Chitosan-Supported Ni particles: An Efficient Nanocatalyst for Direct Amination of Phenols

Article abstract of DOI:10.1002/aoc.4273

A practical method for the direct amination of phenols using 2,4,6-trichloro-1,3,5-triazine (TCT) as an efficient promotor for the activation of phenols in the presence of an efficient and recyclable heterogeneous catalyst prepared by immobilization of nickel particles on triazole modified chitosan is described. This heterogeneous catalyst has demonstrated a promising activity for the conversion of phenolic compounds to their corresponding amine under mild conditions. Moreover, the obtained catalyst can be reused in five consecutive runs with consistent catalytic activity.

Full text of DOI:10.1002/aoc.4273

Received: 7 October 2017
DOI: 10.1002/aoc.4273
Revised: 12 December 2017
Accepted: 14 December 2017
F U L L P A P E R
Chitosan‐Supported Ni particles: An Efficient Nanocatalyst
for Direct Amination of Phenols
Abdol R. Hajipour1,2
| Parisa Abolfathi1
1 Pharmaceutical Research Laboratory,
Department of Chemistry, Isfahan
University of Technology, Isfahan 84156
IR, Iran
2 Department of Neuroscience, University
of Wisconsin, Medical School, 1300
University Avenue, Madison, WI 53706‐
1532, USA
A practical method for the direct amination of phenols using 2,4,6‐trichloro‐
1,3,5‐triazine (TCT) as an efficient promotor for the activation of phenols in
the presence of an efficient and recyclable heterogeneous catalyst prepared by
immobilization of nickel particles on triazole modified chitosan is described.
This heterogeneous catalyst has demonstrated a promising activity for the
conversion of phenolic compounds to their corresponding amine under mild
conditions. Moreover, the obtained catalyst can be reused in five consecutive
runs with consistent catalytic activity.
Correspondence
Abdol R. Hajipour, Pharmaceutical
Research Laboratory, Department of
Chemistry, Isfahan University of
Technology, Isfahan 84156, IR Iran.
Email: haji@cc.iut.ac.ir
KEYWORDS
click reaction, direct amination, heterogenous catalyst, nickel nanoparticle
1 | INTRODUCTION
the best strategie to resolve such a problem and develop
the diversity of functional molecules and could thus be
The synthesis of aryl amines as an important class of
building blocks widely applied in the synthesis of natural
products, pharmaceuticals, agrochemicals and polymers,
has attracted much attention in organic synthesis.[1]
Therefore, the discovery of efficient and practical methods
for the assembly of aromatic C‐N bonds is a matter of
particular interest to synthetic chemists. Among many
synthetic methods available for C–N bond formation,
transition metal‐catalyzed reactions, led by Buchwald
and Hartwig amination of aryl halides[2] and triflates,[3]
are recognized as one of the most practical used methods
in chemical synthesis. Recent progress has been made
toward the catalytic amination of inactive phenolic deriv-
atives,[4–7] which are less expensive and readily available,
in the presence of inexpensive metal catalysts.[8] What is
notable herein is that, for the above method, phenolic
compound as an electrophile require pre‐installation of
reactive functional groups (e.g., esters,[9] carbamates,[10]
used to create new materials. As a result, recent attention
has been focused on the in situ activation of phenols as a
new pathway for creation of an active partner in
cross‐coupling reactions.[14] On the other hand, 2,4,6‐
Trichloro‐1,3,5‐triazine (TCT) as an efficient and mild
promotor for the activation of phenols has received great
attention due to its commercial availability, low cost and
synthetic usage in organic transformations.[15] In fact, this
reagent can active hydroxyl group via conversion to a bet-
ter leaving group (Scheme 1). Along this line, the choice
of nickel complexes as a viable alternative to Pd catalyzed
amination reactions has been attracting considerable
interest in the recent years, due to their low cost and read-
ily availability.[16] However, such amination reactions
applying homogeneous Ni catalytic system always suf-
fered from separation and organic wastes which are very
difficult to reuse. Moreover deactivation of soluble nickel
complex catalysts is often encountered at elevated reac-
tion temperatures and extended reaction times. These
problems associated with homogenous catalyst could be
principally minimized by immobilization of the catalyst
in various solid‐supported.[17]Amongst the different insol-
uble supports, natural materials, especially bio‐based
carbonates,[11] phosphates,[12] triflates and sulfonates[13]
)
to participate in cross‐coupling reactions. Indeed, this
preactivation step limits wider applicability of these proto-
cols in terms of overall yields and step economy.
Undoubtedly, the direct N‐arylation of phenols would be
Appl Organometal Chem. 2018;e4273.
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Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4273

