Preparation of carbon nanotube-supported α-Fe2O 3@CuO nanocomposite: A highly efficient and magnetically separable catalyst in cross-coupling of aryl halides with phenols

Article abstract of DOI:10.1039/c3cy00082f

Herein, we introduce the first magnetic CuO nanoparticles based on carbon nanotubes as a highly intriguing magnetic catalyst in Ullmann-type coupling of aryl halides with phenols. Two facile procedures were used for the preparation of this magnetically separable catalytic system. Having been treated with FeSO₄ and then H₂O₂, nanotubes accommodated the resulting iron hydroxides on the walls. The resulting nanocomposite was then exposed to argon atmosphere at 450°C giving rise to a carbon nanotube-supported α-Fe₂O₃ compound. Ultimately, copper acetate was hydrolysed in the presence of CNT supported α-Fe ₂O₃ at 100°C and our novel catalyst was gained. Some spectroscopic and microscopic techniques such as Infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), Vibrational sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), Inductively coupled plasma (ICP), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) corroborated the structure of the catalyst. The catalyst synthesized showed good activity in C-O cross coupling reactions affording the highest rate of completion. Magnetic feature of the catalyst helped facile separation of it from the reaction medium. The catalyst could also be reused up to six times without any loss of its activity.

Full text of DOI:10.1039/c3cy00082f

Catalysis
Science & Technology
View Article Online
View Journal
PAPER
Preparation of carbon nanotube-supported
a-Fe O @CuO nanocomposite: a highly efficient and
2
3
Cite this: DOI: 10.1039/c3cy00082f
magnetically separable catalyst in cross-coupling of
aryl halides with phenols†
a
b
c
a
Dariush Saberi, Mehdi Sheykhan, Khodabakhsh Niknam and Akbar Heydari*
Herein, we introduce the first magnetic CuO nanoparticles based on carbon nanotubes as a highly
intriguing magnetic catalyst in Ullmann-type coupling of aryl halides with phenols. Two facile
procedures were used for the preparation of this magnetically separable catalytic system. Having been
treated with FeSO
walls. The resulting nanocomposite was then exposed to argon atmosphere at 450 1C giving rise to a
carbon nanotube-supported a-Fe compound. Ultimately, copper acetate was hydrolysed in the
presence of CNT supported a-Fe at 100 1C and our novel catalyst was gained. Some spectroscopic
4 2 2
and then H O , nanotubes accommodated the resulting iron hydroxides on the
2 3
O
2 3
O
and microscopic techniques such as Infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD),
Vibrational sample magnetometry (VSM), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH),
Inductively coupled plasma (ICP), Scanning electron microscopy (SEM) and Transmission electron
microscopy (TEM) corroborated the structure of the catalyst. The catalyst synthesized showed good
activity in C–O cross coupling reactions affording the highest rate of completion. Magnetic feature of
the catalyst helped facile separation of it from the reaction medium. The catalyst could also be reused
up to six times without any loss of its activity.
Received 3rd February 2013,
Accepted 2nd April 2013
DOI: 10.1039/c3cy00082f
www.rsc.org/catalysis
Buchwald and Hartwig, pioneers of C–O cross-couplings based
on Ullmann method, reported palladium-catalyzed coupling
Introduction
Aryl ethers play a significant role as building blocks in a wide reactions using phosphine ligands for the synthesis of aryl
1
6
range of natural products and various pharmaceuticals with ethers. Nevertheless, the use of expensive palladium as well as
2
antibiotic activity, such as antitumoral bouvardin, antiviral air and moisture sensitive phosphine ligands are some draw-
peptide K-13 and vancomycin. One of the most popular backs of this method for large-scale or industrial applications.
methods for synthesis of aryl ethers is the Ullmann-type Consequently, attempts were directed to improve the strict
3
4
5
coupling reaction (copper-catalyzed cross-couplings of aryl conditions of copper-catalyzed C–O coupling reactions. In
halides with phenols). On account of the problems associated 1997 Buchwald et al. reported the first examples of copper-
with this noteworthy reaction such as long reaction time, high catalyzed synthesis of diaryl ethers by the reaction of aryl
temperature (4200 1C) and stoichiometric amount of copper bromides or aryl iodides with phenols using Cu(OTf) .PhH as
2
7
required as catalyst, organic chemists made persevering efforts the catalyst and Cs CO as the base in toluene.
