High surface and magnetically recoverable mPANI/pFe3O 4 nanocomposites for C-S bond formation in water

Article abstract of DOI:10.1039/c2cy20624b

A high surface area mPANI/pFe₃O₄ nanocomposite from mesoporous polyaniline and porous magnetic Fe₃O₄ was used as a catalyst in the S-arylation of thiophenol with aryl chlorides and in the C-S bond formation between aryl iodides and thiourea in water. The mesoporosity of the polyaniline enhances the efficiency and stability of the porous magnetic Fe₃O₄ nanoparticles in both coupling reactions. The mPANI/pFe₃O₄ nanocomposite can be recovered with an external magnet and reused several times due to the superparamagnetic nature of the porous Fe₃O₄ nanoparticles.

Full text of DOI:10.1039/c2cy20624b

Catalysis
Science & Technology
View Article Online
View Journal | View Issue
PAPER
High surface and magnetically recoverable
mPANI/pFe3O4 nanocomposites for C–S bond
formation in water†
Cite this: Catal. Sci. Technol., 2013,
3, 797
D. Damodara,a R. Arundhathiab and Pravin R. Likhar*a
A high surface area mPANI/pFe3O4 nanocomposite from mesoporous polyaniline and porous magnetic
Fe3O4 was used as a catalyst in the S-arylation of thiophenol with aryl chlorides and in the C–S bond
formation between aryl iodides and thiourea in water. The mesoporosity of the polyaniline enhances
the efficiency and stability of the porous magnetic Fe3O4 nanoparticles in both coupling reactions.
The mPANI/pFe3O4 nanocomposite can be recovered with an external magnet and reused several times
due to the superparamagnetic nature of the porous Fe3O4 nanoparticles.
Received 5th September 2012,
Accepted 9th November 2012
DOI: 10.1039/c2cy20624b
www.rsc.org/catalysis
only limited literature reports are available on iron-based
heterogeneous catalysts. Recently, Bolm and co-workers have
1. Introduction
Catalytic methods for C–S bond formation have received con-
siderable attention due to their wide range of applications in
pharmaceuticals and polymer material science.1 Diaryl sulfides
in particular are found in numerous drugs, with a broad
spectrum of therapeutic activities for diverse clinical applications
in the treatment of cancer, HIV, Alzheimer’s and Parkinson’s
diseases.2 Various transition metals were proven to be highly
effective catalysts in C–C, C–O and C–N cross-coupling reactions.3,4
However, their catalytic activity in S-arylation is comparatively
less explored5 due to the tendency of thiols to undergo an
oxidative homocoupling S–S reaction and/or poisoning of the
metal by sulphur containing compounds. The development
of an environmentally friendly catalytic system composed of
inexpensive metal-based heterogeneous catalysts and water as a
reaction medium has drawn much attention in both academia
and industry in recent times due to the easy separation of
heterogeneous catalysts and water, as a green solvent, being
non toxic, low cost and easily available. Iron-based hetero-
geneous catalysts have gained new significant attention in various
cross-coupling reactions because of their low cost, non-toxicity
and interesting catalytic activities. Despite these interesting facts,
explored the FeCl3/DMEDA catalytic system for the S-arylation
of thiol.6 However, the recovery and reusability of the catalyst
remains a major problem with homogenous catalysts.
Nano-sized metals and metal oxides have been extensively
used as catalysts for many organic transformations because of
their high surface area and facile separation. Commensurate
with the aforementioned requirements, we envisage that nano-
sized magnetically recoverable and reusable iron oxide could be
an appropriate heterogeneous catalyst for the S-arylation reaction.
