Preparation of a novel, efficient, and recyclable magnetic catalyst, γ-Fe2O3@HAp-Ag nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives

Article abstract of DOI:10.1016/j.cclet.2016.06.022

In this protocol, Ag supported on the hydroxyapatite-core–shell magnetic γ-Fe₂O₃nanoparticles (γ-Fe₂O₃@HAp-Ag NPs) as a novel, efficient, and magnetically recyclable catalyst is synthesized, and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). The use of the catalyst is described in the synthesis of coumarin derivatives by the Pechmann condensation of various phenols with β-ketoesters under solvent- and halogen-free conditions at 80?°C. This novel and inexpensive method offers advantages, such as recyclability simple experimental protocol, short reaction time, minimal work-up procedure, and excellent yields of products, together with desirable, eco-friendly, green aspects by avoiding toxic elements and solvents, and ease of recovery from the reaction mixture using an external magnet.

Full text of DOI:10.1016/j.cclet.2016.06.022

G Model
CCLET 3745 1–8
Chinese Chemical Letters xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
2
Original article
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5
Preparation of a novel, efficient, and recyclable magnetic catalyst,
-Fe2O3@HAp-Ag nanoparticles, and a solvent- and halogen-free
protocol for the synthesis of coumarin derivatives
g
a
b
Q1 Zahra Abbasi a, Sobhan Rezayati a, , Maryam Bagheri , Rahimeh Hajinasiri
*
6
7
8
a Young Researchers and Elite Club, Ilam Branch, Islamic Azad University, Ilam, Islamic Republic of Iran
b Chemistry Department, Qaemshahr Branch, Islamic Azad University, PO BOX 163, Qaemshahr, Islamic Republic of Iran
A R T I C L E I N F O
A B S T R A C T
In this protocol, Ag supported on the hydroxyapatite-core–shell magnetic
Article history:
g
-Fe2O3 nanoparticles (g-
Received 5 May 2016
Received in revised form 3 June 2016
Accepted 12 June 2016
Available online xxx
Fe2O3@HAp-Ag NPs) as a novel, efficient, and magnetically recyclable catalyst is synthesized, and
characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier
transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and vibrating sample magnetometry
(VSM). The use of the catalyst is described in the synthesis of coumarin derivatives by the Pechmann
condensation of various phenols with b-ketoesters under solvent- and halogen-free conditions at 80 8C.
Keywords:
This novel and inexpensive method offers advantages, such as recyclability simple experimental
protocol, short reaction time, minimal work-up procedure, and excellent yields of products, together
with desirable, eco-friendly, green aspects by avoiding toxic elements and solvents, and ease of recovery
from the reaction mixture using an external magnet.
g-Fe2O3 nanocatalyst
Heterogeneous
Catalyst
Pechman condensation
Ag supported
ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
9
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1. Introduction
hydrogenation of alkynes [21], biginelli synthesis of 3,4-dihydro- 27
pyrimidin-2(1H)-ones/thiones [22], epoxidation of alkenes [23], 28
11
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19
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25
26
Magnetic nanoparticles (MNPs) that have been studied
extensively for various biological and medical applications, such
as magnetic resonance imaging [1], drug delivery [2,3], biosepara-
tions [4,5], biomolecular sensors [6,7], and magneto-thermal
therapy [8,9]. Moreover, other advantages of magnetic nanopar-
ticles as heterogeneous catalyst include their ease of preparation, a
large surface area ratio, and ease of recovery from the reaction
mixture using an external magnet. In recent decades, magnetic
nanoparticles, as efficient and ecofriendly catalysts, have been
used in various organic reactions, such as synthesis of a-amino
