The use of κ-carrageenan/Fe3O4 nanocomposite as a nanomagnetic catalyst for clean synthesis of rhodanines

Article abstract of DOI:10.1016/j.catcom.2015.05.002

In this work, magnetically separable Fe₃O₄ nanoparticles were synthesized in the presence of natural κ-carrageenan (KCAR) biopolymer to provide Fe₃O₄@KCAR. FT-IR analysis, scanning electron microscopy (SEM), X-ray diffraction, VSM analysis, and SEM-EDAX were incorporated for the characterization of Fe₃O₄@KCAR nanocomposite. And then, the first catalytic report of Fe₃O₄@KCAR with no post-modification was achieved by studying its catalytic activity in the multicomponent reaction of rhodanine synthesis. Based on this study, Fe₃O₄@KCAR was an efficient, magnetically separable and recyclable, water-dispersible and green catalyst with natural source. This catalyst also showed 9-run recyclability with no significant yield decrease.

Full text of DOI:10.1016/j.catcom.2015.05.002

The use of κ-Carrageenan/Fe3O4 nanocomposite as a nanomagnetic catalyst
for clean synthesis of rhodanines
Sadegh Rostamnia, Behzad Zeynizadeh, Esmail Doustkhah, Ali Bagh-
ban, Khadijeh Ojaghi Aghbash
PII:
DOI:
Reference:
S1566-7367(15)00191-0
doi: 10.1016/j.catcom.2015.05.002
CATCOM 4321
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
26 March 2015
29 April 2015
1 May 2015
Please cite this article as: Sadegh Rostamnia, Behzad Zeynizadeh, Esmail Doustkhah, Ali
Baghban, Khadijeh Ojaghi Aghbash, The use of κ-Carrageenan/Fe3O4 nanocomposite
as a nanomagnetic catalyst for clean synthesis of rhodanines, Catalysis Communications
(2015), doi: 10.1016/j.catcom.2015.05.002
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ACCEPTED MANUSCRIPT
The use of κ-Carrageenan/Fe3O4 nanocomposite as a nanomagnetic catalyst for clean
synthesis of rhodanines
Sadegh Rostamnia,a,* Behzad Zeynizadeh,b,* Esmail Doustkhah,a,b Ali Baghban,c Khadijeh Ojaghi
Aghbash a
a
Organic and Nano Group (ONG), Department of Chemistry, Faculty of Science, University of
Maragheh, P.O. Box. 55181-83111, Maragheh, Iran. Fax: +98 (41) 37276066. E-
mail:srostamnia@gmail.com; rostamnia@maragheh.ac.ir.
b Department of Chemistry, Faculty of Science, Urmia University, Urmia 57159-165, Iran. E-
mail:bzeynizadeh@gmail.com.
c Department of Chemistry, Faculty of Science, Payame Noor University, P.O. Box 19395-3697,
Tehran, Iran.
Abstract: In this work, magnetically separable Fe3O4 nanoparticles were synthesized in the
presence of natural κ-carrageenan (KCAR) biopolymer to provide Fe3O4@KCAR. FT-IR
analysis, scanning electron microscope (SEM), X-ray diffraction, VSM analysis, and SEM-
EDAX were incorporated for the characterization of Fe3O4@KCAR nanocomposite. And then,
the first catalytic report of Fe3O4@KCAR with no post-modification was achieved by studying
its catalytic activity in the multicomponent reaction of rhodanine synthesis. Based on this study,
Fe3O4@KCAR was an efficient, magnetically separable and recyclable, water-dispersible and
green catalyst with natural source. This catalyst also showed 9 run recyclability with no
significant yield decrease.
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Keywords: Magnetic nanocomposite; Fe3O4; κ-carrageenan (KCAR); Fe3O4@KCAR;
rhodanine.
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Introduction
Magnetically recoverable nanocatalysts give raise in the sustaining and greening the chemical
processes [1-4]. These are very suitable alternative to replace with equimolar, toxic and harsh
reagents, owing to their simple work-up and separation and ability to reuse in next runs [5].
Beyond it, they can be doped, modified, coated, encapsuled, and functionalized with various
organic, inorganic and even hybrid precursors such as polymers, silica sources, and
organosiloxanes, respectively. Among them, polymers have taken an advantages especially
biodegradable and natural polymers with active catalytic centers are interesting for research. In
this case, the toxicity, steps of catalyst preparation decrease. On the other hand, by modification
of polymer surface, a catalyst with tunable activity and favorable functionalities can be obtained.
