Synthesis of a functionalized polymer based on a calix[4]resorcinarene via covalently anchored cationic moieties: A reactive solid support for ring transformation and expansion of thiopyrylium salts

Article abstract of DOI:10.1055/s-0034-1379604

In this work, for the first time, a cationic polymer containing pendant pyridinium groups was synthesized via post-functionalization of the polymeric backbone based on a calix[4]resorcinarene, and characterized by AFM, TEM, analytical CHN, TGA, and DTG te

Full text of DOI:10.1055/s-0034-1379604

SYNTHESIS
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
© Georg Thieme Verlag Stuttgart · New York
2015, 47, 630–640
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Synthesis of a Functionalized Polymer Based on a Calix[4]resorcin-
arene via Covalently Anchored Cationic Moieties: A Reactive Solid
Support for Ring Transformation and Expansion of Thiopyrylium
Salts
Arash Mouradzadegun*
Somayeh Elahi
Fatemeh Abadast
Department of Chemistry, Faculty of Science, Shahid Chamran
University, Ahvaz, Iran
arash_m@scu.ac.ir
Received: 08.10.2014
Accepted after revision: 04.11.2014
Published online: 18.12.2014
the advantages of polymer-supported reagents, and this has
proven to be an important tool to accommodate the princi-
ples of green chemistry in the synthesis of desired prod-
ucts.5
DOI: 10.1055/s-0034-1379604; Art ID: ss-2014-z0615-op
Abstract In this work, for the first time, a cationic polymer containing
pendant pyridinium groups was synthesized via post-functionalization
of the polymeric backbone based on a calix[4]resorcinarene, and char-
acterized by AFM, TEM, analytical CHN, TGA, and DTG techniques. The
functionalized polymer is conveniently loaded with desired anions,
thereby providing novel and recyclable polymer-supported reagents for
achieving synthetic goals. The thermal stability of this cationic polymer
(up to 250 °C by TGA) allows thermally demanding ring transformation
and expansion of 2,4,6-triarylthiopyrylium salts on its side chains and
polymeric backbone without decomposition and leaching of active spe-
cies in the reaction media. This green method furnished a straightfor-
ward route for the synthesis of valuable 2,4,6-triarylpyridines, along
with novel 2,5,7-triaryl-1,3-thiazepine derivatives, which are widely
present as motifs in an assortment of biologically active molecules.
The majority of studies in this area have been per-
formed using porous polymers as carriers to achieve highly
selective and mild chemical reactions. Some of the key ad-
vantages of porous supported reagents, such as the good
dispersion of active sites, the concentration of sites within
small pores, the presence of molecular dimension pores,
and the adsorption of reactant molecules on the material
surface, can lead to significant improvements in activity
and reaction selectivity. These coupled with the normal ad-
vantages of a solid support (e.g., easier recovery and reuse,
easier and safer handling) make porous supported reagents
attractive materials to organic and industrial chemists.
Although a variety of polymeric supports have been re-
ported, some of them suffer from one or more defects in
their synthetic routes or properties, including long reaction
times, multiple steps for synthesis, the use of expensive
catalysts and harsh reaction conditions, solubility in vari-
ous solvents, and low thermal and/or chemical stability.
Considering the ease of preparation and unique proper-
ties of the 3D-network polymer based on calix[4]resorcin-
arenes, such as significant potential for functionalization,
high thermal and chemical stability, and porous surface
(pore radius from approximately 100 to 500 nm),6 it would
be reasonable to consider this polymeric structure as a
promising starting material for the synthesis of a novel and
efficient polymer-supported reagent.
Key words azide, green chemistry, heterocycles, nucleophilic addi-
tion, polymers, ring expansion
Functionalization of polymers has been regarded as an
effective method to improve polymer performance for vari-
ous applications. In this context, covalently anchored cat-
ionic moieties on the polymeric backbone have received
considerable interest due to their utilization as solid-sup-
ported reagents and catalysts,1 anion-exchange membranes
for alkaline fuel cells,2 and adsorbents for anionic azo dyes.3
Moreover, cationic polymers have been applied in various
industries for different purposes (e.g., as strength agents in
papermaking).4
Over the past two decades, a major problem in the field
of organic synthetic chemistry has been a lack of more en-
vironmentally friendly processes using safer reagents and
generating fewer side products. In response to such con-
cerns, a strategy of modern chemistry has been to exploit
The synthesis of heterocyclic moieties has attracted tre-
mendous attention due to the utilization of heterocyclic
compounds in biological, biochemical, pharmaceutical, and
asymmetric chemical investigations. In this context, six-
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OH
HO
OH
HO
OH
CH2
OH
OH
HO
HO
HO
HO
HO
4
OH
O
O
H
+
4
+
H
H
H
OH
OH
OH
HO
HO
n
1
2
Scheme 1 Synthesis of calix[4]resorcinarene 1 and the 3D-network polymer 2
and seven-membered rings containing nitrogen and/or sul-
fur atoms are essential constituents of a range of products,
from pharmacologically active substances to natural prod-
ucts and various materials.7
A possible route for the synthesis of triarylpyridine and
triarylthiazepine derivatives is the nucleophilic reaction of
triarylthiopyrylium salts with azide anion.