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HAJIPOUR AND ABOLFATHI
SCHEME 1 The nanocatalyst preparation
polymers, have recently engrossed immense attention as
an applicable and interesting alternatives to conventional
solid catalysts. As one kind of the extensively used bio-
polymers, chitosan is renewable, biodegradable, cheap
and non‐toxic polysaccharide. Furthermore, the insolubil-
ity of chitosan in common solvents explains the potential
of chitosan as suitable supports for various reagents and
catalysts.[18–20] Recently, Iranpoor et al. reported
amination of phenols using (TCT) as an efficient
promotor under homogeneous catalytic system applying
various Ni sources and ligands.[21] We recently reported
an interesting chitosan based nickel nanocatalyst which
were synthesized via ‘click’ reaction of an alkynlated
imino‐ thiophene ligand with azide functionalized chito-
san for application in Suzuki reaction. As a part of our
ongoing research work on the application of heteroge-
neous catalytic systems in organic synthesis,[22k] and in
order to determine the efficiency of the previously synthe-
sized catalytic system in various organic reactions,[23] we
would like to evaluate performance of this solid catalyst
for the direct nickel‐catalyzed amination of phenols.
2 | RESULTS AND DISCUSSION
2.1 | Preparation and characterization of
the catalyst
Triazole functionalized chitosan, were prepared in several
steps from the azidated chitosan and an alkynlated ligand.
These starting materials were synthetized as follows
(Scheme 1): an alkynlated imino‐ thiophene ligand was
prepared by reaction of the imino‐ thiophene ligand with
propargyl bromide. The azide group was introduced into
chitosan according to the reported procedure.[24] Then
azidated chitosan underwent a click process with
alkynlated ligand in the presence of active copper (I) to
give the chitosan‐triazole support. Afterwards, the immo-
bilization of Ni nanoparticles was carried out by the
reduction of NiCl2.6H2O in the presence of hydrazine
hydrate as reducing agent to afford the desired solid
catalyst.
The modifications of the chitosan we followed by IR
spectroscopy (Figure 1). As shown in Figure 1c, the
FIGURE 1 FT‐IR spectra of alkynlated
imino‐ thiophene ligand (a), pure chitosan
(b), azidated chitosan (c), triazole‐
modified chitosan (d), triazole‐ modified
chitosan‐Ni (e)

HAJIPOUR AND ABOLFATHI
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absorption bond at 2100 cm‐1 corresponds to N3
stretching, which reveals that the azide moiety have been
successfully immobilized on the surface of chitosan. As
can be seen in Figure 1d, the band attributed to the
azide groups completely was disappeared after the click
reaction between alkynlated ligand and all azide groups.
In addition, two new bands emerged, one of low inten-
sity at 1613 cm‐1 and other of higher intensity at
1490 cm‐1 that were assigned to (C=N vibration) and
(C=C vibration of the aryl ring) respectively. In
Figure 1e, the imine group shifts to lower frequency
and appears at 1578 cm‐1 due to the coordination of
the nitrogen with the nickel.
TABLE 1 Elemental analysis (EA) and inductively coupled
plasma analysis (ICP) results
Sample
C% a H% a N%a S%a Ni%b
Pure chitosan
44/73 6/14 8/67
‐
Azidated chitosan
42/19 5/62 10/29
47/21 5/13 10/32 1/14
‐
Triazole‐modified chitosan
Nickel content (final catalyst)
‐
The catalytic system was also characterized using tech-
niques including elemental analysis (EA), inductively
coupled plasma analysis (ICP), EDX, SEM, TEM, ICP and
XRD analysis. The ICP analysis showed that 1.37% of Ni
1/37
aElemental analysis (EA) (wt%). binductively coupled plasma analysis (ICP)
(wt%).
FIGURE 2 TEM images of nanocatalyst (a and b), SEM photographs of catalyst (c) The particle size distribution of nanoparticles (d)