2
3
to set the stage for satisfactory reaction conditions to overcome
this downside and fortunately success was achieved in this area. N,N-dimethylglycine, 1,1,1-tris(hydroxymethyl)ethane, pyrrolidine-
Thereafter, it was found that exploiting additives such as
8
9
1
0
11
2
-phosphonic acid phenyl monoester, 1,10-phenanthroline,
1
2
13
a
neocuproine, 2,2,6,6-tetramethylheptane-3,5-dione, or b-keto
Chemistry Department, Tarbiat Modares University, P.O. Box 14155-4838,
Tehran, Iran. E-mail: heydar_a@modares.ac.ir; Fax: +98-21-82883455;
Tel: +98-21-82883444
1
4
ester resulted in milder conditions, that is, somewhat boosted
reaction rates, diminished amount of catalyst needed and lower
temperatures. Moreover, Bolm et al. reported the Ullmann-type
coupling reactions with part-per-million catalyst loading in the
b
c
Chemistry Department, Guilan University, P.O. Box 41335-1914, Rasht, Iran
Chemistry Department, Faculty of Sciences, Persian Gulf University, Bushehr,
7
5169, Iran
3
presence of FeCl as a low-cost and environmentally green
catalyst. In recent years, magnetic nanoparticles have been
†
Electronic supplementary information (ESI) is available. See DOI: 10.1039/
1
5
c3cy00082f
This journal is c The Royal Society of Chemistry 2013
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
used for the C–O coupling reactions as both support and
1
6
catalyst. Nevertheless, the reaction conditions did not gain
the chemists’ full satisfaction. Therefore, there have remained
endeavours to reach more favourable conditions. In this regard,
using supports to put the catalyst on is one of the measures
taken to alleviate these strenuous conditions. Today, utility of a
platform leading to heterogeneous catalytic systems especially
when a toxic and costly transition metal is exploited as the
catalyst, has warranted attention since it provides recovery and
reusability of the catalyst which is desirable from economical
and environmental point of view. In this context, metal oxides
(
silica, alumina and etc.), various kinds of polymers, zeolites,
1
7
carbon active and carbon nanotubes are typical supports that
1
8
have recently been used in most catalytic systems. Among
them, carbon nanotubes due to their unique features such as large
specific surface area (stemming from their hollow geometries),
high oxidation stability (induced by their structural integrity and
2 3 2 3
Fig. 1 FT-IR spectra of raw CNT, CNT@a-Fe O , CNT@a-Fe O @CuO.
chemical inertia) and significant mechanical and thermal stability, moved on to step 2 in which copper acetate was hydrolysed in
19
have taken up a specific position in industry and academia.
Bear in mind that nano-sized materials have distinguished generated.
hallmark of having high surface area, which is a virtue accounting The prepared catalyst was well characterized by the following
the presence of CNT@a-Fe O and our catalytic system was
2 3
2
3
for various applications of such compounds. In the case of a nano- instrumental techniques: FT-IR, XRD, VSM, BET, BJH, ICP, SEM
sized catalyst, this feature enhances the catalytic activity via and TEM.
increasing its active sites. On the other hand, nano-sized catalyst
2 3
The FT-IR spectra of raw CNT, CNT@a-Fe O and CNT@
2 3
would be more dispersed in solution, hence forming an emulsion a-Fe O
@CuO have been shown in Fig. 1. The broad band
which imposes difficulty in catalyst separation from the reaction at over 3400 cm corresponds to the stretching vibrations
media. However, in this extreme case of immobilized systems, of hydroxyl groups on the external surface of the CNTs. In
À1
too, the same problems of isolation and recycling of homo- addition, the band can also be attributed to hydroxyl groups of
À1
geneous catalysts would be encountered. To circumvent these the physically adsorbed water. The signal at 2900 cm
is
problems, one solution is to employ magnetic nanoparticles. relevant to C–H bond stretching vibrations. The signals related
One drastic impact that such particles possess is that by to stretching vibrations of CQC bond are located within
À1
À1
applying an external magnetic field, they can be dispersed or 1400–1600 cm . The band emerged at 1174 cm is assigned
aggregated which allows for the facile separation and recycling to stretching vibrations of C–O bond. All the above-mentioned
of immobilized catalysts on the nano-sized supports. Lately, signals are typical of the skeleton of carbon nanotubes. The
À1
magnetic nanoparticles have found use as both catalyst and appearance of a strong peak at 400–600 cm in the IR spectra
2
0
support. In this paper and in pursuit of our interests in the of CNT@a-Fe O and CNT@a-Fe O @CuO implies the formation
2
3
2 3
preparation and application of heterogeneous catalytic systems of new phases on carbon nanotubes. These peaks are ascribed to
2
1
19b
based on magnetic nanoparticles in organic reactions, we stretching vibrations of Fe–O and Cu–O bonds.
