioxo-5-phenyl-2,3,4,5-tetrahydro-1H-pyrano[2,3-d]pyrimidine-6-
carbonitriles. All reactions are completed in short times and all products are obtained in good to excellent yields. Also, notably,
the catalyst was reused five times without significant degradation in catalytic activity and performance. Copyright © 2016 John
Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web-site.
Keywords: magnetic-supported organocatalyst; pyridine; heterogeneous catalyst; pyrazolo[3,4-b]pyridines; pyrano[2,3-d]pyrimidines
conditions.[19] So far, pyridines, alkaloids, amino acids and their
derivatives, pyrrolidine, biguanidine, piperidine and sulfamic acid
Introduction
In recent years, organocatalysis has attracted much attention as a
powerful methodology in organic synthesis for the construction
of new compounds. The application of organocatalytic systems
for fine chemical synthesis provides some advantages such as lack
of sensitivity to moisture and oxygen, ready availability, low cost
and low toxicity.[1–3] The interest in these organocatalytic systems
is attributed to the fact that they possess direct benefits in organic
synthesis, when compared with other catalytic systems.[4–6] However,
the capability and applicability of an organocatalyst in organic
transformations can be improved if its recovery and reuse
procedure become increasingly facile.[7–9] So briefly the recycling
capability of an organocatalyst has the following advantages:
simplicity in practical separation of catalyst from products and
reaction mixture, economic impacts, avoiding wastes and
potential for the application in large-scale operations.[10–12]
Considering these points, the development of a recyclable
organocatalyst with high catalytic performance is the main subject
of many current studies.[13,14] There are various reported methods
for the preparation of recyclable organocatalytic systems.[15–18]
Among the strategies used, the preparation of solid-supported
organocatalysts is potentially a highly useful method to obtain
more efficient catalytic systems for the synthesis of fine chemicals
under especially simple, mild and environmentally benign
are the most used materials supported on solid substrate
organocatalysts.[20–26] In this regard, nano-Fe3O4 has attracted
much attention due to its unique physical properties such as high
surface area, excellent thermal and chemical stability, low toxicity
and potential applications. Magnetic catalysts can be recycled
using an external magnetic field and reused in subsequent
reactions. It has also been used to support various metal
nanoparticles as magnetically recoverable nanocatalysts in organic
transformations.[27]
Owing to these properties and attractive features, in continuation
of our research programme to develop selective, efficient and
green methods and catalysts in organic synthesis,[28] we have
used Fe3O4 as a promising support for heterogenization of 3,4-
dihydroxypyridine to make a new magnetically recoverable
heterogeneous catalyst (Scheme 1).
*
Correspondence to: Hojat Veisi, Department of Chemistry, Payame Noor
University, 19395-4697 Tehran, Iran. E-mail: hojatveisi@yahoo.com
a Department of Chemistry, Faculty of Science, Lorestan University, Khoramabad,
Iran
b Department of Chemistry, Payame Noor University, Tehran, Iran
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.

M. Pirhayati et al.
FeCl3.6H2O
FeCl2.4H2O
(40 mg; ca 20 mol%) and ethanol (5 ml) in a round-bottomed flask.
The resulting mixture was vigorously stirred at room temperature
until completion of the reaction as monitored by TLC (n-hexane–-
acetone, 3:1). After completion of the reaction, 10 ml of hot ethanol
was added, and the catalyst was removed using an external mag-
net. The crude product was purified by recrystallization from
ethanol affording pure products.
N
NH4OH, N2
N
OH
O
O
HO
OH
OH
OH
HO
OH
O
HO
O
OH
Fe3O4
Fe3O4
HO
HO
20 min
O
O
OH
N
OH
N
Results and discussion
Fe3O4 NPs
Fe3O4 NPs/Py
The Fe3O4/Py catalyst was prepared using the concise route
outlined in Scheme 1. Naked Fe3O4 MNPs were prepared through
a chemical co-precipitation method, and subsequently were coated
with 3,4-dihydroxypyridine to achieve Fe3O4/Py. Finally, the mixture
was collected using an external magnet, followed by drying in
vacuum. The prepared catalyst was characterized using Fourier
transform infrared (FT-IR) spectroscopy, transmission electron
microscopy (TEM), X-ray diffraction (XRD), vibrating sample magne-
tometry (VSM), energy-dispersive X-ray spectroscopy (EDX) and
field emission scanning electron microscopy (SEM).
