CuFe2O4 nanoparticles: A magnetically recoverable and reusable catalyst for the synthesis of coumarins via pechmann reaction in water

Article abstract of DOI:10.1080/00397911.2013.835423

The synthesis of coumarins by hydroxyalkylation of phenols with ethyl acetoacetate (via Pechmann reaction) is attempted using magnetically separable and reusable CuFe₂O₄ nanoparticles in water. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.] Copyright

Full text of DOI:10.1080/00397911.2013.835423

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CuFe2O4 Nanoparticles: A Magnetically
Recoverable and Reusable Catalyst
for the Synthesis of Coumarins via
Pechmann Reaction in Water
Seyed Meysam Baghbanian a & Maryam Farhang b
a Department of Chemistry , Ayatollah Amoli Branch, Islamic Azad
University , Amol , Iran
b Faculty of Chemistry , Mazandaran University , Babolsar , Iran
Accepted author version posted online: 28 Oct 2013.Published
online: 27 Dec 2013.
To cite this article: Seyed Meysam Baghbanian & Maryam Farhang (2014) CuFe2O4 Nanoparticles: A
Magnetically Recoverable and Reusable Catalyst for the Synthesis of Coumarins via Pechmann Reaction
in Water, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 44:5, 697-706, DOI: 10.1080/00397911.2013.835423
To link to this article: http://dx.doi.org/10.1080/00397911.2013.835423
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Synthetic Communications1, 44: 697–706, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.835423
CuFe2O4 NANOPARTICLES: A MAGNETICALLY
RECOVERABLE AND REUSABLE CATALYST FOR THE
SYNTHESIS OF COUMARINS VIA PECHMANN
REACTION IN WATER
Seyed Meysam Baghbanian1 and Maryam Farhang2
1Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad
University, Amol, Iran
2Faculty of Chemistry, Mazandaran University, Babolsar, Iran
GRAPHICAL ABSTRACT
Abstract The synthesis of coumarins by hydroxyalkylation of phenols with ethyl
acetoacetate (via Pechmann reaction) is attempted using magnetically separable and
reusable CuFe2O4 nanoparticles in water.
[Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for the following free supplemental resource(s):
Full experimental and spectral details.]
Keywords Coumarins; CuFe2O4 nanoparticles; heterogeneous catalyst; Pechmann
reaction
INTRODUCTION
Magnetic nanoparticles are of great interest for researchers from a wide range
of disciplines, including magnetic fluids,[1] catalysis,[2] data storage,[3] and environ-
mental remediation.[4] Nanocatalysts have many important benefits in catalyst
systems and interesting applications, and they provide a broad range of benefits in
catalytic systems. However, in some cases, recovery of the nanocatalysts from the
reaction mixtures is so difficult that conventional techniques such as filtration or
centrifugation are not enough for an efficient recovery. To overcome this issue,
the use of magnetic nanoparticles has emerged as a viable solution; their insoluble
and paramagnetic nature enables easy and efficient separation of the catalysts from
the reaction mixture with an external magnet. Magnetic separation is an attractive
Received April 7, 2013.
Address correspondence to Seyed Meysam Baghbanian, Department of Chemistry, Ayatollah
Amali Branch, Islamic Azad University, Amol, Iran. E-mail: S.M.Baghbanian@iauamol.ac.ir
697

