Polystyrene bis[N-(2-pyridyl) sulfonamide] palladium(II): Synthesis, characterization as a catalyst for coupling reactions

Article abstract of DOI:10.1080/10426507.2017.1418347

The [N-(2-pyridyl)] para-styrene sulfonamide (PSS) was prepared as a monomer, from the reaction of para-styrene sulfonyl chloride and 2-amino pyridine in the presence of potassium hydroxide solution 0.5?M as a base, and CH₃Cl. Polystyrene [N-(2-pyridyl) sulfonamide] (PPSS) was synthesized from the polymerization of [N-(2-pyridyl)] para-styrene sulfonamide (PSS). The Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) as a polymer- supporting palladium complex was also prepared from the reaction of PdCl₂ (CH₃CN)₂ with PPSS in the presence of KOH 0.5?M. Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) is produced as a novel heterogeneous catalyst for coupling reactions for C-C bond formation. This method includes higher yield and has an easier work-up procedure. The structures of the monomer, polymer and its Pd complex were confirmed by using FT-IR and ¹H-NMR spectroscopy. Elemental analysis of Pd by inductively coupled plasma (ICP) technique and hot filtration test showed loading of the metal into solution from the catalyst The heterogeneous catalyst was recycled without any loss in its properties.

Full text of DOI:10.1080/10426507.2017.1418347

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: http://www.tandfonline.com/loi/gpss20
Polystyrene bis[N-(2-pyridyl) sulfonamide]
palladium(II): Synthesis, characterization as a
catalyst for coupling reactions
Parvaneh Shafieyoon, Ebrahim Mehdipour & Hosein Tavakol
To cite this article: Parvaneh Shafieyoon, Ebrahim Mehdipour & Hosein Tavakol (2017):
Polystyrene bis[N-(2-pyridyl) sulfonamide] palladium(II): Synthesis, characterization as a
catalyst for coupling reactions, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
10.1080/10426507.2017.1418347
To link to this article: https://doi.org/10.1080/10426507.2017.1418347
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Polystyrene bis[N-(2-pyridyl) sulfonamide] palladium(II): Synthesis, characterization as a
catalyst for coupling reactions
Parvaneh Shafieyoona, Ebrahim Mehdipoura*, Hosein Tavakolb.
aDepartment of Chemistry, Faculty of Science, Lorestan University, Khorramabad, Iran.
bDepartment of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran
a*Corresponding author: Email: e_mehdipour@yahoo.com, mehdipour.e@lu.ac.ir
Email: parva127@yahoo.com , shafieyoon.pa@fs.lu.ac.ir
Email: hosein_ta@yahoo.com , h_tavakol@cc.iut.ac.ir
Abstract
The [N-(2-pyridyl)] para-styrene sulfonamide (PSS) was prepared as a monomer, from the
reaction of para-styrene sulfonyl chloride and 2-amino pyridine in the presence of potassium
hydroxide solution 0.5M as a base, and CH3Cl. Polystyrene [N-(2-pyridyl) sulfonamide] (PPSS)
was synthesized from the polymerization of [N-(2-pyridyl)] para-styrene sulfonamide (PSS). The
Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) as a polymer- supporting palladium
complex was also prepared from the reaction of PdCl2 (CH3CN)2 with PPSS in the presence of
KOH 0.5M. Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) is produced as a novel
heterogeneous catalyst for coupling reactions for C-C bond formation. This method includes
higher yield and has an easier work-up procedure. The structures of the monomer, polymer and
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its Pd complex were confirmed by using FT-IR and H-NMR spectroscopy. Elemental analysis
of Pd by inductively coupled plasma (ICP) technique and hot filtration test showed loading of the
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metal into solution from the catalyst The heterogeneous catalyst was recycled without any loss in
its properties.
Keywords: [N-(2-pyridyl)] para-styrene sulfonamide; Poly styrene [N-(2-pyridyl) sulfonamide];
Polystyrene bis[N-(2-pyridyl) sulfonamide] palladium)II); Heck reaction.