FT-IR spectra of Fe3O4 and Fe3O4/Py are shown in Fig. 1. The FT-IR
spectrum of the MNPs alone shows a stretching vibration at
3408 cmꢀ1 which incorporates the contributions from both
symmetric and asymmetric modes of the O–H bonds which are at-
tached to the surface of iron atoms.[29] The bands at low
wavenumbers (≤700 cmꢀ1) come from vibrations of Fe–O bonds
of iron oxide, which for bulk Fe3O4 appear at 570 and 375 cmꢀ1
but for Fe3O4 nanoparticles at 624 and 572 cmꢀ1 as a blue shift,
due to the size reduction.[30] The presence of an adsorbed water
layer is confirmed by a band for the vibrational stretch mode of
water found at 1625 cmꢀ1. The FT-IR spectra of Fe3O4/Py and
Fe3O4 show Fe–O vibrations in the same vicinity. The introduction
Scheme 1. Preparation of Fe3O4/Py nanocatalyst.
Experimental
Preparation of Fe3O4 magnetic nanoparticles (MNPs)
MNPs were prepared via co-precipitation of Fe(III) and Fe(II) ions
with a molar ratio of 2:1 in the presence of ammonium hydroxide.
Generally, a mixture of FeCl3ꢁ6H2O (5.838 g, 0.0216 mol) and
FeCl2ꢁ4H2O (2.147 g, 0.0108 mol) was dissolved in 100 ml of
deionized water at 85 °C under nitrogen atmosphere and vigorous
mechanical stirring (500 rpm). Afterwards, 10 ml of 25% NH4OH was
quickly injected into the reaction mixture in one addition. The
addition of the base to the Fe2+/Fe3+ salt solution resulted in the
instant formation of a black precipitate of MNPs. The reaction
continued for another 25 min and the mixture was cooled to room
temperature. The MNPs as a dark solid were isolated from the
solution by magnetic separation and washed several times with
deionized water.
Preparation of Fe3O4/Py
Fe3O4 MNPs (500 mg) were dispersed in ethanol (30 ml) and
sonicated for 20 min. 3,4-Dihydroxypyridine (2 mmol) dissolved in
ethanol (10 ml) was added to this solution and again sonicated
for 20 min. After mechanical agitation at 25 °C for 24 h, the
suspended substance was separated using an external magnet
and washed with water and ethanol. The 3,4-dihydroxypyridine-
functionalized Fe3O4 (Fe3O4/Py) obtained was dried at 40 °C under
vacuum. The pyridine content of the catalyst based on elemental
analysis (CHN) was estimated to be 0.45 mmol gꢀ1
.
General procedure for synthesis of 3-methyl-4-aryl-2,4,5,7-
tetrahydropyrazolo[3,4-b]pyridin-6-ones in presence of Fe3O4/Py
A mixture of aldehydes (1 mmol), Meldrum’s acid (1 mmol) and
5-methylpyrazol-3-amine (1 mmol) was added to a mixture of
Fe3O4/Py (40 mg; ca 20 mol%) and ethanol (3 ml) in a round-
bottomed flask. The resulting mixture was vigorously stirred at
reflux temperature until completion of the reaction as monitored
by TLC (n-hexane–acetone, 4:1). After completion of the reaction,
10 ml of hot ethanol was added, and the catalyst was removed
using an external magnet. The crude product was purified by
recrystallization from ethanol affording pure products.
General procedure for synthesis of 7-Amino-2,4-dioxo-5-phenyl-
2,3,4,5-tetrahydro-1H-pyrano[2,3-d]pyrimidine-6-carbonitrile
derivatives in presence of Fe3O4/Py
A mixture of aldehydes (1 mmol), malononitrile (1 mmol) and
barbituric acid (1 mmol) was added to a mixture of Fe3O4/Py
Figure 1. FT-IR spectra of (a) Fe3O4 and (b) Fe3O4/Py.