In this context, the applications of Fe3O4 nanoparticle-immobilized
or supported catalysts have been successfully demonstrated
by means of various strategies.7–10 However, the direct use of
Fe3O4 nanoparticles without modification as a magnetically
recoverable catalyst for organic reactions is very rare.11
Initially, Fe3O4 nanoparticles were prepared using a solvo-
thermal process and employed in the C–S bond formation
reaction of chlorobenzene and thiophenol in various solvents
at different temperatures. However, the yield of the S-arylated
product could not improved to 42% in water under reflux
conditions after 8 h. The anticipated reason for the low yields
of the S-arylated product could be the size and aggregation
of the Fe3O4 particles during the reaction (verified by TEM
analysis). The catalytic efficiency of the nanoparticles mainly
depends on the thermal and chemical stability and they have a
great tendency to deform and aggregate during the course of
the chemical reaction. Therefore, the surface modification12,13
of metal nanoparticles with the use of an appropriate capping
agent, such as polymers or surfactants, is essential in order to
prevent aggregation. Immobilization of metal nanoparticles at
a Inorganic and Physical Chemistry Division, Indian Institute of Chemical
Technology, Hyderabad-500007, India. E-mail: plikhar@iict.res.in;
Fax: +91-40-2716-0921; Tel: +91-40-2719-3510
b Department of Materials Engineering Science, Graduate School of Engineering
Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
† Electronic supplementary information (ESI) available: Additional characteriza-
tion studies supporting the results which include: TEM, XPS and TPR measure-
ments. See DOI: 10.1039/c2cy20624b
c
This journal is The Royal Society of Chemistry 2013
Catal. Sci. Technol., 2013, 3, 797--802 797

View Article Online
Paper
Catalysis Science & Technology
the pore surface of mesoporous materials is of considerable The progress of the reaction was monitored by TLC. At the end
technological importance in order to improve the accessibility, of the reaction, the reaction mixture was allowed to cool to
lifetime and the reusability of the catalyst in the field of room temperature. The reaction mixture was then treated with
molecular catalysis.14 In order to achieve nano-scale stable an excess of cold water and the organic phase was extracted by
Fe3O4 particles, Fe3O4 was first functionalized with 3-amino- adding ethyl acetate and then dried over anhydrous Na2SO4.
propyltrimethoxysilane (APTMS) and then the pFe3O4 nano- The crude mixture was purified by chromatography on silica gel
particles were encaged in mPANI microspheres, in presence of to afford the coupled product.
polyvinylpyrrolidone (PVP) and sodium dodecyl benzene sulfo-
nate (SDBS), by in situ polymerization to give high surface
Synthesis of symmetrical diaryl sulfides
mesoporous polyaniline/porous magnetic Fe3O4, the mPANI/ A mixture of aryl iodide (1.0 mmol), thiourea (0.75 mmol),
pFe3O4 nanocomposite.15 The porous nature of the magnetic mPANI/pFe3O4 (25 mg, 6.6 mol%) and KOH (1.5 equiv.) was
Fe3O4 nanoparticles of the mPANI/pFe3O4 nanocomposite pro- stirred at the reflux temperature for 24 h in water (3.0 mL). The
vides direct access to the Fe3O4 nanoparticles and the meso- progress of the reaction was monitored by TLC. When the
porous polyaniline enhances both the thermal and chemical reaction was complete, the reaction mixture was allowed to
stability of the magnetic Fe3O4 nanoparticles. The catalytic cool, a mixture of ethyl acetate and water (20 mL) was added
application of mPANI/pFe3O4 was then explored in the S-arylation and the catalyst was separated with the use of an external
of thiophenol with aryl chlorides and in the C–S bond for- magnet. The organic solution was washed with brine water and
mation between aryl iodides and thiourea.
dried with Na2SO4. The solvent and volatiles were completely
removed under vacuum to give the crude product, which was
purified by column chromatography on silica gel to obtain the
desired symmetrical diaryl sulfide.
