Recyclable nano copper oxide catalyzed stereoselective synthesis of vinyl sulfides under ligand-free conditions

Article abstract of DOI:10.1055/s-0029-1217990

A simple and efficient protocol for the cross-coupling of vinyl halides with thiols catalyzed by recyclable CuO nanoparticles under ligand-free conditions is reported. This methodology results in the synthesis of a variety of vinyl sulfides in excellent y

Full text of DOI:10.1055/s-0029-1217990

LETTER
2783
Recyclable Nano Copper Oxide Catalyzed Stereoselective Synthesis of Vinyl
Sulfides under Ligand-Free Conditions
L
igand-Free Stereo
u
selective
S
y
t
nthesis
u
of
V
inyl Sul
k
fides uri Prakash Reddy, Kokkirala Swapna, Akkilagunta Vijay Kumar, Kakulapati Rama Rao*
Organic Chemistry Divison-I, Indian Institute of Chemical Technology, Hyderabad-500 607, India
E-mail: kakulapatirama@gmail.com
Received 3 June 2009
free conditions (Scheme 1). To the best of our knowledge,
Abstract: A simple and efficient protocol for the cross-coupling of
vinyl halides with thiols catalyzed by recyclable CuO nanoparticles
under ligand-free conditions is reported. This methodology results
in the synthesis of a variety of vinyl sulfides in excellent yields with
retention of stereochemistry.
this is the first cross-coupling of vinyl halides with thiols
using CuO nanoparticles as recyclable catalysts in the ab-
sence of any external ligand for the synthesis of vinyl sul-
fides.
Key words: vinyl halides, thiols, vinyl sulfides, ligand free, nano-
crystalline copper oxide
I
SH
CuO (1.5 mol%)
S
+
DMSO (2.0 mL)
KOH (1.5 equiv)
80 °C
Vinyl sulfides are found in many biologically active mol-
ecules and have a broad range of applications in organic
synthesis.1 In particular, vinyl sulfides are utilized as
equivalents of carbonyl compounds,2 Michael acceptors,3
etc.4–6 In view of their significance, several useful strate-
gies have been developed for the synthesis of vinyl sul-
fides over the past decades.7–12 Notable amongst them is
the well defined copper complex [Cu(phen)(PPh3)2]NO3
system developed by Venkataraman et al. for the synthe-
sis of vinyl sulfides in toluene.7 Recently, Cook and co-
workers synthesized vinyl sulfides using copper iodide as
the catalyst and cis-1,2-cyclohexanediol as external
ligand in DMF.13
Scheme 1 CuO nanoparticles catalyzed synthesis of vinyl sulfides
The reaction conditions were optimized using the cross-
coupling of trans-b-iodostyrene and benzene thiol as an
example. In the first instance, the impact of catalyst load-
ing on the yield of the product was evaluated. It was ob-
served that 1.5 mol% of copper oxide gave the optimum
yield (Table 1).
Table 1 Screening of CuO for Vinyl Sulfides Synthesisa
Entry
CuO (mol%)
Yield (%)
Although various reported methods are effective for the
synthesis of vinyl sulfides, most of these metal-catalyzed
reactions involve expensive and moisture-sensitive cata-
lytic systems and ligands, and metal-contamination of the
final product and non recyclability of the catalyst can be
problematic, thus increasing the cost and limiting the
scope of applications. Hence, it is desirable to develop an
1
2
3
4
0.5
1.0
1.5
2.0
61
80
98
98
a Reaction conditions: trans-b-iodostyrene (1.0 mmol), benzenethiol
inexpensive, environmentally benign and recyclable cata- (1.0 mmol), CuO (1.5 mol%), KOH (1.5 equiv), DMSO (2.0 mL),
lytic system for efficient access to such highly useful or-
80 °C, 4 h.
ganic compounds under ligand-free conditions.
Recently, heterogeneous catalysts have become attractive Next, we investigated the effect of the base and solvent on
from both economic and industrial points of view as com- the synthesis of the vinyl sulfides. Amongst the bases test-
pared to homogeneous catalysts. In general, nanoscale ed, KOH was found to be excellent; other bases such as
heterogeneous catalysts offer higher surface area and low- K3PO4, Cs2CO3, and K2CO3 were also effective but the
er coordinating sites, which are responsible for the higher yields were not as encouraging.
catalytic activity.14 Furthermore, heterogeneous catalysis
Among various solvents tested, DMSO yielded the best
has the advantage of high atom-efficiency, easy product
results, whereas DMF gave the products in moderate
purification, and reusability of the catalyst.
yields and solvents such as water and toluene were inef-
In a continuation of our interest in the field of cross- fective (Table 2). The reaction, when conducted at room
coupling reactions,15 we report, herein, the CuO nanopar- temperature and 50 °C, gave very low yields, but proceed-
ticle catalyzed synthesis of vinyl sulfides under ligand ed smoothly at 80 °C; the results obtained at 100 °C were
similar (Table 2).
