Cerium-containing MCM-41 catalyst for selective oxidative arene cross-dehydrogenative coupling reactions

Article abstract of DOI:10.1016/j.cattod.2012.05.029

Cerium (IV)-mediated intermolecular direct biaryl coupling of aromatic tertiary amines and naphthol via dual CH bond activation has been reported. The new CC bond is formed regioselectively ortho to the amino and hydroxyl substituents under oxidative conditions to give substituted bifunctional amino naphthols. We report here the use of Ce-MCM-41 catalyst for the synthesis of these unsymmetrical biaryls via oxidative cross coupling under mild conditions. The catalyst was recovered by simple filtration and reused for several cycles with consistent activity.

Full text of DOI:10.1016/j.cattod.2012.05.029

Catalysis Today 198 (2012) 35–44
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Catalysis Today
journal homepage: www.elsevier.com/locate/cattod
Cerium-containing MCM-41 catalyst for selective oxidative arene
cross-dehydrogenative coupling reactions
Adinarayana Murthy Akondia, Rajiv Trivedia,∗, Bojja Sreedhara, Mannepalli Lakshmi Kantama,b
,
Suresh Bhargavab,c
a Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500607, India
b RMIT-IICT Research Centre, Indian Institute of Chemical Technology, Hyderabad 500607, India
c Advanced Materials & Industrial Chemistry Group, School of Applied Sciences, RMIT University, Melbourne, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Cerium (IV)-mediated intermolecular direct biaryl coupling of aromatic tertiary amines and naphthol
via dual C H bond activation has been reported. The new C C bond is formed regioselectively ortho to
the amino and hydroxyl substituents under oxidative conditions to give substituted bifunctional amino
naphthols. We report here the use of Ce-MCM-41 catalyst for the synthesis of these unsymmetrical biaryls
via oxidative cross coupling under mild conditions. The catalyst was recovered by simple filtration and
reused for several cycles with consistent activity.
Received 16 February 2012
Received in revised form 18 April 2012
Accepted 1 May 2012
Available online 15 June 2012
Keywords:
Ce-MCM-41
© 2012 Elsevier B.V. All rights reserved.
C
H activation
Amino naphthols
Oxidative cross-coupling
Heterogeneous catalysis
1. Introduction
C
C bonds involves the direct oxidative coupling of two arene C
H
substrates under mild conditions [8].
The constructions of C C bonds, especially aryl–aryl linkages,
are among the most important reactions in organic synthesis [1].
Biaryl structures are a ubiquitous motif in biological, pharmaceu-
tical, and material sciences [2]. Numerous economically important
pharmaceuticals and agrochemicals such as valsartan, boscalid, and
liquid-crystalline NCB 807 have biaryl units as indispensable sub-
structures [3]. A vast majority of biaryl linkages are constructed
via metal-mediated cross coupling of two pre-functionalized arene
building blocks [4]. However, the required organometallic nucle-
ophilic reagents are relatively expensive and rarely commercially
available. With the emergence of the concepts of atom econ-
omy and green chemistry, metal-catalyzed C H bond activation
as well as direct use of unactivated C H bonds for C C bond
formation has attracted much interest in recent years [5]. More-
over, it has been reported that biaryls containing amino naphthols
functionalities act as organo catalysts and ligand precursors in
asymmetric catalysis [6]. Although several reports have been pub-
lished on homo-coupling of either naphthols or aniline derivatives,
the regioselective cross-coupling of unactivated moieties is often
challenging [7]. An efficient approach for the formation of new
In recent years, several groups have reported cross dehydro-
genative coupling reactions [9]. In particular, the C H activation
of aromatic tertiary amines and subsequent C C bond formation
with nucleophiles has gained much attraction [10]. These oxida-
tive coupling reactions require the presence of metal ions together
with a one-electron oxidant [11]. A majority of these coupling reac-
tions are catalyzed by salts of transition metals (such as copper,
iron, nickel palladium, ruthenium and rhodium), under appropri-
ate conditions [12]. There is a growing demand for the development
of new catalyst systems based on readily available and relatively
cheap non-noble metals. In this regard, cerium salts are particularly
appealing, since they have low toxicity, reasonable solubility in
many organic media, air stable, easily handled, and are inexpensive
[13].
The propensity of Ce(IV) to efficiently participate in one-
electron transfer reactions while existing in stable oxidation states
+3 and +4, and its high reduction potential (1.61 V vs. normal
hydrogen electrode), makes it a very efficient oxidizing agent
compared to many other metal cations. Its salts, such as the com-
mercially available cerium ammonium nitrate (CAN), have found
wide spread use as one-electron oxidants [14]. The dual role of
CAN as an oxidant and a Lewis acid facilitates its catalytic role
in cross-dehydrogenative coupling (CDC) reactions [15]. Various
oxidative reactions involving CAN in homogeneous media have
∗
Corresponding author. Tel.: +91 40 27191667; fax: +91 40 27160921.
E-mail addresses: trivedi@iict.res.in, rtrajiv401@gmail.com (R. Trivedi).
0920-5861/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2012.05.029

36
A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
been reported by several groups [16]; however, they suffer from
serious limitations such as high catalyst loading, difficulty in recov-
ery and reusability of the catalyst and tedious work-up procedures.
The development of highly active and reusable heterogeneous cat-
alysts for C C cross dehydrogenative coupling reactions is an open
challenge [17].
2.3. Synthesis of catalyst (Ce-MCM-41)
MCM-41 was prepared by the direct hydrothermal method
described in the literature [22] and dried at 80 ◦C for 10 h prior to
use. The cerium-loaded MCM-41 mesoporous material was pre-
pared by a wet impregnation method using 10% and 15% ceric
ammonium nitrate solution respectively [23]. All the characteriza-
tion studies were carried out with Ce-MCM-41 loaded with 15 wt%
of cerium. The calcined template-free MCM-41 (0.21 g) was added
to 10 mL of an aqueous solution of ceric ammonium nitrate (0.12 g,
0.02 M) and stirred vigorously for 24 h at room temperature. The
solid was isolated by evaporation of the solvent, dried overnight at
100 ◦C and then calcined at 500 ◦C in air for 5 h to obtain Ce-MCM-41
containing 15 wt% of cerium.