Previous studies have revealed that the reactivity of
azide anion with thiopyrylium cations at room temperature
depends on the substitution of the heterocyclic cation. Only
sterically hindered thiopyrylium cations lead to the forma-
tion of covalent azide, and trisubstituted examples give
only a donor–acceptor complex.8 The formation of this
complex constitutes a dead-end reaction on the normal
pathway to covalent azide.
In this vein and as a part of our continuing efforts to de-
velop efficient and environmentally friendly transforma-
tions,9 we report herein, for the first time, the functional-
ization of a porous polymeric calix[4]resorcinarene via co-
valently anchored pyridinium moieties, and its application
as a reactive polymer-supported reagent for the synthesis
of triarylpyridine and triaryl-1,3-thiazepine derivatives
through ring transformation and expansion of trisubstitut-
ed thiopyrylium salts.
NMR, 13C NMR; see Supporting Information). Subsequently,
3D-network polymer 2 was prepared by polycondensation
of 1 with formaldehyde (Scheme 1).6,11 The formation of
polymer 2 was confirmed and characterized by atomic force
microscopy (AFM), X-ray diffraction, and scanning electron
microscopy (data available in the Supporting Information).
Following the characterization of polymer 2, due to the
possibility to obtain new functional materials for diverse
applications, we shifted our attention to the functionaliza-
tion of the polymer through covalently anchored cationic
moieties.
Cationic heterocyclic moieties are a class of valuable
headgroups that can be used for the functionalization of
solid supports. Among them, in recent years, the chemically
and thermally stable pyridinium moiety and its deriva-
tives12 have been extensively incorporated into various sup-
ports to achieve desired goals.13
Considering the above point, this part of our study com-
menced with the synthesis of pyridinium-grafted polymer.
Initially, the cationic polymer 3 was synthesized via two
chemical modification steps (Scheme 2, A). Starting from
3D-network polymer 2 and (3-chloropropyl)trimethoxysi-
lane, the chloropropyl-grafted polymer 4 was prepared and
subsequently converted into ionic form 3 by a simple nuc-
leophilic substitution reaction. According to elemental
analysis data, the amount of grafted pyridinium moieties
obtained was 2.4 mmol per gram of polymer 3 (Table 1, en-
try 2).
Starting from resorcinol and acetaldehyde, the ca-
lix[4]resorcinarene 1 was prepared according to a literature
procedure10 (Scheme 1). The structure of compound 1 was
established unambiguously from spectroscopic data (IR, 1H
Table 1 Elemental Analysis Data for Polymer 2 and the Cationic Polymer 3 Bearing Pyridinium Moieties
Entry
Material
Method
Solvent
Time (h)
C (wt %)
H (wt %)
N (wt %)
1
2
3
4
polymer 2
–
–
–
45.72
56.38
48.94
56.38
4.96
5.36
5.25
5.36
0.03
3.37
1.74
3.37
cationic polymer 3
cationic polymer 3
cationic polymer 3
two-step
one-step
one-step
H2O–EtOH + toluene
toluene
48
24
24
H2O–EtOH
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N+
Cl–
Cl
N+
Cl–
HO
Si
OH
N
OH
O
O
OH
OH
HO
Si
O
Si
O
O
OH
CH2
O
HO
HO
Me
Me
Me
CH2
OH
B
O
HO
Si OH
O
OH
O
HO
Si
HO
n
n
OH
Cl–
Cl
2
Cl–
N+
Cl
Cl
N+
HO
Si
OH
OH
O
O
3
Si
O
N
Si
O
Me
O
OH
CH2
O
Me
Me
A
O
HO
Si OH
O
O
Si
HO
n
OH
Cl
Cl
4
Scheme 2 Synthesis of the cationic polymer 3 containing pyridinium moieties via two pathways
The pyridinium-functionalized polymer 3 was also pre-
pared following a one-step procedure (Scheme 2, B). Sur-
prisingly, similar elemental analysis data were obtained via
the one-step chemical modification of polymer in aqueous
ethanol as solvent (Table 1, entry 4; cf. entry 2).
