An efficient, one-pot synthesis of 2-amino-4H-chromenes catalyzed by (α-Fe2O3)-MCM-41-supported dual acidic ionic liquid as a novel and recyclable magnetic nanocatalyst

Article abstract of DOI:10.1007/s11164-015-2152-9

A novel (α-Fe₂O₃)-MCM-41-supported dual acidic ionic liquid (DAIL) catalytic system was prepared. This catalyst was characterized by XRD, TEM, SEM, IR spectra and N₂ adsorption-desorption measurements, TGA and acid-base titration. 1-Methyl-3-(4-sulfobutyl) imidazolium hydrogen sulfate as the DAIL inside the mesochannels of α-Fe₂O₃-MCM-41 led to preparation of a new material which was an efficient magnetic heterogeneous nanocatalyst for one-pot three-component synthesis of some new and known 2-amino-4H-chromenes in water medium conditions. This catalyst was more efficient than other reported catalysts for the synthesis of 2-amino-3-cyano-7-hydroxy-4H-chromenes. High product yields, short reaction times, use of non-corrosives, a robust and reusable magnetic nanocatalyst and water as a green solvent are the most important features of the present work. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s11164-015-2152-9

Res Chem Intermed
DOI 10.1007/s11164-015-2152-9
An efficient, one-pot synthesis of 2-amino-4H-
chromenes catalyzed by (a-Fe2O3)-MCM-41-supported
dual acidic ionic liquid as a novel and recyclable
magnetic nanocatalyst
Shahnaz Rostamizadeh1 Negar Zekri1
•
Received: 13 April 2015 / Accepted: 24 June 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract A novel (a-Fe2O3)-MCM-41-supported dual acidic ionic liquid (DAIL)
catalytic system was prepared. This catalyst was characterized by XRD, TEM, SEM, IR
spectra and N2 adsorption–desorption measurements, TGA and acid–base titration.
1-Methyl-3-(4-sulfobutyl) imidazolium hydrogen sulfate as the DAIL inside the
mesochannels of a-Fe2O3-MCM-41 led to preparation of a new material which was an
efficient magnetic heterogeneous nanocatalyst for one-pot three-component synthesis of
some new and known 2-amino-4H-chromenes in water medium conditions. This catalyst
was more efficient than other reported catalysts for the synthesis of 2-amino-3-cyano-7-
hydroxy-4H-chromenes. High product yields, short reaction times, use of non-corrosives,
a robust and reusable magnetic nanocatalyst and water as a green solvent are the most
important features of the present work.
Graphical Abstract
&
Shahnaz Rostamizadeh
shrostamizadeh@yahoo.com
1
Department of Chemistry, K. N. Toosi University of Technology,
P. O. Box 15875 -4416, Tehran, Iran
123