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HAJIPOUR AND ABOLFATHI
was anchored on the catalyst. The amount of organic moie-
ties on the chitosan surface was determined by elemental
analysis, which was 0.3 mmol/g (Table 1). The particle size,
shape and surface morphologies of the synthesized
nanomaterial were directly visualized by Scanning electron
microscopy (FE‐SEM) and transmission electron micros-
copy (TEM) imaging techniques. As can be seen in
Figure 2 (a and b), TEM image confirms that chitosan
surface is decorated successfully with many well‐
dispersed nickel nanopartices. According to DLS measure-
ment, the average diameter of the spherical particles was
about 10 nm.
The energy dispersive X‐ray (EDX) spectrum in
Figure 3 confirms the presence of C, N, O, S and Ni
species in the structure of catalyst. X‐ray powder diffrac-
tion (XRD) pattern of catalyst is shown in Figure 4. The
strongest peak at 2θ = 20O is attributed to the plane of
the chitosan structure and other diffraction peaks at 2θ
of 44.5O, 51.8O and 76.7O representing (111), (200) and
(220) was attributed to crystal planes of Ni (0), which
matched well with those found in the JCPDS database
(PDF No. 03–1051).[25]
FIGURE 4 XRD pattern of catalyst
summarized in Table 2. Among a variety of solvents that
showed satisfactory conversions (e.g., Toluene, THF and
Dioxane, we chose to proceed with Toluene. In terms of
base, NaH afforded the desired product with the highest
yield. Other bases such as K3PO4, K2CO3 and NaHCO3
resulted in poorer yields. It was found that increasing
the temperature from 80 to 100 °C improved significantly
reaction results. As shown in Table 2, the best result was
obtained when the molar ratio was 3.2, while higher than
this value of substrate ratios did not provide any improved
percentage yields. Under these optimized conditions, we
tried to apply the in situ generated aryl C‐O electrophile
in the cross‐coupling with amines for the preparation of
arylamines. Then, we explored appropriate conditions
for this cross‐coupling reaction using the reaction of
paracresol and morpholine as model reaction. As shown
in Table 3, K2CO3 was the most effective base. On the
basis of this study, the quantitative conversion can be
obtained with increasing the amount of the catalyst to
0.3 mol%. Further scrutiny of the reaction time, amount
of base, temperature and amount of used morpholine
showed that entry 8 has the most effective optimum con-
ditions. To explore the scope of the protocol in the synthe-
sis of diverse arylamines, the present study is extended to
different aryl amines and phenols under the optimized
conditions (Table 4). Aromatic amines including aniline,
n‐methylaniline and diphenylamine carrying either elec-
tron‐withdrawing or electron‐releasing substituents
underwent coupling with phenols and desired product
were synthesized in moderate to good yields. In general,
both electron‐donating and electron‐withdrawing phenols
were suitable substrates in this protocol. The feasibility of
coupling o‐substituted substrate was also examined using
2‐ methyl phenol. Of note, an increasing steric hindrance
of ortho‐ substituted phenols can cause a decrease in the
reaction yield.
2.2 | Catalytic performances
In an initial study to obtain the proper conditions for the
cross‐coupling step, we surveyed the reaction of TCT
under different conditions to achieve a high yield of
2,4,6‐triaryloxy‐1,3,5‐triazine (5),[26] because this step
has a significant role on the progress of the reaction and
total yield. Initially, in order to optimize conditions for
this step, we selected the reaction of TCT and para‐cresol
as the model reaction under various circumstances such
as kind of base and solvent, temperature and the effect
of the molar ratio of phenol to TCT. The results are
FIGURE 3 EDX spectrum of catalyst