With the above results in hand, in the next step, we in-
vestigated the ability of the functionalized polymer 3 in
anion-exchange mode. In this regard, cationic polymer 3
was treated with aqueous sodium azide, ammonium thio-
cyanate, or sodium cyanide for 12 hours (Scheme 3).
It is noteworthy that this polymeric support showed
more potential for covalently anchored moieties than some
previously reported solid supports.14 Moreover, the cationic
polymer 3 is effectively insoluble in various solvents, in-
cluding water, methanol, ethanol, dimethyl sulfoxide, N,N-
dimethylformamide, acetonitrile, dichloromethane, and
chloroform. These features render polymer 3 suitable for
use as a solid-supported reagent or catalyst in various reac-
tion media.
The typical loading of the anions onto the support was
determined by elemental analysis and the potentiometric
method. As shown in Table 2, polymer 3 conveniently load-
ed with the desired anions. This result gave us confidence
that the pyridinium side chain would be tolerated under the
alkali conditions which are produced by sodium azide, sodi-
um cyanide, or ammonium thiocyanate dissolved in water.
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N+
N+
X–
HO
Cl–
N+
Cl–
N+
X–
HO
OH
Si
OH
Si
O
OH
OH
O
O
O
Si
Si
OH
OH
CH2
O
O
MX
CH2
M = Na or NH4
X = CN or N3 or SCN
O
O
HO
HO
Si OH
O
Si OH
O
O
O
Si
Si
HO
HO
n
n
OH
OH
X–
N+ Cl–
N+ X–
Cl–
N+
N+
3
Scheme 3 Preparation of polymer-supported reagents
Table 2 Elemental Analysis Data for Polymer 3 and the Polymer-
Supported Reagents
Transmission electron microscopy (TEM) of the func-
tionalized polymer 3 was undertaken on a LEO 906E instru-
ment operated at the accelerating voltage of 80 KV (Figure
3). The TEM images show that there are some pores which
have a diameter in the nanometer range.
The thermal stability of cationic polymer 3 was investi-
gated by thermogravimetric analysis (TGA, Figure 4) at a
heating rate of 10 °C per minute under nitrogen atmo-
sphere.
Entry
Polymer
X
N (wt %)
S (wt %)
1
2
3
4
3
Cl
3.37
4.99
3.96
1.14
–
supported reagent
supported reagent
supported reagent
N3
–
CN
SCN
–
3.81
The TGA of polymer 3 demonstrated high thermal sta-
bility, with decomposition starting at around 250 °C. The
thermal stability of this cationic polymer allows heat-de-
manding chemical transformations along its backbone and
side chains without leaching of the active species, thereby
providing an excellent means of polymer support for con-
ducting chemical transformations.
Along this line, we decided to investigate the application
of this cationic polymer as a solid-supported reagent for ef-
ficient construction of heterocyclic compounds through
ring transformation and expansion of triarylthiopyrylium
salts.
In the preliminary stage of the investigation, the reac-
tion of 2,4,6-triphenylthiopyrylium perchlorate (5A, 0.1
mmol) with azide anion (0.2 mmol) was selected as the
model reaction to survey the requisite reaction conditions.
After some experimentation (Table 3), it was found that the
use of 0.1 mmol of the triphenylthiopyrylium salt in the
presence of polymer-supported azide (0.5 g polymer con-
taining 0.2 mmol azide anion) in boiling acetonitrile were
the best conditions (Table 3, entry 7).
These significant properties of cationic polymer 3 en-
couraged us to characterize its structure. In order to gain an
insight into the topography of the surface, AFM was utilized
(Figure 1, a, b). All of the AFM scans were taken in ambient
air in tapping mode, which is ideal for this kind of poly-
mer.15 More details could be obtained from the 3D height
and phase plots (Figure 1, b).
Representative 1.5 μm × 1.5 μm AFM height images of
polymer 2 and cationic polymer 3 suggest a series of pores
which have an average surface diameter of about 300 nm6
(see Supporting Information) and 70 nm (Figure 2), respec-
tively. It can be concluded that the introduction of pyridini-
um moieties into the polymer shifted the pores to smaller
diameter.
On the whole, AFM revealed that the 3D-network cat-
ionic polymer 3 exhibits a nanoporous surface that has the
ability for the inclusion of an organic guest.