S. Rostamizadeh, N. Zekri
Keywords Magnetically reusable nanocatalyst Á (a-Fe2O3)-MCM-41-DAIL Á Dual
acidic ionic liquid Á 2-Amino-4H-chromene Á One-pot three-component reaction
Introduction
In DAILs, the existence of both Brønsted acidic functional groups and acidic
counter anions can enhance their acidities [1, 2]. Therefore, these types of DAILs
have recently been prepared by several groups of researchers and applied in various
organic reactions as catalysts [3]. However, the use of heterogeneous catalysts, due
to conveniences in catalyst separation and recovery, is mostly preferred. On the
other hand, most ionic liquids (ILs) are highly viscous, which often limits mass
transfer during catalytic reactions. To overcome these problems, supported ILs have
been developed [4]. Mesoporous materials such as MCMs (Mobil Composition of
Matter) possess unique structural features such as high surface area, large pore
volume, uniform porosity, and excellent thermal, chemical and mechanical stability.
Therefore, they are ideal to use as support [5].
Chromenes are one of the most important classes of biologically active compounds,
which have gained emerging interest in recent research areas due to their
antidepressant, antiviral, antihypertensive, anti-tubulin and antioxidative activities
[6, 7]. These compounds are also used as cosmetics, pigments [8] and potential
biodegradable agrochemicals [9]. Despite the versatile applications of 2-amino-4H-
chromenes, only a few methods have been reported for the preparation of these
compounds from aldehydes, resorcinol and malononitrile using NEt3 [10], 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU) [11], piperazine [12], tungstic acid function-
alized SBA-15 [13], glycine [14], trifluoroethanol [15] and nanocrystalline MgO [16].
Some of these methods are associated with the use of hazardous organic solvents, long
reaction times, low product yields and use of toxic and/or corrosive non-reusable
catalysts. Therefore, there is a need to develop a simple and efficient catalyst for the
synthesis of 2-amino-4H-chromenes under mild and green conditions. As part of our
continuous efforts into the design of magnetic nanocatalysts and application of them in
organic reactions [5, 17–20], herein, we report preparation, characterization and
catalytic application of (a-Fe2O3)-MCM-41-(1-methyl-3-(4-sulfobutyl) imidazolium
hydrogen sulfate) as a novel and efficient nanocatalyst in one-pot three-component
synthesis of 2-amino-4H chromenes in water medium conditions (Scheme 1).
Experimental
Chemicals were purchased from Sigma and Merck chemical companies. Melting
points were determined using an IA 8103 melting point apparatus. FT-IR spectra
were obtained with KBr pellets in the range of 400–4000 cm-1 with a Nicolet-860
spectrometer. 1H-NMR and 13C-NMR spectra were recorded in deuterated dimethyl
sulfoxide (DMSO-d6) solvent using a DRX-300 spectrometer at 300 and 75 MHz,
respectively, and trimethylsilane (TMS) as an internal standard. Elemental analysis
for C, H, and N were performed using an Heraeus CHN rapid analyzer. The pore
structure of the prepared catalyst was verified by the nitrogen sorption isotherm
123

An efficient, one-pot synthesis of 2-amino-4H-chromenes…
Scheme 1 Synthesis of 2-amino-4H chromenes in the presence of (a-Fe2O3)-MCM-41-DAIL catalyst
([5.0.0.3] Belsorp, BEL Japan, Inc.). X-ray powder diffraction (XRD) was carried
out on a Philips X’Pert diffractometer with CoKa radiation. The structure and
morphology of the products were characterized by transmission electron micro-
scopy (TEM) recorded on a Philips CM-10 instrument with an accelerating voltage
of 100 kV, and scanning electron microscopy (SEM) analysis was performed using
a Philips XL-30 scanning electron microscope (Poland) operating at an accelerating
voltage of 17 kV.
Catalyst preparation
Synthesis of 1-methyl-3-(4-sulfobutyl) imidazolium hydrogen sulfate (DAIL)
In a 100-mL round bottom flask, a mixture of 1-methyl imidazole (0.1 mol, 8.21 g)
and 1,4-butane sultone (0.1 mol, 11 mL) in toluene (30 mL) was refluxed for 24 h.
The obtained white solid was washed with toluene (2 9 10 mL) and dried under
reduced pressure. Then, a stoichiometric amount of concentrated sulfuric acid (98 %)
was added to the solid and the mixture was stirred for 24 h at 70 °C to form the
DAIL. It was then washed with diethyl ether (2 9 10 mL) and dried under vacuum.
Synthesis of (a-Fe2O3)-MCM-41
To prepare Fe3O4 nanoparticles, a solution with a molar composition of 3.2
FeCl3:1.6 FeCl2:39 NH4OH:2300 H2O was used. 2 g of iron (III) chloride (FeCl.36-
H2O) and 0.8 g of iron (II) chloride (FeCl2.4H2O) were dissolved in 10 mL of
distilled water under N2 atmosphere. The resulting solution was added drop wise to
a 100-mL solution of 1.0-M NH4OH. The magnetic MCM-41 was prepared by
adding 20 mL of the magnetic colloid to a 1-L solution with a molar composition of
292 NH4OH:1 CTABr:2773 H2O under vigorous mixing and sonication. Then,
sodium silicate (16 mL) was added, and the mixture was allowed to react at room
123

