Recyclable CNT-chitosan nanohybrid film utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media

Article abstract of DOI:10.1016/j.tetlet.2018.11.039

A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.

Full text of DOI:10.1016/j.tetlet.2018.11.039

Accepted Manuscript
Recyclable CNT-Chitosan nanohybrid film utilized in copper-catalyzed aerobic
ipso-hydroxylation of arylboronic acids in aqueous media
Han-Sem Kim, Sung-Ryu Joo, Ueon Sang Shin, Seung-Hoi Kim
PII:
S0040-4039(18)31368-6
https://doi.org/10.1016/j.tetlet.2018.11.039
TETL 50424
DOI:
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
17 September 2018
9 November 2018
13 November 2018
Please cite this article as: Kim, H-S., Joo, S-R., Shin, U.S., Kim, S-H., Recyclable CNT-Chitosan nanohybrid film
utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media, Tetrahedron
Letters (2018), doi: https://doi.org/10.1016/j.tetlet.2018.11.039
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Recyclable CNT-Chitosan Nanohybrid Film
Leave this area blank for abstract
Utilized in Copper-Catalyzed Aerobic Ipso-Hydroxylation of Arylboronic Acids in Aqueous Media
a
b
a,c
b
Han-Sem Kim, Sung-Ryu Joo, Ueon Sang Shin, * Seung-Hoi Kim *

1
Tetrahedron Letters
Recyclable CNT-Chitosan nanohybrid film utilized in copper-catalyzed aerobic
ipso-hydroxylation of arylboronic acids in aqueous media
a
b
a,c
b
Han-Sem Kim, Sung-Ryu Joo, Ueon Sang Shin, * Seung-Hoi Kim *
a Department of Nanobiomedical Science & BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan 31116, Republic of Korea
b Department of Chemistry, Dankook University, Cheonan, 31116 Republic of Korea
c Institute of Tissue Regeneration Engineering (ITREN), Dankook University, Cheonan 31116, Republic of Korea
*
usshin12@dankook.ac.kr (U.S Shin), kimsemail@dankook.ac.kr (S.-H. Kim)
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon
nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-
hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing
or electron-donating groups were smoothly transformed at room temperature in water to afford
the corresponding phenols in high yields.
Available online
2
009 Elsevier Ltd. All rights reserved.
Keywords:
CNT-Chitosan nanohybride
ipso-hydroxylation
heterogeneous
phenol
copper salts
Chitosan is a partially deacetylated chitin which is commonly
found in shells of marine crustaceans, and exists as powders,
films or fibers with low porosity. Owing to its excellent
nanocomposite has been frequently employed in a wide range of
applications such as in biosensors, biofuel cells, drug delivery
systems, scaffold fabrication, wastewater treatment, and catalyst
3
biodegradability, biocompatibility, suitability for cell ingrowth,
and adsorptivity for metal ions, it has been widely applied in a
carriers.
1
Recently, we have successfully developed an advanced
method for preparing CNT-chitosan films that are insoluble in
water and possess a high chitosan surface area using a high-
pressure homogenizer. It provides nanofibers with CNT-core and
chitosan-shell structure and a novel CNT-Chit film formed
through their close-packing. This material has the high strength
variety of chemistry-related areas.
Despite these outstanding features of chitosan, issues related
to its solubility in different media significantly limit its direct
applications in organic chemistry. Since pristine chitosan is
practically insoluble in organic solvents and only soluble in
aqueous acids, efforts to improve its solubility in organic media
or increase its surface area in organic media are required to
expand its utility in organic synthesis.
4
and conductivity suitable for flexible electric circuits. According
to the scanning electron microscopic (SEM) images of the
prepared-CNT-Chit films, the individual CNTs of the CNT-
chitosan nanocomposite are fully wrapped by the hydrophilic
chitosan molecules, which form a network of intermolecular
hydrogen bonds. From an organic synthesis point of view, it is
highly interesting that the chitosan polymer surface consisting of
To address this issue, numerous studies have focused on
improving the physical properties of chitosan including its
surface area, especially by the incorporation of super-strong and
light-weight carbon nanotubes. There are several approaches for
the preparation of CNT/chitosan nanocomposites using the
physical and/or chemical bonding ability between the CNT
surface and chitosan. As-prepared carbon nanotubes/chitosan
OH and NH functionalities can act as a metal chelating ligand.
2
Inspired by this aspect and postulating recyclability, we decided
to apply the prepared-CNT-Chit film in the copper-catalyzed
hydroxylation of arylboronic acids to obtain phenol derivatives.
(referred to as CNT-Chit hereafter) composite has been reported
to show significantly improved physical and chemical
properties. With the modified properties, CNT-Chit
Phenol and its derivatives have been frequently found in a
wide range of chemical materials such as polymers,
2