In the last few decades, mesoporous materials have received
much attention in the field of catalysis, especially for their use as
solid supports [18]. These porous supports have uniform pore size
and large surface area and are ideal materials for heterogenization
of various metal salts. The most widely used mesoporous silica,
MCM-41, exhibits a highly ordered hexagonal array of one dimen-
˚
sional mesopores with diameters varying from 15 to 100 A [19]. In
Ce-MCM-41, cerium (IV) ions are covalently anchored to silica. It
is well known that cerium, coordinated with tetrahedral silicon via
oxygen bridges, acts as a Lewis acid catalyst for selective oxidations
in the presence of peroxides [20]. Therefore, it was conceptual-
ized that the use of Ce-MCM-41 as catalyst should result in good
yields of biaryls under mild conditions as compared to homogenous
system. Herein, we report a facile and reusable heterogeneous cata-
lyst, namely Ce-MCM-41 for the synthesis of unsymmetrical biaryls
through C H activation [21].
2.4. Experimental procedure for the synthesis of N,N-dialkyl
aniline derivatives
To a solution of aniline (1 mmol) in glacial acetic acid (7 mL)
under argon was added paraformaldehyde (10 mmol) and sodium
cyanoborohydride (5 mmol). After stirring overnight, the reaction
mixture was poured into ice cooled water (∼100 mL) containing
NaOH (7 g). This mixture (pH 14) was extracted thrice with CH2Cl2
(3 × 350 mL). The combined organic layers were dried over MgSO4,
filtered, and concentrated under reduced pressure to obtain the
crude product. Flash chromatographic purification of the crude
product using silica gel and a mixture of hexane and ethyl acetate
as the eluent provided the pure product.
2. Experimental
2.1. Chemicals and reagents
Sodium silicate (NaSiO3·9H2O), cetyl trimethyl ammonium
bromide (CTAB), ceric ammonium nitrate (CAN), tertiary butyl
hydrogen peroxide (TBHP, 70 wt% in water), ditertiary butyl perox-
ide (DTBP), H2O2 (30 wt% in water), and all other starting materials
and reagents were purchased from Sigma–Aldrich and are used as
received. All the solvents used are of analytical grade and were pur-
chased from Merck India Ltd. Deionized water was used to prepare
the aqueous solutions. Sulfuric acid and sodium hydroxide were
used to control the pH of the aqueous solutions.
2.5. General procedure for the synthesis of
1-(5-R-2-(piperidin-1-yl)phenyl)naphthalen-2-ol (R = alkyl,
alkoxy, halide)
A suspension of phenyl boronic acid (2.0 mmol), Cu(OAc)2·H2O
˚
(10 mol%) and powdered 4 A molecular sieves (0.75 g) in
dichloromethane (8 mL) was stirred for 5 min at room tempera-
ture. To this mixture was added the amine (1.0 mmol). The reaction
vessel was sealed with a rubber septum and stirred at 40 ◦C under
oxygen for 24 h. The reaction mixture was then filtered through a
plug of Celite and the product was purified by column chromatog-
raphy using silica gel and a mixture of hexane and ethyl acetate as
the eluent.
2.2. Instrumentation
The Thin Layer Chromatography (TLC) was performed on Merck
silica gel 60 F254 plates using ethyl acetate and hexane as eluting
agents. Thin layer chromatography plates were visualized by expo-
sure to UV-light/iodine and/or by immersion in an acidic staining
solution of phosphomolybdic acid followed by heating on a hot
plate. Purification of products was carried out by column chro-
matography using silica gel (100–200 mesh) and a mixture of ethyl
acetate and hexane as eluting agent. All the products were charac-
terized by Mass, 1H and 13C NMR spectroscopy. The NMR spectra
of samples were acquired on a Varian Unity Inova 500 MHz, Inova
400 MHz, and Bruker Avance 300 MHz spectrometer using TMS
as an internal standard in CDCl3. Mass spectra were acquired on
a Thermo LCQ fleet ion trap mass spectrometer. High-resolution
mass spectra were acquired on a Q STAR XL Hybrid LC/MS/MS
system, Applied Biosystems, USA. FT-IR data were acquired on
a Thermo Nicolet Nexus 670 FT-IR spectrometer with DTGS KBr
detector. XPS spectra were recorded on a Kratos AXIS 165 with
a dual anode apparatus using the Mg K␣ anode. X-ray powder
diffraction data were collected on a Siemens/D-5000 diffractometer
using Cu K␣ radiation. The particle size and external morphology
of the samples were observed on a Philips TECNAI F12 FEI trans-
mission electron microscopy (TEM). SEM-EDX was performed on a
Hitachi SEM S-520, EDX-Oxford Link ISIS-300 instrument. Diffuse
reflectance UV/vis spectra for samples as KBr pellets were recorded
on a GBC Cintra 10e UV–vis spectrometer in the range 200–800 nm
with a scan speed 400 nm/min.
2.6. General procedure for the synthesis of unsymmetrical biaryls
A 25 mL round bottomed flask was charged with N,N-dialkyl-
aniline (0.5 mmol), 2-naphthol (0.5 mmol) and acetonitrile (3 mL),
followed by 10 mg of Ce-MCM-41 and TBHP (2 equiv.) via syringe.
The mixture was heated to 60 ◦C and stirred for 3 h in open air.
After completion of the reaction, as judged by TLC, the solution was
cooled and the catalyst was removed by filtration. The resulting
crude mixture was gently evaporated under reduced pressure and
purified by column chromatography using silica gel and a mixture
of hexane and ethyl acetate as the eluent.