S. Rostamizadeh, N. Zekri
temperature for 24 h under well-mixed conditions. The template was then removed
by calcination at 450 °C for 5 h to give the (a-Fe2O3)-MCM-41.
Preparation of (a-Fe2O3)-MCM-41-DAIL
1 mmol of the synthesized DAIL was dissolved in 10 mL of ethanol at room
temperature. Then, 1 g (a-Fe2O3)-MCM-41 was added to the solution with vigorous
stirring. The mixture was then stirred for 24 h at room temperature. The solvent was
removed with a rotary evaporator to afford (a-Fe2O3)-MCM-41-DAIL. Then, it was
washed with acetone (2 9 10 mL) and dried in a vacuum oven.
General procedure for the synthesis of 2-amino-4H-chromenes
The catalytic activity of (a-Fe2O3)-MCM-41-DAIL was examined in the synthesis
of 2-amino-4H-chromenes. For this reason, a mixture of resorcinol (1 mmol),
aldehyde (1 mmol), malononitrile (1 mmol), and catalyst (0.1 g) in 5 mL of H2O
was stirred at 80 °C for an appropriate time. After completion of the reaction
(monitored via thin layer chromatography), the catalyst was separated by an
external magnet. The remaining solution was dried and the product was crystallized
from EtOH to afford the pure product. All of the known products were characterized
by comparison of their physical and spectral data with the reported data.
Physical, spectral and analytical data of the newly synthesized products
2-amino-3-cyano-7-hydroxy-4-(2-bromophenyl)-4H-chromene (4b) yellow pow-
der. m.p.: 205–206 °C. IR (KBr, cm-1): tmax = 3475, 3341, 3251, 2191, 1646,
1585, 1406, 1109. 1H NMR (300 MHz, DMSO-d6): d 5.13 (s, 1H, H-4), 6.41 (s, 1H,
H–Ar), 6.47 (d, 1H, J = 8.1 Hz, H–Ar), 6.72 (d, 1H, J = 8.1 Hz, H–Ar), 6.93 (s,
2H, NH2), 7.12–7.24 (m, 2H, H–Ar), 7.30–7.34 (m, 1H, H–Ar), 7.57 (d, 1H,
J = 7.5 Hz, H–Ar), 9.82 (s, 1H, OH). 13C NMR (75 MHz, DMSO-d6): d 55.11,
102.29, 103.29, 112.55, 120.22, 122.29, 128.48, 128.84, 129.13, 131.00, 132.84,
144.58, 148.87, 157.39, 160.40. Anal. Calcd. for C16H11O2N2Br: C, 55.97; H, 3.21;
N, 8.16 %. Found: C, 55.95; H, 3.24; N, 8.17 %.
2-amino-3-cyano-7-hydroxy-4-(4-cyanophenyl)-4H-chromene (4h) yellow pow-
der. m.p.: 180–181 °C. IR (KBr, cm-1): tmax = 3465, 3337, 3198, 2233, 2190,
1651, 1408, 1508, 1106. 1H NMR (300 MHz, DMSO-d6): d 4.76 (s, 1H, H-4), 6.42
(s, 1H, H–Ar), 6.48 (d, 1H, J = 8.2 Hz, H–Ar), 6.78 (d, 1H, J = 8.2 Hz, H–Ar),
6.98 (s, 2H, NH2), 7.35 (d, 2H, J = 7.6 Hz, H–Ar), 7.77 (d, 2H, J = 7.6 Hz, H–Ar),
9.40 (s, 1H, OH). 13C NMR (75 MHz, DMSO-d6): d 55.26, 102.42, 109.57, 112.49,
112.68, 118.83, 120.42, 128.51, 129.94, 132.76, 148.95, 151.82, 157.55, 160.50.
Anal. Calcd. for C17H11O2N3: C, 70.59; H, 3.80; N, 14.53 %. Found: C, 70.56; H,
3.82; N, 14.51 %.
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An efficient, one-pot synthesis of 2-amino-4H-chromenes…
2-amino-3-cyano-7-hydroxy-4-(4-pyridine)-4H-chromene (4i) yellow powder.
m.p.: 214–215 °C. IR (KBr, cm-1): tmax = 3416, 3209, 2190, 1652, 1510, 1411,
1068. 1H NMR (300 MHz, DMSO-d6): d 4.67 (s, 1H, H-4), 6.42 (s, 1H, H–Ar), 6.49
(d, 1H, J = 8.4 Hz, H–Ar), 6.82 (d, 1H, J = 8.4 Hz, H–Ar), 7.00 (s, 2H, NH2), 7.17
(d, 2H, J = 4.8 Hz, H-pyridine), 8.48 (d, 2H, J = 4.8 Hz, H-pyridine), 9.82 (s, 1H,
OH). 13C NMR (75 MHz, DMSO-d6): d 54.69, 102.35, 112.14, 112.57, 120.34,
122.39, 122.61, 129.81, 148.95, 149.95, 154.48, 157.48, 160.57. Anal. Calcd. for
C15H11O2N3: C, 67.92; H, 4.15; N, 15.85 %. Found: C, 67.93; H, 4.16; N, 15.87 %.
Results and discussion
The prepared catalyst [(a-Fe2O3)-MCM-41-DAIL] was characterized with IR, XRD,
SEM, TEM, nitrogen physisorption measurements, thermal gravimetric analysis
(TGA) and acid–base titration. The acid–base titration showed that the amount of H?
in the catalyst is 1.45 mmol g-1. The TGA thermogram was used to determine the
amount of DAIL supported on (a-Fe2O3)-MCM-41 (Fig. 1). As shown in Fig. 1, the
supported DAIL decomposes at about 341.79 °C. This figure also indicates that
about 21.46 wt% is attributed to the DAIL in the (a-Fe2O3)-MCM-41-DAIL catalyst.
The result obtained by TGA showed good agreement with that of acid–base titration.
The FT-IR spectra of DAIL, (a-Fe2O3)-MCM-41 and (a-Fe2O3)-MCM-41-DAIL
are shown in Fig. 2. As this Figure shows, pure IL exhibited characteristic peaks of
alkyl sulfonate and hydrogen sulfate at 1226, 1165, 1026, 959, 605 cm-1 [21]. In
this spectrum, the bands observed at 1570 and 1627 cm-1 can be assigned to C–N
and C–C vibrations in the imidazole ring [22]. Additional bands at 3162, 3085, 2931
and 1466 cm-1 are due to an imidazole moiety and alkyl chain [22]. In the FT-IR
spectrum of (a-Fe2O3)-MCM-41 (Fig. 2b), the band due to Si–O stretching was
observed at 1077 and 3419 cm-1 can be assigned to the Si–O–H groups [22] and the
bands in the region of 400–800 cm-1 attributed to the stretching vibrations of the
Fig. 1 Thermogram of (a-Fe2O3)-MCM-41-DAIL
123

