Preparation of polystyrene-supported vinyl sulfone and its application in the solid-phase organic synthesis of 1-monosubstituted 1,2,3-triazoles

Article abstract of DOI:10.1016/j.reactfunctpolym.2012.11.002

A polystyrene-supported vinyl sulfone reagent was prepared and used for the solid-phase organic synthesis of 1-monosubstituted 1,2,3-triazoles via a 1,3-dipolar cycloaddition reaction with azides and subsequent cleavage from the polymer support through an elimination reaction in the presence of potassium tert-butoxide. The advantages of this method include straightforward operation, good yield and high purity of the crude products.

Full text of DOI:10.1016/j.reactfunctpolym.2012.11.002

Reactive & Functional Polymers 73 (2013) 224–227
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Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Preparation of polystyrene-supported vinyl sulfone and its application in the
solid-phase organic synthesis of 1-monosubstituted 1,2,3-triazoles
⇑
Zhenzhong Huang, Ruiling Wang, Shouri Sheng , Ruyi Zhou, Mingzhong Cai
College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 July 2012
Received in revised form 4 November 2012
Accepted 6 November 2012
Available online 22 November 2012
A polystyrene-supported vinyl sulfone reagent was prepared and used for the solid-phase organic synthe-
sis of 1-monosubstituted 1,2,3-triazoles via a 1,3-dipolar cycloaddition reaction with azides and subse-
quent cleavage from the polymer support through an elimination reaction in the presence of
potassium tert-butoxide. The advantages of this method include straightforward operation, good yield
and high purity of the crude products.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Solid-phase organic synthesis
1-Monosubstituted 1,2,3-triazoles
Polystyrene-supported vinyl sulfone
1,3-Dipolar cycloaddition
Elimination reaction
1. Introduction
reports from Kurth and co-workers [31,32], Lam’s research group
[33,34], other laboratories [35–40] and ours [41,42] have detailed
Solid-phase organic synthesis (SPOS) is a method in which mol-
ecules are bound to an insoluble solid support, such as polystyrene
resin, and are synthesized step-by-step in a reactant solution.
Compared with normal synthesis performed in a liquid state, the
removal of excess reactant or byproduct from the product is easier,
which allows rapid product purification and allows a given reac-
tion to be driven to completion through the use of an excess of re-
agents [1–3]. SPOS has become a powerful technique for the rapid
generation of a large number of structurally diverse compounds
and for the discovery of new active molecules [4–6]. Heterocyclic
compounds have received special attention because of their broad
range of biological activities. As a result, an increasing number of
pharmaceutically useful heterocyclic compounds have been pre-
pared using solid-phase methodologies [7–9]. Triazole moieties
are found in various biologically active compounds because they
are readily transformed into various biodynamic agents, including
those with antithrombotic, PAF antagonist, and hypolipidemic
properties [10–12]. Because of the importance of triazole, many
practical synthetic methods have been utilized for their prepara-
tion [13–21]. However, the literature contains only a few reports
concerning synthetic methods for 1-monosubstituted 1,2,3-tria-
zoles [22–30]. Sulfinate-functionalized resins have been efficiently
prepared and utilized in SPOS, and the resulting sulfone linker has
been found to be both robust and versatile [9]. Previous and recent
sulfone-linking strategies for SPOS methods to explore sulfone-
based chemical transformations. As a part of our ongoing research
program focused on the use of a versatile traceless sulfone linker in
SPOS, we herein have explored an efficient solid-phase synthetic
methodology for the preparation of 1-monosubstituted 1,2,3-tria-
zoles. To our knowledge, this method has not been previously
reported.
2. Experimental
2.1. General
Melting points were determined on an X4 melting point appara-
tus and are uncorrected. 1H and 13C NMR spectra were recorded on
a Bruker AVANCE 400 NMR spectrometer, using CDCl3 as the sol-
vent and tetramethylsilane (TMS) as an internal standard. FTIR
spectra were collected on a Perkin–Elmer SP One FTIR spectropho-
tometer. Microanalyses were performed with a Carlo Erba 1106
Elemental Analyzer. High-performance liquid chromatography
(HPLC) analysis was performed on an Agilent 1100 automated sys-
tem equipped with a photodiode array (PDA) detector (kmax = 254 -
nm used for this study); a gradient of acetonitrile–H2O was used on
a RP-18e column (150 Â 4.6 mm2). Three kinds of polystyrene/1%
divinylbenzene sodium sulfinates (1) (loading: 2.10, 1.80 and
1.25 mmol – SO2Na/g, respectively) were purchased from Tianjin
Nankai Hecheng Science and Technology Co. (100–200 mesh).