succeeded in innovating a new catalytic system consisting of The crystalline structure of catalyst was characterized by
copper oxide nanoparticles supported on carbon nanotube XRD. As shown in Fig. 2, the patterns can be readily referred to
modified by iron oxide (CNT@a-Fe @CuO) as a highly hematite (JCPDS no. 33-0664), tenorite (JCPDS no. 48-1548) and
2 3
O
efficient and magnetically separable catalyst in C–O coupling graphite (JCPDS no. 12-0212). In the pattern assigned to hematite,
of aryl halides with phenols. This catalytic system is easily diffraction peaks at around 24.11, 33.21, 35.81, 40.91, 49.51, 54.11,
prepared and shows good catalytic activity along with the 57.51, 57.61 , 62.41 and 64.01 correspond to the (012), (104), (110),
straightforward separation from reaction media. Although, (113), (024), (116), (122), (018), (214) and (300) reflections, respec-
the conditions utilized in this reaction are not extremely gentle, tively. For tenorite, diffraction peaks at around 35.71, 38.81, 67.91
it provides a remarkably reduced reaction time in comparison and 68.21 are attributable to the (À111), (111), (022) and (311)
to the previous reports. Presumably, it is because of the high reflections, respectively. Diffraction peak at 26.41 can be indexed to
degree of nanoparticles’ dispersion on the walls of the CNTs.
(022) reflection of the CNTs. No other characteristic peaks due to
the impurities of other oxides of iron and copper were detected.
The large peak widths are ascribed to the formation of nanosized
particles of CuO. The size of particles were calculated by Debye–
Results and discussion
24
New catalytic system was prepared according to the following Scherrer equation using the (À111) peak (2y = 35.51) which is
procedures. Carbon nanotubes were decorated by a-Fe after 20.9 nm.
being exposed to FeSO –H followed by heating at 450 1C Superparamagnetic feature of the catalyst which caused its
under argon atmosphere. Having completed the first stage we easy recovery, was confirmed by vibrating sample magnetometery
2 3
O
4
2 2
O
2
2
Catal. Sci. Technol.
This journal is c The Royal Society of Chemistry 2013

View Article Online
Catalysis Science & Technology
Paper
2 3
Fig. 2 XRD pattern of CNT@a-Fe O @CuO.
2 3
Fig. 4 SEM micrographs of (a) raw CNT; (b) CNT@a-Fe O and (c) CNT@
a-Fe @CuO.
2 3
O
2 3
Fig. 3 Magnetization curve of CNT@a-Fe O @CuO.
analysis (there is no hysteresis loop and the ratio of magnetic
remanence/magnetic saturation (M
s
) is about 0.0004, M
s
=
À1
6.0 emu g ). Magnetization curve of the catalyst is depicted
in Fig. 3.
The surface morphologies of prepared CNT@a-Fe
CNT@a-Fe @CuO were investigated by SEM and the micro-
2 3
O and
2 3
O
graphs have been outlined in Fig. 4 which bears out coating of
new phases on CNTs.
Fig. 5
2
N adsorption–desorption analysis, Brunauer–Emmett–Teller (BET) analy-
sis and Barrett–Joyner–Halenda (BJH) analyseis of CNT@a-Fe O @CuO.