3. Results and discussion
The optimization studies for cross-dehydrogenative coupling
reaction were performed in
a 0.5 mmol scale using N,N,4-
trimethylaniline and 2-naphthol as the model substrates in
acetonitrile at 60 ◦C. Employing 2 equiv. of TBHP as the oxidant, var-
ious cerium salts such as CeCl3, Ce(SO4)2, CAN, 5% Ce-MCM-41,10%
Ce-MCM-41,15% Ce-MCM-1and 20% Ce-MCM-41, were examined
for their catalytic activity. Among cerium salts screened, CAN was
found superior to other salts such as CeCl3 and Ce(SO4)2, and fur-
nished the corresponding cross coupled product in moderate to

A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
37
Table 1
Optimization of reaction conditions for cross-dehydrogenative coupling reactiona,b
.
N
Catalyst
Oxidant
OH
N
+
Solvent
OH
.
Entry
Catalyst
Oxidant
Solvent
Temperature (◦C)
Time (h)
Yieldc (%)
1
2
3
4
5
6
7
8
CeCl3
Ce(SO4)2
CAN
MCM-41
TBHP
TBHP
–
TBHP
TBHP
TBHP
TBHP
H2O2
DTHP
O2
TBHP
TBHP
TBHP
TBHP
K2S2O8
m-CPBA
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
MeOH
DCM
80
60
30
80
80
80
60
80
80
80
100
80
100
100
80
12
12
3
10
12
6
3
6
6
10
8
8
12
8
10
10
Traces
30
40
0
5% Ce-MCM-41
10% Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
20%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
15%Ce-MCM-41
Traces
20
66
30
25
20
10
20
65
40
0
9
10
11
12
13
14
15
16
CH3CN
Toluene
CH3CN
CH3CN
80
0
DTHP - ditertiary butyl hydro peroxide, TBHP - tertiary butyl hydrogen peroxide, mCPBA - meta chloro per benzoic acid.
a
Reactions (entries 1–3) were carried out with N,N,4-trimethylaniline (0.5 mmol), 2-naphthol (0.5 mmol), oxidant (2 equiv.) and catalyst (20 mol%) in acetonitrile (3 mL).
Reactions (entries 4–16) performed in a 0.5 mmol scale (with respect to amine) using 10 mg (0.9 mol% for entries 7–12, 14–16) of catalyst.
Isolated yields (based on amine) after column chromatography.
b
c
good yield in a short reaction time (Table 1, entries 1–3). Notably,
Table 2, this reaction is general for various N,N-disubstituted
anilines containing electron donating substituents in meta- and
para- position of the aromatic ring. For example, the reaction
proceeded smoothly for substituted N,N-dimethylanilines such
as, 4-ethyl-N,N-dimethylaniline, 4-methoxy-N,N-dimethylaniline,
4-isopropyl-N,N-dimethylaniline, and 4-halo-N,N-dimethylaniline,
with 2-naphthol to furnish the corresponding cross dehy-
drogenative coupling products in good yields (Table 2). The
reaction of amines containing two substituents; namely, 3-bromo-
N,N,4-trimethylaniline and N,N,3,4-tetramethylaniline, proceeded
smoothly to yield the respective products (Table 2, entries 11 and
12). It is noteworthy that for these substrates the reactions occurs
regioselectively at the less hindered 6th position of the phenyl ring.
Similarly, cyclic amines also reacted smoothly to afford the respec-
tive products in good yields (Table 2, entries 14–20). In contrast, the
reaction failed to yield the desired products for ortho- substituted
anilines as well as amine containing strong electron withdrawing
groups (Table 2, entries 5, 10 and 13). The ortho regioselectivity
of the oxidative cross coupling presumably arise from the hydro-
gen bonding between amino and hydroxyl groups (geometrical
proximity between ortho C H bonds) [7a], and the unsymmetrical
coupling pattern (through NMR analysis) observed in the coupled
product of unsubstituted N,N-dimethyl aniline and 2-naphthol con-
firmed the ortho regioselectivity of C C bond (Table 2, entry 21).
Furthermore, this protocol is not applicable for mono alkylated ani-
lines as well as simple anilines as their reaction failed to proceed
[24]. In the present work, use of only 0.9 mol% of catalyst gave com-
parative yields to the homogeneous system [7a]. Moreover, the
unacceptable metal contamination in the desired isolated prod-
uct observed with homogeneous iron catalyst was not observed
in the present system. We also extended the scope of reaction in
the cross-coupling of N-phenyl (substituted) piperidine and mor-
pholine derivatives with 2-naphthol (Table 2, entries 14–20). The
catalytic efficacy of mesoporous catalyst Ce-MCM-41 was found
to be much higher than the corresponding homogeneous catalysts.
Hence this system provides greener synthetic pathways for organic
transformations.
it was observed that the use of 10 mg (0.9 mol%) of Ce-MCM-41 con-
taining 15 wt% of ceria increased the product yield to 66% (Table 1,
entry 7). Thereafter, optimization studies for solvents revealed
acetonitrile as the best solvent compared to DCM, methanol and
toluene (Table 1, entries 7, 11, 12, and 14). Later, different oxidants
like H2O2, mCPBA, K2S2O8, DTHP and oxygen were examined; how-
ever, all these were found to be least effective as compared to TBHP
(Table 1, entries 7–10, 15, and 16). Thus, among the various opti-
mization studies listed in the Table 1, the most promising result
was obtained using Ce-MCM-41 (containing 15 wt% of ceria) as cat-
alyst employing TBHP and acetonitrile as the oxidant and solvent
respectively (Table 1, entry 7).