⇑
Corresponding author. Tel./fax: +86 0791 88506404.
E-mail address: shengsr@jxnu.edu.cn (S. Sheng).
1381-5148/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.reactfunctpolym.2012.11.002

Z. Huang et al. / Reactive & Functional Polymers 73 (2013) 224–227
225
Azides [43] were prepared according to procedures reported in the
literature. The other chemicals were obtained from commercial
suppliers (Aldrich, USA and Shanghai Chemical Company, China)
and used without purification. All organic solvents were dried
using standard methods.
93–97% purity determined by HPLC, which were further purified
by flash silica gel column chromatography eluted with ethyl ace-
tate/hexane to provide pure products 5a–5j for their structure
analyses.
2.4.1. 1-Phenyl-1H-1,2,3-triazole (5a)
Light yellow solid, mp 51–52 °C (52–53 °C [25]); 1H NMR
(400 MHz, CDCl3): d = 8.01 (d, J = 1.0 Hz, 1H), 7.85 (d, J = 1.0 Hz,
1H), 7.77–7.74 (m, 2H), 7.56–7.53 (m, 2H), 7.46–7.44 (m, 1H);
13C NMR (100 MHz, CDCl3): d = 137.6, 135.5, 130.1, 128.9, 122.7,
121.1.
2.2. Preparation of polystyrene-supported 2-phenylsulfonylethanol (2)
Resin 1 (2.0 g, 3.6 mmol) was swollen in a mixture of DMF
(10 mL) and THF (20 mL) by gently shaking the resin–DMF–THF
mixture at room temperature for 30 min. 2-Chloroethanol
(2.4 mL), tetrabutylammonium iodide (0.3 g), and potassium io-
dide (1.8 g) were added to this mixture and the resulting reaction
mixture was shaken at 80 °C under a nitrogen atmosphere for 24 h.
After filtration, the resin was washed successively with DMF, H2O,
CH3OH and ether (2 Â 10 mL of each); and then dried under re-
duced pressure over phosphorous pentoxide at 50–60 °C to afford
resin 2 as yellow beads.
2.4.2. 1-(4-Methylphenyl)-1H-1,2,3-triazole (5b)
White solid, mp 84–85 °C (86 °C [25]); 1H NMR (400 MHz,
CDCl3): d = 7.98 (d, J = 0.9 Hz, 1H), 7.84 (d, J = 0.9 Hz, 1H), 7.62 (d,
J = 8.0 Hz, 2H), 7.30 (d, J = 8.0 Hz, 2H), 2.41 (s, 3H); 13C NMR
(100 MHz, CDCl3): d = 138.5, 134.4, 133.9, 130.1, 121.5, 120.3, 20.9.
For analytical purposes, the 3,5-dinitrobenzoate of resin 2 was
prepared according to the published method [44] by the reaction
of resin 2 (0.5 g) with 3,5-dinitrobenzoyl chloride (0.5 g) in dry
pyridine (10 mL). After being stirred at 80 °C for 1.5 h, the resin
was collected on a filter, washed successively with THF, H2O, CH3-
OH and ether (2 Â 10 mL of each), and dried as previously de-
scribed to yield the corresponding 3,5-dinitrobenzoate resin
(0.64 g) that exhibited a strong carbonyl absorption at 1732 cmÀ1
in its FTIR spectrum.
2.4.3. 1-(4-Methoxyphenyl)-1H-1,2,3-triazole (5c)
White solid, mp 77–79 °C (78–80 °C [25]); 1H NMR (400 MHz,
CDCl3): d = 7.92 (d, J = 0.9 Hz, 1H), 7.84 (d, J = 0.9 Hz, 1H), 7.65 (d,
J = 6.8 Hz, 2H), 7.04 (d, J = 6.8 Hz, 2H), 3.88 (s, 3H); 13C NMR
(100 MHz, CDCl3): d = 160.2, 135.6, 131.0, 122.9, 122.5, 115.0, 55.8.