2
Tetrahedron
5
pharmaceuticals, and naturally occurring materials. More
importantly, it is often used as a key building block for the
8
5.0
CuSO •5H O (0.1)
KOH
KOH
NaOH
K CO
52
NR
56
30
32
28
4
2
9
0.0
CuSO •5H O (0.1)
4 2
construction of complicated compounds. It is well-recognized
that phenols are classically prepared by either nucleophilic
aromatic substitution of aryl halides or the hydrolysis of arene
diazonium salts, under limitations such as harsh reaction
conditions, low functional group compatibility and limited
10
10.0
10.0
10.0
10.0
CuSO •5H O (0.1)
4 2
1
1
1
2
3
CuSO •5H O (0.1)
4 2
2
3
CuSO •5H O (0.1)
Cs CO
4
2
2
3
6
accessibility of the starting compounds.
1
CuSO •5H O (0.1)
Na CO
2 3
4
2
Together with these approaches, the oxidative ipso-
a
all reactions were carried out in air otherwise mentioned
hydroxylation of arylboronic acids to produce phenol derivatives
has attracted considerable attention owing to unique properties
such as ease of handling, ready availability, low toxicity, and
high stability. In most cases, strong oxidizing agents, mostly
hydrogen peroxide as well as other oxidants such as oxone, N-
oxide and MCPBA are required in stoichiometric amounts for
the efficient conversion. Despite various protocols, it is highly
desirable to develop mild and environmentally friendly oxidation
processes in industries. In view of these aspects, catalytic
oxidative hydroxylation using a greener oxidant along with a
recyclable ligand in water is highly demanded. Accordingly,
oxidations with molecular oxygen catalyzed by Pd(II) salts,
copper-promoted electrochemical hydroxylation,
electrochemically generated superoxide anions, and
photocatalytic aerobic oxidative hydroxylation mediated by
visible light have been developed.
b
c
isolated yield
stirred for 48h
7
8
9
An initial attempt was made with phenylboronic acid (1a) to
screen suitable copper salts with no additional oxidizing agent
under the following conditions: 10 mg of CNT-Chit
1
0
11
nanocomposite, 3.0 equivalents of KOH, and water as solvent.
Under these conditions, the role of copper salt was first verified
by carring out the reaction in the absence of the copper catalyst,
resulting in no expected product at all (entry 1, Table 1). To our
delight, use of catalytic amounts of CuSO ·5H O led to a
1
2
1
3
4
2
significantly improved result in 24 h at room temperature (entry
, Table 1). Impressed by this result, several other easily
1
4
2
accessible copper salts such as copper (II) oxide, and copper
halides were also examined under the same conditions.
Gratifyingly, phenylboronic acid was completely converted in 24
h at room temperature, except when CuI was used. As shown in
Table 1, most of the copper catalysts afforded generally
satisfactory yields (83 to 92%). Using reduced amounts of
1
5
Furthermore, several groups have recently reported improved
copper-catalyst systems that do not require strong oxidants for
the efficient hydroxylation of arylboronic acids. These
approaches rely on copper-nanoparticles, copper-complexes,
and combination of copper and a support.
1
6
17
1
8
CuSO ·5H O or CNT-Chit significantly affected the reaction
efficiency (entries 7 and 8, respectively). In addition, as
expected, no conversion was observed in the absence of CNT-
4 2
In our continuing research efforts to develop a suitable metal-
catalyst system, we have developed an excellent heterogeneous
Chit (entry 9). When the base was replaced with NaOH, K CO ,
1
9
2
3
catalyst for aerobic ipso-hydroxylation of arylboronic acids. It
consists of a combination of copper salt with recyclable and
reusable CNT-Chit support in water, and more significantly, no
strong oxidants such as peroxides and any extra additives are
required. This protocol provides high stability in air and the
catalytic system is effective because it can be recycled without
losing its catalytic activity.
or Cs CO , no advantage over KOH was observed. Considering
2
3
the operability and practicability, we chose CuSO ·5H O as the
4
2
catalyst and KOH as the base for the desired conversion.
Table 2
Scope of arylboronic acids
Table 1
Optimization of the hydroxylation of phenylboronic acid (1a)
b
entry CNT-Chit catalyst (equiv)
base
yield(%)
a
(mg)
1
2
3
4
5
6
7
10.0
10.0
10.0
10.0
10.0
10.0
10.0
-
KOH
KOH
KOH
KOH
KOH
KOH
NR
98
87
83
91
92
55
CuSO •5H O (0.1)
4
2
Cu O (0.1)
2
CuCl •2H O (0.1)
2
2
CuBr (0.1)
CuI (0.1)
c
CuSO •5H O (0.05) KOH
4
2

