D-Glucosamine as a green ligand for copper catalyzed synthesis of aryl sulfones from aryl halides and sodium sulfinates

Article abstract of DOI:10.1039/c4ra03187c

d-Glucosamine is reported for the first time as a green ligand for copper catalyzed coupling of aryl halides and sodium sulfinates, which provides a simple and extremely efficient new route to unsymmetrical diaryl sulfones. The catalytic reaction proceeded in DMSO-H₂O at 100°C and gave a variety of aryl sulfones in high yields. The high water solubility of the ligand enables easy catalyst removal. The scope of the method was validated by a single step synthesis of marketed drug zolimidine, a drug used for peptic ulcers, in 65% yield.

Full text of DOI:10.1039/c4ra03187c

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D-Glucosamine as a green ligand for copper
catalyzed synthesis of aryl sulfones from aryl
Cite this: RSC Adv., 2014, 4, 26295
halides and sodium sulfinates†
a
Ming Yang,a Hongyun Shen,a Yuanyuan Li,a Chao Shenab and Pengfei Zhang
Received 9th April 2014
Accepted 4th June 2014
*
DOI: 10.1039/c4ra03187c
www.rsc.org/advances
D-Glucosamine is reported for the first time as a green ligand for
The wide usefulness of compounds containing this skeleton
copper catalyzed coupling of aryl halides and sodium sulfinates, which has resulted in the development of synthetic methodologies to
provides a simple and extremely efficient new route to unsymmetrical construct them and until now various methods have been
diaryl sulfones. The catalytic reaction proceeded in DMSO–H2O at 100 developed for synthesizing aryl sulfones, such as: (i) a nucleo-
ꢀC and gave a variety of aryl sulfones in high yields. The high water phile substitution reaction of halide with thiol, followed by
solubility of the ligand enables easy catalyst removal. The scope of the oxidation of the corresponding sulde;3 (ii) Pd- or Cu-catalyzed
method was validated by a single step synthesis of marketed drug coupling reactions between sodium sulnates and aryl halides
zolimidine, a drug used for peptic ulcers, in 65% yield.
or aryl boronic acids have been developed as a milder alterna-
tive.4 (iii) Sulfonylation of heterocycles with aryl sulfonyl chlo-
rides via metal-catalyzed C–H bonds activation;5 (iv) one-pot
synthesis of vinyl sulfones from terminal epoxides and sodium
sulnates.6 Although a number of modications on the
synthesis of aryl sulfones were developed,7 the drawbacks are
the use of expensive phosphine ligand, harsh reaction condi-
tions, multi-step processes, and low yields in the most of the
cases. Meanwhile, to separate the catalyst from the product by a
distillation process aer the reaction is complicated and may
result in the decomposition of the catalyst or formation of by-
products. In addition, many methodologies exhibit poor func-
tional group tolerance or generate large quantities of hazardous
waste. To resolve this problem, many catalysts have been widely
developed,8 while the rapid assembly and exible modication
of structurally diverse ligand systems by simple synthetic
methods are still important for the development of effective
catalysts for the widespread applications of coupling reactions.
Carbohydrates are one of the most naturally abundant bio-
organic molecules which have been widely used in organic
synthesis.9 They represent excellent tools as chiral auxiliaries,
reagents, organocatalysts and ligands for asymmetric
synthesis,10 as carbohydrates can be easily functionalized to
provide efficient catalysts, which are applicable in a large
number of catalytic asymmetric reactions.11 Some mono-
saccharide molecules have generated signicant attention for
their green and essential roles in transition metal catalyzed
reactions.12 However, their effect is still unclear. To this purpose
and continuing our longstanding interest in developing novel
C–S bond-forming reactions for the efficient construction of
hetero-cyclic frameworks,13 we embarked on the development of
Introduction
The sulfones, as the key structural skeletal framework of many
natural products and pharmaceuticals, have attracted consid-
erable interest because of their important biologically active
properties.1 Particularly, aryl sulfones show various pharmaco-
logical properties such as anti-tumor, anti-inammatory, and
anti-fungal activities, or to inhibit HIV-1 reverse transcriptase.2
Recently, aryl sulfones scaffolds were incorporated in some
commercially available drugs such as Bicalutamide (Casodex)
(for the treatment of prostate cancer), zolimidine (used for the
treatment of peptic ulcer), Eletriptan (antimigraine medicine)
(Fig. 1).