Polymers such as poly(styrene-methacrylic acid) [6], chitosan [7-9], poly(ethyleneglycol) (PEG)
[10], polyethyleneimine (PEI) [11, 12], polyvinylidene fluoride (PVDF) [13] are currently used
for magnetization with Fe3O4 nanoparticles. Also, some copolymers and nanocomposites are
designed to produce and magnetic nanocomposites [14-18]. κ-Carrageenan (KCAR) is of those
polymers which has been used to fabricate various nanocomposites [19, 20]. However, Pericàs et
al. [21] functionalized carrageenan and further modified it to obtain a heterogeneous and
magnetic organocatalyst. In spite of these investigations, there is no catalytic study on the κ-
Carrageenan/Fe3O4 nanocomposites (Fe3O4@KCAR) which could be used with no further
modification or extra polymers. Hence we aimed to synthesize and discuss about the catalytic
activity of Fe3O4@KCAR which is directly incorporated as a catalyst in three-component
synthesis of rhodanine derivatives through condensation of an amine, CS2, and dialkyl
acetylenedicarboxylate (DRAD) under aqueous conditions at room temperature. This was to
obtain the catalytic behavior of Fe3O4@KCAR under neutral conditions. Due to the natural
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-
source of KCAR and hence, its biodegradability, active functions (-SO3 and -OH groups), and
-
ability to bind to the surface of Fe3O4 through -SO3 and -OH groups, we wished to examine its
catalytic activity in the organic reactions. In this paper, we have synthesized Fe3O4 in the
presence of KCAR under alkali conditions to obtain Fe3O4@KCAR nanocomposite. This small
amount was enough to catalyze the synthesis of rhodanine.
Synthesis of bioactive rhodanine based heterocycles is a key step in the producing biologically
interesting heterocycles [22-24]. On the other hand, their green and non-toxic synthesis can
accelerate and facilitate the separation, purification steps. Therefore, the obtained product by
green approach may be trustful for biological uses and investigations. Our proposed
nanomagnetic catalyst can play an important part in the synthesis of such compounds. A
schematic pathway for synthesis of Fe3O4@KCAR and rhodanine are shown in Scheme 1.
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Scheme 1. A schematic pathway for synthesis of Fe3O4@KCAR and rhodanine.
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2. Experimental
2.1. Catalytic preparation (Fe3O4-KCAR)
In a typical synthesis, 2 g of KCAR (obtained from Condinson Co. Denmark) was dissolved in
100 mL distilled water. Then, FeCl3.6H2O (5 g) and FeCl2.4H2O (2 g) were slowly added into
o
the mixture. The mixture was stirred strongly at 80 C to obtain a clear solution, and then
o
aqueous ammonia was added to solution until the pH of 12. Then the solution was kept at 80 C
under vigorous stirring for further 30 min. The precipitate was collected with an external magnet
and washed with water and methanol for several times dried in vacuum for 6 h. After that, the
final product was washed with water in the presence of an external magnet.
2.2. Catalytic test
In a typical method, 1 mmol of benzylamine, 1 mmol of dimethyl acetylenedicarboxylate
(DMAD) were mixed together in the presence of water dispersed Fe3O4@KCAR (0.01 g/2 mL)
and then, water dissolved CS2 (1 mmol/1 mL) was added to the reaction mixture during 5 min.
After 5 min, the color of reaction mixture turned to orange and the reaction completion was
monitored by TLC. Finally, an extra amount of water and then dichloromethane were added to
solution to stop the reaction and extract the product. Thus, the product was transferred to
dichloromethane and the catalyst was separated from mixture with a magnet. Then the
dichloromethane was evaporated and the residue was purified by column chromatography if
needed. The catalyst was washed with ethanol/ether and used for next cycles (in the case of
recyclability test). All the products were previously reported [23, 24] and were characterized by
comparing IR and physical data with those (see supporting information). The spectral data for
selected
product:
Ethyl
2-[3-((4-chlorophenyl)methyl)-4-oxo-2-thioxo-1,3-thiazolan-5-
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yliden]ethanoate [Table 1, Entry 4: see supporting Information]: Orange powder. IR (KBr) (νmax
,
1
cm− ): 1728 (CO), 1649 (CC), 1310 and 1177 (CS). 1H NMR (500 MHz, CDCl3): δH = 3.87 (3 H,
3
s, OCH3), 5.24 (2 H, s, CH2Ph), 6.84 (1 H, s, C=CH), 7.28 (2 H, d, JHH = 8.4 Hz, 2 CH of Ar),
3
7.37 (2 H, d, JHH = 8.4 Hz, 2 CH of Ar) ppm. 13C NMR (125.7 MHz, CDCl3): δC = 46.6
(OCH3), 52.9 (CH2Ph), 117.2 (C=CH), 128. 9 (2 CH of Ar), 130.5 (2 CH of Ar), 132.8 (Cipso of
Cl), 134.4 (Cipso of NC), 141.8 (C=CH), 165.45 (CON), 166.5 (CO2CH3), 195.4 (C=S) [25].