2. Experimental section
Preparation of the mPANI/pFe3O4 nanocomposite
Magnetic Fe3O4 particles were prepared using FeCl3.6H2O and
sodium acetate in ethylene glycol through a solvo-thermal
3. Results and discussion
process. The homogeneous solution was transferred to a mPANI/pFe3O4 composites were prepared in three steps:
teflon-lined sealed-steel autoclave and heated at 200 1C. After (1) porous magnetite Fe3O4 nanoparticles were synthesized by
8 h, the autoclave was cooled to room temperature and the a solvo-thermal approach in the presence of sodium acetate
particles were washed with ethanol and dried in a vacuum at and ethylene glycol in a sealed teflon-lined stainless-steel
60 1C for 12 h. Black magnetite particles were obtained. Then, autoclave at 200 1C; (2) chemical modification/functionaliza-
the porous Fe3O4 particles were chemically modified using tion of the Fe3O4 nanoparticles was achieved by APTMS. APTMS
APTMS in anhydrous ethanol and amine functionalised porous acts as an organic spacer, which may induce a steric repulsion
Fe3O4 (NH2–Fe3O4) magnetite particles were obtained. mPANI with Fe3O4 through its –NH2 end group, and also restricts the
coated pFe3O4 microspheres were prepared by an in situ surface crystal growth of magnetic nanoparticles (cluster formation).
polymerization method in the presence of PVP and SDBS. In a (3) mPANI/pFe3O4 nanocomposites were prepared by an in situ
typical procedure, PVP and SDBS were dissolved in deionized surface polymerization method in the presence of PVP and
water and the NH2–Fe3O4 particles were then added. The SDBS. Similarly, the thickness of the mesoporous PANI layers
mixture was ultrasonically dispersed and a solution of aniline for the mPANI/pFe3O4 microsphere core/shell structure was tuned
in HCl was added into the mixture with vigorous stirring. The by changing the relative concentration of the Fe3O4@PVP + SDBS
mixture was mechanically stirred for 30 min at 20 1C and then particles and the aniline/HCl concentration in the solution. The
an aqueous solution of APS was instantly added to the above parameters, such as reaction time (stirring time) and stirring
mixture to start the oxidative polymerization. The reaction was speed (rpm), play an important role in maintaining the thick-
performed under mechanical stirring for 5 h. The resulting ness of the mesostructures of the PANI microspheres. The
precipitates were washed with deionized water and ethanol synthesized mPANI/pFe3O4 was well characterized by various
several times. Finally, the product was dried in a vacuum at analytical tools such as XRD, FTIR, TEM (see the ESI†), mag-
60 1C for 24 h in order to obtain the desired mPANI/pFe3O4 netic analysis, XPS, SEM and surface area analysis.
composite as a dark powder.
Characterization studies
Synthesis of unsymmetrical diaryl sulfides
In order to study the magnetic behaviour of the mPANI/pFe3O4
The catalyst was used for the S-arylation of thiolphenol with nanocomposite, magnetization measurements were performed
deactivated aryl chlorides and also examined for the synthesis and superparamagnetic behaviour was seen from the obtained
of symmetrical diaryl sulfides from the reaction of aryl iodides magnetic hysteresis loop. Almost immeasurable coercivity was
with thiourea under mild reaction conditions using water as a shown for the porous Fe3O4 nanoparticles with and without a
green solvent. The reaction vessel was charged with aryl chloride polyaniline coating. This gives evidence for the superpara-
(1.0 mmol), thiophenol (1.0 mmol), KOH (1.5 mmol) and the magnetic nature of the samples. The saturation magnetization
catalyst (mPANI/pFe3O4) (25 mg, 5 mol%) in water (3 mL). The for the nanoparticles without the coating was detected to be
reaction mixture was then stirred for 8 h at the reflux temperature. 64.13 emu gÀ1 and that for the mesoporous polyanilne-coated
c
798 Catal. Sci. Technol., 2013, 3, 797--802
This journal is The Royal Society of Chemistry 2013

View Article Online
Catalysis Science & Technology
Paper
Fig. 2 (a) SEM images of the freshly prepared mPANI/pFe3O4 nanocomposite,
(b) the mPANI/pFe3O4 nanocomposite recovered after the 5th cycle.
