Fe3O4 nanoparticles as an efficient and magnetically recoverable catalyst for the synthesis of α β-unsaturated heterocyclic and cyclic ketones under solvent-free conditions

Article abstract of DOI:10.1080/00397911.2013.786089

An efficient and green procedure has been developed for the synthesis of monoarylidenes of cyclic and heterocyclic ketones. The reaction was carried out under solvent-free conditions in the presence of a catalytic amount of nanosized magnetite (Fe₃O₄). The catalyst was easily removed by using an external magnet. The structures of the products were deduced from their ¹H NMR, ¹³C NMR, and infrared spectroscopy and mass spectrometry. [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.]

Full text of DOI:10.1080/00397911.2013.786089

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Fe3O4 Nanoparticles as an Efficient
and Magnetically Recoverable Catalyst
for the Synthesis of α,β-Unsaturated
Heterocyclic and Cyclic Ketones under
Solvent-Free Conditions
Tooba Alishiri a , Hossein A. Oskooei a & Majid M. Heravi a
a Department of Chemistry , School of Sciences, Alzahra University ,
Tehran , Iran
Published online: 05 Sep 2013.
To cite this article: Tooba Alishiri , Hossein A. Oskooei & Majid M. Heravi (2013) Fe3O4 Nanoparticles
as an Efficient and Magnetically Recoverable Catalyst for the Synthesis of α,β-Unsaturated
Heterocyclic and Cyclic Ketones under Solvent-Free Conditions, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 43:24, 3357-3362
To link to this article: http://dx.doi.org/10.1080/00397911.2013.786089
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Synthetic Communications1, 43: 3357–3362, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.786089
Fe3O4 NANOPARTICLES AS AN EFFICIENT AND
MAGNETICALLY RECOVERABLE CATALYST FOR THE
SYNTHESIS OF a,b-UNSATURATED HETEROCYCLIC
AND CYCLIC KETONES UNDER SOLVENT-FREE
CONDITIONS
Tooba Alishiri, Hossein A. Oskooei, and Majid M. Heravi
Department of Chemistry, School of Sciences, Alzahra University,
Tehran, Iran
GRAPHICAL ABSTRACT
Abstract An efficient and green procedure has been developed for the synthesis of
monoarylidenes of cyclic and heterocyclic ketones. The reaction was carried out under
solvent-free conditions in the presence of a catalytic amount of nanosized magnetite
(Fe3O4). The catalyst was easily removed by using an external magnet. The structures
of the products were deduced from their 1H NMR, 13C NMR, and infrared spectroscopy
and mass spectrometry.
[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 Heterogeneous catalyst; magnetic nanoparticles; magnetite (Fe3O4);
monoarylidenes
INTRODUCTION
In recent years, Fe3O4 nanoparticles (magnetite nanoparticle) have attracted
worldwide attention[1] because of due to their significant characteristics such as the
ease of magnetical separation from the reaction mixture, which is simpler and
typically more effective than filtration or centrifugation as it prevents the loss of
the catalyst.[2] Various strategies have successfully demonstrated the applications
of Fe3O4 nanoparticle–immobilized or supported catalysts in organic synthesis.[3]
Received January 21, 2013.
Address correspondence to Majid M. Heravi, Department of Chemistry, School of Sciences,
Alzahra University, Vanak, Tehran, Iran. E-mail: mmh1331@yahoo.com
3357

3358
T. ALISHIRI, H. A. OSKOOEI, AND M. M. HERAVI
Scheme 1. General reactionforthe synthesis of monoarylidene derivatives of aldehydes and enolizable ketones.
Direct use of Fe3O4 nanoparticles without modification as magnetically recov-
erable catalysts for organic transformations have been reported by many researchers.
They used them in the protection of alcohols and phenols using hexamethyldisila-
zane;[4] three-component synthesis of a-aminonitriles from aldehydes, amines, and
TMSCN;[5] synthesis of quinoxaline derivatives;[6] preparation of propargyla-
mines;[7,8] four-component aza-Sakurai reaction;[9] selective N-alkylation of aromatic
amines using benzylic alcohols;[10] oxidative C–C bond formation between Csp3–H
bond adjacent to nitrogen and Csp3–H bond of nitroalkanes;[10] carbon–carbon
bond formation via the Sonogashira–Hagihara reaction;[8] synthesis of 3,4-dihydro-
pyrimidin-2(1H)-ones;[12] synthesis of mono-, bis-, and tris-diindolyl methane;[13]
chemoselective reduction of olefins;[14] synthesis of polysubstituted imidazoles;[15]
and synthesis of benzimidazole derivatives.[16]
In continuation of our work in aldol condensation[17] and using magnetite
particles,[5] in this communication we disclose the appropriate use of Fe3O4 in the
synthesis of mono-aldol adducts.
RESULTS AND DISCUSSION
Herein, we report a facile synthesis of a,b-unsaturated compounds involving
the one-pot reaction between cyclic and heterocyclic ketones and different aldehydes
in the presence of TMSCN using the magnetite as a catalyst (Scheme 1).
Table 1. Fe3O4-catalyzed reaction of cyclopentanone, benzaldehyde,
and TMSNMe2
Entry
Catalyst
Solvent
Yield (%)
1
2
—
—
—
60
75
82
88
92
92
85
80
75
82
88
65
88
80
Fe3O4 (1%)
Fe3O4 (3%)
Fe3O4 (5%)
Fe3O4 (7%)
Fe3O4 (10%)
MgBr2OEt2
MgF2
3
—
—
4
5
—
—
6
7
—
—
8
9
MgClO4
LiClO4
LiBr
—
10
11
12
13
14
—
—
Fe3O4 (7%)
Fe3O4 (7%)
Fe3O4 (7%)
H2O
Hexane
Dichloromethane