698
S. M. BAGHBANIAN AND M. FARHANG
Scheme 1. The synthesis of substituted coumarins in the presence of CuFe2O4 nanoparticles at room
temperature.
alternative to filtration or centrifugation as it prevents loss of catalyst and enhances
reusability, making the catalyst inexpensive and promising for industrial applica-
tions. On the other hand, the use of water as a medium for organic reactions has
a number of potential advantages because water is the most abundant, least expens-
ive solvent, nonhazardous and nontoxic, and isolation of the organic products can be
performed by simple phase separation.
Coumarin and its derivatives form an important class of benzo-pyrones found
in nature and have shown significant biological activities, such as antitumor,[5]
anti-HIV,[6] antioxidative,[7] antimicrobial,[8] and anticancer[9] activity. Among the
various coumarin derivatives, 7-hydroxy-4-methyl coumarin (b-methylumbelliferone)
is used as insecticide, fluorescent brightener, and a standard for fluorometric deter-
mination of enzymatic activity and tunable laser dyes.[10] The Pechmann reaction is
one of the most widely applied method for synthesizing coumarins using different
homogeneous or heterogeneous catalysts such as Amberlyst ion-exchange resins,[11]
montmorillonite K-10,[12] nafion resin=silica nanocomposites,[13] nanocrystalline
sulfated-zirconia,[14] furic acid,[15] trifluoroacetic acid,[16] phosphorus pentoxide,[17]
sulfonic acid functionalized SBA-15 silica,[18] ZrCl4,[19] and TiCl4.[20] However,
most of these procedures require a large amount of catalyst long duration, micro-
wave irradiation, and high temperature to complete the reaction. Therefore, the
search continues for a better catalyst for the synthesis of coumarins in terms of
operational simplicity, reusability, economic viability, and greater selectivity.
Herein, we have focused our attention on CuFe2O4 nanoparticles[21] as hetero-
geneous catalysts in the synthesis of coumarins in water at room temperature
(Scheme 1).
RESULTS AND DISCUSSION
To find the optimized condition, the reaction of resorcinol (1 mmol) and ethyl
acetoacetate (1.2 mmol) in an aqueous medium at room temperature as a model reac-
tion in the presence of different amounts of CuFe2O4 nanoparticles (5 mol%) was
examined, and variables affecting on the reaction yields were studied.
In the absence of a catalyst, only a trace amount of the desired 7-hydroxy-4-
methyl-2H-chromen-2-one was obtained under solvent-free conditions even at
70 ꢀC (Table 1, entry 1). In our initial study for the optimization of the reaction con-
ditions, a screening was performed with a variety of different solvents such as etha-
nol, acetonitrile, dichloromethane, and water at room temperature (Table 1, entries
2–7) as well as under solvent-free conditions with CuFe2O4 nanoparticles at different
temperatures (Table 1, entries 8–10). We noticed that the polar protic solvents

CuFe2O4 NANOPARTICLES
699
Table 1. Effect of temperature, solvent, and amount of catalyst on the synthesis of 7-hydroxy-4-methyl-
2H-chromen-2-onea
Entry
Amount of catalyst (mol %)
Temperature (ꢀC)
Solvent
Time (min)
Yield (%)b
1
2
—
5
5
5
5
1
3
5
5
5
70
25
25
25
25
25
25
25
45
70
—
EtOH
CH3CN
CH2Cl2
H2O
H2O
H2O
—
5 h
25
32
30
15
20
20
25
25
25
Trace
70
68
3
4
60
98
5
6
88
92
7
8
55
70
9
10
—
—
80
aReaction conditions: resorcinol (1 mmol) and ethyl acetoacetate (1.2 mmol).
bIsolated yield.
afforded better yield than other solvents and the best catalytic activity of CuFe2O4
nanoparticles (5 mol%) was observed in aqueous medium (Table 1).
The quantity of the catalyst plays a vital role in the formation of the desired
product. To determine the optimum concentration of catalyst, the best yields were
found in the presence of just 5 mol% CuFe2O4 nanoparticles. It was observed that
decrease in the amount of catalyst did not improve the results to an appreciable
extent.
To assess the generality of this approach for the synthesis of coumarins,
various phenols were reacted with ethyl acetoacetate under optimized conditions
(Table 2). A series of a variety of functional groups such as ether, hydroxy, nitro,
alkyl, and amino groups under the present reaction conditions afforded a wide range
of substituted coumarins in good yield. Interestingly, substrates such as phenol, nitro
phenols, and cresols showed better reactivity (compared with that previously
reported) to afford the respective coumarins with good yields and short reaction
times. The reactions of phenols having electron-donating groups furnished greater
yields of phenols compared to that without having electron-donating groups or with
an electron-withdrawing group. Also, 3-aminophenol reacted to provide 7-amino-4-
methyl coumarin in good yield with good chemoselectivity (Table 2, entry 11).
To examine the possible recyclability of the catalyst, the reaction of resorcinol
(1 mmol) with ethyl acetoacetate (1.2 mmol) in the presence of 5 mol% CuFe2O4
nanoparticles in water medium and at room temperature was studied. After
15 min, the reaction was completed and the 7-hydroxy-4-methyl-2H-chromen-2-one
was obtained in 98% yield. After completion of the reaction (monitored by thin-layer
chromatography, TLC), the catalyst was separated from the reaction mixture with
an external magnet and water was added to the resulting reaction mixture, followed
by extraction with EtOAc. The catalyst could be reused six times for the synthesis of
7-hydroxy-4-methyl-2H-chromen-2-one without significant loss of activity (Table 3).
To show the accessibility of the present work we compared this method with
other reported catalysts and summarized the results of the preparation of the
coumarin derivatives. The results of the synthesis 3a are collected in Table 4, which
shows CuFe2O4 nanoparticles are more efficient catalysts with respect to the reaction