2
3
The porous nature of a-Fe O @CuO nanoparticles were clearly
2
3
proved by the BJH method. A type-IV hysteresis loop was detected
which clearly displayed two peaks with the pore size centred at about hydrochloric acid to digest the copper oxide. In the end, copper
À1
2
.7 nm and 12.2 nm, respectively, for two types of pores. The increased content of the catalyst was obtained 1.85 mmol g
active site of the CNT@a-Fe @CuO nanocomposite was studied TEM images of raw CNT, CNT@a-Fe
by the nitrogen adsorption–desorption isotherms from the BET a-Fe
analysis. The specific surface area and pore volume of the mesoporous which can be seen on the external walls of CNTs is representative
.
2
O
3
2
O
3
and CNT@
2 3
O @CuO are shown in Fig. 6. Congestion of nanoparticles
2
À1
3
À1
catalyst were calculated as 112.6 m g and 0.66 cm g , respectively. of the formation of new phases.
From the adsorption branch of the isotherms, the narrow pore size
calculated was gained about 1.6 nm. (Fig. 5).
After characterization of catalyst, its catalytic activity was
tested in cross-coupling of aryl halides with phenols. As a
The copper content in CNT@a-Fe
measured by ICP instrument. To conduct this analysis, the (0.5 equiv.) was treated with phenol (1 equiv.) in the presence of
catalyst was dissolved in a mixture of nitric acid and CNT@a-Fe @CuO (10 mg, 1.85 mol% CuO) (Scheme 1).
2 3
O @CuO catalyst was model study for the optimization of the reaction, the iodobenzene
2 3
O
This journal is c The Royal Society of Chemistry 2013
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
2 3 2 3
Fig. 6 TEM micrographs of (a) raw CNT; (b and c) CNT@a-Fe O and (d–f) CNT@a-Fe O @CuO.
Scheme 1 Devising the first magnetic carbon nanotube coated CuO nano-
particles for diaryl coupling.
Scheme 2 Influence of different 1,3-dicarbonyl compounds as ligands in cou-
pling reaction of iodobenzene (0.5 mmol) with phenol (1 mmol) with following
conditions: DMF (2 mL), catalyst (10 mg), ligand (10 mol%), 130 1C under argon
atmosphere.
The reaction conditions were optimized by taking into
consideration parameters such as ligand, solvent, base, and
amount of catalyst (Table 1). The influence of DMF, toluene and
t
DMSO as solvents on the yield of the reaction was examined bases (K CO , Cs CO , Na CO , NaOH and BuOK) were used in
2
3
2
3
2
3
and DMF was chosen as the most efficient solvent. Different the model reaction and Cs CO proved to be superior to all
2
3
other choices. Additionally, the role of ligand was assessed by
conducting the reaction in its absence. Under these conditions, the
reaction proceeded far more slowly. During the preliminary studies,
Yield (%) miscellaneous assortments of 1,3-dicarbonyl compounds as ligands
a
Table 1 Study of some parameters on model reaction
Entry
Solvent
Base
Cs CO
Temp. (1C)
Time (h)
were screened and acetyl acetone afforded the best yields of diaryl
ethers (Scheme 2).
The effect of temperature was also investigated. It was found
that raising the reaction temperature from 90 to 130 1C resulted
in a drastic improvement in the yield. Also prolonging the
reaction time even at 90 1C rose the yield from 40 to 90%
1
2
3
4
5
6
7
8
9
DMF
DMF
DMF
DMF
DMF
Toluene
DMSO
DMF
DMF
DMF
DMF
DMF
2
3
130
130
130
130
130
130
130
110
90
1
2
3
3
3
4
1
1
1
92
75
60
30
60
NR
80
72
40
90
KOt-Bu
K
Na
2
CO
3
2
CO
3
NaOH
Cs
2
Cs
2
Cs
2
Cs
2
Cs
2
Cs
2
Cs
2
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
(Table 1, entry 10). All reactions were performed under argon
1
1
1
0
1
2
90
130
130
10
1
1
atmosphere.
b
93
60
c
In the presence of CNT@a-Fe O (without CuO loading) as
2 3
catalyst only 30% of starting materials was converted to the
product after 24 h. The reaction was repeated using CNT@CuO as
a
Reaction condition: iodobenzene (0.5 mmol), phenol (1 mmol),
catalyst (10 mg), base (2 equiv.), solvent (2 mL), acetyl acetone
b
c
catalyst. Although, the results were similar to CNT@a-Fe
2 3
O @CuO
(
10 mol%), under Ar atm. 15 mg of catalyst was used. 5 mg of
catalyst was used.
but the easy magnetic recovery was lost.