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Pyridine-functionalized Fe3O4 nanoparticles as basic organocatalyst
of pyridine groups to the surface of MNPs is confirmed by the
bands at 1627, 1432 and 3000 cmꢀ1 assigned to C¼N, C¼C and
C–H stretching vibrations, respectively (Fig. 1).
The morphology and size of the Fe3O4/Py nanocomposite were
investigated using SEM (Fig. 2(a)) and TEM (Fig. 2(b)). TEM
micrographs confirm the spherical shape of Fe3O4. The EDS
spectrum of Fe3O4/Py (Fig. 3) clearly shows the presence of Fe, C
and N in the MNPs.
The XRD pattern of Fe3O4/Py is presented in Fig. 4(a). The
characteristic diffraction peaks at 2θ of 30.3°, 35.7°, 43.4°, 53.8°,
57.2° and 62.8° correspond to the diffraction of (220), (311), (400),
(422), (511) and (440) of Fe3O4. The entire diffraction pattern
matches with the magnetic cubic structure of Fe3O4 (JCPDS
65–3107).[35] The magnetic properties of samples containing a
magnetite component were studied using VSM at room
temperature. The saturation magnetization of Fe3O4/Py was
determined as 61.0 emu gꢀ1 (Fig. 4(b)).
Meldrum’s acid and 5-methylpyrazol-3-amine into 3-methyl-4-phe-
nyl-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridine-6-one in the presence
of Fe3O4/Py was chosen as model. In order to establish the
optimum conditions for this reaction, initially the influences of the
reaction temperature, the amount of catalyst and the reaction time
were tested and optimized. The results are summarized in Table 1.
As is evident from Table 1 (entry 7), the optimal catalyst loading of
20 mol% and at 80 °C in EtOH for the synthetic process affords the
highest yield of product (96%). It should be noted that the optimal
catalyst loading in the synthesis of 3-methyl-4-phenyl-2,4,5,7-
tetrahydropyrazolo[3,4-b]pyridine-6-one product peaks at a con-
centration of 20 mol%. When the amount of catalyst is lower, the
yield of the product decreases (Table 1, entry 9), whereas raising
the catalyst concentration does not lead to a pronounced increase
to the product yield (Table 1, entry 8). In the absence of catalyst,
lower product yield is observed, even after prolonged reaction time
(Table 1, entry 11).
The catalytic activity of Fe3O4/Py was explored in the synthesis of
pyrazolopyridone derivatives. To develop optimal reaction condi-
tions, the one-pot multicomponent condensation of benzaldehyde,
Under the optimal conditions, the scope and generality of the re-
action were explored. A variety of aryl aldehydes were investigated
to react with Meldrum’s acid and 5-methylpyrazol-3-amine over a
120 min reaction period, and the results are summarized in
Table 2. Aldehydes containing various electron-donating and
electron-withdrawing substituents react under the experimental
conditions, and the corresponding products are obtained in good
yields. Therefore, no marked electronic effects are observed in the
reaction. Good yield is also obtained when alkyl aldehydes are
reacted (Table 2, entries 14 and 15).
The structures of all compounds were established using spectro-
scopic (FT-IR, 1H NMR, 13C NMR, mass) and elemental analyses and
those of known products by comparison of their spectral data and
melting points with literature reports.
Finally, to assess the present protocol with respect to other re-
ported methods for the preparation of 3-methyl-4-aryl-2,4,5,7-
tetrahydropyrazolo[3,4-b]pyridine-6-ones, the present procedure
Figure 2. (a) SEM and (b) TEM images of Fe3O4/Py.
Table 1. Effect of solvent, temperature, reaction time and amount of
catalyst on the synthesis of 3-methyl-4-phenyl-2,4,5,7-tetrahydropyrazolo
[3,4-b]pyridine-6-onea
Entry Solvent Catalyst (mol%) Temp. (°C) Time (min) Yield (%)
1
MeOH
H2O
20
20
20
20
20
20
20
40
10
20
0
65
78
60
40
110
82
80
80
80
25
80
240
240
240
240
240
240
120
120
120
240
240
50
45
60
50
55
70
96
96
80
20
55
2
3
CH3Cl
CH2Cl2
Toluene
CH3CN
EtOH
Figure 3. EDS data for Fe3O4/Py.