2.4.4. 1-(4-Chlorophenyl)-1H-1,2,3-triazole (5d)
Light yellow solid, mp 110–112 °C (111–113 °C [25]); 1H NMR
(400 MHz, CDCl3): d = 7.99 (s, 1H), 7.86 (s, 1H), 7.71 (d, J = 8.8 Hz,
2H), 7.51 (d, J = 8.8 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d = 138.7, 134.6, 133.9, 130.0, 121.5, 120.2.
2.3. Preparation of polystyrene-supported vinyl sulfone (3)
Resin 2 (2.0 g) was swollen in THF (30 mL) at 0 °C, and acetic
anhydride (1.3 g, 13.0 mmol) and DBU (3.0 g, 20.0 mmol) were
added. The reaction was shaken at room temperature for 12 h,
and the resin was subsequently collected by filtration, washed
with H2O (2 Â 15 mL), THF/H2O (1:1, 2 Â 10 mL), THF
(2 Â 10 mL), and ether (2 Â 10 mL), and dried in a vacuum over-
night to afford polymer 3 as yellow beads: IR (KBr): v = 2924,
2.4.5. 1-(2-Chlorophenyl)-1H-1,2,3-triazole (5e)
Yellow oil (Yellow oil [26]); 1H NMR (400 MHz, CDCl3): d = 8.05
(s, 1H), 7.86 (s, 1H), 7.62–7.57 (m, 2H), 7.47–7.45 (m, 2H); 13C NMR
(100 MHz, CDCl3): d = 134.6, 133.1, 130.5, 130.3, 128.5, 127.6,
127.3, 125.2.
2855, 1600, 1490, 1450, 1377, 1315, 1147 cmÀ1
.
2.4.6. 1-(4-Fluorophenyl)-1H-1,2,3-triazole (5f)
White solid, mp 63–65 °C ([26]); 1H NMR (400 MHz, CDCl3):
d = 7.94 (d, J = 1.0 Hz, 1H), 7.84 (d, J = 1.0 Hz, 1H), 7.72 (t, 4JHF = 6.8 -
Polymeric 3 was reacted with 5-ethoxy-l,2,3,4-terthydroiso-
quinoline in accordance with the reported method [45] was subse-
quently treated with MeI and diisopropylcthylamine successively
to release N-methyl-5-ethoxy-l,2,3,4-terthydroisoquinoline; the
vinyl functional loading of polymeric 3 based on the amount of
N-methyl-5-ethoxy-l,2,3,4-terthydroisoquinoline was calculated
to be 1.67 mmol/g.
3
Hz, 2H), 7.24 (t, JHF = 8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d = 163.2 (1JCF = 986 Hz), 135.4, 128.5 (4JCF = 13.2 Hz), 124.7
(3JCF = 33.2 Hz), 121.0, 117.2 (2JCF = 86.4 Hz).
2.4.7. 1-(4-Nitrophenyl)-1H-1,2,3-triazole (5g)
Yellow solid, mp 202–204 °C (202–205 °C [25]); 1H NMR
(400 MHz, CDCl3): d = 8.44 (d, J = 8.8 Hz, 2H), 8.14 (s, 1H), 8.01 (d,
J = 8.8 Hz, 2H), 7.93 (s, 1H); 13C NMR (100 MHz, CDCl3): d = 147.5,
141.1, 135.4, 125.6, 121.6, 120.5.