The catalytic cerium species was anchored on the inner sur-
face of the mesopore of MCM-41 to exhibit high activity and good
reusability. The surface acidity of the catalyst calculated by using
NH3-TPD analysis was 0.6330 mmol/g. The enhanced efficacy of Ce-
MCM-41 in the catalytic C C coupling reaction is attributed to the
high internal surface area of the mesoporous catalyst that provides
enough space for organic substrate to interact with active acidic
sites present on the solid surface inside the ordered mesopore
[19a,20]. It was observed that the yields for this reaction were not
encouraging with ≤5% loading of ceria whereas, the yields obtained
with 15% Ce-MCM-41 loading was higher than that for 10% Ce-
MCM-41. This implied that a higher amount of cerium in the frame
work was favorable for an increased catalytic activity of Ce-MCM-
41. However, further increase in the metal loading (20–25%) did not
change the reactivity of the catalyst and percentage of conversion
even at elevated temperature. This is probably due to a relatively
disordered mesostructure arising from the excessive ceria loading,
as evidenced by the decreasing intensities of the low angle peaks in
powder XRD pattern and gradual change in the structural morphol-
ogy of catalyst confirmed by SEM and TEM [19a]. Notably, cerium
doped commercially available silica remained virtually inactive in
this reaction.
Using the above optimized conditions, the scope of this method
was explored for different amine substrates. As depicted in

38
A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
Table 2
Oxidative cross-coupling of substituted N,N dialkyl anilines and 2-naphthol in the presence of Ce-MCM-41 and TBHPa,b
.
R
X
H
OH
N
X
N
OH
Ce-MCM-41/ [O]
CH3CN, 600C
H
R
3
1
2
45-66% yield
R = alkyl, alkoxy, halide; X =carbon, oxygen
Entry
.
1
Productb
Yieldc
N
N
OH
1.
3a
3b
66, 63d
N
N
OH
2.
63
N
N
OH
3.
4.
3c
61
62
O
N
O
N
OH
3d
O
N
N
N
O
OH
5.
3e
3f
0
F
N
OH
F
6.
58
54
45
48
0
Cl
N
N
OH
Cl
N
7.
3g
3h
3i
Br
N
OH
Br
N
8.
I
N
OH
I
9.
O N
2
N
N
OH
NO2
10.
3j

A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
39
Table 2 (Continued)
Entry
1
Productb
Yieldc
N
N
OH
11.
3k
65
Br
N
N
N
OH
Br
12.
13.
14.
3l
60
0
N
OH
3m
3n
N
OH
N
N
N
N
N
62
O
N
O
OH
15.
16.
17.
3o
3p
3q
60
48
45
F
N
F
OH
Cl
N
Cl
Br
OH
Br
N
OH
18.
19.
3r
3s
50
N
O
OH
N
O
O
64, 61d
O
N
O
O
OH
N
20.
3t
62
61
N
N
OH
21.
3u
a
Reaction conditions: amine (0.5 mmol), 2-naphthol (0.5 mmol), Ce-MCM-41 (0.9 mol%) and TBHP (2 equiv.), 60–80 ◦C, 3 h.
All products are characterized by NMR and mass spectroscopy.
Isolated yields after column chromatography.
b
c
d
Yield after fifth cycle.
3.1. Proposed mechanism
potential as compared to 2-naphthol, is more susceptible to
oxidation by Ce(IV) to form radical cation and in turn
a
The plausible mechanism for the Ce-MCM-41 catalyzed
cross-dehydrogenative coupling reaction is described as fol-
lows (Scheme 1). N,N-dialkylaniline, having higher reduction
yielding a Ce(III) species. This should be followed by the con-
current partial coordination of nitrogen and oxygen of amine
and naphthol respectively to the Ce-MCM-41.
A sequential

40
A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
R
H
R
H
OH
Si
N
O
O
N
H
H
N
-H+
N
O
Si
Ce(III)
O
Ce(IV)
-e-
H
OH
Si
R
R
-e-/-H
+
TBHP
R
N
OH
Scheme 1. Proposed reaction pathway for the oxidative cross-coupling with Ce-MCM-41.
3.2. Characterization of the Ce-MCM-41 catalyst
3.2.1. FT-IR analysis
From the Fig. 1 (IR spectra), it has been observed that the band
around 960 cm−1 (in MCM-41 Fig. 1a) is shifted toward the higher
wave number side (shown by dotted lines in the Fig. 1) in the case
of Ce impregnated MCM-41samples (Fig. 1a and b) and thus can
be assigned to asymmetric stretching vibration of Si
O Ce bond
[26]. This is in accordance with a similar higher wave number shift
Fig. 1. FT-IR spectra of (a) MCM-41 (b) fresh Ce-MCM-41 and (c) used Ce-MCM-41
(after 1st recycle).
deprotonation and oxidation (by TBHP) step provides the
final product. Later, Ce(IV) is regenerated via the oxidation
of Ce(III) by TBHP, and hence the catalytic cycle continues
[25].
Fig. 2. X-ray diffraction patterns of (a) MCM-41, (b) fresh Ce-MCM-41 and (c) used
Fig. 3. XPS spectra of (a) fresh Ce-MCM-41 and (b) used Ce-MCM-41 (after 3rd
Ce-MCM-41 (after 1st recycle).
recycle).

A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
41
Fig. 4. SEM images of (a) MCM-41 (b) fresh Ce-MCM-41 (c) used Ce-MCM-41 (1st cycle) and (d) Ce-MCM-41 (5th cycle).
observed by Kumar and co-workers for the Si
O
Ce absorption
(fresh), and Ce-MCM-41 (after 1st recycle) samples suggesting that
there mesoporous frameworks are similar. In addition, the diffrac-
tion peaks observed at 2ꢀ = 28.5◦, 47.4◦ and 56.3◦ in the high angle
XRD patterns of Ce-MCM-41 and Ce-MCM-41 (after 1st recycle)
confirms the presence of ceria [27].
band [19a]. Notably, IR spectra of both the fresh Ce-MCM-41 and
used Ce-MCM-41 (after 1st recycle) were rather identical to that
of MCM-41, suggesting the framework of MCM-41 is retained after
incorporation of cerium.