4
5
6
7
8
EtOH
9
EtOH
10
11
EtOH
EtOH
aReaction conditions: 5-methylpyrazol-3-amine (1 mmol), aldehydes
(1 mmol), Meldrum’s acid (1 mmol) and solvent (3 ml).
Figure 4. (a) XRD pattern and (b) VSM curve of Fe3O4/Py.
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.
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M. Pirhayati et al.
Table 2. Synthesis of 3-methyl-4-aryl-2,4,5,7-tetrahydropyrazolo[3,4-b]
pyridine-6-onesa
Entry
Aldehyde
C6H5CHO
Yield (%)b
M.p. (°C)
M.p. (°C)
1
96
95
96
96
90
90
95
92
95
92
85
90
90
75
75
303–305 304–306[32]
2
4-MeC6H4CHO
4-MeOC6H4CHO
3-NO2C6H4CHO
4-ClC6H4CHO
>300
>300[31]
308–310[32]
3
>300
4
266–268 264–266[34]
5
>300
>300
>300
>300
>300
>300
>300[34]
>300[31]
>300[34]
>300[35]
>300[35]
>300[34]
6
2-MeC6H4CHO
4-N(Me)2C6H4CHO
2-ClC6H4CHO
7
Figure 5. Reusability of Fe3O4/Py.
8
9
3,4,5-(MeO)3C6H2CHO
2,4-Cl2C6H3CHO
4-OHC6H4CHO
2-MeOC6H4CHO
2-Thienylaldehyde
Butanal
derivatives based on condensation of an aromatic aldehyde,
barbituric acid and malononitrile under optimized conditions.
Various aryl aldehydes were reacted with barbituric acid and
malononitrile over a 60 min reaction period, and the results are
summarized in Table 4. Aldehydes containing electron-donating
and electron-withdrawing substituents give the corresponding
products in good yields, and hence no electronic effects are
observed in the reactions.
10
11
12
13
14
15
274–276 274–276[34]
278–280 279–280[34]
300–302 303–305[32]
258–260 259–260[31]
290–292 290–292[34]
2-Propanal
aGeneral procedure: 5-methylpyrazol-3-amine (1 mmol), aldehydes
(1 mmol), Meldrum’s acid (1 mmol), Fe3O4/Py (20 mol%), EtOH (3 ml),
120 min at 80 °C.
bYield of isolated product.
Table 4. Synthesis of 7-amino-2,4-dioxo-5-phenyl-2,3,4,5-tetrahydro-
1H-pyrano[2,3-d]pyrimidine-6-carbonitrilea
was compared with some results for previously reported catalysts.
From Table 3, it can be seen that the present system exhibits higher
conversions and yields compared to the other reported systems.
The reusability of the catalyst in the reaction of benzaldehyde,
Meldrum’s acid and 5-methylpyrazol-3-amine in ethanol at 80 °C
was studied. In this procedure, after completion of each reaction,
hot ethanol was added to the reaction mixture which was then
shaken for a few minutes to dissolve the product. The catalyst
was separated using a magnet, washed with hot ethanol and dried.
The recovered catalyst was reused five times without any signifi-
cant loss of activity (Fig. 5). In addition, attractive features of this
novel catalyst system are the rapid (within 15 s) and efficient sepa-
ration of the catalyst (100%) using an appropriate external magnet,
which minimizes the loss of catalyst during separation.
Entry
Aldehyde
C6H5CHO
Yield (%)b
M.p. (°C)
M.p. (°C)
1
2
3
4
5
6
96
95
96
96
90
95
206–208
162–164
280–282
232–234
242–244
180–182
205–207[36]
160–163[36]
279–280[36]
230–234[36]
242–244[37]
182–184[36]
4-MeC6H4CHO
4-MeOC6H4CHO
4-NO2C6H4CHO
4-ClC6H4CHO
4-N(Me)2C6H4CHO
aGeneral procedure: barbituric acid (1 mmol), aldehydes (1 mmol),
malononitrile (1 mmol), Fe3O4/Py (20 mol%), EtOH (5 ml), 60 min at
25 °C.
bYield of isolated product.