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Figure 1 AFM images (1.5 μm × 1.5 μm) of cationic polymer 3: (a) 2D and (b) 3D height and phase plots
Figure 2 Image profile (the analysis of height along a linear path) of cationic polymer 3
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Figure 3 TEM images of cationic polymer 3
Table 3 Reaction of Triphenylthiopyrylium Salt 5A with Azide Anion under Various Conditions
Entry
Azide source
Solvent
Temp (°C)
Time
Result
Total yield (%) of 7A + 8A
1
2
3
4
5
6
NaN3
NaN3
NaN3
NaN3
NaN3
NaN3
CH2Cl2
EtOH
r.t.
24 h
24 h
24 h
24 h
24 h
24 h
starting material + byproduct 6A
starting material + byproduct 6A
starting material + byproduct 6A
starting material + byproduct 6A
starting material + byproduct 6A
0
0
0
0
0
8
r.t.
MeCN
CH2Cl2
EtOH
r.t.
reflux
reflux
reflux
MeCN
starting material + byproduct 6A +
desired products 7A and 8A
7
polymer-supported azide
MeCN
reflux
90 min
desired products 7A and 8A
65
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Figure 4 TGA and differential thermogravimetric (DTG) profile of cationic polymer 3
Briefly, in our optimization studies, when the reaction
of triphenylthiopyrylium salt 5A with sodium azide was
carried out in different solvents at room temperature,
charge-transfer complex 6A was obtained as the sole prod-
uct (Table 3, entries 1–3). According to TLC analysis, there
was no evidence of the transformation of 6A into the de-
sired products 7A and 8A, even after 24 hours, which is
completely in agreement with the previously reported da-
ta.8 Raising the temperature led to the formation of a small
amount of products 7A and 8A, along with a considerable
amount of charge-transfer complex 6A as byproduct, in
boiling acetonitrile after 24 hours (Table 3, entry 6).
that the byproduct 6A produced as a consequence of the
competing side reaction I occurs in parallel to the intended
reaction II; the two pathways are summarized in Scheme 4.
Surprisingly, as illustrated in Table 3 (entry 7), using
polymer-supported azide as the nucleophile source dra-
matically reduced the reaction time and considerably in-
creased the yield of the desired products 7A and 8A without
any concentration of unreacted starting material 5A and
byproduct 6A (Scheme 5).
A weak interaction between azide anion and the pyri-
dinium moieties on the cationic polymer, which increases
the nucleophilicity of the azide anion, might contribute to
the suppression of byproduct formation and to the rapid
progress of the nucleophilic reaction. Furthermore, the ad-
sorption of thiopyrylium salt onto the surface of the func-
tionalized polymer based on hydrophobic interactions be-
tween the aromatic substrate and the polymeric backbone
As stated earlier, the formation of a charge-transfer
complex constitutes a dead-end reaction on the normal
pathway to covalent azide, and prevents the formation of
the desired products. Under this light, it could be concluded
Ph
Ph
S+
Ph
S+
Ph
NaN3
NaN3
–
N3
Ph
N
+
Ph
I
II
Ph
Ph
Ph
Ph
S
N
Ph
Ph
–
ClO4
5A
6A
7A
8A
Scheme 4 Two pathways for the reaction of model compound 5A with sodium azide in boiling acetonitrile
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donating groups led to longer reaction time (Table 4, entry
4). In contrast, the presence of an electron-withdrawing
group (Table 4, entries 5 and 6) accelerated the reaction.
A conceivable mechanism for the synthesis of 2,5,7-tri-
aryl-1,3-thiazepine 7 and 2,4,6-triarylpyridine 8 derivatives
via a nucleophilic attack route is outlined in Scheme 6. The
first step of the reaction affords the 2-azidothiopyran 9
which undergoes electrocyclic ring opening to form the
acyclic valence tautomer 10. Subsequently, thermal elimi-
nation of an N2 molecule from compound 10 followed by in-
tramolecular nitrogen insertion into the adjacent C–C dou-
ble bond (path a) yields azirine 11 which readily rearranges
to the stable 2,5,7-triaryl-1,3-thiazepine 7. Another plausi-
ble pathway which can occur after release of the N2 mole-
cule from compound 10 is the insertion of the nitrogen
atom into the C–S double bond (path b) which affords bicy-
clic thiaziridine 12. Finally, extrusion of the sulfur atom
from compound 12 leads to the formation of 2,4,6-tri-
arylpyridine 8.