3
It is of interest that our new platform worked for
phenylboronic acid surrogates as well in a similar fashion.
Transformation of both potassium phenyltrifluoroborate (3a) and
phenyl boronic acid pinacol ester (4a) to phenol required an
extended reaction time under the same conditions used before,
and the reaction proceeded at a slightly reduced rate, affording
phenol (2a) in lower yields (Scheme 1).
Scheme 2
Control reaction
To gain insights into the possible mechanism, a control
experiment was executed (Scheme 2). When the model reaction
was carried out under positive argon pressure, conversion of 1a
to 2a was not complete in 24 h at room temperature, leading to
severely reduced isolated yield, which is consistent with the
a
number in parenthesis is isolated yield
1
8a
result of previous study. This observation clearly indicate that
our reaction also proceeds in a similar fashion as illustrated in
Having identified the optimal conditions, we next explored the
1
7b
efficiency of CNT-Chit platform in copper-catalyzed aerobic
oxidation of various arylboronic acids to phenols (Table 2).
Regardless of the electronic properties of the arylboronic acids,
the transformation was successful, resulting in the corresponding
phenols in high yields. The sterically hindered arylboronic acid
previous report.
Table 3
(2e) was well adapted, and the steric hindrance did not
Reusability test
signicantly affect transformation. Various functional groups such
as alkoxy (2f), amino (2g), vinyl (2h), phenyl (2i), carbonyls (2j
and 2k), nitro (2l), trifluoro (2m), halogens (2n and 2o), and
naphthalene ring (2q) were compatible with the reaction.
Notably, heteroaryl boronic acids are also amenable to this
protocol. A couple of heteroaryl boronic acids were examined
under the same conditions, leading to the desired products,
hydroxyl heterocyclic aromatics (2r and 2s) in satisfactory
yields.
1a (3.0 mmol)
2a
st
nd
rd
th
th
run
1
2
3
4
5
95
yield (%) 98
98
95
95
The recyclability of the CNT-Chit film was also investigated.
The platform, which is insoluble in water, could be simply
recovered by filtration after the completion of the reaction. Then,
the collected platform could be washed with water followed by
diethyl ether and allowed to dry in air, and reused directly in the
subsequent reactions without any further purification. The
recovered platform was reused up to 5-times without losing its
activity in terms of the isolated product yield (Table 3).
Scheme 1
Hydroxylation of phenylboronic acid surrogates
As described previously, the surface of the CNT-Chit films,
in which each CNT fiber is coated with Chit molecules to form
CNT/Chit core/shell nanohybrid structure and closely packed by
self-assembly, is composed of numerous chitosan molecules
bearing both -OH and -NH functional groups. Presumably, these
2