Continuing our work, the catalytic activity of Fe3O4/Py was also
evaluated in the multicomponent synthesis of 7-amino-2,4-dioxo-
5-phenyl-2,3,4,5-tetrahydro-1H-pyrano[2,3-d]pyrimidine-6-carbonitrile
Table 3. Comparison of activity of various catalysts in the synthesis of pyrazolo[3,4-b]pyridine-6-ones
Aldehyde
Catalyst
Reaction conditions
Yield (%)
Ref.
4-MeOC6H4CHO
Fe3O4/Py
EtOH, 80 °C, 120 min
EtOH, 60 °C, 3 min
100 °C, 8 min
96
87
92
90
89
96
90
90
95
This study
[32]
Ultrasound
[33]
[34]
[31]
Microwave irradiation
Fe3+@K10
H2O 100 °C, 12 min
90 °C, 15 min
(PEG)-400
C6H5CHO
Fe3O4/Py
Fe3+@K10
EtOH, 80 °C, 120 min
90 °C, 10 min
This study
[34]
[33]
[32]
Microwave irradiation
Ultrasound
100 °C, 9 min
EtOH, 60 °C, 3 min
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Copyright © 2016 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. (2016)

Pyridine-functionalized Fe3O4 nanoparticles as basic organocatalyst
[17] Q. Gao, S.-M. Lu, Y. Liu, C. Li, Tetrahedron Lett. 2011, 52, 3779.
[18] F. Giacalone, M. Gruttadauria, P. Agrigento, V. Campisciano, R. Noto,
Catal. Commun. 2011, 16, 75.
[19] A. Schatz, O. Reiser, W. J. Stark, Chem. Eur. J. 2010, 16, 8950.
[20] A. R. Karimi, H. R. Momeni, R. Pashazadeh, Tetrahedron Lett. 2012, 53,
3440.
[21] R. Willand-Charnley, T. J. Fisher, B. M. Johnson, P. H. Dussault, Org. Lett.
2012, 14, 2242.
[22] H. S. Kim, Y.-M. Song, J. S. Choi, J. W. Yang, H. Han, Tetrahedron 2004, 60,
12051.
[23] C.-L. Cao, M.-C. Ye, X.-L. Sun, Y. Tang, Org. Lett. 2006, 8, 2901.
[24] A. Alizadeh, M. M. Khodaei, D. Kordestani, A. H. Fallah, M. Beygzadeh,
Micropor. Mesopor. Mater. 2012, 159, 9.
[25] C. Mukhopadhyay, S. Ray, Catal. Commun. 2011, 12, 1496.
[26] H. Veisi, A. Sedrpoushan, B. Maleki, M. Hekmati, M. Heidari, S. Hemmati,
Appl. Organometal. Chem. 2015, 29, 834.
Conclusions
In summary, we have synthesized the first MNPs–pyridine (Fe3O4/
Py) for use as a magnetically heterogeneous basic nanocatalyst.
The catalyst is easily synthesized and can catalyse the synthesis of
3-methyl-4-aryl-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridine-6-ones
via the domino condensation of various aromatic aldehydes,
Meldrum’s acid and 5-methylpyrazol-3-amine under mild condi-
tions. Moreover, the synthesized catalyst was found to be environ-
mentally friendly with a high catalytic performance for one-pot,
three-component condensation of aromatic aldehydes with
barbituric acid and malononitrile to produce 7-amino-2,4-dioxo-5-
phenyl-2,3,4,5-tetrahydro-1H-pyrano[2,3-d]pyrimidine-6-
carbonitriles. The characteristic aspects of this catalyst are rapid,
simple and efficient separation using an appropriate external mag-
net, which minimizes the loss of catalyst during separation and re-
usability several times without any significant loss of activity.
[27] V. Polshettiwar, R. Luque, A. Fihri, H. Zhu, M. Bouhrara, J.-M. Basset,
Chem. Rev. 2011, 111, 3036.
[28] a) M. Pirhayati, H. Veisi, A. Kakanejadifard, RSC Adv. 2016, 6, 27252. b)
H. Veisi, A. Maleki, S. Jahangard, Tetrahedron Lett. 2015, 56, 1882. c)
H. Veisi, N. Morakabati, New J. Chem. 2015, 39, 2901. d) H. Veisi,
A. Sedrpoushan, B. Maleki, M. Hekmati, M. Heidari, S. Hemmati, Appl.
Organometal. Chem. 2015, 29, 834. e) H. Veisi, A. Sedrpoushan,
S. Hemmati, Appl. Organometal. Chem. 2015, 29, 825. f) B. Maleki,
S. Hemmati, A. Sedrpoushan, S. Sedigh Ashrafi, H. Veisi, RSC Adv.
2014, 4, 40505. g) H. Veisi, A. Rashtiani, V. Barjasteh, Appl.