Catal. Sci. Technol.
This journal is c The Royal Society of Chemistry 2013

View Article Online
Catalysis Science & Technology
Paper
a
Eventually, the coupling reaction between phenols and aryl Table 2 Diversity of CNT@a-Fe
2
O
3
@CuOcatalyzed C–O cross coupling reaction
iodides and bromides was studied in the presence of CNT
b
Entry Aryl halide Phenol
Product
Time (h) Yield (%)
supported a-Fe O @CuO nanoparticles acting as the hetero-
2
3
1
4
1
92
95
geneous catalyst as well as Cs CO as the base and DMF as the
2
3
1
2
solvent at 130 1C under argon atmosphere.
Motivated by the profound change brought about in the rate
2 3
of reactions of choice by utilizing CNT supported a-Fe O @
CuO, we extended the scope of the C–O coupling reactions
using this novel catalyst and exploited various phenols to treat
with some other derivatives of iodo and bromo benzenes
0
Trace
1
2
90
85
(
Table 2). Generally speaking, the reactions were performed both
10
10
50
45
3
4
5
6
faster and cleaner than all other C–O cross coupling reactions
ever reported. As is seen in Table 2, besides aryl iodides, less
reactive aryl bromides can be efficiently coupled with phenol
derivatives. The effects of various substituents on each reagent
were explored. As expected, the presence of electron withdrawing
groups on the phenol moiety (Table 2, entry 3) decreases the
yield of the product, plus prolonging the reaction time tangibly.
In contrast, electron-releasing groups such as methoxy and
methyl on phenol enhance the yield of the reaction (Table 2,
entry 2, 4, 6 and 7). In comparison, electron donating groups on
aryl halide give rise to the same effects as electron withdrawing
groups on the phenol (Table 2, entry 13) contrary to electron-
withdrawing group which cause the reaction to proceed even
2
4
95
95
5
5
60
40
2
90
93
2.5
without CNT@a-Fe
denote that the latter reaction is performed through a nucleo-
philic addition-elimination mechanism rather than a copper
2
O
3
@CuO (Table 2, entry 14). These findings
1
2
85
85
7
8
2
5
oxide catalyzed coupling reaction as was reported previously.
1
95
Needless to say that chlorobenzene and its derivatives have
the least reactivity among aryl halides in the coupling reactions.
Thus, in this special reaction, even using our catalytic system
led to only a trace of product when chlorobenzene and phenol
reacted with one another, (Table 2, entry 1).
Having assessed most facets of our catalyst, now it was time
to examine another overriding attribute of it. Undoubtedly, one of
the main criteria in the evaluation of a catalyst especially from an
industrial standpoint is its lifetime. Leaching process is one of the
factors that affect longevity of the catalyst substantially. To
vindicate that our reaction does not suffer from leaching process,
3
4
5
90
70
70
9
1
0
1
5
72
7
7
75
70
1
confirmation of the heterogeneous nature of the catalyst in the 12
model reaction was achieved by a decantation experiment, in
which the reaction mixture was decanted using a magnet after
3
78
70
30 min (50% conversion). No catalytic activity was observed in the
13
8
filtrate during 6 h after the filtration. To rule out the deactivation
of catalyst, its efficient recovery was accomplished by decantation
of the reaction mixture using an external magnet and the
recovered catalyst was successively used in a second run. When
the reaction time was set to 1 h, comparably excellent yields were
obtained in six subsequent runs using the same catalyst with
only a negligible decrease of its aptitude (Fig. 7).
The efficacy of the CuO nanoparticles supported on magnetic
CNTs in comparison with some previously reported catalysts
including supported and unsupported copper source is illu-
strated in Table 3. As can be seen, our catalytic system performs
c
1
4
0.5
96
c
0.5
95
a
Reaction conditions: aryl halide (0.5 equiv.), phenol (1 equiv.), catalyst
CO (1 equiv.), acetyl acetone (10 mol%),
(10 mg), DMF (2 mL), Cs
2
3
b
c
under Ar atmosphere. Isolated yield. Without catalyst.
Conclusion
the reaction at the highest rate. Clearly, it is this decreased We developed a novel and alternative route to catalyse C–O cross
reaction time that provides such high turnover frequency.