3. Results and discussion
In this work, Fe3O4 was synthesized in the presence of KCAR which led to the synthesis of
Fe3O4@KCAR. During the synthesis, KCAR acted as a stabilizer and in after the synthesis,
Fe3O4 nanoparticles are functionalized by KCAR. Hydroxyl riched KCAR herein can act as a
reaction mediator to proceed the reaction. Functionalization of Fe3O4 can be performed by both
hydroxyl and sulfate groups.
By comparing the FT-IR spectrums of Fe3O4@KCAR nanocomposite and KCAR, the presence
of KCAR surrounding the Fe3O4 can be clearly observed by related peaks can be exclaimed
(Figure 1a). The two samples showed the typical absorptions bands of k-carrageenan
polysaccharide: ~1230 cm-1, S-O asymmetric sulfate stretch; ~1010-1065 cm-1, C-O and C-OH
stretching and 843 cm-1, α(1,3)-D-galactose C-O-S stretch [26] thus indicating that the
biopolymer chains maintained their chemical characteristics when in contact with the Fe3O4 (see
Supporting Information). The EDS of Fe3O4@KCAR nanocomposite spectrum indicates that
there were only C, O, S and Fe elements in the nanocomposite (Figure 1b). The magnetic
hysteresis loops measurements (Figure 1c) of the Fe3O4@KCAR indicate that its saturation
magnetization value (Ms) is 29.05 emu.g-1.
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Fig. 1. FT-IR spectrum of KCAR and Fe3O4@KCAR (a), EDS (b) and magnetization curves at 300 K (c)
of Fe3O4@KCAR.
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SEM images show the morphology of Fe3O4@KCAR. The morphology of the nanocomposite
displayed homogeneous structure and the SEM image show a large particles. However, based on
the X-ray diffraction, the calculated average crystal size was 19 nm. It shows that Fe3O4
nanoparticles are synthesized and embedded inside the KCAR network. Therefore, Fe3O4
nanoparticles are surrounded by KCAR and have generated Fe3O4@KCAR nanocomposite.
Also, X-ray diffraction peaks indicate the presence of formation of Fe3O4 (Figure 2).
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Fig. 2. SEM images of as-synthesized (a) and (b) Fe3O4@KCAR. X-ray diffraction pattern of
Fe3O4@KCAR (c).
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To understand the catalytic effect of Fe3O4@KCAR, several amount of that were added to
reaction mixture of a benzyl amine, carbon disulfide and DMAD as model reaction. In this study,
the reaction in the absence of Fe3O4@KCAR had few progress during 5-10 min. While in the
presence of 0.01 g per each mmol of reaction, a remarkable amount of rhodanine was produced
which proves the effective catalytic activity of Fe3O4@KCAR in the three-component reaction of
rhodanine synthesis. In the presence of 0.02 g and 0.03 g of Fe3O4@KCAR, the reaction media
turns to pasty and the reaction yield decreases (Figure 3a).
In this work, various solvents were tested to find a suitable solvent for this synthetic pathway.
The solvent was selected based on its ability to produce a high yield while being a green and
economical solvent according to twelve roles of green chemistry (Figure 3b). EtOH and H2O had
high product yield, however, H2O is greener solvent rather to EtOH.
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Fig. 3. a) The effect of catalyst amount. Conditions: b) The solvent effect in Fe3O4@KCAR accelerate.
Reaction conditions: 1 mmol benzyl amine, 1 mmol CS2, 1 mmol DMAD, and Fe3O4@KCAR at room
temperature for 15 min.
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Among the several criteria, the optimum temperature was the room temperature (Scheme 2).