700
S. M. BAGHBANIAN AND M. FARHANG
Table 2. Pechmann reactions of various phenols
Entry
Phenol
Product
Time (min)
Yield (%)a
Ref.
[18]
1
15
98
2
15
95
[22]
3
4
18
20
92
92
[18]
[18]
5
22
96
[22]
6
7
18
17
85
82
[18]
[18]
(Continued )

CuFe2O4 NANOPARTICLES
701
Table 2. Continued
Entry
Phenol
Product
Time (min)
Yield (%)a
Ref.
8
20
90
[18]
[24]
9
10
11
30
32
30
85
88
80
[24]
[18]
12
34
85
[18]
aIsolated yields of pure products.
Table 3. Reusability studies of catalysts for the synthesis of
compound 3a (Table 2, entry 1)a
Experiment
Isolated yield (%)b
1
2
3
4
5
6
98
96
95
95
92
90
aReaction condition: resorcinol (1 mmol), ethyl acetoacetate
(1.2 mmol), CuFe2O4 nanoparticles as a catalyst 5 mol% in
water.
bIsolated yield.

702
S. M. BAGHBANIAN AND M. FARHANG
Table 4. Comparison of the catalytic efficiency of CuFe2O4 nanoparticles with some reported catalysts in
the synthesis of compound 3a
Entry
Catalyst
PMSCl, 7 mol%, 130 ꢀC
Time (min)
Yield (%)
Ref.
1
2
60
10
40
30
42
30
20
15
12
15
94
96
94
94
96
98
98
94
80
98
[25]
[26]
[27]
[28]
[29]
[23]
[30]
[31]
[32]
—
Zr(IV)-HMNQ@ASMPs, solvent-free, 110 ꢀC
ZrOCl2 ꢂ 8H2O=SiO2, 10 mol%, 90 ꢀC
Zirconium(IV)-modified silica gel, 10 mol%, 130 ꢀC
GaI3, 10 mol%, reflux, CH2Cl2
3
4
5
6
InCl3, 10 mol%, 65 ꢀC
7
Sm(NO3)3 ꢂ 6H2O, 10 mol%, 80 ꢀC
8
Bi(NO3)3 ꢂ 5H2O, 5 mol%, 80 ꢀC
9
10
Ionic liquid anhydrous FeCl3, 20 mol%, 70 ꢀC
CuFe2O4 nanoparticles, rt, water, 5 mol%
time and require lower catalyst content under very mild conditions at room tempera-
ture in aqueous media. They exhibited broad applicability in terms of yields.
CONCLUSION
In summary, we have described here the synthesis of coumarin derivatives
using CuFe2O4 nanoparticles as catalysts in water at room temperature. The meth-
odology has several advantages such as using water as solvent, high reaction rates,
excellent yields, simplicity in the extraction of the product, magnetically separable
catalysts, and elimination of catalyst filtration after completion of the reaction.
EXPERIMENTAL
All reagents were purchased from Merck and Aldrich and used without further
purification. The CuFe2O4 nanoparticles were prepared according to the procedure
described in the literature.[21] Melting points were measured with an Electrothermal
1
9100 apparatus. H and 13C spectra were measured with Bruker DRX-400 Avance
spectrometers, and infrared (IR) spectra were recorded on a FT-IR Bruker Vector
22 spectrometer.
General Procedure for the Preparation of Coumarins
Resorcinol (1 mmol) and ethyl acetoacetate (1.2 mmol) were placed in a 10 ml,
round-bottomed flask in H2O (3 mL). Sequentially CuFe2O4 (5 mol%, 12 mg) was
added. After completion of the reaction, the catalyst was separated from the reaction
mixture with an external magnet, and the catalyst was washed several times with
H2O and dried under vacuum. Water (10 mL) was added to the resulting reaction
mixture, followed by extraction with EtOAc (3 ꢁ 5 mL). The collected organic phases
were dried with Na2SO4, and the solvent was removed under vacuum to give the cor-
responding coumarin, which did not require any further purification. The physical
data (mp, NMR) of these known compounds were found to be identical with those
reported in the literature. Spectroscopic data for selected examples are shown.