Ph
Ph
Ph
polymer-
supported azide
N
+
Ph
Ph
S+
ClO4
5A
Ph
S
N
Ph
Ph
Ph
–
7A
8A
Scheme 5 Reaction of model compound 5A with polymer-supported
azide
could increase local concentration of the substrate around
the active sites of the polymer and effectively promote the
nucleophilic reaction.
It is noteworthy that the formation of 7 and 8 by this
method is of considerable interest, since this is the first re-
port of the synthesis of these privileged heterocyclic com-
pounds via ring expansion and transformation of triarylth-
iopyrylium salts.
These results encouraged us to demonstrate the effi-
ciency and the applicability of the present method. We per-
formed the reaction of a variety of 2,4,6-triarylthiopyryli-
um salts containing electron-withdrawing or electron-
donating groups with azide anion under the optimized re-
action conditions. Representative results for this synthetic
modification are listed in Table 4.
The structures of all known products (the 2,4,6-tri-
arylpyridine derivatives) were established unambiguously
from their physical (mp) and spectroscopic data (IR, 1H
NMR, 13C NMR), and by direct comparison with authentic
samples.16 Moreover, the structures of all novel products
(the 2,5,7-triaryl-1,3-thiazepine derivatives) were settled
unambiguously from spectroscopic data (IR, 1H NMR, 13C
NMR, MS) (all physical and spectroscopic data are available
in the Supporting Information).
Overall, the use of the polymer-supported reagent
therefore offers the possibility of considerably decreasing
the reaction times and improving the yields of desired
products relative to conventional conditions. Furthermore,
the immobilized reagent is generally more stable and easy
to handle, and can easily be separated by filtration after the
reaction. Even in a large excess of solid-supported reagent
used to drive the reaction to completion, products require
no further purification which has driven continued interest
in solid-supported reagents. Finally, the polymer-supported
reagents are much less hazardous to use, because the re-
agent residues (such as azide, cyanide, and thiocyanate) are
retained on the cationic polymer and are not extracted into
the reaction media.
In conclusion, by combining the advantages of 3D-net-
work polymer 2 with pyridinium moieties, the first pyri-
dinium-functionalized polymer based on a calix[4]resorc-
inarene as a novel and thermally stable solid support was
developed. The remarkable advantages offered by this ap-
proach are operational simplicity, a one-pot one-step pro-
cedure, no use of an acidic or basic catalyst, ease of isolation
and purification of the functionalized polymer, and a high
amount of grafted cationic moieties. We believe that this
method is a useful alternative to the existing methodologies
for the synthesis of functionalized polymers. Following
the characterization of functionalized polymer 3, azide-
impregnated cationic polymer was prepared and used as a
Table 4 Conversion of Various 2,4,6-Triarylthiopyrylium Salts 5 into
the Corresponding 2,5,7-Triaryl-1,3-thiazepine 7 and 2,4,6-Triarylpyri-
dine 8 Derivatives Using Polymer-Supported Azide under Optimized
Conditions
Ar2
Ar2
4
Ar2
5
4
polymer-supported
6
3
azide
5
6
3
N
+
2
Ar1
80 °C
7
Ar1
Ar1
S
1
Ar1
S+
ClO4
Ar1
N
1
2
Ar1
–
7
8
5
Entry
5/7/8
Ar1
Ar2
Time
Yield (%) of
7/8
1
2
3
4
5
6
A
B
C
D
E
Ph
Ph
90 min 30/35
Ph
Ph
4-MeC6H4
4-MeOC6H4
Ph
2 h
15/40
30/35
30/35
3 h
4-MeOC6H4
20 h
Ph
Ph
4-ClC6H4
4-BrC6H4
13 min 25/33
15 min 27/30
F
Electron-donating substituents resulted in a decreased
reaction rate (Table 4, entries 2–4), possibly because these
groups decrease the positive charge at the α-position of the
heterocyclic ring. The presence of more strongly electron-
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Ar2
Ar2
S
Ar2
–
N
N
N+
Ar1
Ar1
S
Ar1
C
Ar1
S
Ar1
Ar1
7
11
a
Δ / – N2
Ar2
Ar2
Ar2
S
Ar2
Ar2
–
N3
N3
Ar1
Ar1
Ar1
Ar1
S+
Ar1
Ar1
S
Ar1
Ar1
S
Ar1
S
Ar1
N
N
N
N3
N
N
N
–
–
+
ClO4
–
+
5
9
10
Δ / – N2
Ar2
b
Ar1 = Ph, 4-MeOC6H4
Ar2 = Ph, 4-MeC6H4, 4-MeOC6H4, 4-ClC6H4, 4-BrC6H4
Ar2
– S
Ar1
Ar1
N
Ar1
Ar1
N
S
12
8
Scheme 6 Plausible mechanism for the reaction of 2,4,6-triarylthiopyrylium salts 5 with azide nucleophile
reactive reagent for the clean and efficient synthesis of bio-
active 2,4,6-triarylpyridine and novel 2,5,7-triaryl-1,3-thi-
azepine derivatives, starting from 2,4,6-triarylthiopyrylium
salts as simple and readily available starting materials. The
cationic polymer as solid support has the potential to be re-
cycled, thereby offering both a green and economical ap-
proach for many chemical transformations. Currently, work
on developing a variety of functionalized polymers derived
from polymeric calix[4]resorcinarenes is in progress in our
laboratory.