Fig. 1 XPS spectra of the fresh mPANI/pFe3O4 nanocomposites [A] and the used
mPANI/pFe3O4 nanocomposites [B].
the narrow pore size of the Fe3O4 nanoparticles, calculated
nanoparticles was found to be 54.13 emu gÀ1. All the results from the adsorption branch of the isotherms, is 2.1 nm. The
were compared to our earlier reports.15
To examine the physico-chemical change of the catalyst in nanocomposite are calculated as 445 m2 gÀ1 and 0.29 cm3 gÀ1
BET surface area and total pore volume of the mPANI/pFe3O4
,
the S-arylation reaction, we studied the X-ray photoelectron respectively. Thus, the increase in surface area and decrease in
spectra (XPS) and scanning electron microscope (SEM) analysis pore volume suggest that the active sites are reasonably increased
of fresh mPANI/pFe3O4 nanocomposites and the used mPANI/ due to the porosity of the magnetic Fe3O4 nanoparticles and the
pFe3O4 nanocomposites.
thickness of the mesoporous PANI layers decreased. TEM images
The XPS spectra of the fresh mPANI/pFe3O4 nanocomposites of the Fe3O4 particles reveal that the average diameter of the
and used mPANI/pFe3O4 nanocomposites are shown in Fig. 1(A) porous Fe3O4 particles is around 6 nm and the presence of white
and (B). The XPS of the C1s, O2p, N1s and Fe2p level give proof patches on the surface of magnetic Fe3O4 is due to the porous
for the approximate chemical structure of the mPANI coated nature of the materials, which was confirmed by BET analysis
pFe3O4 nanocomposites. Peaks at 284, 398, 538 eV were (see the ESI†). The formed magnetite Fe3O4 nanoparticles are
ascribed to the carbon, nitrogen and oxygen in polyaniline. porous in nature and this was confirmed by the Barrett–Joyner–
The binding energies at 712 and 725 eV are the characteristic Halenda (BJH) method. The hystersis of the mPANI/pFe3O4
peaks of Fe2p3/2 and Fe2p1/2 core level electrons. The binding nanocomposite was found to be of type-IV and clearly shows
energies for Fe3O4 of the fresh mPANI/pFe3O4 nanocomposites two peaks for the pore size centred at about 2.5 nm and 5.5 nm
in Fig. 1(A) and of the used mPANI/pFe3O4 nanocomposites in respectively for two types of mesopores Fig. 2.
Fig. 1(B) are in good agreement with the values reported for
Initially, we tested the catalytic activity of mPANI/pFe3O4 in
Fe3O4 in the literature, which indicates that there is no the S-arylation of thiophenol with the more challenging
chemical change occurring in the Fe2p3/2 and Fe2p1/2 core level. 4-methyl-chlorobenzene and found that the mPANI/pFe3O4
Scanning electron microscopy (SEM) images of the freshly catalyst could give the S-arylated product in the presence of
prepared mPANI/pFe3O4 nanocomposite and the nanocompo- various bases and solvents (Table 1). Subsequently in the optimi-
site recovered after its 5th cycle suggest that there is no change zation, various reaction parameters such as catalysts, solvents,
in the morphology of the catalyst. The BET surface area and bases and temperature were studied. We have also compared the
pore volume of the mesoporous PANI (mPANI) are calculated as activity and efficiency of mPANI/pFe3O4 with other iron-based
190 m2 gÀ1 and 0.78 cm3 gÀ1, respectively. The mean value for catalysts and found that the mPANI/pFe3O4 catalyst afforded a
c
This journal is The Royal Society of Chemistry 2013
Catal. Sci. Technol., 2013, 3, 797--802 799

View Article Online
Paper
Catalysis Science & Technology
Table 1 Optimization of mPANI/pFe3O4 catalyzed S-arylation of thiophenol with
Table 2 mPANI/pFe3O4 catalyzed S-arylation of aryl, alkyl and heterocyclic
4-methyl-cholrobenzene
chlorides with thiophenol
Entry
1
Substrate
Product
Isolated yielda (%)
85
87
92
Time (h)/
Entry Catalyst/wt.