2.4. General procedure for the preparation of 1-monosubstituted 1,2,3-
triazoles (5a–5j)
Azide (3.0 mmol), CuSO4Á5H2O (18.5 mg, 0.05 mmol) and so-
dium ascorbate (50 mg, 0.25 mmol) were added to the suspension
of resin 3 (1.67 mmol, 1.0 g) pre-swollen in CH2Cl2/H2O (1:1,
20 mL), and then shaken at room temperature for 12 h. After which
the resin was collected by filtration, washed with H2O (2 Â 15 mL),
THF/H2O (1:1, 2 Â 10 mL), THF (2 Â 10 mL), CH2Cl2 (2 Â 10 mL)
and ether (2 Â 10 mL), and dried in a vacuum overnight, affording
yellow resin 4. Subsequently, resin 4 was swollen in THF (15 mL)
for 1 h. Then potassium tert-butoxide (0.4 g, 3.5 mmol) was added
to the suspension at 0 °C. The reaction mixture was stirred at the
same temperature for 1 h, and then was warmed to room temper-
ature and shaken for 12 h. After which the resin was filtered and
washed with THF (2 Â 10 mL), THF/H2O (1/1, 2 Â 10 mL), and
H2O (2 Â 10 mL). The combined filtrate and washings were con-
centrated to remove organic solvent, and the residue was extracted
with EtOAc, dried over anhydrous magnesium sulfate, and then
concentrated under reduced pressure to give crude products 5 with
2.4.8. 1-(3-Nitrophenyl)-1H-1,2,3-triazole (5h)
Light yellow solid, mp 114–115 °C (114–116 °C [25]); 1H NMR
(400 MHz, CDCl3): d = 8.63 (t, J = 2.0 Hz, 1H), 8.34–8.31 (m, 1H),
8.22–8.20 (m, 1H), 8.12 (d, J = 1.0 Hz, 1 H), 7.92 (d, J = 1.0 Hz, 1H),
7.78 (t, J = 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3): d = 148.7, 137.8,
135.0, 130.9, 126.2, 123.4, 120.1, 115.5.
2.4.9. (E)-1-Cinnamyl-1H-1,2,3-triazole (5i)
Light yellow solid, mp 45–47 °C; 1H NMR (400 MHz, CDCl3):
d = 7.92 (d, J = 1.0 Hz, 1H), 7.85 (t, J = 14.8 Hz, 1H), 7.43–7.25 (m,
5H), 6.66 (d, J = 15.8 Hz, 1H), 6.34 (dt, J = 15.8, 6.6 Hz, 1H), 5.11
(dd, J = 6.6, 1.2 Hz, 2H); 13C NMR (100 MHz, CDCl3): d = 146.9,
135.5, 134.8, 128.7, 128.5, 126.6, 122.0, 119.2, 52.0. IR (KBr):
v = 3060, 2922, 2854, 1595, 1489, 1445, 1137, 1214, 1052, 961,
773, 747, 690 cmÀ1. Anal. Calcd. for C11H11N3: C, 71.33; H, 5.98;
N, 22.69. Found: C, 71.26; H, 5.90; N, 22.61.

226
Z. Huang et al. / Reactive & Functional Polymers 73 (2013) 224–227
Table 1
2.4.10. 1-Benzyl-1H-1,2,3-triazole (5j)
White solid, mp 51–52 °C (51–53 °C [25]); 1H NMR (400 MHz,
CDCl3): d = 7.72 (s, 1H), 7.47 (s, 1H), 7.40–7.38 (m, 3H), 7.28–7.26
(m, 2H), 5.57 (s, 2H); 13C NMR (100 MHz, CDCl3): d = 134.7,
134.2, 129.0, 128.6, 127.7, 123.5, 53.8.
Yields and purities of 1-monosubstituted 1,2,3-triazoles (5a–5j).
Entry
R
Product
Yielda (%)
Purityb (%)
1
2
3
4
5
6
7
8
9
C6H5
5a
5b
5c
5d
5e
5f
5g
5h
5i
93
93
95
87
81
90
85
88
89
92
97
96
97
95
93
97
94
95
96
96
4-CH3C6H4
4-CH3OC6H4
4-ClC6H4
2-ClC6H4
4-FC6H4
4-NO2C6H4
3-NO2C6H4
(E)-C6H5CH@CHCH2
C6H5CH2
3. Results and discussion
Initially, the procedure for the preparation of polystyrene-
bound vinyl sulfone 3 was investigated. As shown in Scheme 1,
in our preliminary experiments, polystyrene/1% divinylbenzene
sodium sulfinate 1 (1.80 mmol – SO2Na/g) was selected to react
with 2-chloroethanol in DMF–THF (1/2) in the presence of tetrabu-
tylammonium iodide (TBAI) and potassium iodide to afford poly-
styrene-bound 2-phenylsulfonylethanol 2, which was amenable
to FTIR monitoring for the appearance of the expected a large hy-
droxyl stretch at 3500 cmÀ1, as well as the characteristic sulfone
absorption bands at 1317 and 1119 cmÀ1. Encouraged by this posi-
tive result, the other two sodium sulfinate resins with loading of
2.10 and 1.25 mmol–SO2Na/g were further evaluated, respectively.