SYNLETT 2009, No. 17, pp 2783–2788
Advanced online publication: 24.09.2009
DOI: 10.1055/s-0029-1217990; Art ID: G16409ST
x
x
.x
x
.2
0
0
9
The reaction was then screened with several metal nano-
oxides as catalysts for the synthesis of vinyl sulfides; the
© Georg Thieme Verlag Stuttgart · New York

2784
V. P. Reddy et al.
LETTER
Table 2 Cross-Coupling of Benzene Thiol with trans-b-Iodostyrenea
Table 3 Effect of Catalysts on the Synthesis of Vinyl Sulfidesa
I
S
Entry
1
Base
Solvent
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
Toluene
DMSO
DMF
Yield (%)b
catalyst
R
+
RSH
DMSO, KOH
K3PO4
K2CO3
KOH
KOH
79
61
97
25c
69d
97e
0
Entry
Thiol
Catalyst
Time (h) Yield (%)b
2
1
2
3
4
5
6
7
8
9
nano-ZnO
nano-Bi2O3
nano-In2O3
nano-Sb2O3
nano-Co3O4
nano-CuO
nano-Fe2O3
nano-NiO
CuO
15
15
15
15
15
4
15
15
15
24
79
75
89
85
86
97
85
90
64
SH
3
4
5
KOH
6
KOH
7
Cs2CO3
Cs2CO3
K3PO4
K2CO3
K3PO4
KOH
10
–
0c
8
63
51
0
9
a Reaction conditions: trans-b-iodostyrene (1.0 mmol), thiol (1.0
mmol), catalyst (1.5 mol%), KOH (1.5 equiv), DMSO (2.0 mL),
10
11
12
13
14
15
16
Toluene
Toluene
Toluene
DMF
80 °C.
b Isolated yield.
0
c In the absence of metal catalyst.
trace
79
trace
0
pled trans-b-iodostyrene having electron-rich, electron-
neutral and electron-deficient groups with thiols to pro-
duce the corresponding products in excellent yields
(Table 4, entries 1–9). Utilizing these conditions, various
aliphatic thiols were reacted with trans-b-iodostyrenes
(Table 4, entries 10–11) to give the corresponding vinyl
sulfides in very good yields.
KOH
K2CO3
KOH
DMF
H2O
none
DMSO
0
a Reaction conditions: trans-b-iodostyrene (1.0 mmol), benzenethiol
(1.0 mmol), CuO (1.5 mol%), base (1.5 equiv), solvent (2.0 mL),
Vinyl bromides were also found to be reactive for the
cross-coupling (Table 5). However, the coupling reaction
of various benzene thiols with vinyl bromides required
longer reaction times in order to get reasonable yields of
vinyl sulfides, whereas shorter reaction times led to de-
creased yields (Table 5, entries 1 and 2).
80 °C, 4 h.
b Isolated yield.
c At r.t.
d At 50 °C.
e At 100 °C
When this protocol was applied to the cross-coupling of
alkyl vinyl iodides with different thiols, the corresponding
vinyl sulfides were obtained in excellent yields (Table 6,
entries 1–3). Furthermore, the stereochemistry of the vi-
nyl sulfides was retained in all the cases.
results are summarized in Table 3. The combination of
nano-CuO with KOH in DMSO provided the best results
(Table 3, entry 6). However, the coupling reaction with
ordinary CuO required longer reaction times and gave the
product in only moderate yield (64%). While reactions
with other metal oxide nanoparticles, such as ZnO, Bi2O3,
In2O3, Sb2O3, Co3O4, Fe2O3, and NiO required longer
reaction times to produce significant amounts of vinyl
sulfides.
The recyclability of the catalyst was checked using the
coupling of trans-b-iodostyrene with benzene thiol as the
model reaction. After each cycle, the catalyst was recov-
ered by simple centrifugation, washing with ethyl acetate
and then drying in vacuo. The recovered nano-CuO was
used directly in the next cycle. The recycling results are
listed in Table 7 and show that the yields of vinyl sulfides
after three to four cycles were fairly good.