Solvent Base
Temp. 1C Yielda (%)
1
2
3
4
5
6
7
8
nanoFe3O4/3.86 mg
nanoFe2O3/3.99 mg
Fe/C/56.81 mg
Water
Water
Water
KOH
KOH
KOH
K2CO3 8/120
K3PO4 10/120
Cs2CO3 8/120
NaOH 9/120
KOH
KOH
KOH
KOH
8/reflux
8/reflux
8/reflux
15
12
21
56
58
67
68
85
n.r
83
52
47
71
44
2
3
81
79
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg DMF
mPANI/pFe3O4/25 mg Water
mPANI/pFe3O4/25 mg THF
4
88
8/120
24/rt
8/reflux
10/120
10/120
8/120
9
10
11
12
13
14
5
6
86
82
mPANI/pFe3O4/25 mg Dioxane KOH
mPANI/pFe3O4/25 mg DMSO
mPANI/pFe3O4/25 mg PhMe
KOH
KOH
10/120
Reaction conditions: aryl chloride (1.0 mmol), thiophenol (1.0 mmol),
catalyst (5 mol%, Fe 2.79 mg), base (1.5 mmol; 1.5 equiv.), solvent
(3.0 mL). Isolated yield of product, n.r. = no reaction, r.t = room
7
77
a
temperature.
8
83
71
84
9
high yield due to its nano-size coupled with high surface porous
Fe3O4. The effect of solvents was also studied and it was observed
that the reaction was highly effective in polar solvents, such as
DMF, water and DMSO, whereas the yield of the desired product
was low in toluene, THF and dioxane. Although the yield afforded
in DMF and water was 85% and 83% respectively, we preferred to
use water as a reaction medium in the subsequent S-arylation
reactions16 as water has several advantages over the other organic
solvents. Among the various bases studied (e.g., K2CO3, K3PO4,
Cs2CO3, NaOH and KOH), KOH proved to be a suitable base in
combination with water. Thus, the optimized reaction conditions
for S-arylation of 4-methyl-chlorobenzene (1.0 mmol), thiophenol
(1.0 mmol) mPANI/pFe3O4 (25 mg, 5 mol%) and KOH (1.5 equiv.)
in water (3.0 mL) at the reflux temperature afforded the desired
product in an excellent yield (83%).
10
11
68
12
13
14
61
69
67
C4H9Cl
15
16
C5H11Cl
C6H13Cl
65
64
To explore the scope of the reaction and efficiency of mPANI/
pFe3O4, S-arylation was studied with various functionalized aryl
chlorides. The present mPANI/pFe3O4 catalyst could efficiently
catalyze the coupling of thiophenol with electron-rich and
electron-deficient aryl chlorides and unsymmetrical diaryl
sulfides were obtained in moderate to high yields (Table 2).
Reaction conditions: substrate (1.0 mmol), thiophenol (1.0 mmol),
catalyst (25 mg, 5 mol%, Fe 2.79 mg), KOH (1.5 mmol; 1.5 equiv.),
water (3.0 mL), reflux temperature for 8 h. Isolated yield.
a
iodides and thiourea. Despite the enormous applications of
From the Table 2, it was observed that there is a slight these symmetrical diary sulfides in various therapeutics, very
decrease in the yields of the diaryl sulfides with electron- few methodologies have been developed.17 To our knowledge,
donating substituents on the aryl chlorides whereas the yields this is the first report on heterogeneous iron catalyzed C–S
of the desired products increase in the presence of electron- bond formation using thiourea and aryl halides in water. The
withdrawing group containing aryl chlorides. The couplings of optimized reaction conditions studied for the mPANI/pFe3O4
the aliphatic and heterocyclic chlorides with thiophenol also catalyzed C–S bond formation were iodobenzene, thiourea
successfully afforded the corresponding product in moderate (1 : 0.75), mPANI/pFe3O4 (25 mg, 6.6 mol%) and KOH (1.5 equiv.)
yields (Table 2, entries 13–16). We have successfully studied the in water (3.0 mL) at the reflux temperature for 24 h to afford the
application of porous Fe3O4 stabilized with mesoporous PANI desired product in a good yield (88%) (Table 3, entry 3).
in the synthesis of various diaryl sulfides.