2 3
couplings. To this end, carbon nanotube-supported a-Fe O @CuO
This journal is c The Royal Society of Chemistry 2013
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
which was purified by silica gel chromatography to produce the
corresponding diaryl ether.
Acknowledgements
We are thankful to Tarbiat Modares University for partial
support of this work and the University of Manchester for
1
13
taking the H NMR and C NMR of some compounds.
Notes and references
1
2
3
4
5
6
K. C. Nicolau, C. N. C. Boddy, S. Brase and N. Winssinger,
Angew. Chem., Int. Ed., 1999, 38, 2096–2152.
D. L. Boger, M. A. Patane and J. Zhou, J. Am. Chem. Soc.,
1994, 116, 8544–8556.
2 3
Fig. 7 Reusability of CNT@a-Fe O @CuO in reaction between iodobenzene
and phenol.
J. W. Janetka and D. H. Rich, J. Am. Chem. Soc., 1997, 119,
6488–6495.
K. C. Nicolaou and C. N. C Boddy, J. Am. Chem. Soc., 2002,
124, 10451–10455.
F. Ullmann, Ber. Dtsch. Chem. Ges., 1904, 37, 853–857;
F. Ullmann, Ber. Dtsch. Chem. Ges., 1903, 36, 2382–2384.
G. Mann and J. F. Hartwig, Tetrahedron Lett., 1997, 46,
Table 3 Comparison of different catalysts in O-arylation reaction between
a
iodobenzene and phenol
À1
Entry Catalyst
Time (h) Yield (%) Ref.
TOF (h
)
1
2
3
4
5
6
7
8
9
1
CuO nanoparticles 15
93
95
93
97
95
84
87
76
8
26
27
28
29
30
31
15
32
32
2.48
0.63
3.87
0.48
3.04
0.175
36.25
0.038
0.004
8005–8008; M. Palucki, J. P. Wolfe and S. L. Bukhwald,
CuI
Cu
15
24
20
12
24
24
10
10
1
2
O
J. Am. Chem. Soc., 1996, 118, 10333–10334; G. Mann and
J. F. Hartwig, J. Am. Chem. Soc., 1996, 118, 13109–13110;
A. Aranyos, D. W. Old, A. Kiyomori, J. P. Wolfe, J. P. Sadighi
and S. L. Buchwald, J. Am. Chem. Soc., 1999, 121, 4369–4378;
G. Mann and J. F. Hartwig, J. Org. Chem., 1997, 62,
CuBr
Polymer-Cu(Oac)
2
b
CuFe
CuO
CuO/g-Al
CuO/SBA-15
CNT@a-Fe
2
O
4
c
2 3
O
c
5413–5418; M. Palucki, J. P. Wolfe and S. Buchwald, J. Am.
0
2
O
3
@CuO
92
Present work 49.73
Chem. Soc., 1997, 119, 3395–3396; R. A. Widenhoefer,
H. A. Zhong and S. L. Buchwald, J. Am. Chem. Soc., 1997,
119, 6787–6795.
J. F. Marcoux, S. Doye and S. L. Buchwald, J. Am. Chem. Soc.,
1997, 119, 10539–10540.
a
Condition: base/solvent/temp. For entries: (1) KOH/DMSO/110 1C; (2)
CO /DMF/110 1C; (3) Cs CO /CH CN/80 1C; (4) Cs CO /DMSO/60 1C;
5) Cs CO /DMSO/120 1C; (6) Cs CO /DMF/135 1C; (7) Cs CO /toluene/
35 1C; (8) K PO /DMSO/150 1C; (9) K PO /DMSO/150 1C (10) Cs CO
Cs
(
2
3
2
3
3
2
3
2
3
2
3
2
3
1
3
4
3
4
2
3
/
7
b
DMF/130 1C. 4-Methyliodobenzene has compared instead of iodo-
c
benzene. 3-Methyl phenol has compared instead of phenol.
8
9
D. Ma and Q. Cai, Org. Lett., 2003, 5, 3799–3802.
Y. J. Chen and H. H. Chen, Org. Lett., 2006, 8, 5609–5612.
was prepared and its catalytic activity was explored in Ullmann-
type coupling of aryl iodides and bromides with phenols. As a
result, the time of the reaction was reduced tremendously.