In the absence of metal oxide nanoparticles, the reaction
did not yield any C–S cross-coupling product (Table 3,
entry10). The yields were highly dependent upon the
reaction temperature, base, solvent and the catalyst. The
optimum reaction conditions for the synthesis of vinyl sul-
fides were found to be: CuO (1.5 mol%), KOH (1.5
equiv), at 80 °C with DMSO (2.0 mL) as the solvent.
In conclusion, we have developed a mild and efficient
method for the stereoselective synthesis of vinyl sulfides
in excellent yields using catalytic amounts of CuO nano-
particles as recyclable catalyst under ligand-free condi-
tions. This method does not require the use of external
ligands, moisture-sensitive catalytic systems and pro-
vides, in most cases, the desired vinyl sulfides in high
yields. The catalyst can be easily recovered and reused.
We are in the process of expanding the substrate scope of
these reactions.
In order to explore the scope of this novel transformation,
we first examined the cross-coupling of various substitut-
ed aryl and aliphatic thiols with different trans-b-iodosty-
renes (Table 4). In general, all reactions were very clean,
and the vinyl sulfides were obtained in high yields under
the optimized conditions.16 This protocol efficiently cou-
Synlett 2009, No. 17, 2783–2788 © Thieme Stuttgart · New York

LETTER
Ligand-Free Stereoselective Synthesis of Vinyl Sulfides
2785
Table 4 Nano CuO-Catalyzed Cross-Coupling of Various trans-b-Iodostyrenes with Aryl and Aliphatic Thiolsa
I
S
CuO (1.5 mol%)
R
RSH
+
DMSO, KOH
4 h
R
R
Entry
Iodide
Thiol
Product
Yield(%)b
97
I
I
SH
S
S
S
1
2
SH
94
95
SH
I
3
OMe
Cl
MeO
Cl
SH
S
S
I
I
4
5
6
94
96
91
SH
SH
I
S
F
F
S
I
SH
SH
7
8
93
90
I
S
F3C
F3C
SH
S
I
9
88
90
Br
Br
I
I
S
S
10
SH
SH
11
90
a Reaction conditions: trans-b-Iodostyrene (1.0 mmol), thiol (1.0 mmol), catalyst (1.5 mol%), KOH (1.5 equiv), DMSO (2.0 mL), 80 °C.
b Isolated yield.
Table 5 Nano CuO-Catalyzed Cross-Coupling of Various trans-b-Bromostyrenes with Aryl Thiolsa
Br
S
CuO (1.5 mol%)
DMSO, KOH
R
+
RSH
R
Entry
Bromide
Thiol
Product
Time (h)
Yield (%)b
Br
SH
SH
S
4
12
32
75
1
2
S
Br
4
12
24
59
Synlett 2009, No. 17, 2783–2788 © Thieme Stuttgart · New York

2786
V. P. Reddy et al.
LETTER
Table 5 Nano CuO-Catalyzed Cross-Coupling of Various trans-b-Bromostyrenes with Aryl Thiolsa (continued)
Br
S
CuO (1.5 mol%)
DMSO, KOH
R
+
RSH
R
Entry
Bromide
Thiol
Product
Time (h)
12
Yield (%)b
56
Br
Br
Br
SH
S
S
S
3
4
5
SH
12
12
58
49
SH
Br
Br
a Reaction conditions: trans-b-Bromostyrenes (1.0 mmol), benzenethiol (1.0 mmol), catalyst (1.5 mol%), KOH (1.5 equiv), DMSO (2.0 mL),
80 °C.
b Isolated yield.
Table 6 Nano CuO-Catalyzed Cross-Coupling of (Z)-Ethyl 3-Iodo-
References and Notes
acrylate with Aryl Thiolsa
(1) (a) Ceruti, M.; Balliano, G.; Rocco, F.; Milla, P.; Arpicco,
O
O
CuO (1.5 mol%)
DMSO, KOH
S.; Cattel, L.; Viola, F. Lipids 2001, 36, 629. (b) Lam, H.
W.; Cooke, P. A.; Pattenden, G.; Bandaranayake, W. M.;
Wickramasinghe, W. A. J. Chem. Soc., Perkin Trans. 1
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Miyata, N.; Uchida, A.; Osawa, R.; Kitsutaka, H.;
Takahashi, A. Carcinogenesis 1991, 12, 703.