HAJIPOUR AND ABOLFATHI
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TABLE 2 Optimization of reaction conditions for synthesis of 2,4,6‐triaryloxy‐1,3,5‐triazinea
Entry
base
Solvent
molar ratiob
T (°C)
Yield (%)c
1
K2CO3
Toluene
3
100
85
2
K2CO3
K2CO3
K2CO3
K3PO4
NaHCO3
NaH
THF
3
70
100
100
100
100
100
90
80
82
44
83
71
91
91
86
92
94
94
91d
90e
3
Dioxane
DMF
3
4
3
5
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
3
6
3
7
3
8
NaH
3
9
NaH
3
80
10
11
12
13
14
NaH
3.1
3.2
3.3
3.2
3.2
90
NaH
90
NaH
90
NaH
90
NaH
90
aReaction conditions: para‐cresol (1 mmol), TCT (0.34 mmol), base (2 mmol), solvent (5 ml). bThe ratio of para‐cresol to TCT. cIsolated yield. d2.5 mmol of base
e
was used. 1.5 mmol of base was used.
of the reaction, which indicating the truly heterogeneous
nature of the nanocatalyst.
2.3 | Reusability and heterogeneity test
Reusability is one of the important purposes for design-
ing heterogeneous catalysts, which can give effective evi-
2.4 | Plausible mechanism
dence about the catalytic stability along successive cycles.
Thus, the potential reuse of catalyst was examined by the
model reaction under optimized conditions. For this pur-
pose, at the end of the reaction as monitored by TLC
analysis, the catalyst was isolated as black powders by
centrifugation, washed with water and ethanol, and
dried at room temperature. The isolated catalyst was
redispersed to the reaction mixture under the same con-
ditions and reused for subsequent runs. It is notable that
catalyst retains 74% of its initial activity even at the fifth
run of the synthesis of desired product (Figure 5). To
determine if the metal is leached out into the solution
during the degradation reaction, the catalyst was col-
lected from the solution after 13 h. The residual solution
was then allowed to react, but no further progress in the
conversion percentage of the reactants was observed after
24 h. Additionally, the ICP result of the solution only
showed 0.061 ppm of the Ni species is leach out from
the supported heterogeneous catalyst during the course
The reaction mechanism for this reaction is suggested
based on reported procedure.[21] In all likelihood, the
nickel metal can coordinate with ortho nitrogen atom of
2,4,6‐triaryloxy‐1,3,5‐triazine and this conveniences the
oxidative addition in which Ni inserts into the C‐O bond
to produce Ni (II) intermediate. In step 2, such an inter-
mediate could react with amine in the presence of
K2CO3 as a base to render intermediates B. Finally, the
Ni (0) catalyst is regenerated by the reductive elimination
of the Ni (II) compound and the expected products are
formed (Scheme 2).
3 | EXPERIMENTAL
All chemical reagents were purchased from Merck Chem-
ical Company and used without further purification. H‐
NMR spectra were recorded on a Bruker 400 spectrometer
1

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HAJIPOUR AND ABOLFATHI
TABLE 3 Optimization of the coupling reaction conditionsa
Entry
base
Catalyst (mol%)
Time (h)
Yield (%)b
1
K2CO3
0.2
8
80
2
K3PO4
NaHCO3
KO‐t‐Bu
KOH
0.2
0.2
0.2
0.2
0.2
0.1
0.3
0.4
0.3
0.3
0.3
0.3
0.3
8
8
8
8
8
8
8
8
8
8
8
8
8
72
68
3
4
67
5
75
6
NEt3
50
7
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
64
8
85
9
78
10
11
12
13
14
84c
85d
68e
86f
88g
aReaction conditions: para‐cresol (1 mmol), morpholine. (1.5 mmol), base (2 mmol), and solvent (5 ml). bIsolated yield. c1.5 mmol of base were used. d2.0 mmol of
e
f
morpholine were used. At 70 °C. At 100 °C. gReaction time was 24 h.
using deutrated CDCl3 as solvent and tetramethylsilane
(TMS) as internal standard. X‐ray diffraction (XRD) pow-
der patterns were obtained using an X’PERT MPD, with
Cu Kα radiation (40 kV, 30 mA). Transmission electron
microscopy (TEM) images were obtained using a Philips
CM10 microscope. FT‐IR spectroscopy (JASCO FT‐IR
680‐Plus spectrophotometer) was employed for characteri-
zation of products. Also we used Inductive coupled plasma
Perkin Elmer Optima 7300 DV, gas chromatography (GC)
(BEIFIN 3420 gas chromatograph equipped with a Varian
CP SIL 5CB column: 30 m, 0.32 mm, 0.25 mm), field emis-
sion scanning electron microscopy [FE‐SEM, HITACHI (S‐
4160)], for consideration of reactions conversions. The
acknowledgements come at the end of an article after the
conclusions and before the notes and references.
(Supplemental Data). Yellow crystals; 1H NMR
(400 MHz, DMSO‐d6): 9.53 (s, 1H), 8.76 (s, 1H), 7.74 (d,
J = 6.8 Hz 1H), 7.60 (d, J = 4 Hz, 1H), 7.17–7.21 (m,
3H), 6.79 (d, J = 11.6 Hz, 2H).
3.2 | Synthesis of propargyl imino‐
thiophene (2)
A 50 ml flask was charged with 5 mmol of compound 1,
10 mmol K2CO3 and 10 ml of acetone. Then 5.2 mmol
of propargyl bromide was added dropwise to this suspen-
sion. The resulting mixture was stirred at 50 °C for 24 h
under a nitrogen atmosphere. After this time the solvent
was removed and the crude was recrystallized from etha-
nol to give a brown crystalline solid. The product was
1
characterized by H NMR spectra (Supplemental Data).
1H NMR (400 MHz, CDCl3): 8.55 (s, 1H), 7.46 (d, J =
6.8 Hz, 1H), 7.43 (d, J = 4.4 Hz, 1H), 7.2 (d, J = 8 Hz,
2H), 7.09–7.12 (m, 1H), 6.97 (d, J = 8 Hz, 2H), 4.68 (s,
2H), 3.56 (s, 1H)
3.1 | Synthesis of imino‐thiophene ligand
(1)
In a 100 ml flask equipped with mechanical stirring and
condenser, 10 mmol of Thiophene‐2‐carbaldehyde and
25 ml of methanol were added. To this suspension was
added 10 mmol p‐aminophenol and solution was refluxed
for 3 h. The solid was filtered and washed with mthanol
and acetone and the pure product 1 was obtained. The
product was characterized by 1H NMR spectra
3.3 | Synthesis of precursors for azidation
Trifluoromethane sulfonyl (triflyl) azide (TFA) solution
was obtained according to a reported procedure.[27]