nitriles [10], nucleophilic substitution reactions of benzyl halides
[11], 14-aryl-14H-dibenzo[a,j]xanthene derivatives [12], Fried-
la¨nder quinoline reaction [13], oxidation of sulfides and oxidative
coupling of thiols [14], suzuki coupling reactions [15], dihydro-
pyrimidinones derivatives [16,17], esterifications [18], regioselec-
tive azidolysis of epoxides [19], knoevenagel reaction [20],
CO2 cycloaddition reactions [24], and three-component condensa- 29
tions [25]. 30
2H-Chromen-2-ones (coumarins) are an important class of 31
compounds that have been studied extensively for various 32
biological and pharmaceutical applications. Biological and phar- 33
maceutical properties, such as anticancer [26], inhibitory of HIV-1 34
protease [27], and antibacterial [28]. They are also present or used 35
in additives in food, perfumes, cosmetics [29], alcoholic beverages 36
[30], optical brighteners [31], and dispersed fluorescent and laser 37
dyes [32]. Also, these compounds are well documented as 38
therapeutic agents and have been utilized as medicines in ancient 39
Egypt and in aboriginal cultures [33,34]. 2H-Chromen-2-ones 40
(coumarins) have been prepared by various procedures, including 41
Knoevenagel condensation, Perkin, Pechmann condensation, 42
Reformatsky reaction, Wittig and Claisen rearrangement [35], of 43
which the Pechmann reaction is the most common procedure. The 44
one-pot condensation reaction of various phenols with ethyl 45
acetoacetate has been used as the best procedure for the 46
preparation of coumarin derivatives. Some acidic catalysts have 47
been reported to promote this reaction, including strong mineral 48
*
Corresponding author.
E-mail address: sobhan.rezayati@yahoo.com (S. Rezayati).
http://dx.doi.org/10.1016/j.cclet.2016.06.022
1001-8417/ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst, g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

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acids like sulfuric acid [36], trifluoroacetic acid [37], phosphorous
pentachloride [38], and many others of the same type including
expensive metal halides of indium [39], and palladium [40] and
recently Bi2(NO3)3 [41]. Furthermore, the Pechmann condensation
has been used in the presence of different acids, such as
Fe3O4@SiO2@EtSO3H [42], CMK-5 supported sulfonic acid [43],
sulfated zirconia [44], molecular iodine [45], Wells-Dawson
heteropolyacid [46], and mesoporous zirconium phosphate
[47]. However, some of these procedures suffer from at least
one of the following disadvantages: unsatisfactory yields, harsh
reaction conditions, use of toxic catalysts, longer reaction times,
tedious work-up procedures, strongly acidic wastes, and non-
recyclable reagents.
2.1. Preparation of Ag supported on hydroxyapatite-core-shell
magnetic -Fe2O3
89
90
g
In this study, hydroxyapatite-core–shell
g
-Fe2O3 NPs were
91
92
93
94
95
96
97
98
prepared according to the literature procedure [49]. Then the
hydroxyapatite-core–shell
g
-Fe2O3 NPs (0.6 g) was introduced into
150 mL aqueous solution of silver nitrate (6.7 Â 10À3 mol/L) and
stirred at r.t. for 6 h. The resulting slurry was filtered, washed, and
dried at r.t. under vacuum. Next, the
g
-Fe2O3@HAp NPs containing
Ag was treated with an aqueous solution of KBH4
(5.0 Â 10À2 mol/L) for 1 h at r.t. Again, the slurry was filtered,
washed, and dried at r.t. under vacuum, giving Ag supported on
Fe2O3@HAp NPs (Scheme 1). The mean size and the surface
morphology of the Ag supported on hydroxyapatite-core–shell
99
100
101
102
103
In continuing our work on catalyzed reactions using green
catalyst [48], we have synthesized Ag supported on hydroxyapa-
magnetic g-Fe2O3 were characterized by TEM, SEM, VSM, XRD and
FT-IR techniques.
tite-core–shell magnetic
g
-Fe2O3 nanoparticles as
a
novel,
efficient, and magnetically recyclable catalyst (
NPs) (Scheme 1).