3.2.2. XRD analysis
3.2.3. XPS analysis
Fig. 2 shows the powder X-ray diffraction patterns of the MCM-
41, Ce-MCM-41 (fresh), and Ce-MCM-41 (after 1st recycle). The
most intense diffraction peak of MCM-41 appears at 2ꢀ = 2◦–3◦.
Other low intensity diffraction peaks of higher order appear at
2ꢀ = 4◦–5◦. This diffraction pattern is observed in Ce-MCM-41
Fig. 3 displays the XPS spectra of fresh Ce-MCM-41 (Fig. 3a)
and used Ce-MCM-41 (after 3rd recycle, Fig. 3b). The peak located
at 883.1and 899.0 eV can be assigned to the Ce 3d5/2, while the
peaks located at 901.3 and 917.1 eV can be assigned to the Ce 3d3/2
.
These values are consistent with CeO2. It is also observed that a
peak located at about 530.4 eV, corresponds to the O 1s and can
be attributed to the oxygen in Ce O linkages. The intense peak
at ca. 532.4 eV can be assigned to the Si O bond [22,28]. Similar
results were also obtained for the used catalyst. Therefore, it can be
concluded that the cerium cations in both the fresh and used cat-
alysts are retained in the pore wall of the mesoporous molecular
sieves through Ce
O Si bond. On quantification it is observed that
the ratio of SiO2:CeO2 is 2:1 in both the fresh and used catalyst,
which also confirms that the homogeneity of the catalyst remains
unaltered even after five catalytic cycles.
3.2.4. SEM and EDX
Fig. 4 shows the SEM micrographs of MCM-41, fresh Ce-MCM-
41, used Ce-MCM-41 (after 1st cycle) and Ce-MCM-41 (after 5th
cycle). The SEM micrographs for the fresh and used Ce-MCM-41
(after 1st cycle) showed similar particle morphology and the Si/Ce
ratios of these samples do not differ significantly as demonstrated
by EDX analysis, indicating the incorporation of well-dispersed
cerium into the framework of the MCM-41 [19a]. However, there
Fig. 5. The diffuse reflectance UV–vis spectra of (B) MCM-41 and (D) Ce-MCM-41.

42
A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
Fig. 6. TEM images of (a) fresh catalyst, and (b) used catalyst (after 5th cycle).
was a gradual change in the catalyst morphologies with the increas-
ing number of recycles.
Appendix A.
A.1. Spectral information
1-(2-(Dimethylamino)-5-methylphenyl)naphthalene-2-ol1
[3a]: colorless solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.7), mp 158–159 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.82–7.71 (m, 3H), 7.38–7.30 (m, 3H), 7.21 (m, 3H),
2.71 (s, 6H), 2.34 (s, 3H); 13C NMR (75 MHz, CDCl3, ppm): ı 152.1,
147.6, 135.8, 130.6, 130.2, 129.9, 129.6, 129.2, 128.9, 128.1, 126.0,
125.3, 123.0, 120.6, 117.9, 112.5, 43.7, 20.7; FTIR (cm−1): 2924,
2860, 1724, 1620, 1509, 1462, 1342, 1234, 1177, 1090, 1041, 963,
932, 816, 751, 511, 433; MS (ESI) m/z: 278 [M+H]+; HRMS (ESI)
calcd. for C19H20NO [M+H]+: 278.1544; found: 278.1535.
3.2.5. Diffuse reflectance UV–visible spectroscopy
Fig. 5 shows the overlay of the diffuse reflectance UV–vis spec-
tra of the MCM-41 and Ce-MCM-41. The UV–vis spectrum of
Ce-MCM-41 clearly displays a high intensity band with a maxi-
mum around 250, 265 and 280 nm attributed to the presence of
Ceria, and two types of well dispersed Ce+4 species (higher energy
tetra-coordinated, lower energy hexa-coordinated) [29]. This is also
evident by the high reactivity of the catalyst. Hence, we predict that
the synthesized Ce-MCM-41 sample is mixture of ceria along with
some Ce+4 species [19a,22].
1-(2-(Dimethyl amino)-5-ethyl phenyl) naphthalene-2-ol1
[3b]: brownish solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.6), mp 186–187 ◦C; 1H NMR (500 MHz,
CDCl3, ppm): ı 7.76–7.70 (m, 3H), 7.32–7.26 (m, 2H), 7.21–7.12
(m, 4H), 2.67 (s, 6H), 2.64–2.60 (q, 2H, J = 8.0 Hz), 1.24–1.21 (t, 3H,
J = 8.0 Hz); 13C NMR (75 MHz, CDCl3, ppm): ı 152.2, 147.2, 139.2,
134.8, 133.5, 130.6, 129.9, 129.3, 128.2, 127.8, 126.1, 125.2, 123,
122.4, 120.6, 118.2, 44, 28.2, 15.8; FTIR (cm−1): 3391, 3059, 2963,
1718, 1662, 1621, 1503, 1457, 1348, 1274, 1219, 1119, 969, 896,
822, 752, 622, 548; MS (ESI) m/z: 292 [M+H]+; HRMS (ESI) calcd.
3.3. Reusability of the catalyst
After completion of the reaction, the catalyst was removed from
the reaction mixture by simple filtration and washed sequentially
with dichloromethane and methanol to remove organic material.
Finally, it was oven dried and reused without any further treatment.
However, there was a slight decrease in the catalytic activities with
the increasing number of recycles (Table 2, entries 1, 19). This was
evident from the SEM (Fig. 5) as well as from TEM analysis (Fig. 6) of
the used catalyst, wherein these analyses reveal a gradual change
in the catalyst morphologies with increasing number of recycles. In
addition, no quantifiable amount of leached cerium was detected
in the filtrate by ICP-AES analysis, hence it can be concluded that
the catalytic process is truly heterogeneous.
for C20H
22NO [M+H]+: 292.1701; found: 292.1711.