CuFe2O4 NANOPARTICLES
703
7-Hydroxy-4-methyl-2H-chromen-2-one(3a). Colorlesssolid,mp185–186 ꢀC;
1
IR (KBr): n 3165, 1675, 1383, 1237, 1067, 985, 856, 758, 572, 525, 426 cmꢃ1; H
NMR (400 MHz; DMSO-d6; TMS): dH ¼ 10.52 (brs, 1H), 7.35 (d, J ¼ 8.4 Hz, 1H),
6.78 (d, J ¼ 8.0 Hz, 1H), 6.65 (s, 1H), 6.10 (brs, 1H), 2.29 (brs, 3H); 13C NMR
(100 MHz, DMSO-d6; TMS): dC ¼ 161.6, 160.7, 155.2, 153.8, 126.9, 113.6, 112.8,
110.4, 102.2, 18.8.
7-Amino-4-methyl-2H-chromen-2-one (3k). Light yellow solid, mp
224–225 ꢀC; IR (KBr): n 3436, 3353, 3250, 1617, 1543, 1448, 1389, 1263, 1213,
1
1155, 1056, 835, 710, 649, 539, 452 cmꢃ1; H NMR (400 MHz, DMSO-d6; TMS):
dH ¼ 7.42 (d, J ¼ 8.0 Hz, 1H), 6.43 (dd, J ¼ 7.2 Hz, J ¼ 2.5 Hz, 1H), 6.42 (d, J ¼ 2.5 Hz,
Hz, 1H), 6.12 (brs, 2H), 5.92 (s, 1H), 2.26 (s, 3H); 13C NMR (100 MHz, DMSO-d6;
TMS): dC ¼ 163.2, 154.9, 154.1, 153.5, 125.7, 111.6, 109.5, 107.6, 97.9, 18.2.
Preparation of Nano CuFe2O4
CuFe2O4 nanoparticles were prepared by thermal decomposition of Cu(NO3)2
and Fe(NO3)3 in water in the presence of sodium hydroxide. Briefly, to a solution of
Fe(NO3)3 ꢂ 9H2O (3.34 g, 8.2 mmol) and Cu(NO3)2 ꢂ 3H2O (1 g, 4.1 mmol) in 75 ml
of distilled water, 3 g (75 mmol) of NaOH dissolved in 15 ml of water was added
at room temperature over a period of 10 min, during which a reddish-black precipi-
tate was formed. Then the reaction mixture was warmed to 90 ꢀC and stirred. After
2 h, it was cooled to room temperature, and the magnetic particles so formed were
separated by a magnetic separator. It was then washed with water (3 ꢁ 30 ml), and
the catalyst was kept in an air oven overnight at 80 ꢀC. Then the catalyst was ground
in a mortar and pestle, kept in a furnace at 700 ꢀC for 5 h (step up temperature
20 ꢀC=min), and then cooled to room temperature slowly; 820 mg of magnetic
CuFe2O4 nanoparticles were obtained.
Catalyst Characterizations
The systematic characterization of CuFe2O4 catalyst was carried out by x-ray
diffraction (XRD), scanning electron microscope (SEM), and transmission electron
microscopy (TEM). The XRD analysis was done in a Philips PW 1830 x-ray diffract-
ꢀ
˚
ometer with CuKa source (k ¼ 1.5418 A) in a range of Bragg’s angle (5–60 ) at room
temperature. The XRD pattern of the calcined sample (Fig. 1) perfectly matches with
the expected cubic spinel structure of CuFe2O4. The average crystallite size (L) was
calculated from X-ray line broadening using (3 1 1) peak and Debye-Sherrer’s
equation; L ¼ 0.89k=bcosh, where b is the FWHF and k is the wavelength of the
radiation, found to be L ¼ 10.3 nm. SEM picture was taken using a Jeol JSM-5300
microscope (acceleration voltage 10 kV). The sample powder was deposited on
a carbon tape before mounting on a sample holder. To reduce the charge developed
on the sample, gold sputtering was done for 3 min. The SEM of the CuFe2O4 sample
is shown in Fig. 2a. As indicated in this figure, small agglomerated nanoparticles of
disordered surface morphology are observed. The TEM were obtained with a Philips
CM-10 microscope. The CuFe2O4 sample for TEM was prepared by dispersing
the powdered sample in ethanol by sonication and then drop drying on a copper grid

704
S. M. BAGHBANIAN AND M. FARHANG
Figure 1. X-ray diffraction pattern of CuFe2O4 nanoparticles.
Figure 2. (a) SEM image of CuFe2O4 nanoparticles. (b) TEM image of CuFe2O4 nanoparticles.
(400 mesh) coated with carbon film. As the TEM figure shows, the average size of
particles resulted from this method is approximately 5–15 nm. The particle sizes
obtained from TEM are in good agreement with XRD measurement (Fig. 2b).
ACKNOWLEDGMENT
This research is supported by the Islamic Azad University, Ayatollah Amoli
Branch.
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