S. Rostamizadeh, N. Zekri
Fig. 2 The FT-IR spectra of (a) DAIL; (b) (a-Fe2O3)-MCM-41; (c) (a-Fe2O3)-MCM-41-DAIL
Fig. 3 XRD patterns of (a-Fe2O3)-MCM-41-DAIL in the region of a 2.0° (2h) to 10.0° (2h); and b 20.0°
(2h) to 80.0° (2h)
Fe–O band. In the FT-IR spectrum of (a-Fe2O3)-MCM-41-DAIL (Fig. 2c), apart
from the main peaks of (a-Fe2O3)-MCM-41, additional peaks attributed to the
functional groups of DAIL were also observed. This indicates the successful
supporting of the DAIL into the (a-Fe2O3)-MCM-41.
XRD patterns of the synthesized catalyst at the low angle region (Fig. 3a)
indicates a high degree of pore symmetry of MCM-41. Also the XRD spectra of the
catalyst at 20.0° (2h) to 80.0° (2h) (Fig. 3b) are in good agreement with the standard
XRD pattern of a-Fe2O3 [23].
The TEM image clearly shows the ordered mesopore system of (a-Fe2O3)-MCM-
41-DAIL catalyst and the particles with an average diameter of about 100 nm
(Fig. 4a). The SEM image also shows that the diameter of these spherical particles
is about 100 nm (Fig. 4b).
123