After several experiments, it was found that quite similar result
was obtained under the same reaction conditions with higher load-
ing resin 1, but it is expensive relatively comparing with the resin 1
with 1.80 mmol/g loading. When using lower loading resin 1, its
lower activity was observed, the similar reaction generated the de-
sired product in a lower yield with longer reaction time. The hy-
droxyl group attachment on the resin 2 was calculated to be
1.65 mmol–CH2CH2OH/g from the nitrogen elemental analysis of
its corresponding 3,5-dinitrobenzoate ester intermediate prepared
by treatment of 2 with 3,5-dinitrobenzoyl chloride according to the
method described in literature [44]. Polystyrene-bound vinyl sul-
fone 3 was then obtained in near quantitative yield from 2-hydro-
xy sulfone resin 2 by acetylation followed by in situ elimination in
the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). It
should be noted that reaction 2 ? 3 was not amenable to FTIR
analysis, nevertheless, the complete conversion of the hydroxy
group of resin 2–3 was further confirmed by treating 3 with acetyl
chloride/triethylamine: no acetoxy absorption band was observed
in the FTIR spectrum of the product. On the other hand, the loading
of vinyl functional group of resin 3 was determined to be
1.67 mmol/g following the published protocol [45].
10
5j
a
Overall isolated yields based on polystyrene-supported vinyl sulfone 3.
Determined by HPLC of crude cleavage product.
b
absorption peaks in the FTIR spectra, the elimination release step
was undertaken. After a number of basic (Et3N, DBU and t-BuOK)
elimination conditions were evaluated, and optimal results were
obtained by treating resin 4 with potassium tert-butoxide in THF
at room temperature for 12 h to afford 1-monosubstituted 1,2,3-
triazoles 5a–5j. The results are summarized in Table 1. As can be
observed in Table 1, aryl azides carrying either an electron donat-
ing substituent, such as methyl and methoxy (Table 1, entries 2
and 3) or an electron with drawing group including halogens (Ta-
ble 1, entries 4–6) and nitro (Table 1, entries 7 and 8) could per-
form efficiently with good to excellent yields. However, aryl
azides bearing an ortho-substituent (e.g., the chloro group) (Table
1, entry 5) showed a slight decrease in yield (81%) due to the steric
hindrance. For other substrates such as (E)-cinnamyl azide and
benzyl azide, higher yields were obtained (Table 1, entries 9 and
10). It should be noted that, besides of good isolated yields of the
target compounds 5a–5j (Table 1), HPLC analysis of the crude prod-
ucts cleaved from the resin directly indicated their high purities in
all cases (93–97%). The impurities included in the cleavage prod-
ucts may be generated from the possible side reactions or the
residual trace reactants embedded in the resins in the reactions.
4. Conclusions
We have developed a facile protocol for the traceless solid-phase
synthesis of 1-monosubstituted 1,2,3-triazoles by 1,3-dipolar
cycloaddition reaction of polystyrene-bound vinyl sulfone with
azides, and subsequent elimination reaction. This method provides
a novel access to 1-monosubstituted aryl-, alkyl- and vinyl-1,2,3-
triazoles respectively in good yields and purities with simplification
of product work-up, which are important heterocycle compounds
in medicinal chemistry and materials science. Further studies on
the application of the present methodology to the synthesis of
biological active compounds are proceeding.
Secondly, the construction of the triazolyl heterocycles using
polystyrene-bound vinyl sulfone 3 was further examined. As illus-
trated in Scheme 2, azides were also found to undergo 1,3-dipolar
cycloadditions with resin 3 smoothly in the presence of CuSO4Á5H2-
O and sodium ascorbate in CH2Cl2/H2O (1/1) with the solution-
phase method established [46] at room temperature to form resin
4. Since this transformation exhibited no reliably diagnostic
Scheme 1. Preparation of polystyrene-bound vinyl sulfone 3.
Scheme 2. SOPS of 1-monosubstituted 1,2,3-triazoles 5a–5j.

Z. Huang et al. / Reactive & Functional Polymers 73 (2013) 224–227
227
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