g-Fe2O3@HAp-Ag
2.2. General procedure for the Pechmann condensation
104
The
g
-Fe2O3@HAp-Ag NPs were characterized by FT-IR, TEM,
novel,
SEM, XRD, and VSM techniques, and applied as
a
In a round bottom flask,
g
-Fe2O3@HAp-Ag NPs (10 mg) were
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111
112
113
114
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123
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125
126
127
magnetically recyclable, and heterogeneous nanocatalyst for the
synthesis of coumarin derivatives by the one-pot condensation of
various phenols with ethyl acetoacetate under solvent- and
halogen-free conditions (Scheme 2).
added to the mixture of the phenolic compound (1 mmol) and
ethyl acetoacetate (1 mmol) at 80 8C and the reaction mixture
stirred for the appropriate time (Table 3). The progress of the
reaction was monitored by TLC (eluent, n-hexane:ethyl acetate,
4:1) analysis. Upon completion of the reaction, EtOH was added to
the reaction mixture and the g-Fe2O3@HAp-Ag NPs were separated
73
2. Experimental
with an external magnet. The solvent was then removed under
reduced pressure and the resulting product was purified by
recrystallization using ethanol. The coumarin derivatives were
obtained in good to excellent isolated yields (83–96%). The spectral
data (1H NMR and 13C NMR) of some representative compounds
are given below:
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75
76
77
78
79
80
81
82
83
84
85
86
87
88
Reagents and solvents were purchased from Merck, Fluka or
Aldrich companies. Melting points were determined in capillary
tubes in an electro-thermal C14500 apparatus. The progress of the
reaction and the purity of compounds were monitored by TLC
using analytical silica gel plates (Merck 60 F250). All known
compounds were identified by comparison of their melting points
and 1H NMR and 13C NMR data with those of authentic samples.
The 1H NMR (250 MHz) and 13C NMR (62.9 MHz) spectra were
acquired on a Bruker Avance DPX-250, FT-NMR spectrometer. IR
7-Hydroxy-4-methyl-2H-chromen-2-one (Table 3, entry 1): 1H
NMR (250 MHz; CDCl3):
J = 9 Hz), 6.76–6.73 (d, 1H, J = 8 Hz), 6.65 (s, 1H), 6.072 (brs, 1H),
2.30 (brs, 3H); 13C NMR (62.9 MHz, CDCl3):
161.5, 160.7, 155.2,
153.8, 126.9, 113.2, 112.4, 110.6, 102.5, 18.4.
4,7-Dimethyl-2H-chromen-2-one (Table 3, entry 4): 1H NMR
(250 MHz; CDCl3): 7.64–7.61 (d, 1H, J = 8.25 Hz), 7.19 (brs, 1H),
7.16 (s, 1H), 6.29 (s, 1H), 2.391 (br, 6H); 13C NMR (62.9 MHz,
CDCl3): 160.3, 153.6, 153.4, 143.2, 125.8, 125.5, 117.6, 116.9,
113.7, 21.4, 18.4.
d 10.50 (brs, 1H), 7.54–7.50 (d, 1H,
d
spectra were recorded on
a Frontier FT-IR (Perkin Elmer)
spectrometer using KBr disks. The phases present in the magnetic
materials were analyzed using powder XRD on a Philips (Holland)
d
spectrometer, model X0 Pert with X’Pert with CuK
˚
(l = 1.5401 A), with the X-ray generator operated at 40 kV and
a radiation
d
30 mA. Diffraction patterns were collected from 2u = 20–808.
Scheme 1. The synthesis of g-Fe2O3@HAp-Ag NPs.
Scheme 2. Synthesis of coumarin derivatives catalyzed by g-Fe2O3@HAp-Ag NPs.