Novel Functionalized Polymer 3 via a Two-Step Chemical Modifi-
cation (Scheme 2, A)
Chloropropyl-Grafted Polymer 4
Polymer 2 (1 g) was added to a flask containing H2O–EtOH (1:1, 10
mL) and (3-chloropropyl)trimethoxysilane (3.4 g, 16 mmol). The reac-
tion mixture was heated at 90 °C with stirring for 20 h. Then, the ma-
terial was collected by filtration, washed several times with deionized
water, and dried at 80 °C.
Functionalized Polymer 3 Bearing Cationic Moieties
Chloropropyl-grafted polymer 4 (1 g) and an excess of pyridine (25
mmol) were stirred in toluene (10 mL) at 90 °C for 20 h. Then, the sol-
id product was recovered by filtration and washed with deionized
water several times before being dried at 80 °C.
Chemicals were purchased from Fluka, Merck and Aldrich chemi-
cal companies and used without further purification. Products were
characterized by physical data, IR, 1H NMR, 13C NMR and HRMS spec-
tra. Melting points were determined on a Thermo Scientific 9200 ap-
paratus. IR spectra were obtained on a Bomen MB:102 FT-IR spectro-
photometer. 1H NMR and 13C NMR spectra were recorded on a Bruker
spectrometer at 400 and 100 MHz, respectively, in CDCl3 or DMSO
with tetramethylsilane as an internal standard. HRMS spectra were
measured on an Agilent 5975 mass spectrometer and elemental anal-
yses were performed on a Thermo Finnigan Flash EA 1112 CHNS-An-
alyzer. The polymer morphology was examined by AFM (Nano Wiz-
ard II) and TEM (LEO-906E). The thermal stability of functionalized
polymers was investigated by NETZSCH STA 409 PC/PG.
Novel Functionalized Polymer 3 via a One-Step Chemical Modifi-
cation (Scheme 2, B)
Polymer 2 (1 g), (3-chloropropyl)trimethoxysilane (3.4 g, 16 mmol),
and an excess of pyridine (25 mmol) were added to a flask containing
H2O–EtOH (1:1, 10 mL) or toluene (10 mL). The reaction mixture was
heated at 90 °C for 20 h. The desired cationic polymer 3 was collected
by filtration and washed with deionized water several times before
being dried at 80 °C.
Preparation of Polymer-Supported Reagents as Novel and Efficient
Reagents (Scheme 3)
Monitoring of the reactions and the purity determination of the prod-
ucts were accomplished by TLC on PolyGram SILG/UV 254 silica gel
plates.
The dried cationic polymer 3 (1 g) was stirred with NaN3 (15 g),
NH4SCN (10 g), or NaCN (2.8 g) in H2O (40 mL) for 12 h. The azide,
thiocyanate, or cyanide solution was decanted, and the polymer was
washed with distilled water several times.
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Determination of the Capacity of the Polymer-Supported Reagents
4-(4-Methylphenyl)-2,6-diphenylpyridine (8B)
The capacity of the polymer-supported azide or thiocyanate was de-
termined by elemental analysis. The capacity was generally found to
be 0.4 and 1.19 mmol per gram of dried cationic polymer 3 for azide
and thiocyanate anion, respectively.
Yield: 12.84 mg (40%); white crystals; mp 114–116 °C (from EtOH).
1H NMR (400 MHz, CDCl3): δ = 2.47 (s, 3 H, CH3), 7.33–7.91, 8.21–8.22
(m, 14 H, Ar-H), 7.92 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 21.30 (CH3), 117.10 (C-3, C-5), 127.08,
127.41, 128.74, 129.31, 129.92 (ArC), 135.68, 136.42, 138.98 (ArCq),
149.29 (C-4), 157.54 (C-2, C-6).