1-(2-(Dimethyl amino)-5-isopropyl phenyl) naphthalene-2-ol1
[3c]: reddish brown solid, isolated by column chromatogra-
phy (ethyl acetate:hexane = 1:9, Rf = 0.5), mp 98–100 ◦C; 1H NMR
(300 MHz, CDCl3, ppm): ı 7.84–7.77 (m, 3H), 7.37–7.29 (m, 4H),
7.20–7.13 (m, 2H), 2.82 (m, 1H), 2.66 (s, 6H), 1.24–1.21 (m, 6H);13
C
NMR (75 MHz, CDCl3, ppm): ı 152.1, 147.5, 143.3, 133.4, 130.4,
129.8, 129.5, 129.1, 128.1, 126.2, 125.9, 125.3, 124.9, 122.9, 120.6,
117.9, 43.6, 33.4, 23.9; FTIR (cm−1): 3446, 2959, 2870, 1716, 1672,
1621, 1595, 1498, 1461, 1363, 1232, 1095, 955, 819, 753, 625; MS
(ESI) m/z: 306.2 [M+H]+; HRMS (ESI) calcd. for C20H24NO [M+H]+:
306.1852; found: 306.1857.
4. Conclusions
In conclusion, we have prepared a heterogeneous Ce-MCM-
41 catalyst and successfully used it for the oxidative arylation of
N,N-dialkyl anilines. The catalyst showed notable activity for the
carbon–carbon coupling of a variety of substituted anilines with
2-naphthol under mild conditions. Thus, the Ce-MCM-41 offers an
effective and facile catalytic method for the synthesis of a wide
variety of bifunctional amino naphthols.
1-(2-(Dimethyl amino)-5-methoxy phenyl) naphthalene-2-ol1
[3d]: brownish solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.4), mp 136–137 ◦C; 1H NMR (500 MHz,
CDCl3, ppm): ı 7.80–7.71 (m, 3H), 7.33–7.27 (m, 2H), 7.20 (d, 1H,
J = 8.9 Hz), 7.14 (d, 1H, J = 8.9 Hz), 6.92–6.88 (m, 2H), 3.73 (s, 3H),
2.65(s, 6H); 13C NMR (75 MHz, CDCl3, ppm): ı 155.4, 152.1, 142.7,
133.3, 132.1, 129.8, 129.5, 128.1, 127.6, 126.1, 125.0, 123.0, 120.6,
119.8, 119.2, 114.1, 55.5, 44.1; FTIR (cm−1): 2924, 2854, 1732, 1623,
1503, 1461, 1342, 1239, 1171, 1092, 1035, 957, 929, 813, 752,
475; MS (ESI) m/z: 294 [M+H]+; HRMS (ESI) calcd. for C19H20NO2
(M+H)+: 294.1494; found: 294.1491.
Acknowledgments
R.T. acknowledges the in-house project of CSIR-IICT MLP-0008
for financial support. A.A.M thanks the Council of Scientific and
Industrial Research, India for the award of a Research Fellowship.
The authors thank Dr. A. Venugopal for useful suggestions.
1-(2-(Dimethyl amino)-5-fluoro phenyl) naphthalene-2-
ol1 [3f]: brownish yellow sticky solid, isolated by column

A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
43
53.5, 26.0, 23.7, 20.6; FTIR (cm−1): 3433, 2962, 2933,2854, 1618,
1497, 1261, 1234, 1097, 1026, 864, 807, 749; MS (ESI) m/z: 318
[M+H]+; HRMS (ESI) calcd. for C22H24NO [M+H]+: 318.1852; found:
318.1856.
chromatography (ethyl acetate:hexane = 1:9, Rf = 0.3), mp
64–65 ◦C; 1H NMR (300 MHz, CDCl3, ppm):
7.78–7.72 (m,
ı
3H), 7.38–7.27 (m, 2H), 7.22–7.0 (m, 4H), 2.68 (s, 6H);13C NMR
(75 MHz, CDCl3, ppm): ı 152.2, 146.0, 133.0, 129.8, 129.0, 128.2,
126.4, 124.8, 123.2, 121.6, 121.3, 120.7, 119.4, 119.3, 114.9, 114.6,
43.8; FTIR (cm−1): 3061, 2955, 2926, 2858, 1725, 1665, 1619, 1592,
1497, 1462, 1341, 1271, 1231, 1171, 929, 889, 818; MS (ESI) m/z:
282 [M+H]+; HRMS (ESI) calcd. for C18H17NOF [M+H]+: 282.1294;
found: 282.1302.
1-(5-Methoxy-2-(piperidin-1-yl) phenyl) naphthalen-2-ol [3o]:
brownish solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.5), mp 87–89 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.85–7.77 (m, 3H), 7.39–7.29 (m, 3H), 7.19–7.16
(m, 1H), 6.97–6.94 (m, 2H), 3.74 (s, 3H), 2.92 (m, 4H), 1.58 (m,
6H); 13C NMR (75 MHz, CDCl3, ppm): ı 155.2, 152.0, 133.9, 133.5,
132.6, 129.9, 129.4, 128.1, 126.0, 125.2, 122.9, 122.5, 121.0, 120.0,
119.6, 114.1, 55.6, 53.9, 26.0, 23.6; FTIR (cm−1): 3445, 2926, 2853,
1740, 1598, 1496, 1461, 1410, 1339, 1287, 1263, 1236, 1148, 1099,
1047, 912, 815; MS (ESI) m/z: 334 [M+H]+; HRMS (ESI) calcd. for
1-(5-chloro-2-(dimethyl amino) phenyl) naphthalene-2-ol1
[3 g]: brownish yellow solid, isolated by column chromatogra-
phy (ethyl acetate:hexane = 1:9, Rf = 0.4), mp 135–136 ◦C; 1H NMR
(300 MHz, CDCl3, ppm): ı 7.80–7.70 (m, 3H), 7.41–7.30 (m, 4H),
7.21–7.17 (m, 2H), 2.68 (s, 6H); 13C NMR (75 MHz, CDCl3, ppm): ı
152.0, 148.6, 134.6, 132.9, 132.3, 131.6, 129.8, 128.2, 128.0, 126.5,
124.8, 123.3, 120.5, 119.7, 119.4, 116.3, 43.5; FTIR (cm−1): 3048,
2925, 2740, 1730, 1663, 1622, 1591, 1482, 1400, 1339, 1270, 1234,
1149, 1038, 991, 952. MS (ESI) m/z: 298 [M+H]+; HRMS (ESI) calcd.
for C18H17NOCl [M+H]+: 298.0998; found: 298.0995.