Fe3O4 NANOPARTICLES AS CATALYST
3359
Figure 1. Efficient recovery of the catalyst.
Initially we evaluated the reaction of cyclopentanone with benzaldehyde in the
presence of various Lewis acides and silylated amines. The optimum results were
obtained when an equimolar solvent-free mixture of two reactants came in to contact
with TMSNMe2 and nano-Fe3O4, leading to the formation of the respective pro-
ducts in good yields. The best result was obtained by 7 mol% of Fe3O4 (Table 1).
The recycling capacity of the magnetite was examined under the optimized
reaction conditions. The catalyst was separated by using a bar magnet after com-
pletion of the reaction. The recovered catalyst was washed with dichloromethane
and, after drying, was reused for the next cycle of the reaction. The results are shown
in Fig. 1. The catalyst showed negligible loss of reactivity up to seven runs.
Based on optimized reaction conditions, a series of a,b-unsaturated compounds
were synthesized, which are listed in Table 2.
Table 2. Synthesis of a,b-unsaturated heterocyclic and cyclic ketones 3
Entry
X
R
Product
Time (h)
Yield (%)
1
2
-(CH2)0-
-(CH2)1-
-(CH2)2-
S
C6H5
C6H5
C6H5
C6H5
A1
A2
4
20
20
7
92
95
90
75
87
88
72
80
80
64
87
66
80
80
65
85
3
A3
A4
4
5
-(CH2)0-
-(CH2)1-
S
(p-NO2)C6H4
(p-NO2)C6H4
(p-NO2)C6H4
p-FC6H4
A5
A6
1
6
6
7
A7
A8
4
8
S
4
9
-(CH2)1-
S
p-ClC6H4
A9
20
6
10
11
12
13
14
15
16
(p-CO2Me)C6H4
(p-OMe)C6H4
(p-OMe)C6H4
2- thienyl
A10
A11
A12
A13
A14
A16
A17
-(CH2)1-
S
22
9
S
4
-(CH2)1-
-(CH2)1-
-(CH2)1-
2-furyl
Me2CHCH2
(p-OH)C6H4
14
16
15

3360
T. ALISHIRI, H. A. OSKOOEI, AND M. M. HERAVI
Scheme 2. The plausible mechanism.
The suggested mechanism is schematized in Scheme 2 in accordance with the
characterized products.
CONCLUSION
In summary, we reported a highly efficient method for the synthesis of a,b-
unsaturated compounds in the presence of magnetic nanoparticles. Good yields,
mild reaction conditions, and simplicity of removing the catalyst and recycling it
for further application can be mentioned as the advantages of our protocol.
In comparison with other methods that required solvent to separate the
catalyst,[17–22] in this method catalyst removed without use of any hazardous organic
solvent. Magnetite is an efficient, eco-friendly and inexpensive catalyst.
EXPERIMENTAL
Melting points were measured using a capillary tube method with a Barnstead
Electrothermal 9200 apparatus. Fourier transform infrared (FTIR) spectra were
1
recorded using KBr discs on a FTIR Brucker Tensor 27 instrument. H and 13C
NMR spectra were recorded on a Bruker AQS-Avance spectrometer at 500 and
125 MHz, using tetramethylsilane (TMS) as an internal standard. Mass spectra were
documented on an Agilent Technology (HP) mass spectrometer operating at an
ionization potential of 70 eV.
Preparation of Catalyst
Fe3O4 magnetic nanoparticles (MNPs) were synthesized by a coprecipitation
method using an aqueous NaOH solution as the precipitating agent for FeCl3 and
FeCl2.[22]

Fe3O4 NANOPARTICLES AS CATALYST
3361
Synthesis of a,b-Unsaturated Heterocyclic and Cyclic Ketones:
General Procedure
A mixture of an aldehyde (4 mmol), an amine (2 mmol), and nanosized magnet-
ite (7 mol% with respect to aldehyde) was stirred at room temperature. An appropri-
ate ketone (4 mmol) was then added almost immediately to the mixture. The progress
of reaction was monitored by thin-layer chromatography (TLC). After completion
of the reaction, magnetite was removed easily by dropping a bar magnet to the reac-
tion vessel. The product was isolated and purified by column chromatography using
hexane–ethyl acetate (30:70) as solvent system (Table 2).
ACKNOWLEDGMENT
The Department of Chemistry, Alzahra University, is gratefully appreciated.
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