MCM-41-SO3H: A novel reusable nanocatalyst for synthesis of amidoalkyl naphthols under solvent-free conditions

Article abstract of DOI:10.1007/s00706-013-0936-4

Nanosized MCM-41-SO₃H based on an ordered mesoporous material with covalently anchored sulfuric acid groups inside the mesochannels was used as an acid catalyst for synthesis of amidoalkyl naphthols in the multicomponent reaction of 2-naphthol,

Full text of DOI:10.1007/s00706-013-0936-4

Monatsh Chem
DOI 10.1007/s00706-013-0936-4
ORIGINAL PAPER
MCM-41-SO3H: a novel reusable nanocatalyst for synthesis
of amidoalkyl naphthols under solvent-free conditions
•
Shahnaz Rostamizadeh Fatemeh Abdollahi
•
•
Nasrin Shadjou Ali Mohammad Amani
Received: 2 June 2012 / Accepted: 24 January 2013
Ó Springer-Verlag Wien 2013
Abstract Nanosized MCM-41-SO3H based on an ordered
mesoporous material with covalently anchored sulfuric
acid groups inside the mesochannels was used as an acid
catalyst for synthesis of amidoalkyl naphthols in the mul-
ticomponent reaction of 2-naphthol, aromatic aldehydes,
and an amide. The products were characterized by Fourier-
transform infrared (FT–IR), nuclear magnetic resonance
(NMR), and mass spectroscopy. The surface area and pore
size of MCM-41-SO3H were also determined by the Bru-
nauer–Emmett–Teller (BET) calculation model. This novel
approach for preparation of amidoalkyl naphthols offers
several advantages: short reaction times, simple purifica-
tion and simple isolation of products, high reusability of
the catalyst, to name but a few.
synthesis. One of the best examples is MCM-41, which is a
structurally well-ordered material with a narrow pore size
distribution between 1.5 and 10 nm, high surface area up to
1,500 m2 g-1, and thermal stability [1]. It has been dem-
onstrated that Si-MCM-41 has poor Brønsted acid sites and
exhibits only weak hydrogen-bonding sites [2, 3] which can
be improved via modification of the pore walls by covalent
anchoring of different organic or inorganic moieties.
On the one hand several types of solid sulfonic acid have
been created in recent years, but on the other hand there
have been only a few reports of their application as catalysts
in chemical transformations. Regarding our research to
develop new and ecofriendly synthetic methodologies
towards synthesis of different organic compounds [4–6], we
have extended the MCM-41-SO3H-catalyzed method for
synthesis of 1-amidoalkyl-2-naphthol derivatives, which
can be converted to important biologically active and drug-
like molecules such as aminoalkyl naphthols. It is reported
that aminoalkyl naphthol derivatives can be prepared by
amide hydrolysis of amidoalkyl naphthols [7]. The hypo-
tensive and bradycardic effects of these compounds in
normotensive rats as well as their in vitro inotropic and
aortic contraction effects in isolated rats’ left atria and aorta
have been evaluated [8]. Moreover, the intramolecular
cyclization of amidoalkyl naphthols produces 1,3-oxazines
by the Vilsmeier reagent. These compounds have attracted
interest because of their potential as antibiotics, antitumor
agents, analgesics, and anticonvulsants [9].
Keywords MCM-41-SO3H Á Nanocatalyst Á
Amidoalkyl naphthols Á Solvent-free conditions Á
Multicomponent reactions
Introduction
In recent years, silica mesoporous materials have attracted
considerable attention in several scientific areas. Silica
materials containing nanopores of constant molecular
dimension can be used as heterogeneous catalysts in organic
S. Rostamizadeh (&) Á F. Abdollahi Á A. M. Amani
Department of Chemistry, Faculty of Sciences,
K.N.Toosi University of Technology, Tehran, Iran
e-mail: shrostamizadeh@yahoo.com;
Several efficient methods have been reported for syn-
thesis of amidoalkyl naphthols, employing different acid
catalysts such as benzimidazolium-based ionic liquid [10],
dodecylphosphonic acid (DPA) [11], Bi(NO3)3Á5H2O [12],
imidazolium salts [13], MoO3–ZrO2 [14], silica chloride
[15], Ph3CCl [16], molten zwitterionic salt [17],
H3Mo12O40P [18], P2O5 [19], ferrocene-labeled supported
rostamizadeh@hotmail.com
N. Shadjou
Biochemistry Lab, Pasteur Institute of Iran,
P.O. Box 13164, Tehran, Iran
123