RSH
O
I
+
O
S
R
Entry Thiol
Product
Yield (%)b
94
O
O
SH
O
S
S
1
Br
Br
(e) Marcantoni, E.; Massaccesi, M.; Bartoli, M. P.; Bellucci,
M. C.; Bosco, M.; Sambri, L. J. Org. Chem. 2000, 65, 4553.
(f) Monte, A.; Kabir Shahjahan, M.; Cook, J. M.; Rott, M.;
Schwan, W. R.; Defoe, L. U.S. Pat. Appl. Publ. 37, 2007.
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5075.
(3) Miller, R. D.; Hassig, R. Tetrahedron Lett. 1985, 26, 2395.
(4) Morris, T. H.; Smith, E. H.; Walsh, R. Chem. Commun.
1987, 964.
SH
O
2
92
94
Cl
Cl
O
SH
O
S
3
(5) Magnus, P.; Quagliato, D. J. Org. Chem. 1985, 50, 1621.
(6) (a) Mizuno, H.; Domon, K.; Masuya, K.; Tanino, K.;
Kuwajima, I. J. Org. Chem. 1999, 64, 2648. (b) Domon,
K. M. K.; Masuya, K.; Tanino, K.; Kuwajima, I. Synlett
1996, 157.
a Reaction conditions: (Z)-Ethyl 3-iodoacrylate (1.0 mmol), thiol (1.0
mmol), catalyst (1.5 mol%), KOH (1.5 equiv), DMSO (2.0 mL) at
80 °C.
b Isolated yield.
(7) Bates, C. G.; Saejueng, P.; Doherty, M. Q.; Venkataraman,
D. Org. Lett. 2004, 6, 5005.
Table 7 Recycling of CuO Nanoparticles
(8) (a) Aucagne, V.; Tatibouet, A.; Rollin, P. Tetrahedron 2004,
60, 1817. (b) Benati, L.; Capella, L.; Montevecchi, P. C.;
Spagnolo, P. J. Chem. Soc., Perkin Trans. 1 1995, 1035.
(c) Benati, L.; Montevecchi, P. C.; Spagnolo, P. J. Chem.
Soc., Perkin Trans. 1 1991, 2103. (d) Mikolajczak, M.;
Grzejszczak, S.; Midura, W.; Zatorski, A. Synthesis 1975,
278.
(9) (a) Ogawa, A.; Ikeda, T.; Kimura, K.; Hirao, T. J. Am. Chem.
Soc. 1999, 121, 5108. (b) Koelle, U.; Rietmann, C.; Tjoe, J.;
Wagner, T.; Englert, U. Organometallics 1995, 14, 703.
(c) Sugoh, K.; Kuniyasu, H.; Sugae, T.; Ohtaka, A.; Takai,
Y.; Tanaka, A.; Machino, C.; Kambe, N.; Kurosawa, H.
J. Am. Chem. Soc. 2001, 123, 5108. (d) Kuniyasu, H.;
Ogawa, A.; Sato, K. I.; Ryu, I.; Kambe, N.; Sonoda, N.
J. Am. Chem. Soc. 1992, 114, 5902. (e) Mcdonald, J. W.;
Corbin, J. L.; Newton, W. E. Inorg. Chem. 1976, 15, 2056.
Run
1
Yield (%)
Catalyst recovery (%)
97
97
94
94
95
91
89
89
2
3
4
Acknowledgment
V.P.R. thanks CSIR, and K.S. and A.V.K. thank UGC, New Delhi,
for the award of fellowships.
Synlett 2009, No. 17, 2783–2788 © Thieme Stuttgart · New York

LETTER
Ligand-Free Stereoselective Synthesis of Vinyl Sulfides
2787
(10) Zyk, N. V.; Beloglazkina, E. K.; Belova, M. A.; Dubinina,
N. S. Russ. Chem. Rev. 2003, 72, 769; and references cited
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Jaouen, G. Tetrahedron Lett. 1999, 40, 8571. (c)Ishida, M.;
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(14) (a) Pacchioni, G. Surf. Rev. Lett. 2000, 7, 277. (b) Knight,
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1988, 70, 211.
Synthesis of Vinyl Iodides; Typical Procedure:
To a solution of trans-2-phenyl vinylboronic acid (1.0
mmol) in MeCN (6 mL), which was protected from light,
was added N-iodosuccinimide (1.2 mmol). After stirring for
2 h at r.t., the product was extracted with ethyl acetate
(3 × 30 mL), washed with aqueous Na2S2O5 (2 × 20 mL),
water (2 × 20 mL), and dried (MgSO4). Solvent evaporation
in vacuo and purification by flash column chromatography
afforded the vinyl iodides.