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst, g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

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Z. Abbasi et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
3
128
129
130
131
132
133
134
135
136
137
7-Methoxy-4-methyl-2H-chromen-2-one (Table 3, entry 5): 1H
NMR (250 MHz; CDCl3): 7.67–7.64 (d, 1H, J = 8.5 Hz), 6.95 (s, 1H),
6.92–6.91 (d, 1H, J = 2.5 Hz), 6.18 (s, 1H), 3.8 (s, 3H), 2.3 (s, 3H); 13
NMR (62.9 MHz, CDCl3): 162.8, 160.5, 155.2, 153.8, 126.8, 113.5,
112.5, 111.5, 101.1, 56.3, 18.5.
7-Hydroxy-4,8-dimethyl-2H-chromen-2-one (Table 3, entry
17): 1H NMR (250 MHz; CDCl3):
10.33 (s, 1H), 7.39–7.35 (d,
1H, J = 8.75 Hz), 6.83–6.79 (d, 1H, J = 8.5 Hz), 6.05 (s, 1H), 2.30 (s,
3H), 2.11 (s, 3H); 13C NMR (62.9 MHz, CDCl3):
160.8, 159.3, 154.0,
As shown in Fig. 3, X-ray diffraction (XRD) patterns of the 160
d
synthesized Ag supported on hydroxyapatite-core–shell
MNPs display several relatively strong reflection peaks in the 2
region of 20–708. Fig. 3B shows the XRD for Ag supported on 163
hydroxyapatite-core–shell magnetic -Fe2O3 nanoparticles. The 164
crystallinity of the prepared -Fe2O3@HAp NPs (A) was confirmed 165
by the reflections observed at 2 values of 31.2, 32.3, 33.1, 34.3, 166
g-Fe2O3 161
C
u
162
d
g
g
d
u
45.9 and 49.2. It also identified the metallic Ag phase at 2
u
of 32.28 167
d
and 45.38 attributed to Ag doped catalysts.
168
153.2, 123.4, 112.3, 112.0, 111.0, 110.3, 18.5, 11.1.
In another investigation, magnetic measurements of Ag 169
supported on hydroxyapatite-core–shell -Fe2O3 MNPs were 170
g
performed at r.t. using a vibrating sample magnetometer (VSM). 171
The magnetization curve in Fig. 4 gives a saturation magnetization 172
138
139
3. Results and discussion
value of 13.21 emu/g.
173
3.1. Characterization of catalyst
The structural properties of synthesized
g
-Fe2O3@HAp-Ag 174
MNPs (trace A), HAp supported with Fe3O4 MNPs (B) [48], and 175
HAp (C) [48] are analyzed by FT-IR (Fig. 5). The band at 3570 cmÀ1 176
corresponds to O–H stretching in the hydroxyapatite structure. The 177
bands at 1095 cmÀ1, 1025, and 958 correspond to asymmetric and 178
symmetric stretching vibrations of the phosphate group (PO4À3). 179
140
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142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
Herein, we present an efficient and simple procedure for the
Pechmann reaction using Ag supported on hydroxyapatite-core–
shell magnetic
g-Fe2O3 nanoparticles as a novel, efficient, and
magnetically recyclable catalyst under solvent- and halogen-free
conditions at 80 8C (Scheme 2). This procedure provides an easy
access to a variety of coumarin derivatives. In this study, the
structure of the g-Fe2O3@HAp-Ag NPs was characterized by TEM,
SEM, VSM, XRD and FT-IR techniques. The scanning electronic
microscopy (SEM) image of Ag supported on hydroxyapatite-core–
shell magnetic
clearly seen, the SEM of the
g
-Fe2O3 nanoparticles is given in Fig. 1. As can be
-Fe2O3@HAp-Ag NPs showed that the
g
particles of the catalyst were nanosize.