An efficient, one-pot synthesis of 2-amino-4H-chromenes…
Fig. 4 a TEM image; and b SEM image of (a-Fe2O3)-MCM-41-DAIL
Fig. 5 a Nitrogen adsorption/desorption; and b BJH analysis of (a-Fe2O3)-MCM-41 and (a-Fe2O3)-
MCM-41-DAIL
The N2 adsorption/desorption isotherms of (a-Fe2O3)-MCM-41 and (a-Fe2O3)-
MCM-41-DAIL (Fig. 5a) show hysteresis loops resembling the type IV isotherm
with an H1-type, which is characteristic of highly ordered, two-dimensional
hexagonal mesostructure materials with cylindrical channels. Comparison of these
two isotherms shows that in (a-Fe2O3)-MCM-41-DAIL, the N2 was adsorbed at
lower values than in (a-Fe2O3)-MCM-41 and this indicates that the pores were
occupied with DAIL. The specific surface area and total pore volume obtained by
N2 adsorption isotherms and calculated by the Brunauer–Emmet–Teller (BET)
method [24], were 1075 m2 g-1 and 0.87 cm3 g-1, respectively, before DAIL
loading, and 430 m2 g-1 and 0.39 cm3 g-1, respectively, after loading DAIL into
the catalyst. These data also indicate that DAIL was successfully introduced inside
the nanochannels of (a-Fe2O3)-MCM-41. The (a-Fe2O3)-MCM-41-DAIL Barrett-
Joyner-Halenda (BJH) analysis, with a very narrow pore size distribution and pore
diameter of 2.4 nm, indicates the highly ordered structure of this catalyst (Fig. 5b).
123

S. Rostamizadeh, N. Zekri
The efficiency of the prepared catalyst was tested in the synthesis of 2-amino-4H
chromenes. In order to optimize the reaction conditions, the reaction between
malononitrile, resorcinol and 4-chlorobenzaldehyde was studied as a model. The
results are summarized in Table 1. As this table shows, the highest yield of the
product was obtained in the presence of 0.1 g of the catalyst per each mmol of the
reactants, using water as a solvent and a reaction temperature of 80 °C.
In order to show the unique catalytic behavior of (a-Fe2O3)-MCM-41-DAIL and
compare its efficiency with other reported catalysts and its building components, the
reaction for synthesis of 2-amino-3-cyano-7-hydroxy-4-(phenyl)-4H-chromene (4d)
was performed using different catalysts (Table 2). The data showed that (a-Fe2O3)-
Table 1 Optimization of reaction conditions for the synthesis of 2-amino-3-cyano-7-hydroxy-4-(4-
chlorophenyl)-4H chromene (4a)
Entry
Solvent
Temperature (°C)
Amount of catalyst (g)
Yield (%)
1
H2O
r.t.
60
70
80
90
80
80
78
65
80
80
80
0.1
0.1
0.1
0.1
0.1
0.07
0.15
0.1
0.1
0.1
0.1
0.1
90
90
93
95
92
89
95
88
85
90
87
75
2
H2O
3
H2O
4
H2O
5
H2O
6
H2O
7
H2O
8
EtOH
9
MeOH
H2O/EtOH
H2O/MeOH
Solvent-free
10
11
12
1 mmol of the reactants were used in all experiments. r.t. room temperature
Table 2 Effect of different catalysts in the synthesis of 2-amino-3-cyano-7-hydroxy-4-(phenyl)-4H-
chromene (4d)
Entry
Catalyst
Time (min)
Yield (%)
Refs.
1
No catalyst
180
Trace
64
This work
This work
This work
This work
This work
This work
[11]
2
DAIL
180
3
MCM-41
180
Trace
32
4
(a-Fe2O3)-MCM-41
MCM-41-DAIL
(a-Fe2O3)-MCM-41-DAIL
DBUa
180
5
8
90
6
8
95
7
40
76
8
Trifluoroethanol
Glycine/sonic condition
SBA-15-tugestic acid
Piperazine/microwave irradiation
Not reported
90
[15]
9
9
94
[14]
10
11
a
720
7
86
[13]
90
[12]
DBU = 1,8-Diazabicyclo[5.4.0]undec-7-ene
123