1. Introduction
Palladium- catalyzed coupling reactions are of major importance in organic synthesis such as
natural product1 and drugs2, 3. The catalysis containing palladium complex are significant due to
their nontoxicity and versatility. Heck reaction is one of the most useful tools for C – C bond
formation. The coupling reactions are widely used in synthetic organic chemistry. These
reactions can be performed by using palladium complexes4, 5. They are practically carried out in
laboratory and industry. The excellent coordination properties of palladium with versatile ligands
containing P, N, S, O and C atoms converted to heterogonous and recyclable catalysts6, 7. In this
line, some of the ligands contain nitrogen atoms as a class of interesting compounds such as
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10
bipyridine8, sulfonamide9,
and thiourea11 which have been applied. The N-heterocyclic
carbenes (NHCs) compounds have excellent air and moisture stability. Many homogeneous
catalysis have been introduced using the NHCs as a liganad12, 13. Synthesis of palladium – NHC
complexes (Pd-NHC) and their application in coupling reaction were reported14, 15. The use of
ligands containing nitrogen has been employed as a new class to demonstrate catalytic activity in
coupling reactions16-18. Sulfonamides are important compounds which have been used in
medicine. They possess interesting biological activities such as antimicrobial properties.19, 20
.
Development of these compounds and applying their complexes as an efficient catalysts is
important. The use of polymer supported catalyst has been extensively reported. Heterogeneous
system can be commercialized because of the ease of the recovery of the catalyst21, 22, 23, 24. A
variety of polymer-supported catalysts with different functionalities have been employed. In
recent years, significant efforts have been made to develop significant ligands and palladium
catalysts for Heck reaction25-27. In our previous report, we synthesized the polymer-supported
palladium (II) complexes and their applications28, 29. These results encouraged us to synthesize
and evaluate a new polymer- supported palladium (II) for Heck reactions.
2. Result and discussion
2.1. Preparation of monomer [N-(2-pyridyl)] para-styrene sulfonamide (PSS)
PSS was synthesized from the reaction of para-styrene sulfonyl chloride and 2-amino pyridine.
This compound was prepared by method shown in Scheme 1. The new monomer was
characterized by FT- IR, and 1H NMR spectroscopy (data in the experimental section).
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[Insert Scheme 1]
2.2. Preparation of Poly styrene [N-(2-pyridyl) sulfonamide] (PPSS) and its complex
The synthetic route of PPSS and its complex is reported in the experimental section is shown in
Scheme 2 and Scheme 3.
[Insert Scheme 2]
[Insert Scheme 3]
2.3. Spectroscopic characterization of compounds
The experimental FT- IR of the compounds will be listed in experimental section. The
vibrational band present at 3340 cm-1 is assigned to ν(N-H) for monomer and polymer. This
band disappears for polymer- supporting palladium complex, due to the deprotonation of amide
group. The C–H stretching frequencies of benzene can be observed in the range of 3100–3000
cm-1. The aliphatic C–H stretching frequencies also appear below 3000 cm-1. The C= C
stretching vibration in the range of 1650–1430 cm-1. The C–H bending bands appear in the
regions 1275–1000 cm-1 (in-plane C-H bend) and 900–690 cm-1 (out-of plane C-H bend). In
addition, the stretching mode of NH group is generally in the range 3500-3300 cm-1 .The
stretching mode symmetrical and asymmetrical O=S=O is observed at 1138 cm-1and 1388 cm-1.
The experimental 1H-NMR spectrum of the compounds are reported in experimental section. The
1H-NMR spectrum of compounds were recorded in DMSO-d6 as solvent with TMS as internal
1
standard. The H-NMR spectrum of the ligand showed a broad singlet at 3.40 ppm for –NH
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group. The absence of this signal in the spectrum of the complex, due to deprotonating and
coordinating of anions to palladium and the formation of Pd-N bonds. Determination of Pd
content was performed on catalyst followed by ICP analysis. The Pd content of the catalyst was
0.11 mmol/g.
2.4. Heck reactions
The performance of coupling reactions was investigated in a variety of parameters. In order to
optimize the reaction condition, we applied different temperatures (80 °C, 100 °C), solvent
(DMF and DMF/H2O) and amounts of catalyst (0.25, 0.5, 1 mol %) in the presence of base. We
found that the using Na2CO3 as a base, DMF as a solvent, 0.5mol % catalyst at 100 °C has the
highest yield. The result is shown in Table 1. In these processes, after the reaction, the catalyst
was filtrated, and it was washed with ethanol and dried. It was shown that the catalyst is stable
and can be applied for several reaction.