We observed that aryl iodides are more reactive with thiourea
In the next part, we examined the catalytic activity of mPANI/ than aryl chlorides and bromides under the optimized reac-
pFe3O4 in the synthesis of symmetric diaryl sulphides from aryl tion conditions. A variety of aryl iodides, including electron
c
800 Catal. Sci. Technol., 2013, 3, 797--802
This journal is The Royal Society of Chemistry 2013

View Article Online
Catalysis Science & Technology
Paper
Table 3 mPANI/pFe3O4 catalyzed C–S bond formation between thiourea and
aryl halides
Yielda (%)
92
Product
Entry
1
Aryl halide
2
80
Scheme 1 Possible reaction mechanism for the S-arylation of thiol.
3
4
88
83
Fe3O4 nanoparticles. In the next step, the approach of the
nucleophile (thiol) in the presence of a base may result in the
formation of intermediate [B]. The catalytic cycle can be completed
by a reductive elimination step via the generation of the cross-
coupled product along with efficient separation of the catalyst.
To confirm that the catalytic activity originated from the
porous Fe3O4 and not from temporarily leached Fe3O4, a
control experiment was performed by carrying out a reaction
between 4-nitro-chlorobenzene and thiophenol which was termi-
nated after 20% conversion (80 min). The catalyst was separated
using an external magnet under hot conditions and the reaction
was continued with the filtrate for 12 hours. No change in the
5
6
79
74
7
8
72
67
Reaction conditions: aryl halide (1.0 mmol), thiourea (0.75 mmol), conversion of 4-nitro-chlorobenzene to the desired product was
catalyst (25 mg, 6.6 mol%, Fe 2.79 mg, w.r.t. to thiourea), KOH
observed. This result confirms the heterogeneous nature of the
catalysis by the magnetic Fe3O4 nanoparticles.
(1.5 mmol; 1.5 equiv.), water (3.0 mL), reflux temperature for 24 h.
a
Isolated yield.
Recyclability study
donating- and electron-withdrawing, and heterocyclic aryl iodides
were used for the transformation into their corresponding
symmetrical diaryl sulfides (Table 3, entries 2–8).
The separation of the mPANI/pFe3O4 nanocomposite catalyst
using an external magnetic field from the reaction mixture is a
very convenient and efficient process. Magnetic separation of the
catalyst using an external magnet is an attractive alternative to
filtration or centrifugation as it prevents loss of the catalyst and
increases the reusability of the catalyst. The magnetite Fe3O4
particles are known for their paramagnetic property, which
makes them amenable to magnetic separation. To investigate
the consistency in terms of activity and efficiency of the catalysts
using these impressive properties, a recoverability and reusabil-
ity study was performed in the S-arylation reaction using 4-nitro-
chlorobenzene with thiophenol and in the synthesis of
symmetric diaryl sulfides from thiourea and 4-methoxy-
iodobenzene (see the Recyclability study section). No significant
loss of catalytic activity was observed for up to five cycles.
A: Reaction conditions: 4-nitro-chlorobenzene (1.0 mmol), thio-
The possible reaction mechanism for the S-arylation of thiol phenol (1.0 mmol), catalyst (25 mg, 5 mol%), KOH (1.5 mmol;
is shown in Scheme 1. In the first step, the high surface porous 1.5 equiv.), water (3.0 mL), reflux temperature for 8 h.
Fe3O4 nanoparticles may undergo a reaction with aryl chloride B: Reaction conditions: 4-methoxy-iodobenzene (1.0 mmol),
to give intermediate [A]. The mesoporosity of the polyaniline in thiourea (0.75 mmol), catalyst (25 mg, 6.6 mol%), KOH
the mPANI/pFe3O4 composite provides direct access to the (1.5 mmol; 1.5 equiv.) water (3.0 mL), reflux temperature for 24 h.
c
This journal is The Royal Society of Chemistry 2013
Catal. Sci. Technol., 2013, 3, 797--802 801

View Article Online
Paper
Catalysis Science & Technology
6 (a) A. Correa, M. Carril and C. Bolm, Angew. Chem., Int. Ed.,
2008, 47, 2880; (b) S. L. Buchwald and C. Bolm, Angew.