Reduction in time causes a high TOF. Facile preparation,
straightforward separation, remarkable aptitude to be recycled
up to six times and good stability are all salient features of this
catalytic system.
1
1
1
1
0 H. Rao, Y. Jin, H. Fu, Y. Jiang and Y. Zhao, Chem.–Eur. J.,
2006, 12, 3636–3646.
1 M. Wolter, G. Nordmann, G. E. Job and S. L. Buchwald, Org.
Lett., 2002, 4, 973–976.
2 R. K. Gujadhur, C. G. Bates and D. Venkataraman, Org. Lett.,
2001, 3, 4315–4317.
3 E. Buck, Z. J. Song, D. Tschaen, P. G. Dormer, R. P. Volante
and P. J. Reider, Org. Lett., 2002, 4, 1623–1626.
1
1
4 X. Lv and W. Bao, J. Org. Chem., 2007, 72, 3863–3867.
5 S. L. Buchwald and C. Bolm, Angew. Chem., Int. Ed., 2009, 48,
Experimental section
General procedure for the O-arylation of phenols
5586–5587; P. F. Larsson, A. Correa, M. Carril, P. O. Norrby
and C. Bolm, Angew. Chem., Int. Ed., 2009, 48, 5691–5693;
O. Bistri, A. Correa and C. Bolm, Angew. Chem., Int. Ed.,
2008, 47, 586–588.
A mixture of aryl halide (0.5 equiv.), phenol (1.0 equiv.), Cs
2 3
CO
(
1.0 equiv.), CNT@a-Fe @CuO (10 mg, 1.85 mol%), acetyla-
2 3
O
cetone (10 mol%), and DMF (2 mL) in a two-necked flask was 16 R. Arundhathi, D. Damodara, P. R. Likhar, M. L. Kantam,
heated at 130 1C under argon atmosphere for a specified time.
The cooled mixture was partitioned between ethyl acetate and
water. The organic layer was separated, and the aqueous layer
was extracted with ethyl acetate. The combined organic layers
P. Saravanan, T. Magdaleno and S. H. Kwon, Adv. Synth.
Catal., 2011, 353, 2875–2883; S. Yang, C. Wu, H. Zhou,
Y. Yang, Y. Zhao, C. Wang, W. Yang and J. Xu, Adv. Synth.
Catal., 2013, 355, 53–58.
2 4
were dried over Na SO , and concentrated to yield product, 17 S. Iijima, Nature, 1991, 354, 56–58.
Catal. Sci. Technol.
This journal is c The Royal Society of Chemistry 2013

View Article Online
Catalysis Science & Technology
Paper
1
8 T. Miao and L. Wang, Tetrahedron Lett., 2007, 48, 95–99;
S. M. Islam, S. Mondal, P. Mondal, A. S. Roy, K. Tuhina,
N. Salam and M. Mobarak, J. Organomet. Chem., 2012, 696,
Commun., 2005, 4435–4437; P. D. Stevens, J. Fan, H. M. R.
Gardimalla, M. Yen and Y. Gao, Org. Lett., 2005, 7, 2085–2088;
D. Lee, J. Lee, H. Lee, S. Jin, T. Hyeon and B. M. Kim,
Adv. Synth. Catal., 2006, 348, 41–46; S. Luo, X. Zheng, H. Xu,
X. Me, L. Zhang and J. P. Cheng, Adv. Synth. Catal., 2007, 349,
2431–2434; H. Firouzabadi, N. Iranpoor, M. Gholinejad and
J. Hoseini, Adv. Synth. Catal., 2011, 353, 125–132.
4
2
264–4274; P. Ling, D. Li and X. Wang, J. Mol. Catal. A: Chem.,
012, 357, 112–116; M. Islam, S. Mondal, P. Mondal,
A. S. Roy, D. Hossain and M. Mobarak, Transition Met. Chem.,
2
2
011, 36, 1–11; G. M. Neelgund and A. Oki, Appl. Catal., A,
011, 399, 154–160; A. Corma, H. Garcia and A. Leyva, J. Mol. 21 M. Sheykhan, L. Ma’mani, A. Ebrahimi and A. Heydari,
Catal. A: Chem., 2005, 230, 97–105; J. M. Planeix, N. Coustel,
B. Coq, V. Bretons, P. S. Kumbhar, R. Dutartre, P. Geneste,
P. Bernier and P. M. Ajayan, J. Am. Chem. Soc., 1994, 116,
J. Mol. Catal. A: Chem., 2011, 335, 253–261; L. Ma’mani,
M. Sheykhan and A. Heydari, Appl. Catal., A, 2011, 395,
34–38; L. Ma’mani, A. Heydari and M. Sheykhan, Appl.