[Insert Table 1]
After optimizing, various aryl halides and olefins were used as substrate for coupling Heck
reaction. The results are given in Table 2.
[Insert Table 2]
3. Experimental
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3.1. Physical measurements and materials
All compounds were purchased from Merck and Aldrich companies. Fourier transform infrared
spectra of prepared compounds were obtained in the 400–4000 cm−1 region using KBr pellets on
1
Shimadzu FT-IR 8400 spectrometer. H-NMR spectrum was recorded on a Bruker Ultrashield
400 MHz spectrometer using DMSO-d6 as solvent and tetramethylsilane as internal standard.
The Pd analysis and loading test were carried out by inductively coupled plasma
ICP_OES_730_ES_Varian.
3.2. Synthesis of compounds
3.2.1. Preparation of Para-Styrene Sulfonyl Chloride
Para-styrene sulfonyl chloride was synthesized by the reaction of of para-styrene sulfonic acid
sodium salt (5.00 g, 24 mmol) with of PCl5, (7.50 g, 36 mmol) as a chlorinating agent. The
product was separated from inorganic materials by chloroform and ice water. The chloroform
was evaporated from the para-styrene sulfonyl chloride. Experimental details are described in
elsewhere30.
3.2.2. Preparation of monomer [N-(2-pyridyl)] para-styrene sulfonamide
The synthetic method for the preparation of the monomer (PSS with chemical formula as
C13H12N2O2S) is as follows: para-styrene sulfonyl chloride (4.86 g, 24 mmol), 2-amino pyridine
(2.25 g, 24 mmol), KOH 0.5M (2.4 mL) and CHCl3 (50 mL, used as solvent) were placed in a
100 mL round-bottomed flask, equipped with a magnetic stirrer. The reaction mixture was stirred
for 4 h at room temperature, the solvent was evaporated. The obtained product was washed 3
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times with water and analyzed without further purification. The IR (Figure S 1 Supplemental
Materials), 1H NMR (Figure S 2) and 13C NMR (Figure S 3) spectra confirmed that the monomer
was synthesized and the purity of [N-(2-pyridyl)] para-styrene sulfonamide was shown.
IR (KBr, cm-1): 3340(m), 3057(m), 3028(m), 1631(s), 1600(m), 1529(m), 1460(m), 1388(s),
1356(s), 1276(m), 1138(s), 1084(m), 999(m). 1H NMR (DMSO-d6, ppm): 3.40(NH), 5.45(CH in
vinyl), 6.01(CH in vinyl), 6.82(CH in vinyl), 7.67 (CH Benzene) 7. 88(CH Benzene), 6.91, 7.21,
7.77 and 8.04 (pyridine ring). 13C NMR (DMSO-d6, ppm):153.2(Cpyridine), 142.9(CHpyridine),
140.9(CHpyridine), 140.6(CHpyridine), 140.5(CHvinyl), 135.3(Cphenyl), 126.9(CHphenyl),
126.5(CHphenyl), 117.3(CHphenyl), 115.4(CHpyridine), 113.8(CH2vinyl).
3.2.3. Preparation of polystyrene2-pyridyl sulfonamide (PPSS)
0.1 mol monomer, 50 mL THF as a solvent and 0.05 mol AIBN (Azoisobutyronitrile) used as an
initiator were placed in a round- bottomed flask, equipped with a reflux condenser, atmosphere
of nitrogen and a magnetic stirrer. The reaction mixture was refluxed at 80°c for 10 h. After the
time reaction, the solvent was evaporated. The polymer was washed with water and dried with
1
MgSO4. The IR (Figure S 4) and H NMR (Figure S 5) spectra confirmed that the polymer was
synthesized and the purity of polystyrene-2-pyridyl sulfonamide was shown.