HAJIPOUR AND ABOLFATHI
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TABLE 4 Amination of various amines with phenols
Entry
1
Phenols
Amines
Producta
Yield (%)a
85
2
3
93
98
4
5
92
98
6
79
77
72
87
90
7
8
9
10
11
82
(Continues)

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HAJIPOUR AND ABOLFATHI
TABLE 4 (Continued)
Entry
12
Phenols
Amines
Producta
Yield (%)a
92
13
53
aIsolated yield.
3.6 | Preparation of triazole‐modified
chitosan @ nickel (0)
At first, 0.2 g of the modified chitosan was dispersed into
ethanol. Afterward, 3.4 ml of 0.1 mol L‐1 NiCl2/ethanol
solution was added to this solution and stirred for 12 h
at room temperature. Then, 2 ml of hydrazine as reducing
agent was then dropwise added to the above mixture at a
temperature of 60 °C. Then the catalyst was separated
from the mixture washed with ethanol and water, and
finally vacuum dried at room temperature.[28]
FIGURE 5 Reusability of the catalyst
3.4 | Synthesis of azide‐functionalized
chitosan
A 50 ml flask equipped with mechanical stirring was
charged 0.5 g of chitosan, 0.5 M aqueous HCl. NaHCO3
(9.3 mmol, 20 ml), 0.09 mmol of CuSO4.5H2O, 5.95 mmol
of triflyl azide (TFA) solution and 15 ml of acetonitrile.
The reaction mixture was stirred at room temperature
for 5 days. Finally, the solid was filtered and washed with
acetonitrile, HCl solution (5% solution in water) and then
water and dried at room temperature.[24]
3.7 | General procedure for direct
amination of phenols
A mixture of phenol (1 mmol), and NaH (1.5 mmol) in dry
toluene (4 ml) was stirred at room temperature for 2 h. Then
0.31 mmol of TCT were added to the mixture and the solu-
tion was stirred at 90 °C. The reaction monitoring was car-
ried out by TLC. After completion of the reaction, amine
(1.5 mmol), catalyst (0.3 mol%), and K2CO3 (2.0 mmol) were
added to the reaction mixture. The progress of the reaction
was checked by TLC. After the specified time, the mixture
was cooled to room temperature, and the catalyst was sepa-
rated from the reaction mixture by centrifugation. The reac-
tion mixture was quenched with water and extracted with
CH2Cl2, and the organic phase was dried over Na2SO4.
The crude product was purified by column chromatography
3.5 | Click Reaction
In a 50 ml flask equipped with magnetic stirring contain-
ing azide functionalized chitosan (0.5 g) and compound 2
(2 mmol), CuI (0.1 mmol) in DMF/THF (1:1, V/V) solu-
tion were added and the mixture was stirred for 72 h at
that temperature. Finally, the solid particles were filtered
from the mixture, washed several times with Et2O, H2O
and then acetone and dried in vacuum at 60 °C.
1
(hexane/ethyl acetate) to achieve the desired purity. H
NMR spectrum of some of the products has been given in
the supporting information.