Synthesis of Vinyl Bromides; General Procedure:
a,b-Unsaturated carboxylic acid (2 mmol) was added to a
solution of LiOAc (0.2 mmol) in MeCN–H2O (97:3 v/v, 4.5
mL). After the mixture was stirred for 5 min at room
temperature, N-bromosuccinimide (2.1 mmol) was added as
a solid. The progress of the reaction was monitored by TLC.
After completion of the reaction, the product was extracted
with ethyl acetate (3 × 30 mL), washed with aqueous
Na2S2O5 (2 × 20 mL), water (2 × 20 mL), and dried
(MgSO4). Solvent evaporation in vacuo and purification by
flash column chromatography afforded the vinyl bromides.
Recycling of the Catalyst:
(15) (a) Reddy, V. P.; Kumar, A. V.; Swapna, K.; Rao, K. R. Org.
Lett. 2009, 11, 951. (b) Reddy, V. P.; Kumar, A. V.;
Swapna, K.; Rao, K. R. Org. Lett. 2009, 11, 1697.
(16) CuO nanoparticles (mean particle size: 33 nm; surface area:
29 m2/g and purity: 99.99%) were purchased from Sigma–
Aldrich. Analytical thin layer chromatography (TLC) was
carried out using silica gel 60 F254 pre-coated plates.
Visualization was accomplished with a UV lamp or I2 stain.
1H and 13C NMR were recorded on 200 and 300 MHz
instruments, in CDCl3 using TMS as the internal standard,
chemical shifts (d) are reported in parts per million(ppm)
downfield from tetramethylsilane. Melting points were
determined on a Fischer–Johns melting point apparatus.
Centrifugation was carried out using Kubota centrifuge
(model 3500), for 1 h at 15000 rpm.
After the reaction was complete, the reaction mixture was
allowed to cool, and a 1:1 mixture of ethyl acetate–water
(2.0 mL) was added and CuO was removed by centrifu-
gation. After each cycle, the catalyst was recovered by
simple centrifugation, washing with deionized water and
ethyl acetate and then drying in vacuo. The recovered nano-
CuO was used directly in the next cycle.
Demonstration of Heterogeneous Catalysis:
To a stirred solution of trans-b-iodostyrene (1.0 mmol) and
benzenethiol (1.0 mmol) in anhydrous DMSO (2.0 mL) at
r.t., was added CuO nanoparticles (1.5 mol%) followed by
KOH (1.5 equiv) and the mixture was heated at 80 °C for 1.5
h. The reaction mixture was allowed to cool and the catalyst
was separated via centrifugation and 0.5 mL of the reaction
mixture was worked-up. The 1H NMR spectrum of the
reaction mass indicated 50% product formation. This filtrate
obtained after the catalyst separation was further stirred for
2.5 h at 80 °C and the reaction mixture was worked-up. No
further progress of the reaction was observed as seen by 1H
NMR spectroscopy and the product remained at 50% only.
This experiment clearly demonstrated that no leaching of
the catalyst was taking place and that the reaction was
heterogeneous. TEM images of the catalyst indicated no
change before and after the reaction, which further confirms
the heterogeneous nature of the catalyst (Figure 1 a and b).
(E)-(4-Methoxyphenyl)(styryl)sulfane (Table 4, entry 3):
White solid; mp 58–60 °C; IR (KBr): 3055, 2953, 1598,
1415, 1232, 957, 742 cm–1; 1H NMR (300 MHz, CDCl3,
TMS): d = 7.35 (d, J = 8.87 Hz, 2 H), 7.28–7.09 (m, 5 H),
6.84 (d, J = 8.87 Hz, 2 H), 6.75 (d, J = 15.48 Hz, 1 H), 6.44
(d, J = 15.48 Hz, 1 H), 3.80 (s, 3 H); 13C NMR (100 MHz,
CDCl3, TMS): d = 159.4, 136.6, 133.3, 130.0, 128.8, 128.5,
127.1, 124.4, 114.8, 114.5, 55.2; MS (ESI): m/z = 265 [M +
Na]; Anal. Calcd for C15H14OS: C, 74.34; H, 5.82; S, 13.23.
Found: C, 74.28; H, 5.76; S, 13.17.