Catal., A, 2010, 384, 122–127.
7935–7936; V. G. Ramu, A. Bordoloi, T. C. Nagaiah,
W. Schuhmann, M. Muhler and C. Cabrele, Appl. Catal., A, 22 P. Feng, F. Xiao-Bo, Y. Hao and W. Hong-juan, New Carbon
012, 431–432, 88–94; S. M. Chergui, A. Ledebt, F. Mammeri, Mater., 2007, 22, 213–217.
F. Herbst, B. Carbonnier, H. B. Romdhane, M. Delamar and 23 J. Zhu, H. Bi, Y. Wang, X. Wang, X. Yang and L. Lu, New
M. M. Chehimi, Langmuir, 2010, 26, 16115–16121; S. Heylen, Carbon Mater., 2007, 61, 5236–5238.
N. Delcour, C. E. A. Kirschhock and J. A. Martens, Chem- 24 N. A. Smith, N. Sekido, J. H. Perepezko, A. B. Ellis and
2
CatChem, 2012, 4, 1162–1166; J. Wang, F. Zhang, W. Hua,
Y. Yue and Z. Gao, Catal. Commun., 2012, 18, 63–67.
9 P. G. F. Harris, Carbon Nanotubes and Related Structures,
W. C. Crone, Scr. Mater., 2004, 51, 423–426.
25 A. B. Naidu, E. A. Jaseer and G. Sekar, J. Org. Chem., 2009, 74,
3675–3679.
1
Cambridge University Press, Cambridge, UK, 2003; Carbon 26 S. Jammi, S. Sakthivel, L. Rout, T. Mukherjee, S. Mandal,
Nanotubes: Synthesis, Structure, Properties, and Applications,
ed. M. S. Dresselhaus, G. Dresselhaus and P. Avouris,
R. Mitra, P. Saha and T. Punniyamurthy, J. Org. Chem., 2009,
74, 1971–1976.
Springer, New York, 2000; R. Saito, G. Dresselhaus and 27 H. Rao, Y. Jin, H. Fu, Y. Jiang and Y. Zhao, Chem.–Eur. J.,
M. S. Dresselhaus, Physical Properties of Carbon Nanotubes, 2006, 12, 3636–3646.
Imperial College Press, London, 1998; P. M. Ajayan, Chem. 28 A. Y. Cheng and J. C. Hsieh, Tetrahedron Lett., 2012, 53, 71–75.
Rev., 1999, 99, 1787–1799; M. Terrones, Annu. Rev. Mater. 29 X. Lv and W. Bao, J. Org. Chem., 2007, 72, 3863–3867.
Res., 2003, 33, 419–501; M. S. Dresselhaus, G. Dresselhaus, 30 S. M. Islam, S. Mondal, P. Mondal, A. S. Roy. K. Tuhina,
J. C. Charlier and E. Hernandez, Philos. Trans. R. Soc.
London, Ser. A, 2004, 362, 2065–2098.
N. Salam and M. Mobarak, J. Organomet. Chem., 2012, 696,
4264–4274.
2
0 R. A. Reziq, H. Alper, D. Wang and M. L. Post, J. Am. Chem. 31 R. Zhang, J. Liu, S. Wang, J. Niu, C. Xia and W. Sun,
Soc., 2006, 128, 5279–5283; A. Hu, T. Gordon, G. T. Yee and ChemCatChem, 2011, 3, 146–149.
W. Lin, J. Am. Chem. Soc., 2005, 127, 12486–12487; 32 P. Ling, D. Li and X. Wang, J. Mol. Catal. A: Chem., 2012, 357,
P. D. Stevhens, G. Li, J. Fan, M. Yen and Y. Gao, Chem. 112–116.
This journal is c The Royal Society of Chemistry 2013
Catal. Sci. Technol.