This is due to low boiling point of CS2 and production of side products such as thiourea
(Evolution of H2S gas indicates the formation of side products). When the reaction temperature
is high, a additional amine can attack to intermediate dithiocarbamate to form thiourea.
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Scheme 2. Clean synthesis of rhodanine.
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Under the optimized conditions, we extended our methodology to synthesize diverse derivatives
of rhodanine. In this derivatization, rhodanine-based heterocycles were synthesized in high
yields and with insignificant side products. The variation of derivatives was based on changing
amine and methoxy carboxylate moieties. The used amines in this work was aliphatic or benzylic
which their yields had no distinctive difference.
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Table 1. Synthesis of rhodanine under the catalysis of Fe3O4@KCAR.a
Entry
R
R’/E
Time
(min)
Yield
(%)b
Mp ᵒC
Reported [19]
Found
130-132
115-117
111-114
103-106
88-90
89-90
141-143
58-63
-
1
2
3
4
5
6
7
8
9
C6H5CH2
Me/CO2Me
Me/CO2Me
Me/CO2Me
Et/CO2Et
15
15
96
95
96
94
95
95
93
92
-
131-133
-
p-Cl-C6H4CH2
o-Cl-C6H4CH2
o-Cl-C6H4CH2
C6H5CH(CH3)
15
113-115
105-109
87-90
85-90
139-144
60-66
-
15
Me/CO2Me
15
CH3CH(CH3)CH2 Me/CO2Me
15
CH2=CHCH2
CH3CH(CH3)
C6H5
Me/CO2Me
Me/CO2Me
Et/CO2Et
15
15
120
120
10 p-Cl-C6H4
Me/CO2Me
-
-
-
a Reaction conditions; 1 mmol amine, 1 mmol CS2, 1 mmol DMAD, and 0.01 g of Fe3O4@KCAR in the
presence of 2 ml H2O at room temperature.
b Isolated yield based on DMAD.
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Therefore, the synthesis of rhodanine was performed by the reaction of an amine and CS2 to in
situ production of dithiocarbamate and its subsequent reaction with DMAD under the aqueous
conditions at room temperature for 10-15 min. The progress of reaction is represented by
photography during several minutes. Also, the final step, work-up, is simply done by adding
dichloromethane and an external magnet. The catalyst can be collected by the external magnet
and the catalyst transfers to organic phase (Figure 4).
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Fig. 4. Photograph representation of the reaction progress.
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The catalytic activity of Fe3O4@KCAR in the domino three-component process to synthesis of
rhodanine A and B was also studies under the optimized conditions. When we set the reaction
with a mixture of an aromatic amine (aniline) and aliphatic amine (benzyl amine) in presence of
the carbon disulfide and dimethyl acetylenedicarboxylate (DMAD), after 15 min the yield of A
was 84% without any detected product of B (Scheme 3).
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Scheme 3. Chemoselective synthesis of alkyl rhodanines vs aryl rhodanines.
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Also, the recyclability of our proposed catalyst was studied in the reaction of benzylamine, CS2
and DMAD. Results exhibited that the catalyst has recyclability in addition to its easy and simple
recovery. In this study, Fe3O4@KCAR has ability to be recycled at least for 9 runs (Figure 5).
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Fig. 5. Recyclability of Fe3O4@KCAR.
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4. Conclusion
The synthesis of Fe3O4 in the presence of KCAR has converted it to a magnetically recoverable
nanocomposite. It was concluded that Fe3O4@KCAR can be used as a catalyst in a
multicomponent reaction with no further requirement for a post-modification step. Also, the first
direct catalytic use of Fe3O4@KCAR nanocomposite in the catalysis was studied and reported in
the three-component synthesis of rhodanine. The clean and rapid synthesis on one hand and
simple work-up and product separation on the other hand were successfully achieved by
biodegradable and magnetically recoverable Fe3O4@KCAR. Higher temperatures caused to a
significant decrease in the product yield. Recyclability of Fe3O4@KCAR was also accomplished
at least for 9 successful runs. This catalyst can have great impact on the development on the
Fe3O4-KCAR catalyst and also some oncoming works about supporting catalytically active
metal and even enzymes can be anticipated for this nanocomposite.
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► Fe3O4@KCAR nanocomposite as a nanomagnetically catalyst. ► Green synthesis of the rhodanines.
►A reusable magnetic nanocatalyst synthesis using commercially available compounds. ►Represents
advantages, operational simplicity, no waste, higher yield and with easy workup.
Research highlights
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