The capacity of the polymer-supported cyanide was determined by
the potentiometric method. Briefly, a sample of polymer-supported
cyanide anion (0.10 g) was stirred for 12 h with KI (8.3 mg) in H2O (10
mL). The polymer was collected by filtration and washed several
times with distilled H2O. The combined filtrate and washings were ti-
trated against 0.01 M aq AgNO3 using a potentiometer. The capacity
was generally found to be 0.4 mmol per gram of dried cationic poly-
mer 3. Used polymer could be readily regenerated by sequential
washing with 1 M aq NaCl and NaCN.
5-(4-Methoxyphenyl)-2,7-diphenyl-1,3-thiazepine (7C)
Yield: 11.07 mg (30%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 3.76 (s, 3 H, OCH3), 6.69–7.73 (m, 16 H,
Ar-H).
13C NMR (100 MHz, CDCl3): δ = 55.27 (OCH3), 113.54 (C3 of C6H4-
OCH3), 126.18, 126.68, 127.83, 128.28, 128.91, 129.14 (ArC), 129.65
(C-6), 130.48, 132.09, 133.28 (ArCq), 137.81 (C-4), 147.70 (C-5),
149.15 (C-7), 159.24 (C-OCH3), 189.89 (C-2).
2,5,7-Triaryl-1,3-thiazepine 7 and 2,4,6-Triarylpyridine 8 Deriva-
tives from the Reaction of 2,4,6-Triarylthiopyrylium Perchlorates
5 with Azide-Impregnated Cationic Polymer (Table 4); General
Procedure
MS: m/z = 369 [M+•].
The 2,4,6-triarylthiopyrylium salt 5 (0.1 mmol) was stirred with the
azide-impregnated cationic polymer (0.5 g polymer containing 0.2
mmol azide anion) in refluxing MeCN (5 mL) until the reaction was
complete (TLC). The polymer was then removed by filtration, the sol-
vent was evaporated under vacuum and the residue was adsorbed
onto silica gel, transferred to a silica gel column and eluted with a
mixture of n-hexane–ether (4:1). Thereby, the first and second parts
containing the corresponding 2,4,6-triarylpyridine 8 and 2,5,7-tri-
aryl-1,3-thiazepine 7, respectively, were obtained. The sampled parts
were concentrated and analyzed by IR and NMR spectroscopy, and
mass spectrometry (see Supporting Information).
4-(4-Methoxyphenyl)-2,6-diphenylpyridine (8C)
Yield: 11.79 mg (35%); white crystals; mp 130–132 °C (from EtOH).
1H NMR (400 MHz, CDCl3): δ = 3.90 (s, 3 H, OCH3), 7.03–7.74, 8.19–
8.21 (m, 14 H, Ar-H), 7.88 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 55.50 (OCH3), 114.70 (C3 of C6H4-
OCH3), 117.24 (C-3, C-5), 127.53, 128.58, 128.78, 129.53, 130.50 (ArC),
138.31, 150.21 (ArCq), 150.23 (C-4), 156.93 (C-2, C-6), 160.92 (ArCq).
2,7-Bis(4-methoxyphenyl)-5-phenyl-1,3-thiazepine (7D)
Yield: 11.97 mg (30%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 3.79, 3.88 (s, 6 H, OCH3), 6.68–7.69 (m,
15 H, Ar-H).
13C NMR (100 MHz, CDCl3): δ = 55.37, 55.42 (OCH3), 113.09, 114.51
(C3 of C6H4-OCH3), 125.44, 126.08, 127.49, 127.60, 128.12 (ArC),
129.17 (C-6), 130.43, 132.12 (ArCq), 135.99 (C-4), 147.15 (C-5), 148.56
(C-7), 160.20, 162.87 (C-OCH3), 188.50 (C-2).
2,5,7-Triphenyl-1,3-thiazepine (7A)
Yield: 10.17 mg (30%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 7.18–7.75 (m, 17 H, Ar-H).
13C NMR (100 MHz, CDCl3): δ = 126.22, 126.72, 127.76, 127.82,
128.09, 128.98, 129.19, 129.25, 129.67 (ArC), 132.17 (C-6), 133.23,
135.11, 136.01 (ArCq), 137.71 (C-4), 149.30 (C-5), 149.94 (C-7), 189.92
(C-2).
MS: m/z = 339 [M+•].
MS: m/z = 339 [M+•].