C
22H24NO2 [M+H]+: 334.1801; found: 334.1803.
1-(5-Fluoro-2-(piperidin-1-yl) phenyl) naphthalen-2-ol [3p]:
yellow viscous liquid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.4); 1H NMR (300 MHz, CDCl3, ppm):
ı 7.85–7.78 (m, 3H), 7.43–7.28 (m, 3H), 7.21–7.07 (m, 3H), 2.94
(m, 4H), 1.58 (m, 6H); 13C NMR (75 MHz, CDCl3, ppm): ı 152.0,
146.3, 133.2, 129.9, 129.8, 128.2, 126.3, 124.8, 123.2, 121.6, 121.4,
121.0, 119.9, 119.8, 114.9, 114.7, 53.7, 26.0, 23.6; FTIR (cm−1): 3438,
2928, 2854, 1737, 1619, 1596, 1493, 1466, 1260, 1235, 1098, 1026,
816; MS (ESI) m/z: 322 [M+H]+; HRMS (ESI) calcd. for C21H21NOF
[M+H]+: 322.1601; found: 322.1601.
1-(5-Chloro-2-(piperidin-1-yl) phenyl) naphthalen-2-ol [3q]:
colorless solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.5), mp 118–119 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.85–7.75 (m, 3H), 7.44–7.28 (m, 5H), 7.17–7.15 (m,
1H), 2.94 (m, 4H), 1.58 (m, 6H).; 13C NMR (75 MHz, CDCl3, ppm):
ı 151.9, 148.8, 134.6, 133.17, 133.12, 129.9, 129.8, 128.3, 128.24,
128.21, 126.4, 124.8, 123.2, 120.8, 120.0, 119.7, 53.4, 25.9, 23.6;
FTIR (cm−1): 3432, 2923, 2851, 1731, 1626, 1459, 1256, 1028, 798,
600; MS (ESI) m/z: 338 [M+H]+; HRMS (ESI) calcd. for C21H21NOCl
[M+H]+: 338.1306; found: 338.1308.
1-(5-Bromo-2-(piperidin-1-yl) phenyl) naphthalen-2-ol [3r]:
pale yellow solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.6), mp 80–82 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.85–7.75 (m, 3H), 7.53–7.27 (m, 5H), 7.12–7.09
(m, 1H), 2.94 (m, 4H), 1.57 (m, 6H); 13C NMR (75 MHz, CDCl3,
ppm): ı 152.0, 149.3, 137.5, 133.5, 133.1, 131.1, 129.9, 129.8, 128.2,
126.4, 124.8, 123.2, 120.8, 120.4, 119.6, 115.9, 53.3, 25.9, 23.6;
FTIR (cm−1): 3436, 2929, 2853, 1618, 1595, 1479, 1466, 1358,
1261, 1234, 1096, 1026, 906, 749; MS (ESI) m/z: 382 [M+H]+;
HRMS (ESI) calcd. for C21H21NOBr [M+H]+: 384.0797; found:
384.0784.
1-(5-Methyl-2-morpholino phenyl) naphthalen-2-ol [3s]:
colorless solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.5), mp 105–106 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.83–7.74 (m, 2H), 7.40–7.28 (m, 4H), 7.22 (m, 1H),
7.12–7.0 (m, 2H), 3.67–3.54 (m, 4H), 3.0–2.9 (m, 4H), 2.33 (s, 3H);
13C NMR (75 MHz, CDCl3, ppm): ı 151.2, 146.5, 142.1, 135.7, 133.0,
130.2, 130.0, 129.4, 129.3, 128.1, 126.1, 125.2, 124.0, 123.2, 120.5,
118.0, 66.8, 52.1, 20.6; FTIR (cm−1): 3443, 2922, 2854, 1666, 1608,
1500, 1451, 1393, 1266, 1222, 1114, 1058, 923, 818, 756, 672; MS
(ESI) m/z: 319 [M+H]+; HRMS (ESI) calcd. for C21H22NO2 [M+H]+:
320.1645; found: 320.1642.
1-(5-Bromo-2-(dimethyl amino) phenyl) naphthalene-2-ol1
[3h]: brownish solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.5), mp 90 ◦C; 1H NMR (300 MHz, CDCl3,
ppm): ı 7.78–7.70 (m, 3H), 7.51–7.27 (m, 4H), 7.21–7.18 (m, 1H),
7.10–7.0 (m, 1H), 2.67 (s, 6H); 13C NMR (75 MHz, CDCl3, ppm): ı
152.0, 147.1, 137.4, 132.9, 132.8, 131.1, 129.9, 129.8, 128.2, 126.5,
124.7, 123.3, 120.4, 119.8, 117.4, 112.0, 43.4; FTIR (cm−1): 3448,
2934, 2908, 1621, 1485, 1468, 1374, 1308, 1259, 1156, 1080, 1024,
885, 846, 635.; MS (ESI) m/z: 342 [M+H]+; HRMS (ESI) calcd. for
C18H17NOBr [M+H]+: 342.0493; found: 342.0485.