Fig. 1 Aryl sulfones-containing drugs.
aCollege of Material, Chemistry and Chemical Engineering, Hangzhou Normal
University, Hangzhou 310036, China. E-mail: chxyzpf@hotmail.com; Fax: +86-571-
28862867; Tel: +86-571-28862867
bCollege of Biology and Environmental Engineering, Zhejiang Shuren University,
Hangzhou 310015, China
† Electronic supplementary information (ESI) available: 1H NMR spectra, 13C
NMR spectrum, GC/MS prole, HRMS prole. See DOI: 10.1039/c4ra03187c
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Table 1 Optimization of reaction conditionsa
C–S bond formation under mild condition. Herein, we describe
an efficient catalytic system for the cross-coupling of a wide
range of aryl halides with sodium benzenesulfonates using D-
glucosamine as a green ligand.
Results and discussion
Entry TM salt Solvent–H2O (1 : 1) Base
Temp. [ꢀC] Yieldb (%)
First, 4-iodoanisole (1a) and sodium benzensulnate (2a) was
chosen as a model and screened a series of ligands under the
conditions of 10 mol% CuI, 20 mol% ligand, K2CO3 as the base
and DMSO–H2O (1 : 1) mixture as the solvent at 100 ꢀC for 24 h.
In the very rst reaction, D-glucose L1 was used as ligand and
this condition gave the desired product in 31% yield. This
encouraged us to continue the screening using other mono-
saccharide molecules as ligands (Fig. 2). Out of all the ligands
screened, D-glucosamine L5 provided 55% as the maximum
yield of the product. Surprisingly, it was found that mono-
saccharide-based ligands gave a better result than several
conventional ligands such as 2-aminopyridine (L9), 1,2-phen-
ylene diamine (L10), L-proline (L11), ethane-1,2-diamine (L12),
1,10-phenanthroline (L13), which are very well known in the
literature of coupling chemistry.
Next, several organic solvent–H2O (1 : 1) mixtures, bases,
catalyst loading and temperatures were screened for this reac-
tion. Further experimentations revealed that this C–S cross-
coupling reaction was effective in polar aprotic organic solvent–
H2O (1 : 1) mixtures such as DMSO and DMF (Table 1, entries
1 and 2). In stark contrast, the coupling reaction proceeded less
efficiently in nonpolar solvent such as 1,4-dioxane and toluene
(Table 1, entries 3 and 4). While trying the reaction using only
water as solvent, no product was obtained. Notably, the reac-
tions through use of strong bases, including Na2CO3, Cs2CO3,
KOH, and NaOH, occurred with low reaction conversions (Table
1, entries 6, 7, 10, 11). The reaction with KOAc as the base
resulted in the formation of 3a in 93% yield (Table 1, entry 8).
While checking the minimum requirement of catalyst loading
for the best performance of the reaction, it has been found that
10 mol% of CuI and 20 mol% of L5 is the optimal catalyst
1
2
3
4
5
6
7
8
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
None
CuBr
CuBr2
DMSO
DMF
Toluene
1,4-Dioxane
H2O
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
K2CO3 100
55
50
6
Trace
Trace
23
K2CO3 100
K2CO3 100
K2CO3 100
K2CO3 100
Na2CO3 100
Cs2CO3 100
20
KOAc
K3PO4 100
KOH 100
NaOH 100
100
93 (78)c
17
9
10
11
12
13
14
15
16
17
18
19
20
Trace
Trace
30
93
0
25
71
75
33
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
80
110
110
100
100
100
100
120
110
Cu(OAc)2 DMSO
Cu(OTf)2 DMSO
Pd(OAc)2 DMSO
12
Trace
AgOAc
DMSO
a
Reaction conditions: CuI (0.1 mmol), D-glucosamine L5 (0.2 mmol),
4-iodoanisole 1a (1 mmol), sodium benzenesulfonate 2a (1.2 mmol),
base (2.0 mmol), solvent: H2O (4 mL 1 : 1), 100 ꢀC under air.
b
Isolated yield. c 10 mol% of D-glucosamine L5 was used.
requirement. On either decreasing the catalyst loading, the
yield of the product got affected. For example, when 10 mol% of
L5 was used, only 78% yield was achieved. When the reaction
was performed at 80 ꢀC, the reaction was found to be inefficient
(Table 1, entry 12).