2,6-Bis(4-methoxyphenyl)-4-phenylpyridine (8D)
Yield: 12.84 mg (35%); white crystals; mp 133–135 °C (from EtOH).
1H NMR (400 MHz, CDCl3): δ = 3.90 (s, 6 H, OCH3), 7.05–7.83, 8.14–
8.17 (m, 13 H, Ar-H), 7.85 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 55.43 (OCH3), 113.29 (C3 of C6H4-
OCH3), 116.92 (C-3, C-5), 127.31, 128.53, 129.06 (ArC), 136.25, 139.15
(ArCq), 151.21 (C-4), 159.33 (ArCq), 159.60 (C-2, C-6).
2,4,6-Triphenylpyridine (8A)
Yield: 10.74 mg (35%); white crystals; mp 132–134 °C (from EtOH).
1H NMR (400 MHz, CDCl3): δ = 7.47–7.77, 8.22–8.24 (m, 15 H, Ar-H),
7.92 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 117.23 (C-3, C-5), 127.20, 128.72,
129.04, 129.14 (ArC), 139.10, 139.50 (ArCq), 150.13 (C-4), 157.49 (C-2,
C-6).
5-(4-Chlorophenyl)-2,7-diphenyl-1,3-thiazepine (7E)
Yield: 9.32 mg (25%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 7.17–7.73 (m, 16 H, Ar-H).
13C NMR (100 MHz, CDCl3): δ = 123.17, 123.95, 124.44, 126.18,
126.41, 127.95, 128.24, 129.06, 129.17 (ArC), 129.58 (C-6), 130.38,
132.36, 138.07, 140.24 (ArCq), 144.26 (C-4), 145.37 (C-5), 158.68 (C-
7), 190.15 (C-2).
5-(4-Methylphenyl)-2,7-diphenyl-1,3-thiazepine (7B)
Yield: 5.29 mg (15%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 2.28 (s, 3 H, CH3), 6.98–7.73 (m, 16 H,
Ar-H).
13C NMR (100 MHz, CDCl3): δ = 29.71 (CH3), 126.19, 126.74, 127.80,
128.77, 128.89, 129.09, 129.14 (ArC), 129.67 (C-6), 132.05, 132.86,
133.28, 137.60 (ArCq), 137.84 (C-4), 148.06 (C-5), 149.08 (C-7), 189.89
(C-2).
MS: m/z = 373.5 [M+•].
4-(4-Chlorophenyl)-2,6-diphenylpyridine (8E)
MS: m/z = 353.2 [M+•].
Yield: 15.14 mg (33%); white crystals; mp 121–123 °C (from EtOH).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2015, 47, 630–640

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A. Mouradzadegun et al.
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1H NMR (400 MHz, CDCl3): δ = 7.48–7.70, 8.21–8.23 (m, 14 H, Ar-H),
7.87 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 116.78 (C-3, C-5), 127.13, 128.76,
129.19, 132.31 (ArC), 123.42, 137.97, 139.38 (ArCq), 149.00 (C-4),
157.71 (C-2, C-6).
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5-(4-Bromophenyl)-2,7-diphenyl-1,3-thiazepine (7F)
Yield: 11.28 mg (27%); yellow liquid.
1H NMR (400 MHz, CDCl3): δ = 7.15–7.73 (m, 16 H, Ar-H).
13C NMR (100 MHz, CDCl3): δ = 118.85 (C-6), 119.09 (C-Br), 122.06,
123.49, 124.00, 124.38, 124.47, 126.21, 126.38, 127.14, 128.72,
128.81, 129.11, 129.20, 129.61, 130.70 (ArC), 130.90, 131.22, 132.99,
134.69, 137.71 (ArCq), 146.60 (C-4), 147.06 (C-5), 149.60 (C-7), 189.50
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4-(4-Bromophenyl)-2,6-diphenylpyridine (8F)
Yield: 15.09 mg (30%); white crystals; mp 104–106 °C (from EtOH).
1H NMR (400 MHz, CDCl3): δ = 7.48–7.70, 8.21–8.23 (m, 14 H, Ar-H),
7.87 (s, 2 H, H-3, H-5).
13C NMR (100 MHz, CDCl3): δ = 116.78 (C-3, C-5), 127.13, 128.76,
129.19, 132.31 (ArC), 123.42, 137.97, 139.38 (ArCq), 149.00 (C-4),
157.71 (C-2, C-6).
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Acknowledgment
This work was supported by the Research Council at the Shahid
Chamran University.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0034-1379604.
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2015, 47, 630–640