IR (KBr, cm-1): 3340m, 3057m, 2995m, 2945m, 2879m, 1631s, 1600m, 1529m, 1460m, 1388s,
1356s, 1276m, 1138s, 1084m, 999m. 1H NMR (DMSO-d6, ppm):1.8(CH2, in polymer), 3.40(NH),
2.11(CH, in polymer), 7.68 (d, CH Benzene) 7. 87(d, CH Benzene), 6.91, 7.21, 7.77 and 8.04
(pyridine ring)
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3.2.4. Preparation of palladium complex as a catalyst
The synthetic method for the preparation of the palladium (II) complex is as follows. PdCl2 (0.09
g, 0.5 mmol) and CH3CN (50 mL) were placed in a 100 mL round-bottomed flask, equipped
with a reflux condenser and a magnetic stirrer. The mixture was stirred and warmed to 70 °C to
give a light orange solution. Then the ligand (0.26 g, 1 mmol) and potassium hydroxide 0.5M (2
mL) were added. The reaction mixture was refluxed for 12 h. A green solid appeared. The green
1
solution was filtered and washed with CH3CN (3×10 mL). The IR (Figure S 6) and H NMR
(Fig. S 7) spectra confirmed that the complex was synthesized and the purity of polystyrene
bis[N-(2-pyridyl) sulfonamide] palladium(II) was shown. In order to determine the Pd content of
the catalyst, it was treated with 30 mL of mixture of concentrated HCl and H2SO4 (1:1). Then, it
was filtered. The filtrate, with distilled water, was diluted to 50 mL and subjected to ICP
determination using a calibration curve method.
IR (KBr, cm-1): 3100m, 3050m, 2945m, 2879m, 1656s, 1621s, 1533m, 1464s, 1389s, 1359s,
1280s, 1139m, 1084m. 1H NMR (DMSO-d6, ppm): 1.70(CH2, in polymer), 2.11(CH, in polymer), 7.31-
7.71 (benzene ring), 6.48, 7.23, 7.87 and 8.21 (pyridine ring).
3.2.5. General Procedure for Heck Reaction
A round bottom flask was charged with aryl halide (15 mmol), olefins such as methyl and methyl
methacrylate and acrylonitrile (15 mmol) using DMF as a solvent (100 mL), Then Na2CO3 as
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base (15 mmol) and catalyst (0.5mol %) were added. The stirring solution was refluxed at 100
°C for 12 h. After requisite time, the reaction mixture was cooled to room temperature. The
palladium catalyst was separated from the mixture by filtration. The solution diluted with water
(30 mL) and product extracted with ethyl acetate (3 × 10 mL). Then, the product was
concentrated under reduced pressure. This product was purified and crystallized with ethanol and
water (1:1).
4. Conclusion
In order to show the application of polymer- supported palladium as the catalyst in organic
synthesis, for the first time, we applied Poly styrene bis [N-(2-pyridyl) sulfonamide] palladium
as the catalyst in the Heck reaction. The Heck reaction occurred using iodo and bromobenzene
with olefins as substrates in the presence of Na2CO3 as base and DMF as solvent at 100 °C for
12h (Table 1). The Heck coupling reactions represent a powerful method for the C-C bond
formation. In conclusion, this complex was evaluated for the first time as a catalyst for the Heck
reaction under low catalyst loading (0.5 mol %) which can be easily separated.
Acknowledgment
We would like to thank Lorestan University for its financial support.
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Scheme 1. The reaction involving synthesis of PSS
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Scheme 2. The reaction involving synthesis of PPSS
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Scheme 3. Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium
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Table 1. Optimization of reaction condition for Heck reaction catalyzed by polymer supported
palladium
Entrya
Solvent
DMF
Cat (mol %)
0.5
T/oC
80
Yield b (%)
1
2
3
4
5
81
99
85
99
82
DMF
0.5
100
100
100
100
DMF
0.25
DMF
1.00
DMF/H2O
0.5
a Reaction conditions: iodo benzene (15 mmol), methyl acrylate (15 mmol), Na2CO3 (15 mmol ),
for 12 h
b Isolated yield
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Table 2. Heck coupling of aryl halides with olefins catalyzed by polymer- supporting
palladium complex.
Entrya
Aryl halide
Olefin
Product
Yieldb (%)
1
2
99
98
3
4
96
95
93
5
6
82
79
7
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8
9
76
74
71
10
a Reaction conditions: aryl halide (15 mmol), olefin (15 mmol), Na2CO3 (15 mmol),
DMF (100 mL), catalyst (0.5 mol%), for 12 h, at 100 °C under air.
b Isolated yields
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