4
Tetrahedron
functionalities could be acting as chelating ligands for the
In conclusion, we have developed a convenient and efficient
method for the synthesis of substituted phenols via a copper-
mediated ipso-hydroxylation of arylboronic acids. The use of
recyclable CNT-Chit film and water as the solvent render the
protocol economical and environmentally friendly. Regardless of
whether the boronic acid substrates bear electron-withdrawing or
electron-donating groups, the transformation occurred smoothly
to afford the corresponding phenols in high yields. This result
could be attributed to the chelating effect of nitrogen and/or
oxygen atoms in chitosan. Remarkably, the targeted products can
be easily obtained by a simple workup operation after the
completion of the reaction. High product yield and recyclability
of the CNT-Chit film should be emphasized.
copper catalyst. Consequently, the deformation of the surface
area could be crucial for the present catalytic system Therefore,
the change in the morphology of CNT-Chit, especially after
catalytic cycles should be investigated. To this end, we further
analyzed and compared the surface of the CNT-Chit films before
and after use by SEM. As shown in Figure 1 below, no obvious
change can be detected even after five consecutive uses.
Figure 1
SEM images of CNT-Chit before (a) and after (b) the reaction
(a)
References and notes
1
.
(a) Noble, L.; Gray, A. I.; Sadiq, L; Uchegbu, I. F. Int. J.
Pharm. 1999, 192, 173. (b) Majeti, N. V.; Kumar R.
React. Funct. Polym. 2000, 46, 1. (c) Chang, Y. Y.;
Chen, S. J.; Liang, H. C.; Sung, H. W.; Lin, C. C.;
Huang, R. N. Biomaterials 2004, 25, 3603.
2
.
(a) Lau, C.; Cooney, M. J.; Atanssov, P. Langmuir 2008,
2
4, 7004. (b) Yan, J.; Wu, T.; Ding, Z.; Li, Z.
Carbohydrate Polymers 2016, 136, 1288. (c) Carson,
L.; Kelly-Brown, C.; Stewart, M.; Oki, A.; Regisford,
G.; Luo, Z.; Barkhmutov, V. I. Mater. Lett. 2009, 63,
6
2
17. (d) Liu, Y.; Tang, J.; Chen, X.; Xin, J. H. Carbon
005, 43, 3178.
(b)
3
.
(a) Zhang, M.; Smith, A.; Gorski, W. Anal. Chem. 2004,
7
2
6, 5045. (b) Zhang, M.; Gorski, W.; J. Am. Chem. Soc.
005, 127, 2058. (c) Luo, X. L.; Xu, J. J.; Wang, J. L.;
Chen, H. Y. Chem. Commun. 2005, 16, 2169. (d)
Aryaei, A.; Jayatissa, A. H.; Jayasuriya, A. C. J.
Biomed. Mater. Res. A 2013, 102, 2704. (e) Kumar, A.;
Jena, P. K.; Behera, S.; Lockey, R. F.; Mohapatra, S. J.
Biomed. Nanotechnol. 2005, 1, 392. (f) Zhang, M.;
Smith, A.; Gorski, W. Anal. Chem. 2004, 76, 5045.
4
5
.
.
Hwang, J. Y.; Kim, H. S.; Kim, J. H.; Shin, U. S.; Lee, S.
H. Langmuir 2015, 31, 7844.
(a) Tyman, J. H. P. Synthetic and Natural Phenols;
Elsevier: New York, 1996. (b) Rappoport, Z. The
Chemistry of Phenols; Wiley-VCH: Weinheim, 2003.
6
.
(a) Hanson, P.; Jones, J. R.; Taylor, A. B.; Walton, P. H.;
Timms, A. W. J. Chem. Soc.; Perkins Trans. 2002, 2,
1
135. (b) Sergeev, G. A.; Schultz, T.; Torbog, C.;
Spenenberge, A.; Neumann, H. Angew. Chem., Int. Ed.
009, 48, 7595. (c) Fier, P. S.; Maloney, K. M. Org.
Another potential aspect of our reaction system is a sorption
of copper-metal in chitosan. According to the previous reports,
20
2
Lett. 2017, 19, 3033. (d) Xia, S.; Gan, L.; Wang, K.; Li,
Z.; Ma, D. J. Am. Chem. Soc. 2016, 138, 13493. (e) Xu,
H.-J.; Liang, Y.-F.; Cai, Z.-Y.; Qi, H.-X.; Yang, C.-Y.;
Feng, Y.-S. J. Org. Chem. 2011, 76, 2296. (f) Tan, B.
Y.-H.; Teo, Y.-C. Synlett 2016, 27, 1814. (g) Zhang, X.;
Wu, G.; Gao, W.; Ding, J.; Huang, X.; Liu, M.; Wu, H.
Org. Lett. 2018, 20, 708. (h) Anderson, K. W.; Ikawa,
T.; Tundel, R. E.; Buchwald, S. L. J. Am. Chem. Soc.
both chitosan and chitosan derivatives can bind with copper (II)
ion to form a complex in an aqueous solution. To address this
issue, we also carried out a supplementary experiment to figure
out the possibility of copper complexation in our reaction system.
The hydroxylation of 1a was carried out using the CNT-Chit
film recovered from the initial hydroxylation of 1a without any
further treatment. No additional copper catalyst was used in this
supplementary experiment, providing 2a in a severely lowered
isolated yield (31%). Despite the paucity of comprehensive
investigation on copper absorption, it could be inferred that Cu-
complexation was partially occurred and the resulting complex
2
006, 128, 10694. (i) Yu, C. -W.; Chen, G. S.; Huang,
C.-W.; Chern, J.-W. Org. Lett. 2012, 14, 3688.
2
1
7. Hall, D. G. Boronic Acids: Preparation and
catalyzed the transformation in our reaction system.
Applications in Organic Synthesis, Medicine and