Chem., Int. Ed., 2009, 48, 5586; (c) J.-R. Wu, C.-H. Lin and
C.-F. Lee, Chem. Commun., 2009, 4450.
7 (a) S. Sun and H. Zeng, J. Am. Chem. Soc., 2002, 124, 8204;
(b) A. H. Latham and M. E. Williams, Acc. Chem. Res., 2008,
41, 411.
8 (a) S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L. V.
Elst and R. N. Muller, Chem. Rev., 2008, 108, 2064;
(b) V. Polshettiwar, B. Baruwati and R. S. Varma, Chem.
Commun., 2009, 1837; (c) S. Luo, X. Zheng, H. Xu, X. Mi,
L. Zhang and J.-P. Cheng, Adv. Synth. Catal., 2007, 349, 2431.
9 (a) V. Polshettiwar, B. Baruwati and R. S. Varma, Green Chem.,
2009, 11, 127; (b) M. Kotani, T. Koike, K. Yamaguchi and
N. Mizuno, Green Chem., 2006, 8, 735; (c) R. S. Schwab,
D. Singh, E. E. Alberto, P. Piquini, O. E. D. Rodrigues and
A. L. Braga, Catal. Sci. Technol., 2011, 1, 569.
4. Conclusions
We have developed a magnetically separable and efficient
porous Fe3O4 catalyst stabilized with mesoporous PANI for
the S-arylation of various aryl, alkyl and heterocyclic halides
with thiophenol to obtain unsymmetrical diaryl sulfides in
moderate to high yields. The application of the catalyst was
also extended to the S-arylation of various aryl iodides with
thiourea to obtain symmetrical diaryl sulfides selectively. The
most attractive features of this protocol are the easy preparation
of the catalyst from readily accessible reagents and that the
catalyst can be used in a green solvent, water. In addition to
this, the catalyst can be easily recovered under an external
magnetic field and reused in the next consecutive S-arylation
reaction.
Acknowledgements
10 (a) D.-H. Zhang, G.-D. Li, J.-X. Lia and J.-S. Chen,
Chem. Commun., 2008, 3414; (b) M. Kawamura and K. Sato,
Chem. Commun., 2006, 4714; (c) M. Kawamura and
K. Sato, Chem. Commun., 2007, 3404; (d) A. Hu, G. T. Yee
and W. Lin, J. Am. Chem. Soc., 2005, 127, 12486;
(e) G. Chouhan, D. Wang and H. Alper, Chem. Commun.,
2007, 4809.
D.D. thanks UGC and R.A. thanks DST (GAP-0152), India for
their fellowships. We also thank Dr. S. V. Manorama, Nano-
material Science, IPC Division, CSIR-IICT for TEM analysis.
Notes and references
1 (a) G. Liu, J. R. Huth, E. T. Olejniczak, R. Mendoza, P. DeVries, 11 For using superparamagnetic iron oxide as a catalyst for the
S. Leitza, E. B. Reilly, G. F. Okasinski, S. W. Fesik and T. W.
von Geldern, J. Med. Chem., 2001, 44, 1202; (b) G. De Martino,
synthesis of a-aminonitriles, see: M. M. Mojtahedi,
M. S. Abaee and T. Alishiri, Tetrahedron Lett., 2009, 50, 2322.
M. C. Edler, G. La Regina, A. Coluccia, M. C. Barbera, D. Barrow, 12 (a) D. Bourissou, O. Guerret, F. P. Gabbai and G. Bertrand,