The transmission electronic microscopy (TEM) image of Ag
supported on hydroxyapatite-core–shell magnetic
particles (MNPs) is given in Fig. 2. As can be clearly seen, the TEM
micrograph of the -Fe2O3@HAp-Ag NPs clearly proved that the
g-Fe2O3 nano-
g
particles are nanosize. These nanoparticles consist of relatively
small, nearly spherical particles, which is nicely consistent with
the value obtained from XRD measurements with diameters of
approximately 30 nm for the catalyst.
Fig. 3. XRD pattern of (A) g-Fe2O3@HAp and (B) g-Fe2O3@HAp-Ag NPs.
Fig. 1. SEM images of g-Fe2O3@HAp-Ag NPs.
Fig. 2. TEM images of g-Fe2O3@HAp-Ag NPs.
Fig. 4. Magnetization curve of g-Fe2O3@HAp-Ag NPs.
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst, g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

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Z. Abbasi et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
Table 2
Effect of temperature on the reaction of resorcinol (1 mmol) with ethyl acetoacetate
(1 mmol), in the presence of -Fe2O3@HAp-Ag NPs (10 mg).
g
Entry
Temperature (8C)
Time (min)
Yield (%)a
1
2
3
4
5
60
80
30
20
20
20
20
87
95
95
91
90
90
100
120
a
Isolated yield.
best results were obtained when the reaction was performed at
80 8C after 20 min in excellent yield (95%). After optimizing the
conditions, this reaction was developed with other phenolic
compounds under solvent-free conditions at 80 8C, and the results
are summarized in Table 3.
208
209
210
211
212
3.3. Using the optimal conditions for the reaction
213
Fig. 5. FT-IR spectra of (A) g-Fe2O3@HAp-Ag NPs, (B) g-Fe2O3@HAp, and (C) HAp.
Resorcinol (Table 3, entries 1, 2, 3 and 10), 3-methoxyphenol
(Table 3, entry 6), 4-methoxyphenol (Table 3, entry 8), 3-
aminophenol (Table 3, entry 9), phloroglucinol (Table 3, entries
11, 12 and 13), 3,5-dihydroxy toluene (Table 3, entry 16), 2,6-
dihydroxy toluene (Table 3, entry 17) reacted with a variety of
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
180
181
182
183
184
The peak observed at ꢀ2344 cmÀ1 is due to asymmetric stretching
C–H. The stretching modes of C–O and C55O are observed at
ꢀ1388 cmÀ1 and 1521 cmÀ1, respectively. On doping, stronger and
wider absorption bands are observed in the region ꢀ1170–
698 cmÀ1 due to the organic capping of silver.
b
-ketoesters in the short reaction time and excellent yield of the
corresponding coumarin derivatives were obtained. 3-Methylphe-
nol (Table 3, entry 4), 3-methoxylphenol (Table 3, entry 5), 3,5-
dihydroxy toluene (Table 3, entry 15) reacted with a variety of
185
3.2. Optimization the reaction condition
b
-ketoesters in good yields with slightly longer reaction times. The
reaction of 1-naphthol, however, requires a longer reaction time to
obtain the corresponding coumarin derivative due to presence of
another phenyl ring (Table 2, entries 19 and 20). In the case of
phenol, one of the interesting feature of this procedure over most
of the previous heterogeneous and homogeneous systems, is the
formation of 4-methylcoumarin in good yield which required a
longer reaction time vs. the reaction of unsubstituted phenol
(Table 2, entry 21). Finally, in all cases, the reactions successfully
proceeded to give the corresponding coumarin derivatives in good
to excellent yield and in short and acceptable reaction time.