5
Materials, 2nd Ed; Wiley-VCH Verlag GmbH & Co.,
011.
General 2013, 466, 60. (b) Bora, S. J.; Chetia, B. J.
Organometal. Chem. 2017, 851, 52.
2
8
.
(a) Gupta, S.; Chaudhary, P.; Srivastava, V.; Kandasamy,
J. Tetrahedron Lett. 2016, 57, 2506. (b) Mahanta, A.;
Adhikari, P.; Bora, U.; Thakur, A. J. Tetrahedron Lett.
18. (a) Xu, J.; Wang, X.; Shao, C.; Su, D.; Cheng, G.; Hu, Y.
Org. Lett. 2010, 12, 1964. (b) Inamoto, K.; Nozawa,
K.; Yonemoto, M.; Kondo, Y. Chem. Comm. 2011, 47,
11775. (c) Yang, H.; Li, Y.; Jiang, M.; Wang, J.; Fu, H.
Chem. Eur. J. 2011, 17, 5652.
2
015, 56, 1780. (c) Gohain, M., du Plessis, M.; van
Tonder, J. H.; Bezuidenhoudt, B. C. B. Tetrahedron
Lett. 2014, 55, 2082. (d) Gogoi, K.; Dewan, A.; Gogoi,
A.; Borah, G.; Bora, U. Heteroatom Chem. 2014, 25,
1
9. General procedure for reduction of aryl/heteroaryl
boronic acids to phenols: a flask was charged with 3,4-
dimethoxyphenylboronic acid (1.0 mmol), CuSO •H O
1
5
1
27. (e) Gogoi, A.; Bora, U.; Tetrahedron Lett. 2013,
4, 1821. (f) Gogoi, A.; Bora, U.; Synlett 2012, 23,
079. (g) Mulakayala, N.; Ismail; Kumar, K. M.;
4
2
(0.02 g, 0.1 mmol), CNT-Chit film (10.0 mg), KOH
(
0.17 g, 3.0 mmol), and H O (5.00 mL). Then, the flask
2
Rapolu, R. K.; Kandagatla, B.; Rao, P.; Oruganti, S.;
Pal, M. Tetrahedron Lett. 2012, 53, 6004. (h) Prakash,
G. K. S.; Chacko, S.; Panja, C.; Thomas, T. E.; Gurung,
L.; Rasul, G.; Mathew, T.; Olah, G. A. Adv. Synth. Catal.
was stirred at room temperature in open air for 24
hours. At the end of the reaction, the reaction mixture
was filtered and washed with water. Then, the filtrate
was acidified with dilute aqueous HCl and extracted
with diethyl ether (3 × 10 mL). The organic phases
were combined, and the volatile components were
evaporated under reduced pressure. Purification by
flash column chromatography on silica gel (70%
hexanes/ 30% ethyl acetate) afforded 0.1433 g of 3,4-
dimethoxyphenol (2f) in 93% isolated yield as an off-
2
009, 351, 1567. (i) Khazaei, M.; Khazaei, A.;
Nasrollahzadeh, M.; Tahsili, M. R. Tetrahedron 2017,
3, 5613. (j) Saikiam I.; Hazarika, M.; Hussian, N.;
Das, M. R.; Tamuly, C. Tetrahedron Lett. 2017, 58,
255. (k) Begum, T.; Gogoi, A.; Gogoi, P. K.; Bora, U.
7
4
Tetrahedron Lett. 2015, 56, 95. (l) Borah, R.; Saikia,
E.; Bora, S. J.; Chetia, B. Tetrahedron Lett. 2017, 58,
o
1
white solid (m.p. = 79-82 C); H NMR (400 MHz,
1
211.
CDCl ) δ = 6.70 (d, 1H, J=8.8 Hz), 6.46 (d, 1H,
3
9
1
.