At last, several Cu, Pd or Ag salts such as CuBr, Cu(OAc)2,
Pd(OAc)2 and AgOAc were screened for this coupling reaction.
No C–S coupling product was obtained when the reaction was
carried out without ligand L5 (Table 1, entry 14). This result
clearly shows that ligand L5 is necessary for the best perfor-
mance of the coupling reaction. It was found that CuI gave the
best result and Cu salts generally showed better reactivity than
Pd and Ag salts (Table 1, entries 15–20).
Aer optimizing all parameters such as ligand, solvent, base,
catalyst loading, temperature and metal-salt, we initiated our
investigation into the scope of the D-glucosamine L5 catalyzed
coupling of aryl halides and sodium benzenesulfonate and the
results are summarized in Table 2. Many valuable functional
groups such as hydroxyl-, carbonyl-, chloro-, and tri-
uoromethyl groups were well tolerated. Substrates containing
either an electron donating (Table 2, entries 1 and 2) or with-
drawing group (Table 2, entries 3–6) at the para-position showed
similar reactivity to the parent 3a. Furthermore, substituents at
meta-, or ortho-positions of the benzene ring do not affect the
efficiency of this transformation (76–92%, Table 2, entries 7–9).
Fig. 2 Optimization and comparison of reactivity between mono-
saccharide ligands and conventional ligands in aryl sulfones synthesis.
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Table 2 Reaction between aryl halides and sodium sulfinatesa
The recyclability of the catalyst was then studied in the C–S
coupling reaction and the results are shown in Table 3. In the
recycling experiment, the separated catalyst was recharged with
fresh substrate for the next run under the same reaction
conditions. The results show that good yield can be obtained
aer second cycle (Table 3, run 2) and the reaction yield
continue to decrease for the next cycle. We speculated that the
good solubility of ligand in water is the main cause of yield
decrease and additional work aimed at improving the recycla-
bility of the ligand will be continued.
Entry
Ar
X
R
Yieldb (%)
1
2
3
4
5
6
7
8
Ar ¼ p-Me-C6H4
Ar ¼ p-HO-C6H4
Ar ¼ p-Cl-C6H4
Ar ¼ p-NO2-C6H4
Ar ¼ p-CF3-C6H4
Ar ¼ p-CH3CO-C6H4
Ar ¼ m-NO2-C6H4
Ar ¼ o-Me-C6H4
Ar ¼ o-MeCOO-C6H4
Ar ¼ Ph
I
I
I
I
I
I
I
I
I
I
Br
I
I
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
p-Me-C6H4
p-Cl-C6H4
Me
94(3b)
90(3c)
86(3d)
88(3e)
92(3f)
75(3g)
87(3h)
76(3i)
92(3j)
96(3k)
72(3k)c
95(3b)
80(3d)
97(3l)
With this methodology in hand, we turned our attention to
the synthesis of zolimidine,14 a drug used for peptic ulcers, in a
single step (Scheme 2). When 2-(4-iodophenyl)imidazo[1,2-a]-
pyridine (1.0 mmol) was treated with sodium methanesulnate
(1.2 mmol) in the presence of 10 mol% of CuI and 20 mol% of
D-glucosamine in DMSO–H2O at 120 ꢀC for 24 h, zolimidine was
isolated in 65% yield.
9
10
11
12
13
14
Based on the results of experiments and literatures,4
a
Ar ¼ Ph
plausible mechanism for the green and practical method to
construct aryl sulfones is illustrated in Fig. 3. Initially, under
alkaline conditions CuI electrophilic attack at the 1-OH and
2-NH2 of the D-glucosamine afforded intermediate (A), a
Ar ¼ Ph
Ar ¼ Ph
Ar ¼ Ph
I
a
Reaction conditions: CuI (0.1 mmol), D-glucosamine (0.2 mmol), 1b–h
(1 mmol), 2a–d (1.2 mmol), KOAc (2.0 mmol), DMSO : H2O (4 mL 1 : 1),
100 ꢀC under air. b Isolated yield. c 120 ꢀC, 48 h.