R. I. Nicholson, G. Chiosis, A. Brancale, E. Hamel, M. Artico and
R. Silvestri, J. Med. Chem., 2006, 49, 947; (c) A. Gangjee, Y. Zeng,
T. Talreja, J. J. McGuire, R. L. Kisliuk and S. F. Queener,
J. Med. Chem., 2007, 50, 3046.
2 (a) S. F. Nielsen, E. Ø. Nielsen, G. M. Olsen, T. Liljefors and
D. Peters, J. Med. Chem., 2000, 43, 2217.
3 (a) J. Tsuji, Transition Metal Reagents and Catalysts: Inno-
vations in Organic Synthesis, John Wiley & Sons, New York,
2000; (b) M. Beller and C. Bolm, Transition Metals for Organic
Chem. Rev., 2000, 100, 39; (b) S. K. Yen, L. L. Koh, F. E. Hahn,
H. V. Huynh and T. S. A. Hor, Organometallics, 2006,
25, 5105; (c) J. Ye, W. Chen and D. Wang, Dalton Trans.,
2008, 4015; (d) N. Marion and S. P. Nolan, Acc. Chem. Res.,
2008, 41, 1440.
13 (a) X. Zhang, Z. Xi, A. Liu and W. Chen, Organometallics,
2008, 27, 4401; (b) D. Meyer, M. A. Taige, A. Zeller,
K. Hohlfeld, S. Ahrens and T. Strassner, Organometallics,
2009, 28, 2142.
Synthesis, Wiley-VCH, Weinheim, Germany, 2nd edn, 2004; 14 (a) G. A. Somorjai and R. M. Rioux, Catal. Today, 2005,
(c) A. de Meijere and F. Diederich, Metal-Catalyzed Cross-
Coupling Reactions, Wiley-VCH, Weinheim, Germany, 2nd edn,
100, 201; (b) C. J. Zhong and M. M. Maye, Adv. Mater., 2001,
13, 1507; (c) W. Schartl, Adv. Mater., 2000, 12, 1899.
2004; (d) J. Montgomery, Angew. Chem., Int. Ed., 2004, 15 R. Arundhathi, D. Damodara, P. R. Likhar, M. L. Kantam,
43, 3890; (e) T. Kurita, M. Abe, T. Maegawa, Y. Monguchi
and H. Sajiki, Synlett, 2007, 2521.
P. Saravanan, T. Magdaleno and S. H. Kwon, Adv. Synth.
Catal., 2011, 353, 1591.
4 (a) Z. Li, Y. Fu, L. Liu and Q.-X. Guo, Chin. J. Org. Chem., 2005, 16 (a) M. Oba, K. Tanaka, K. Nishiyama and W. Ando, J. Org.
25, 1508; (b) S. V. Ley and A. W. Thomas, Angew. Chem., Int. Ed.,
2003, 42, 5400; (c) E. M. Beccalli, G. Broggini, M. Martinelli and
S. Sottocornola, Chem. Rev., 2007, 107, 5318; (d) J. Tsuji,
Palladium Reagents and Catalysts, John Wiley & Sons, New York,
Chem., 2011, 76, 4173; (b) F. Ke, Y. Qu, Z. Jiang, Z. Li, D. Wu
and X. Zhou, Org. Lett., 2011, 13, 454; (c) D. J. C. Prasad and
G. Sekar, Org. Lett., 2011, 13, 1008; (d) I. W. J. Still and
F. D. Toste, J. Org. Chem., 1996, 61, 7677.
2004; (e) D. Prim, J.-M. Campagne, D. Joseph and 17 (a) M. Carril, R. SanMartin, E. Dominguez and I. Tellitu,
B. Andrioletti, Tetrahedron, 2002, 58, 2041.
Chem.–Eur. J., 2007, 13, 5100; (b) H.-J. Xu, Y.-F. Liang,
X.-F. Zhou and Y.-S. Feng, Org. Biomol. Chem., 2012,
10, 2562; (c) L. Rout, P. Saha, S. Jammi and
T. Punniyamurthy, Eur. J. Org. Chem., 2008, 640.
5 For a review, see: (a) F. Monnier and M. Taillefer,
Angew. Chem., Int. Ed., 2009, 48, 6954–6971; (b) T. Kondo
and T.-A. Mitsudo, Chem. Rev., 2000, 100, 3205–3220.
c
802 Catal. Sci. Technol., 2013, 3, 797--802
This journal is The Royal Society of Chemistry 2013