The reusability of the catalysts is an important advantage in
green chemistry and heterogeneous catalysis; and also important
from an industrial point of view in the large scale operations and
commercial applications. In the next stage, recyclability of
186
187
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189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
After full characterization of g-Fe2O3@HAp-Ag NPs by TEM,
SEM, VSM, XRD and FT-IR techniques, its catalytic activity was
examined by the Pechmann condensation of various phenols with
ethyl acetoacetate to provide coumarin derivatives (Scheme 2). In
the first step, as a model reaction, the condensation of ethyl
acetoacetate (1 mmol) with resorcinol (1 mmol) under solvent-
free conditions at r.t. afforded the corresponding 7-hydroxy-4-
methyl-2H-chromen-2-one which was conducted using different
amounts of
after 90 min, no product was obtained in the absence of the
-Fe2O3@HAp-Ag NPs (Table 1, entry 1). We found that the best
results were obtained with 10 mg of the -Fe2O3@HAp-Ag NPs
g-Fe2O3@HAp-Ag NPs (Table 1). As evident in Table 1,
g
g
which was sufficient to promote the reaction efficiently under
solvent-free conditions at r.t., and provides the product in 80%
yield and in 30 min (Table 1, entry 6). Furthermore, Table 1
indicates that the higher temperature is necessary for the reaction
conditions.
In the second step, the various temperature effects on the
condensation of ethyl acetoacetate (1 mmol) with resorcinol
(1 mmol) in the presence of g-Fe2O3@HAp-Ag NPs (10 mg) under
g
-Fe2O3@HAp-Ag NPs was investigated (Fig. 6). For this purpose,
the condensation of ethyl acetoacetate (1 mmol) with resorcinol
(1 mmol) under solvent-free conditions at 80 8C in the presence of
10 mg of
g-Fe2O3@HAp-Ag NPs afforded the corresponding
7-hydroxy-4-methyl-2H-chromen-2-one and was selected as the
model reaction. After the reaction was carried out under the
optimized reaction conditions, the catalyst was separated using an
external magnetic field, washed with methanol dried in air and
reused for the next reaction. The recovered catalyst was reused for
ten consecutive cycles without any significant loss in catalytic
activity (Fig. 6).
In order to investigate the efficiency of this new procedure in
comparison with some recently reported protocols, we provide the
results of the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-
one with various catalysts, such as PVPP-BF3, CMK-5-SO3H,
sulfated zirconia, I2, H6P2W18O62Á24H2O, and m-ZrP with respect
to the amounts of catalyst, reusability of catalyst, and reaction
times and yields of the products (Table 4). As presented in Table 4,
some of these methods suffer from at least one of the following
disadvantages: use of toxic or harmful solvents like toluene
[45,46], reflux conditions [42,46], very long reaction time for
completion of the reaction [42,44–47], low yield of product
solvent-free conditions afforded the corresponding 7-hydroxy-4-
methyl-2H-chromen-2-one as a model are studied (Table 2). The
Table 1
The Pechmann reaction between resorcinol and ethyl acetoacetate with different
amounts of
g-Fe2O3@HAp-Ag NPs.
Entry
Catalyst amount (mg)
Time (min)
Yield (%)a
1
2
3
4
5
6
7
None
1
90
60
60
45
40
30
30
No reaction
53
60
60
75
80
80
3
5
7
10
15
a
Isolated yield.
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst, g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

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Table 3
Syntheses of coumarins via Pechmann condensation of phenols with ethyl acetoacetate in g-Fe2O3@HAp-Ag NPs.
Entry
1
Phenolic compound
b
-Ketoester
Product
Time (min)/Yield (%)a
20/95
M.P. (8C) (Lit.)
183–184 [50]
2
3
33/96
20/91
252–254 [50]
178–180 [50]
4
5
6
50/86
30/87
18/89
130–132 [50]
161–163 [51]
181–183 [51]
7
25/85
150–152 [50]
8
9
30/88
27/89
162–163 [50]
221–223 [50]
10
30/90
241–243 [50]
11
12
13
25/88
30/91
10/93
284–285 [50]
240–242 [50]
184–186 [50]
14
15
35/90
42/85
255–257 [51]
210–212 [51]
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst,
g
-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

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Z. Abbasi et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
Table 3 (Continued )
Entry
16
Phenolic compound
b
-Ketoester
Product
Time (min)/Yield (%)a
18/89
M.P. (8C) (Lit.)