Table 3 Catalyst recycling for C–S coupling reactiona
We also found that the aryl bromides worked well in our
reaction condition although higher reaction temperature and
longer reaction time were required in comparison with aryl
iodides (Table 2, entry 11). Both aryl sulnates and alkyl sul-
nates afforded sulfones in excellent yields (Table 2, entries
12–14). It seemed that the reactivity was inuenced by the
nucleophilic ability of sulnates. In addition, we found sul-
nates with electron-donating group on the benzene ring per-
formed better than those with electron-withdrawing group
(entry 12 vs. entry 13).
Run
1
2
3
4
5
Yield (%)
93
85
77
70
65
a
Reaction conditions: see Table 1, entry 8. The catalyst was recovered by
simple ltration aer reaction.
To test the feasibility of a large-scale reaction, the reaction of
4-iodoanisole (1a) (25 mmol) and sodium benzenesulnate (2a)
(30 mmol) was investigated. The reaction could afford 5.58 g of
3a in 90% yield aer recrystallization (Scheme 1). Therefore,
this protocol could be used as a practical method to synthesize
the precursors of some important bioactive molecules. Next the
recyclability of catalyst was subsequently tested. Aer comple-
tion of the reaction under the optimal conditions reaction,
taking advantage of the good solubility of products and the
insolubility of catalyst in solvent, so a simple ltration was
sufficient to separate the catalyst solution from the products.
Scheme 2 One-step synthesis of zolimidine.
Scheme 1 Large-scale reaction: 1a (25 mmol), 2a (30 mmol), DMSO–
H2O (1 : 1, 100 mL), KOAc (50 mmol), 100 ꢀC, 24 h. Isolated yield after
recrystallization.
Fig. 3 A plausible mechanism.
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subsequent oxidative addition process results in formation of
intermediate (B), nucleophilic displacement of halogen to give
an intermediate (C) by reductive elimination with the regener-
ation of the intermediate (A) and provided the target product.
General procedure for the catalyst recycling experiment
To check if the catalyst is recyclable, the C–S coupling reaction
was repeated ve times with the same catalyst sample, which
was recovered aer each reaction. Aer completion of the
reaction under the optimal conditions reaction, a simple
ltration was sufficient to separate the catalyst solution from
the products when the reaction was cool down. The catalyst was
washed with ethyl acetate twice and was dried for 6 h at 75 C.
Then the separated catalyst was recharged with fresh substrate
for the next run under the same reaction conditions.
Conclusions
ꢀ
To the best of our knowledge, this is the rst example of using
D-glucosamine as a green ligand for copper catalyzed coupling
of aryl halides and sodium sulnates. The methodology can
tolerate many important functional groups, including those
containing ether, ester, and nitro groups, and we anticipate that
it will nd wide applicability due to its simple operating
procedure. By using this protocol, the marketed drug zolimi-
dine (antiulcer) could be easily synthesized in a concise route.
Further studies to clearly understand the reaction mechanism
and the synthetic applications are ongoing in our laboratory.
Selected spectral data of the products
1-(4-Methoxyphenylsulfonyl)benzene 3a. White solid; m.p.:
90–91 ꢀC. 1H NMR (400 MHz, CDCl3): d 7.85–7.79 (m, 4H), 7.46–
7.41 (m, 3H), 6.90–6.88 (m, 2H), 3.77 (s, 3H). 13C NMR (100 MHz,
CDCl3): d 162.4, 141.3, 131.8, 128.9, 128.2, 126.3, 113.5, 54.6.
GC-MS (EI) [M]+: m/z calcd for C13H12O3S: 248.0, found: 248.
1-(p-Tolylsulfonyl)benzene 3b. White solid; m.p.: 125–127
1
ꢀC. H NMR (400 MHz, CDCl3): d 7.87–7.85 (m, 2H), 7.77–7.75
Experimental section
General information
(m, 2H), 7.48–7.40 (m, 3H), 7.23 (d, J ¼ 8.0 Hz, 2H), 2.32 (s, 3H).
13C NMR (100 MHz, CDCl3): d 143.1, 140.9, 137.5, 131.9, 128.9,
128.2, 126.6, 126.4, 20.5. GC-MS (EI) [M]+: m/z calcd for
The starting materials were commercially available and were
used without further purication except solvents. The products
were isolated by column chromatography on silica gel (200–300
mesh) using petroleum ether (60–90 ꢀC) and ethyl acetate.
Melting points were determined on an X-5 Data microscopic
C
13H12O2S: 232.0, found: 232.