An efficient, one-pot synthesis of 2-amino-4H-chromenes…
Table 3 Synthesis of 2-amino-4-H-chromenes over the (a-Fe2O3)-MCM-41-DAIL in water medium
Entry
Product
Time
(min)
Yielda (%)
Measured m.p. (°C)/Lit.
m.p. (°C) [Refs.]
Cl
O
1
10
95
162–163/161–162 [12]
CN
HO
HO
HO
HO
NH2
4a
2
3
4
5
10
12
8
91
96
95
90
205–206/New
Br
CN
O
O
O
NH2
NO2
4b
170–171/169–170 [15]
232–233/231–233 [11]
256–258/256–258 [16]
CN
NH2
4c
CN
NH2
4d
Cl
12
Cl
CN
HO
HO
O
NH2
4e
4f
6
7
15
12
90
95
188–189/188–190 [12]
186–187/186–188 [11]
Cl
CN
NH2
O
F
CN
HO
HO
O
NH2
4g
4h
CN
8
12
96
180–181/New
CN
O
NH2
123

S. Rostamizadeh, N. Zekri
Table 3 continued
Entry
Product
Time
(min)
Yielda (%)
95
Measured m.p. (°C)/Lit.
m.p. (°C) [Refs.]
N
9
8
214–215/New
CN
HO
NH2
O
4i
Me
10
15
90
182–183/184–186 [11]
CN
NH2
HO
HO
O
4j
11
12
15
15
85
89
220–222/222–224 [16]
111–112/110–112 [11]
OMe
CN
O
NH2
4k
OMe
CN
NH2
OH
HO
HO
O
4l
13
14
15
15
85
88
214–216/215–217 [16]
214–216/213–215 [16]
CN
NH2
O
4m
OH
CN
NH2
O
HO
4n
a
Isolated yield
MCM-41-DAIL is the most efficient catalyst for this reaction (Table 2, entry 6).
This shows that the acidic character (DAIL) or high surface area [(a-Fe2O3)-MCM-
41 and MCM-41] alone is not sufficient for the reaction. Comparison the data in the
entries 5 and 6 of Table 2 also shows that the presence of ferric oxide as Lewis acids
resulted in higher yields of the product.
To examine the scope and generality of the process, various 2-amino-4H-
chromenes were then synthesized under optimized reaction conditions. The results
summarized in Table 3 indicate that use of only 0.1 g of (a-Fe2O3)-MCM-41-DAIL
shows a marked efficiency for all of the reactions tested.
123

An efficient, one-pot synthesis of 2-amino-4H-chromenes…
Scheme 2 A plausible mechanism for the synthesis of 2-amino-4H chromenes in the presence of (a-
Fe2O3)-MCM-41-DAIL catalyst
A plausible mechanism for the formation of 2-amino-4H chromenes is shown in
Scheme 2. First, the reactants absorb into the mesochannels of the high surface area
catalyst. The dual Brønsted acidity of the IL and the Lewis acidity of Fe3? all
activate the aldehyde. The Knovenagel condensation reaction between aldehyde and
malononitrile leads to the formation of intermediate A. Then, Michael addition
takes place between intermediate A and resorcinol to form intermediate B, which is
followed by intra-molecular cyclization to yield the desired product (D). In these
reactions, the catalyst increases the electrophilicity of aldehyde carbon atoms,
followed by dehydration to give intermediate A. Again, this catalyst increases the
electrophilicity of the CN group so that Michael addition and cyclization steps can
easily occur to yield the product [14–16].
It is important to note that the presence of ferric oxide in the catalyst facilitates its
recovery from the reaction mixture during the work-up procedure by use of an
external magnet in less than 1 min. Thus, the catalyst was simply collected and the
recovered catalyst was used in subsequent runs without significant loss of its activity
even after six runs (Scheme 3).
The FT-IR spectra of the fresh and recycled catalyst after 6 circles are
respectively presented in Fig. 6a, b. This figure shows the presence of the IL in the
catalyst after six runs.
123