Organometal. Chem. 2016, 30, 231. h) H. Veisi, M. Ghadermazi,
A. Naderi, Appl. Organometal. Chem. 2016, 30, 341.
Acknowledgements
We are grateful to Payame Noor University and Lorestan University
for partial support of this work.
[29] S. Luo, X. Zheng, H. Xu, X. Mi, L. Zhang, J.-P. Cheng, Adv. Synth. Catal.
2007, 349, 2431.
[30] A. K. Diallo, C. Ornelas, L. Salmon, J. Ruiz Aranzaes, D. Astruc, Angew.
Chem. Int. Ed. Engl. 2007, 46, 8644.
References
[1] B. List, Chem. Rev. 2007, 107, 5413.
[2] K. N. Houk, B. List, Acc. Chem. Res. 2004, 37, 487.
[3] D. Enders, O. Niemeier, A. Henseler, Chem. Rev. 2007, 107, 5606.
[4] C. Allemann, R. Gordillo, F. R. Clemente, P. H.-Y. Cheong, K. N. Houk, Acc.
Chem. Res. 2004, 37, 558.
[5] D. Enders, C. Wang, J. X. Liebich, Chem. Eur. J. 2009, 15, 11058.
[6] W. Sun, G. Zhu, L. Hong, R. Wang, Chem. Eur. J. 2011, 17, 13958.
[7] S. H. Youk, S. H. Oh, H. S. Rho, J. E. Lee, J. W. Lee, C. E. Song, Chem.
Commun. 2009, 2220.
[31] X. Zhong, G. Dou, D. Wang, Molecules 2013, 18, 13139.
[32] A. Azimi-Roshan, M. Mamaghani, N. O. Mahmoodi, F. Shirini, Chin.
Chem. Lett. 2012, 23, 399.
[33] N. Ma, B. Jiang, G. Zhang, W. Tu, S.-J. Wever, G. Li, Green Chem. 2010, 12,
1357.
[34] M. Mamaghani, F. Shirini, N. O. Mahmoodi, A. Azimi-Roshan,
H. Hashemlou, J. Mol. Struct. 2013, 1051, 169.
[35] A. Stein, Adv. Mater. 2003, 15, 763.
[8] Y. Zhang, Y. Zhang, Y. L. Sun, X. Du, J. Y. Shi, W. D. Wang, W. Wang,
[36] D. K. Yadav, M. A. Quraishi, J. Mater. Environ. Sci. 2014, 5, 1075.
[37] J. Yu, H. Wang, Synth. Commun. 2005, 35, 3133.
Chem. Eur. J. 2012, 18, 6328.
[9] J. Zhou, J. Wan, X. Ma, W. Wang, Org. Biomol. Chem. 2012, 10, 4179.
[10] M. C. Varela, S. M. Dixon, K. S. Lam, N. E. Schore, Tetrahedron 2008, 64,
10087.
Supporting Information
[11] F. Cozzi, Adv. Synth. Catal. 2006, 348, 1367.
[12] M. Benaglia, A. Puglisi, F. Cozzi, Chem. Rev. 2003, 103, 3401.
[13] K. Schulz, L. Ratjen, J. Martens, Tetrahedron 2011, 67, 546.
[14] S. Saravanan, A. Sadhukhan, N. H. Khan, R. I. Kureshy, S. H. R. Abdi,
H. C. Bajaj, J. Org. Chem. 2012, 77, 4375.
Additional supporting information may be found in the online ver-
sion of this article at the publisher’s web-site.
[15] C. Mukhopadhyay, S. Ray, Tetrahedron 2011, 67, 7936.
[16] J. Mondal, M. Nandi, A. Modak, A. Bhaumik, J. Mol. Catal. A 2012,
363–364, 254.
Appl. Organometal. Chem. (2016)
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