S. Rostamizadeh et al.
Scheme 1
R1
O
O
NHCOR2
OH
OH
MCM-41-SO3
H
H
R1
+
+
H2N
R2
neatcondition
100 °C
ionic liquid phase (SILP) [20], HClO4–SiO2 [21, 22],
molten tetraethylammonium chloride [23], silica sulfuric
acid [24], cation-exchanged resins [25], Fe(HSO4)3 [7], and
wet cyanuric chloride [26, 27]. Some of these methods
suffer from drawbacks such as use of nonreusable and
highly acidic catalysts, toxic organic solvents, high tem-
perature, moderate yield, very long reaction time and
expensive instruments. Therefore, in this article we intro-
duce a green and efficient procedure based on a nanocata-
lyst for preparation of the biologically active molecules
1-amidoalkyl-2-naphthols by condensation of b-naphthol,
aromatic aldehydes, and an amide using MCM-41-SO3H
(Scheme 1).
Fig. 1 Preparation of MCM-41-SO3H
Results and discussion
In regard to our research program to develop new and
ecofriendly synthetic methodologies towards heterocyclic
compounds, herein we disclose a novel, green, rapid and
one-pot method for synthesis of amidoalkyl naphthol
derivatives catalyzed by MCM-41-SO3H as heterogeneous
nanocatalyst. In the present work, MCM-41 was modified
by covalently bonded sulfonic acid on the inside surface of
channels to provide the silica-supported material with
Brønsted acid properties. MCM-41 was synthesized
according to the previously described method [28]. Then,
MCM-41 was reacted with chlorosulfonic acid to give a
white powder that was named MCM-41-SO3H. It is notable
that not only is the reaction easy and clean, but also no
special workup procedure is needed, because HCl gas is
released from the reaction vessel immediately (caution:
HCl gas is corrosive and precaution is advised) (Fig. 1).
The obtained MCM-41-SO3H was then characterized by
thermogravimetric analysis (TGA), scanning electron
microscopy (SEM), X-ray diffraction (XRD), and acid–
base titration according to the previous report [5]. Nitrogen
absorption and desorption isotherms were obtained at 77 K
after the sample was dried at 100 °C for 6 h. Calculations
based on the BET plot reveal a high specific surface area of
872.64 m2 g-1 and an expected mean pore diameter of
3.2 nm (Fig. 2).
Fig. 2 Plot of BET isotherm
Initially, to illustrate the high efficiency and catalytic
activity of MCM-41-SO3H, in the model reaction 3-nitro-
benzaldehyde (1, 1 mmol), b-naphthol (2, 1 mmol), and
acetamide (3, 1.2 mmol) were used in the presence of
different types of acidic catalyst (Scheme 1).
123