S. Rostamizadeh, N. Zekri
Scheme 3 Catalyst recovery for the model reaction
Fig. 6 The FT-IR spectra of (a) fresh; and (b) recycled catalyst after 6 circles
Conclusion
In summary, we have developed a novel magnetic (a-Fe2O3)-MCM-41-DAIL
nanocatalyst that shows remarkable catalytic activity in one-pot three-component
synthesis of 2-amino-3-cyano-7-hydroxy-4-H-chromenes. The Brønsted dual acidic
property of the IL together with the Lewis acidity of ferric oxide and high surface
area of MCM-41 have increased the catalytic activity of the catalyst. The results of
our studies showed that this catalyst is more efficient than other reported catalysts
for the synthesis of 2-amino-3-cyano-7-hydroxy-4H-chromenes. High product
123

An efficient, one-pot synthesis of 2-amino-4H-chromenes…
yields, short reaction times, use of non-corrosives, a robust and reusable magnetic
nanocatalyst and water as a green solvent are the most important features of the
present work.
Acknowledgments We gratefully acknowledge the K. N. Toosi University Research Council for partial
financial support of this work.
References
1. X.M. Liu, M. Liu, X.W. Guo, J.X. Zhou, Catal. Commun. 9, 1 (2010)
2. Y.Y. Wang, X. Gong, Z. Wang, L.D. Dai, J. Mol. Catal. A: Chem. 322, 7 (2010)
3. Q. Yang, Z. Wei, H. Zing, Q. Ren, Catal. Commun. 9, 1307 (2008)
4. A. Riisager, R. Fehrmann, M. Haumann, P. Wasserscheid, Top. Catal. 40, 91 (2006)
5. S. Rostamizadeh, M. Nojavan, R. Arian, E. Isapoor, M. Azad, J. Mol. Catal. A 374–375, 102 (2013)
6. M. Curini, G. Cravotto, F. Epifano, G. Giannone, Curr. Med. Chem. 13, 199 (2006)
7. P.O. Kennedy, R.D. Thornes, Coumarins: biology, applications and mode of action (Wiley,
Chichester, 1997)
8. G.P. Ellis, Chromenes, Cheromenes, and Chromenes, in The chemistry of heterocyclic compounds,
ed. by A. Weissberger, E.C. Taylor (Wiley, New York, 1977), pp. 11–139
9. E.A. Hafez, M.H. Elnagdi, A.G.A. Elagemey, F.M.A.A. El-Taweel, Heterocycles 26, 903 (1987)
10. A.M. Shestopalov, Y.M. Emelianov, V.N. Nesterov, Russ. Chem. Bull. Int. Ed. 51, 2238 (2002)
11. D.S. Raghuvanshi, K.N. Singh, ARKIVOC X, 305 (2010)
12. A. Mobinikhaledi, H. Moghanian, F. Sasani, Synth. React. Inorg., Met.-Org., Nano-Met. Chem. 41,
262 (2011)
13. S.K. Kunda, J. Mondel, A. Bhaumik, Dalton Trans. 42, 10515 (2013)
14. B. Datta, M.A. Pasha, Ultrason. Sonochem. 19, 725 (2012)
15. S. Khaksar, A. Rouhollahpour, S. Mohammadzadeh Talesh, J. Fluor. Chem. 141, 11 (2012)
16. J. Safari, Z. Zarnegar, M. Heydarian, J. Taibah Univ. Sci. 7, 17 (2013)
17. S. Rostamizadeh, M. Azad, N. Shadjou, M. Hasanzadeh, Catal. Commun. 25, 83 (2012)
18. S. Rostamizadeh, N. Shadjou, M. Azad, N. Jalali, Catal. Commun. 26, 218 (2012)
19. S. Rostamizadeh, M. Nojavan, R. Aryan, M. Azad, Catal. Lett. 144, 1772 (2014)
20. S. Rostamizadeh, H. Estiri, M. Azad, Catal. Commun. 57, 29 (2014)
21. M. Abdollahi-Alibeik, M. Pouriayevali, Catal. Commun. 22, 13 (2012)
22. A. Bordoloi, S. Sahoo, F. Lefevre, S.B. Halligudi, J. Catal. 259, 232 (2008)
23. Q. Wei, Z. Zhang, Z. Li, Q. Zhou, Y. Zhu, J. Phys. D Appl. Phys. 41, 202002 (2008)
24. H. Takahashi, B. Li, T. Sasaki, C. Miyazaki, T. Kajino, S. Inagaki, Microporous Mesoporous Mater.
44–45, 755 (2001)
123