159–161 [51]
17
18
20/88
30/85
135–137 [50]
281–283 [50]
19
35/85
159–161 [51]
20
45/83
150–151 [51]
21
60/86
81–83 [49]
a
Isolated yield.
260
261
262
263
264
265
266
267
268
269
270
271
272
273
[45,46], high temperature [43,46,47], tedious work-up procedures,
and non-recyclable reagents [42,44–46]. As we have determined,
g
-Fe2O3@HAp-Ag NPs remarkably improves the synthesis of
coumarin derivatives; affords excellent yields of product, results
in shorter reaction time, requires low (or lower) temperatures,
uses recyclable or no reagents and an external magnetic field to
reduce purification requirements. These results show that
g
-Fe2O3@HAp-Ag NPs is a powerful catalyst for the synthesis of
coumarin derivatives.
A proposed mechanism for preparation of 7-hydroxy-4-methyl-
2H-chromen-2-one from the reaction of ethyl acetoacetate with
resorcinol is shown in Scheme 3. The mechanism for the reaction is
assumed to be the same as proposed by Rezaee Nezhad et al.
Fig. 6. Reusability of the nanocatalyst.
[12,17] using g
-Fe2O3@HAp-Fe2+ NPs as a Lewis acid.
Table 4
Comparison of various procedures for the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one with different catalysts.1.
Entry
Catalyst
Condition
Time (h)
Yield (%)a
Ref.
1
2
3
4
5
6
7
8
PVPP-BF3
EtOH/reflux/0.1 g
2
20 min
24
91
95
91
82
82
87
94
95
[42]
[43]
[44]
[45]
[46]
[46]
[47]
–
CMK-5-SO3H
Sulfated zirconia
I2
130 8C/solvent-free/3 mol%
80 8C/solvent-free/10 mol%
90 8C/toluene/25 mol%
130 8C/toluene/reflux/45 mg
130 8C/solvent-free/45 mg
160 8C/solvent-free/15 mol%
80 8C/solvent-free/10 mg
18
H6P2W18O62Á24H2O
H6P2W18O62Á24H2O
m-ZrP
4.5
0.7
5
g-Fe2O3@HAp-Ag NPs
20 min
a
Isolated yield.
Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst,
g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022

G Model
CCLET 3745 1–8
Z. Abbasi et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
7
Scheme 3. Proposed reaction mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one promoted by g-Fe2O3@HAp-Ag NPs.
[6] J.M. Perez, F.J. Simeone, Y. Saeki, L. Josephson, R. Weissleder, Viral-induced self- 309
assembly of magnetic nanoparticles allows the detection of viral particles in 310
274
4. Conclusion
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311
313
315
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283
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285
286
In summary, we prepared g-Fe2O3@HAp-Ag NPs as a novel,
efficient, and magnetically recyclable catalyst and characterized
the material by SEM, TEM, FT-IR, XRD, and VSM spectroscopy. In
this study, we have developed an efficient, green, and simple
procedure for the synthesis coumarin derivatives by the Pechmann
condensation reaction under solvent- and halogen-free conditions
at 80 8C. The significant advantages of the present method include
the non-chromatographic purification of the products, a simple
experimental procedure, short reaction times and green content of
the procedure, high yields of products, and ease of recovery of the
reusable catalyst from the reaction mixture using an external
magnet.
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(MFH): cancer treatment with AC magnetic field induced excitation of biocom- 317
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We gratefully acknowledge funding from the National Elites
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Appendix A. Supplementary data
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338
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Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.cclet.2016.06.
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Please cite this article in press as: Z. Abbasi, et al., Preparation of a novel, efficient, and recyclable magnetic catalyst, g-Fe2O3@HAp-Ag
nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives, Chin. Chem. Lett. (2016), http://
dx.doi.org/10.1016/j.cclet.2016.06.022