4-(Benzenesulfonyl)phenol 3c. Brown solid; m.p.: 135–137
ꢀC. 1H NMR (400 MHz, CDCl3): d 6.51 (br s, 1H), 6.92 (d, J ¼ 8.0
Hz, 2H), 7.56–7.47 (m, 3H), 7.82 (d, J ¼ 8.0 Hz, 2H), 7.91 (d, J ¼
8.0 Hz, 2H). 13C NMR (100 MHz, CDCl3): d 159.2, 131.8, 129.1,
128.1, 126.2, 115.0. GC-MS (EI) [M]+: m/z calcd for C12H10O3S:
234.0, found: 234.
1
melting point apparatus. H NMR and 13C NMR spectra were
recorded on a Bruker Advance 400 spectrometer at ambient
temperature with CDCl3 or DMSO-d6 as solvent unless other-
wise noted and tetramethylsilane (TMS) as the internal stan-
dard. 1H NMR data were reported as follows: chemical shi
(d ppm), multiplicity (s ¼ singlet, d ¼ doublet, t ¼ triplet, q ¼
quartet, dd ¼ double–doublet, m ¼ multiplet and br ¼ broad),
coupling constant (J values, Hz). 13C NMR data were reported in
terms of chemical shi (d ppm). Mass spectra (EI-MS) were
acquired on an Agilent 5975 spectrometer. Analytical thin layer
chromatography (TLC) was performed on Merck precoated TLC
(silica gel 60 F254) plates.
1-(4-Chlorophenylsulfonyl)benzene 3d. White solid; m.p.:
96–97 ꢀC. 1H NMR (400 MHz, CDCl3): d 7.95–7.88 (m, 4H), 7.60–
7.46 (m, 5H). 13C NMR (100 MHz, CDCl3): d 141.1, 140.0, 139.8,
133.4, 129.6, 129.4, 129.1, 127.6. GC-MS (EI) [M]+: m/z calcd for
C
12H9ClO2S: 252.0, found: 252.
1-(4-Nitrophenylsulfonyl)benzene 3e. Yellow solid; m.p.:
1
143–145 ꢀC. H NMR (400 MHz, CDCl3): d 8.36–8.34 (m, 2H),
8.15–8.13 (m, 2H), 7.99–7.97 (m, 2H), 7.67–7.63 (m, 1H), 7.61–
7.55 (m, 2H). 13C NMR (100 MHz, CDCl3): d 150.3, 147.3, 140.0,
134.1, 129.7, 128.9, 128.0, 124.5. GC-MS (EI) [M]+: m/z calcd for
C
12H9NO4S: 263.0, found: 263.
1-(Triuoromethyl)-4-(phenylsulfonyl)benzene 3f. White
General procedure for CuI-catalyzed coupling of aryl halides
and sodium sulnates
solid; m.p.: 90–91 ꢀC. 1H NMR (400 MHz, CDCl3): d 8.07 (d, J ¼
A mixture of aryl halide (1 mmol), sodium benzenesulfonate 6.8 Hz, 2H), 8.99–7.98 (m, 2H), 7.78 (d, J ¼ 6.8 Hz, 2H), 7.64–7.54
(1.2 mmol), copper iodide (0.1 mmol), D-glucosamine (m, 3H). 13C NMR (100 MHz, CDCl3): d 145.3, 140.6, 133.7, 129.5,
(0.2 mmol), and 4 mL of DMSO–H2O (1 : 1) in a sealed tube was 128.2, 127.9, 126.4, 126.4, 126.3. GC-MS (EI) [M]+: m/z calcd for
heated to 100 ꢀC under air. The cooled mixture was partitioned
between ethyl acetate and water. The organic layer was sepa-
C
13H9F3O2S: 286.0, found: 286.