MCM-41-SO3H: a novel reusable nanocatalyst for synthesis of amidoalkyl naphthols
oxygen and sulfonic acid groups, the electron density of
Table 1 Synthesis of N-[(2-hydroxynaphthalen-1-yl)(3-nitrophenyl)
methyl]acetamide using different catalysts
carbonyl decreases, which results in higher susceptibility to
nucleophilic attack on carbonyl groups. Nucleophilic addi-
tion of 2 to 1 followed by dehydration of its product 4 results
in formation of an intermediate named ortho-quinone met-
hide 5. It is well documented that preparation of amidoalkyl
naphthols proceeds through the formation of 5, which was
introduced by Khodaei et al. [32] for the first time. As is clear
from Table 3, electron-withdrawing substituents on an
aldehyde increase the reaction rate compared with an alde-
hyde containing electron-releasing groups. This may be due
to lower energy of ortho-quinone methide alkene lowest
unoccupied molecular orbital (LUMO) in the presence of
electron-withdrawing groups, as Shaterian et al. [33] have
declared. Conjunction addition of 3 to 5 led to formation of
1-amidoalkyl-2-naphthol 6.
Entry
Catalyst
Time/min
Yield/%
1
2
3
4
5
6
7
NaHSO4
120
240
20
30
8
55
30
78
63
80
90
88
SiO2
NaHSO4/SiO2
NH4H2PO4/SiO2
MCM-41-SO3H (0.01 g)
MCM-41-SO3H (0.02 g)
MCM-41-SO3H (0.03 g)
7
6
Table 2 Synthesis of N-[(2-hydroxynaphthalen-1-yl)(3-nitrophenyl)
methyl]acetamide using different amounts of catalyst and reaction
conditions
Entry
Condition
Temperature/°C
Time
Yield/%
Reusability of MCM-41-SO3H
1
2
3
4
5
6
7
8
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
CH3OH
120
6 min
7 min
7 min
12 min
15 min
45 h
86
110
87
As is known, recycling and reusability is a valuable factor
to assess the efficiency and cost-effectiveness of hetero-
geneous catalysts. We examined the reusability of the
catalyst by the reaction of benzaldehyde (5 mmol), b-
naphthol (5 mmol), acetamide (6 mmol), and catalyst
(0.1 g). The recovered catalyst was used in the subsequent
reaction after drying at 100 °C. Although some decrease in
catalytic activity was observed after four runs (Fig. 4), this
can be mainly attributed to errors during filtration, collec-
tion, and drying the catalyst that may cause a reduction in
the initial amount of used catalyst.
100
90
90
85
80
83
Reflux
Reflux
Reflux
20
C2H5OH
30 h
40
H2O
48 h
Trace
As shown in Table 1 (entries 1–5), it was found that
MCM-41-SO3H provides a better acidic condition for this
transformation. Meanwhile, it is observed that 0.02 g cat-
alyst shows the best result, while increasing the quantity of
the catalyst had no considerable effect on the yield and
reaction times. Consequently, 0.02 g was chosen as an
optimum amount of catalyst to start the reaction (Table 1,
entries 5–7).
Conclusions
In the current study, a one-pot multicomponent method for
synthesis of amidoalkyl naphthol derivatives using MCM-
41-SO3H as an appropriate nanocatalyst was developed. This
catalyst is highly efficient, easily available, economical, and
requires mild reaction conditions. The innovative aspects of
the proposed method are short reaction times omitting toxic
solvents or catalyst, very simple work-up procedure, inex-
pensive starting materials, and improved yield.
To evaluate the effect of solvent and find the optimum
reaction temperature, the model reaction was performed
under different reaction conditions. The results collected in
Table 2 show that 100 °C and solvent-free conditions were
the optimum reaction conditions for synthesis of amid-
oalkyl naphthols 6.
In the next step, the generality of this procedure catalyzed
by MCM-41-SO3H under the optimum conditions using var-
iousaromatic aldehydes containing both electron-donating and
electron-releasinggroups was examined (Table 3). Allofthese
reactions proceeded smoothly and gave the corresponding
products in high yields and short reaction times.
Experimental
The physical and spectral data of known products are com-
parable to corresponding samples prepared via previous
method. New products were characterized by IR, 1H NMR,
13C NMR, and mass spectroscopy (MS). Melting points were
recorded on a Bu¨chi B-540 apparatus. IR spectra were
recorded on an ABB Bomem model FTLA200-100 instru-
The proposed mechanism for formation of amidoalkyl
naphtholis presented in Fig. 3. The reaction occurs inside the
pores on the surface of supported sulfonic acid groups which
are capable of bonding with the carbonyl oxygen of the
aldehyde. Because of hydrogen bonding between carbonyl
1
ment. H NMR and 13C NMR spectra were measured on a
123