(a) Molander, G. A.; Cavalcanti, L. N. J. Org. Chem.
J=2.4 Hz), 6.34 (dd, 1H, J=8.8, 2.4 Hz), 5.84 (br s, 1H),
3.79 (s, 3H), 3.76 (s, 3H) ppm. C NMR (100 MHz,
13
2
011, 76, 623. (b) Maleczka, R. E. Jr.; Shi, F.; Holmes,
D.; Smith III, M. R. J. Am. Chem. Soc. 2003, 125, 7792.
c) Travis, B. R.; Ciaramitaro, B. P.; Borhan, B. Eur. J.
Org. Chem. 2002, 3429.
CDCl ) δ = 150.3, 149.8, 142.9, 112.5, 105.9, 100.6,
3
+
(
56.6, 55.7 ppm. HRMS (EI ): m/z calcd. for C H O :
8
10
3
155.0703, found: 155.0707.
0. Zhu, C.; Wang, R.; Falck, J. R. Org. Lett. 2012, 14,
494.
20. (a) Pestov, A.; Bratskaya, S. Molecules 2016, 21, 330.
(b) Sajomsang, W. Carbohydr. Polym. 2010, 80, 631.
3
(
c) Rodrigues, C. A.; Laranjeira, M. C. M.; de Favere,
1
1
1. Chen, D. S.; Huang, J. M. Synlett. 2013, 24, 499.
V. T.; Stadler, E. Polymer 1998, 39, 5121. (d) Park, J.
W.; Park, M.-O.; Park, K. K. Bull. Korean Chem. Soc.
1
2. Khazaei, M.; Khazaei, A.; Nasrollahzadeh, M.; Tahsili,
984, 5, 108. (e) Park, J. W.; Choi, K.-H.; Park, K. K.
M. R. Tetrahedron 2017, 73, 5613.
Bull. Korean Chem. Soc. 1983, 4, 68.
1
1
1
3. Qi, H.-L.; Chen, D.-S.; Ye, J.-S.; Huang, J.-M. J. Org.
Chem. 2013, 78, 7482.
2
1. Further studies on the preparation of metal-
(functionalized)chitosan complexes and their catalytic
applications in organic synthesis are currently
undertaken in our laboratory and the results will be
reported in due course.
4. Hosoi, K.; Kuriyama, Y.; Inagi, S.; Fuchigami, T. Chem.
Commun. 2010, 46, 1284.
5. (a) Xie, H.-Y.; Han, L.-S.; Huang, S.; Lei, X.; Cheng,
Y.; Zhao, W.; Sun, H.; Wen, X.; Xu, Q.-L. J. Org.
Chem. 2017, 82, 5236. (b) Matsui, K.; Ishigami, T.;
Yamaguchi, T.; Yamaguchi, E.; Tada, N.; Miura, T.;
Itoh, A. Synlett. 2014, 25, 2613. (c) Pitre, S. P.;
McTiernan, C. D.; Ismaili, H.; Scaiano, J. C. J. Am.
Chem. Soc. 2013, 135, 13286.
Click here to remove instruction text...
1
1
6. (a) Affrose, A.; Azath, I. A.; Dhakshinamoorthy, A.;
Pitchumani, K. J. Mol. Catal. A: Chem. 2014, 395, 500.
(b) Yang, D.; An, B.; Wei, W.; Jiang, M.; You J.; Wang,
H. Tetrahedron 2014, 70, 3630.
7. (a) Dar, B. H.; Bhatti, P.; Singh, A. P.; Lazar, A.;
Sharma, P. R.; Sharma, M.; Singh, B. Appl. Catal. A:

6
Tetrahedron
Highlights:

Convenient heterogeneous catalytic system

Greener conditions; recyclable and reusable
catalyst in water



Facile carbon nanotube(CNT)-chitosan
nanohybrid film
Versatile copper-catalyzed aerobic ipso-
hydroxylation
Satisfactory isolated yield of the
corresponding product phenols