1-(2-(Dimethyl amino)-5-iodo phenyl) naphthalene-2-ol1 [3i]:
brownish solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.6), mp 160–162 ◦C; 1H NMR (500 MHz,
CDCl3, ppm): ␦ 7.77–7.64 (m, 5H), 7.40–7.36 (m, 1H), 7.31–7.28 (m,
1H), 7.19–7.18 (m, 1H), 6.95–6.94 (m, 1H), 2.65 (s, 6H); 13C NMR
(75 MHz, CDCl3, ppm): ␦ 152.0, 149.9, 143.3, 137.1, 132.9, 132.7,
129.8, 128.2, 126.5, 124.7, 123.3, 120.4, 120.1, 119.6, 113.4, 86.1,
43.3; FTIR (cm−1): 3416, 2922, 2852, 1729, 1591, 1501, 1467, 1351,
1304, 1232, 1098, 926, 815, 751; MS (ESI) m/z: 390 [M+H]+; HRMS
(ESI) calcd. for C18H17NOI [M+H]+: 390.0354; found: 390.0367.
1-(2-(Dimethyl amino)-4, 5 dimethyl phenyl) naphthalene-2-
ol1 [3k]: pale yellow solid, isolated by column chromatography
(ethyl acetate:hexane = 1:9, Rf = 0.6), mp 130 ◦C; 1H NMR (500 MHz,
CDCl3, ppm): ı 7.77–7.70 (m, 3H), 7.33–7.26 (m, 2H), 7.22 (m, 1H),
7.14 (s, 1H), 7.05 (m, 1H), 2.70 (s, 6H), 2.35 (s, 3H), 2.24 (s, 3H); 13
C
NMR (75 MHz, CDCl3, ppm): ı 152.0, 147.2, 136.8, 136, 133.3, 131.5,
129.8, 129.0, 128.0, 127.7, 125.9, 125.3, 124.9, 122.9, 120.5, 119.4,
43.8, 19.8, 18.9; FTIR (cm−1): 3434, 2924, 2851, 1621, 1596, 1459,
1383, 1121, 817, 667; MS (ESI) m/z: 292 [M+H]+; HRMS (ESI) calcd.
for C20H22NO [M+H]+: 292.1701; found: 292.1706.
1-(4-Bromo-2-(dimethyl
amino)-5-methyl
phenyl)
naphthalene-2-ol [3l]: pale yellow solid, isolated by column chro-
matography (ethyl acetate:hexane = 1:9, Rf = 0.5), mp 105–107 ◦C;
1H NMR (300 MHz, CDCl3, ppm): ı 7.84–7.73 (m, 3H), 7.42–7.27
(m, 4H), 7.24 (m, 1H), 2.65 (s, 6H), 2.35 (s, 3H); 13C NMR (75 MHz,
CDCl3, ppm): ı 151.9, 148.9, 136.7, 133.0, 129.8, 129.5, 128.1,
127.3, 126.2, 124.9, 123.2, 122.1, 120.4, 120.0, 113.0, 111.9, 43.5,
21.9; FTIR (cm−1): 3431, 2923, 2851, 1733, 1623, 1457, 1262, 1171,
1037, 814, 721; MS (ESI) m/z: 356 [M + H]+; HRMS (ESI) calcd. for
C19H19NOBr [M + H]+: 356.0644; found: 356.0647.
1-(5-methyl-2-(piperidin-1-yl) phenyl) naphthalen-2-ol [3n]:
colorless solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.7), mp 132–134 ◦C; 1H NMR (400 MHz,
CDCl3, ppm): ı 7.77–7.70 (m, 3H), 7.33–7.30 (m, 1H), 7.25–7.0 (m,
5H), 3.0–2.87 (m, 4H), 2.32 (s, 3H), 1.58–1.50 (m, 6H); 13C NMR
(75 MHz, CDCl3, ppm): ı 151.9, 147.7, 135.7, 133.4, 132.4, 131.1,
129.9, 129.1, 128.9, 128.0, 125.8, 125.4, 122.9, 121.0, 120.9, 118.5,
1-(5-Methoxy-2-morpholino phenyl) naphthalen-2-ol [3t]:
reddish brown solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.3), mp 91–92 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.83–7.78 (m, 2H), 7.40–7.28 (m, 3H), 7.16–7.14 (m,
1H), 7.0–6.95 (m, 2H), 6.87–6.86 (m, 1H), 3.75 (s, 3H), 3.66 (m, 4H),
3.1–2.87 (m, 4H); 13C NMR (75 MHz, CDCl3, ppm): ı 151.3, 148.8,
142.4, 129.9, 129.7, 128.1, 126.2, 125.1, 123.2, 120.6, 120.1, 119.1,
118.3, 117.2, 114.7, 114.3, 66.8, 55.6, 52.4; FTIR (cm−1): 3444, 2924,
2853, 1737, 1622, 1596, 1512, 1459, 1261, 1235, 1116, 1036, 926,

44
A.M. Akondi et al. / Catalysis Today 198 (2012) 35–44
818; MS (ESI) m/z: 336 [M+H]+; HRMS (ESI) calcd. for C21H22NO3
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[M+H]+: 336.1594; found: 336.1600.
1-(2-(Dimethylamino)phenyl)naphthalen-2-ol1
[3u]:
yel-
low sticky solid, isolated by column chromatography (ethyl
acetate:hexane = 1:9, Rf = 0.7) mp 73–74 ◦C; 1H NMR (300 MHz,
CDCl3, ppm): ı 7.78–7.72 (m, 3H), 7.39–7.26 (m, 4H), 7.23–7.20
(m, 2H), 7.14–7.09 (m, 1H), 2.70 (m, 6H); 13C NMR (75 MHz, CDCl3,
ppm): ı 152.0, 149.9, 135.2, 133.2, 130.6, 129.8, 129.3, 128.3, 128.0,
126.0, 125.2, 123.0, 122.9, 120.9, 120.5, 118, 43.5; FTIR (cm−1):
3441, 2924, 2857, 1615, 1595, 1486, 1459, 1335, 1232, 1155, 1045,
927, 817, 749, 672; MS (ESI) m/z: 264 [M+H]+; HRMS (ESI) calcd.
for C19H20NO [M+H]+: 264.1388; found: 264.1376.
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