S. Rostamizadeh et al.
References
Table 3 Preparation of amidoalkyl naphthols 6 catalyzed by MCM-41-SO3H under solvent-free conditions
Compound
R1
R2
Time/min
Yield/%
M.p. (lit. m.p.)/°C
6a
6b
6c
6d
6e
6f
4–Cl–
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
15
7
86
90
85
87
75
80
86
88
96
90
90
97
97
80
82
89
90
95
237–238 (228–229)
240–241 (241–242)
206–208 (198–199)
220–221
[29]
[29]
[29]
[30]
–
3–NO2–
2,4–Cl2–
4–OH–
4–PhOCH2–
4–NO2–
4–CH3–
4–F–
12
20
40
15
15
11
10
18
10
9
217–218
237–239 (248–250)
[21]
6g
6h
6i
220.5–222.5 (222–223)
229–229.5 (209–210)
242–243 (241–243)
228–230 (228–230)
195–197 (194–196)
260–262 (261–262)
227–227.5 (216–217)
237–237.5 (262–263)
210–212
[21]
[29]
[29]
[31]
[25]
[26]
[25]
[19]
–
H–
6j
4-Br–
6k
6l
2-Cl–
4-CN–
6m
6n
6o
6p
6q
6r
3-NO2–
2,4-Cl2–
4-PhOCH2–
4-NO2–
4-CH3–
4-CN–
8
8
10
8
230–231 (228–229)
204–205 (192–193)
173–174 (176–178)
[19]
[25]
[26]
12
15
Bruker DRX-300 spectrometer at 300 and 75 MHz, using
tetramethylsilane (TMS) as internal standard. Chemical
shifts (d) are reported relative to TMS, and coupling con-
stants (J) are reported in Hertz (Hz). Nitrogen absorption and
desorption isotherms were recorded on BELSORP-max
(Japan). Mass spectra were recorded on a Shimadzu QP 1100
EX mass spectrometer with 70 eV ionization potential.
mixture was cooled to room temperature and excess acet-
amide or benzamide was washed away by water. The solid
was filtered and dissolved in acetone after drying. The
catalyst was recovered, and the solution was then con-
centrated in vacuum to afford crude product. The
crystalline pure product was obtained by further recrys-
tallization from EtOH.
N-[(4-Benzyloxyphenyl)(2-hydroxynaphthalen-1-
yl)methyl]acetamide (6e, C26H23NO3)
Synthesis and functionalization of MCM-41
A
mixture of 0.397 g 4-(benzyloxy)benzaldehyde
MCM-41 was modified using a 100 cm3 suction flask
equipped with a constant pressure dropping funnel con-
taining 81.13 g chlorosulfonic acid (0.7 mol) and a gas inlet
tube for conducting HCl gas over an adsorbing solution.
Into it was charged 60.0 g MCM-41, and chlorosulfonic acid
was then added dropwise over a period of 30 min at
room temperature. HCl gas evolved from the reaction vessel
immediately, being conducted over the aqueous solution
of sodium hydroxide. After completion of addition, the
mixture was shaken for 30 min and 115.9 g white solid
(MCM-41-SO3H) was obtained.
(1 mmol), 0.144 g b-naphthol (1 mmol), and 0.070 g
acetamide (1.2 mmol) was reacted for 40 min according
to the general procedure, affording 0.297 g (75 %) crys-
talline pure product. M.p.: 217–218 °C; 1H NMR
(300 MHz, acetone-d6): d = 9.24 (sbr, 1H, OH), 8.24 (d,
J = 8.2 Hz, 1H, NH), 7.94 (d, J = 8.2 Hz, 1H, NCH),
6.87-7.85 (15H, Ar), 5.00 (s, 2H, OCH2), 1.91 (s, 3H,
CH3) ppm; 13C NMR (75 MHz, acetone-d6): d = 168.7
(C=O), 158.4, 154.2, 138.4, 135.6, 133.5, 130.3, 130.2,
129.5, 129.2, 128.5, 128.3, 128.2, 127.2, 123.6, 120.6,
119.7, 115.2 (C–Ar), 70.3 (OCH2), 49.1 (CH), 22.9 (CH3)
ꢀ
ppm; IR (KBr):m = 3,424, 3,286, 3,039, 2,849, 1,668,
General procedure for synthesis of 1-amidoalkyl-2-
naphthols 6
1,622, 1,514, 1,437, 1,247, 1,190 cm-1; MS (EI): m/z
(%) = 396 (15), 337 (75), 302 (81), 269 (20), 247 (30), 144
(30), 115 (25), 91 (85), 65 (50), 43 (75).
A mixture of aldehyde (1 mmol), b-naphthol (1 mmol),
acetamide or benzamide (1.2 mmol), and 0.02 g MCM-41-
SO3H was heated in an oil bath at 100 °C for different
periods of time (Table 3). After completion of reaction
[monitored by thin-layer chromatography (TLC)], the
N-[(4-Benzyloxyphenyl)(2-hydroxynaphthalen-1-
yl)methyl]benzamide (6o, C31H25NO3)
A
mixture of 0.397 g 4-(benzyloxy)benzaldehyde
(1 mmol), 0.144 g b-naphthol (1 mmol), and 0.145 g
123

MCM-41-SO3H: a novel reusable nanocatalyst for synthesis of amidoalkyl naphthols
Fig. 3 Proposed mechanism for
preparation of amidoalkyl
naphthols
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