Synthesis of Vinyl Sulfides; Typical Procedure: To a
stirred solution of trans-b-iodostyrene (1.0 mmol) and
benzenethiol (1.0 mmol) in anhydrous DMSO (2.0 mL) at
r.t., was added CuO nanoparticles (1.5 mol%) followed by
KOH (1.5 equiv) and heated at 80 °C for 4 h. The progress
of the reaction was monitored by TLC. After the reaction
was complete, the reaction mixture was allowed to cool, and
a 1:1 mixture of ethyl acetate–water (20 mL) was added and
CuO was removed by centrifuging for 1 h at 15000 rpm. The
combined organic extracts were dried with anhydrous
Na2SO4. The solvent and volatiles were completely removed
under vacuum to give the crude product, which was purified
by column chromatography (petroleum ether–ethyl acetate,
99:1) to yield the expected product 1a (205.71 mg, 97%
yield) as a colorless oil. The identity and purity of the
product was confirmed by 1H and 13C NMR spectroscopic
analysis.
(E)-(4-Fluorostyryl)(naphthalen-2-yl)sulfane (Table 4,
entry 6):
White solid; mp 101–103 °C; IR (KBr): 3049, 2992, 1602,
1453, 1274, 954, 739 cm–1; 1H NMR (200 MHz, CDCl3,
TMS): d = 7.81–7.72 (m, 4 H), 7.52–7.40 (m, 3 H), 7.32–
7.24 (m, 2 H), 6.97 (t, J = 8.30 Hz, 2 H), 6.86 (d, J = 15.86
Hz, 1 H), 6.68 (d, J = 15.86 Hz, 1 H); 13C NMR (100 MHz,
CDCl3, TMS): d = 163, 133.8, 132.7, 132.4, 132.2, 130.9,
128.8, 128.2, 127.8, 127.6, 127.5, 127.3, 126.7, 126.2,
122.9, 115.8, 115.5; MS (ESI): m/z = 303 [M + Na]; Anal.
Calcd for C18H13FS: C, 77.11; H, 4.67; S, 11.44. Found: C,
77.01; H, 4.58; S, 11.36.
Figure 1 TEM images of (a) fresh nano-CuO particles and (b) nano-
CuO particles after the fourth reaction cycle
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V. P. Reddy et al.
LETTER
(E)-[2-(Biphenyl-4-yl)vinyl](naphthalen-2-yl)sulfane
(Table 4, entry 7):
(Z)-Ethyl 3-(4-Chlorophenylthio)acrylate (Table 6, entry
2):
Yellow solid; mp 138–140 °C; IR (KBr): 3059, 2987, 1653,
1471, 1201, 944, 759 cm–1; 1H NMR (300 MHz, CDCl3,
TMS): d = 7.83 (s, 1 H), 7.75 (t, J = 8.68 Hz, 3 H), 7.60–7.36
(m, 11 H), 7.31–7.23 (m, 1 H), 6.97 (d, J = 15.48 Hz, 1 H),
6.77 (d, J = 15.48 Hz, 1 H); 13C NMR (100 MHz, CDCl3,
TMS): d = 140.5, 140.3, 135.5, 133.7, 132.5, 132.2, 131.6,
128.7, 128.2, 127.7, 127.6, 127.3, 126.8, 126.7, 126.4,
126.1, 123.2; MS (ESI): m/z = 361 [M + Na]; Anal. Calcd for
C24H18S: C, 85.17; H, 5.36; S, 9.47. Found: C, 85.11; H,
5.28; S, 9.39.
Yellow solid; mp 64–65 °C; IR (KBr): 3056, 2925, 1702,
1577, 1214, 959, 744 cm–1; 1H NMR (200 MHz, CDCl3,
TMS): d = 7.39 (d, J = 8.49 Hz, 2 H), 7.31 (d, J = 8.49 Hz,
2 H), 7.11 (d, J = 10.00 Hz, 1 H), 5.89 (d, J = 10.00 Hz,
1 H), 4.21 (q, J = 6.98 Hz, 2 H), 1.33 (t, J = 7.17 Hz, 3 H);
13C NMR (100 MHz, CDCl3, TMS): d = 166.3, 148.8, 134.5,
134.4, 132.2, 129.4, 113.7, 60.3, 14.2; MS (ESI): m/z = 265
[M + Na]; Anal. Calcd for C11H11ClO2S: C, 54.43; H, 4.57;
S, 13.21. Found: C, 54.37; H, 4.49; S, 13.15.
Synlett 2009, No. 17, 2783–2788 © Thieme Stuttgart · New York

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