1-(4-(Phenylsulfonyl)phenyl)ethanone 3g. White solid; m.p.:
1
ꢀ
rated, and the aqueous layer was extracted with ethyl acetate 97–99 C. H NMR (400 MHz, CDCl3): d 8.07 (m, 4H), 7.97 (m,
twice. The combined organic layers were washed with brine, 2H), 7.61 (m, 1H), 7.54 (m, 2H). 13C NMR (100 MHz, CDCl3): d
dried over MgSO4, and concentrated in vacuo. Aer drying with 196.7, 145.4, 140.7, 140.3, 133.6, 130.9, 129.4, 129.0, 128.0,
anhydrous MgSO4 overnight, the liquid was analyzed by GC-MS. 127.8, 115.3, 26.8. GC-MS (EI) [M]+: m/z calcd for C14H12O3S:
The residue was concentrated under reduced pressure to afford 260.0, found: 260.
the desired product without further purication. All
3-Nitrol-(phenylsulfonyl)benzene 3h. Yellow solid; m.p.:
1
compounds were characterized by 1H NMR, 13C NMR and mass 163–165 ꢀC. H NMR (400 MHz, CDCl3): d 8.36–8.24 (m, 2H),
spectroscopy, which are consistent with those reported in the 8.15–8.13 (m, 2H), 7.99–7.97 (m, 2H), 7.67–7.63 (m, 1H), 7.61–
literature.3,4
7.55 (m, 2H). 13C NMR (100 MHz, CDCl3): d 147.3, 142.9, 139.0,
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133.0, 132.0, 129.7, 128.7, 126.9, 126.6, 121.9. GC-MS (EI) [M]+:
m/z calcd for C12H9NO4S: 263.0, found: 263.
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1-Methyl-2-(phenylsulfonyl)benzene 3i. White solid; m.p.:
73–75 ꢀC. 1H NMR (400 MHz, CDCl3): d 8.24 (dd, J ¼ 0.8, 0.8 Hz,
1H), 7.90 (m, 2H), 7.61–7.49 (m, 4H), 7.44–7.41 (m, 1H), 7.25 (d,
J ¼ 6 Hz, 1H), 2.47 (s, 3H). 13C NMR (100 MHz, CDCl3): d 141.4,
138.9, 138.0, 133.5, 132.9, 132.6, 129.4, 129.0, 127.6, 126.4, 20.1.
GC-MS (EI) [M]+: m/z calcd for C13H12O2S: 232.0, found: 232.
Methyl 2-(phenylsulfonyl)benzoate 3j. White solid; m.p.: 88–
90 ꢀC. 1H NMR (400 MHz, CDCl3): d 8.18 (m, 1H), 7.98 (m, 2H),
7.65–7.52 (m, 6H), 3.94 (s, 3H). 13C NMR (100 MHz, CDCl3): d
167.7, 141.4, 138.9, 133.4, 133.3, 133.2, 130.9, 130.2, 129.2,
129.0, 127.8, 53.1. GC-MS (EI) [M]+: m/z calcd for C14H12O4S:
276.0, found: 276.
1-(Phenylsulfonyl)benzene 3k. White solid; m.p.: 122–124 ꢀC.
1H NMR (400 MHz, CDCl3): d 7.97–7.96 (m, 4H), 7.59–7.50 (m,
6H). 13C NMR (100 MHz, CDCl3): d 141.7, 133.1, 129.2, 127.6.
GC-MS (EI) [M]+: m/z calcd for C12H10O2S: 218.0, found: 218.
4-(Methanesulfonyl)benzene 3l. White solid; m.p.: 90–91 ꢀC.
1H NMR (400 MHz, CDCl3): d 7.94–7.92 (m, 2H), 7.64–7.62 (m,
1H), 7.57–7.54 (m, 2H), 3.04 (s, 3H). 13C NMR (100 MHz, CDCl3):
d 140.6, 133.6, 129.3, 127.2, 44.4. GC-MS (EI) [M]+: m/z calcd for
C7H8O2S: 156.0, found: 156.
Zolimidine. Yellowish white solid; 1H NMR (400 MHz,
CDCl3): d 8.17–8.15 (m, 3H), 8.03–7.97 (m, 3H), 7.73 (d, J ¼ 9.2
Hz, 1H), 7.31–7.29 (m, 1H), 6.89 (t, J ¼ 5.6 Hz, 1H). 13C NMR (100
MHz, CDCl3): d 145.4, 142.6, 139.6, 127.9, 126.7, 126.3, 126.0,
117.4, 113.5, 109.8, 44.5. GC-MS (EI) [M]+: m/z calcd for
C
14H12N2O2S: 272.0, found: 272.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (no. 21376058, 21302171), Zhejiang
Provincial Natural Science Foundation of China (no.
LZ13B020001) and Major scientic and technological innova-
tion projects of Hangzhou City (no. 20122511A43).
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