HAJIPOUR AND ABOLFATHI
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SCHEME 2 A plausible mechanism for
the formation of the amination of phenols
by TCT reagent
A. Ricc), Wiley‐VCH, Weinheim 2007. c) M.‐Y. Chou, M.‐K.
Leung, Y. O. Su, C. L. Chiang, C.‐C. Lin, J.‐H. Liu, C.‐K. Kuo,
C.‐Y. Mou, Chem. Mater. 2004, 16, 654. d) P. Strohriegl, J. V.
Grazulevicius, Adv. Mater. 2002, 14, 1439. e) R. Hili, A. K.
Yudin, Nat. Chem. Biol. 2006, 2, 284.
4 | CONCLUSIONS
In summary, we have applied nickel nanoparticles sup-
ported on modified chitosan as economical and efficient
heterogeneous catalysts in the direct amination of phe-
nols by 2,4,6‐trichloro‐1,3,5‐triazine (TCT) for the activa-
tion of phenols. Additionally, broad substrate scope and
the use of an inexpensive chitosan and nickel metal make
it a favorable strategy from industrial view point.
[2] (a) J. Louie, J. F. Hartwig, Tetrahedron Lett. 1995, 36, 3609. (b)
A. S. Guram, R. A. Rennels, S. L. Buchwald, Angew. Chem.
Int. Ed. Engl. 1995, 34, 1348. (c) J. P. Wolfe, S. L. Buchwald,
J. Org. Chem. 1996, 61, 1133. (d) A. Gniewek, J. Org. Chem.
2016, 823, 90.
[3] (a) J. P. Wolfe, S. L. Buchwald, J. Org. Chem. 1997, 62, 1264. (b)
S. Cacchi, P. G. Ciattini, E. Morera, G. Ortar, Tetrahedron Lett.
1986, 27, 3931. (c) J. Louie, M. S. Driver, B. C. Hamann, J. F.
Hartwig, J. Org. Chem. 1997, 62, 1268.
ACKNOWLEDGEMENTS
We gratefully acknowledge the funding support received
for this project from the Isfahan University of Technology
(IUT), IR of Iran, and Isfahan Science and Technology
Town (ISTT), IR of Iran. Further financial support from
the Center of Excellence in Sensor and Green Chemistry
Research (IUT) is gratefully acknowledged.
[4] For examples of tosylate and mesylate amination, see: (a) B. C.
Hamann, J. F. Hartwig, J. Am. Chem. Soc. 1998, 120, 7369; (b)
A. H. Roy, J. F. Hartwig, J. Am. Chem. Soc. 2003, 125, 8704.
(c) T. Ogata, J. F. Hartwig, J. Am. Chem. Soc. 2008, 130,
13848. (d) C.‐Y. Gao, L.‐M. Yang, J. Org. Chem. 2008, 73, 1624.
(e) B. P. Fors, D. A. Watson, M. R. Biscoe, S. L. Buchwald,
J. Am. Chem. Soc. 2008, 130, 13552. (f) C. M. So, Z. Zhou, C.
P. Lau, F. Y. Kwong, Angew. Chem. Int. Ed. 2008, 47, 64026.
ORCID
Abdol R. Hajipour http://orcid.org/0000-0002-7737-0558
[5] The amination of aryl methyl ethers is largely limited to the
coupling of 2‐methoxynaphthalene with cyclic secondary
amines. Deviation from these substrates leads to significantly
lower yields (ca. 30– 50%). M. Tobisu, T. Shimasaki, N. Chatani,
Chem. Lett. 2009, 38, 710.
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SUPPORTING INFORMATION
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How to cite this article: Hajipour AR, Abolfathi
P. Chitosan‐Supported Ni particles: An Efficient
Nanocatalyst for Direct Amination of Phenols. Appl
Organometal Chem. 2018;e4273. https://doi.org/
10.1002/aoc.4273
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