Lanthanum-catalyzed stereoselective synthesis of vinyl sulfides and selenides

Article abstract of DOI:10.1016/j.tetlet.2009.11.004

Lanthanum oxide/TMEDA-catalyzed cross-coupling of vinyl halides with thiols/diphenyl diselenide in anhydrous DMSO and KOH is reported. Utilizing this protocol various vinyl sulfides and selenides were synthesized in excellent yields with retention of the stereochemistry. The catalyst was recyclable.

Full text of DOI:10.1016/j.tetlet.2009.11.004

Tetrahedron Letters 51 (2010) 293–296
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Tetrahedron Letters
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Lanthanum-catalyzed stereoselective synthesis of vinyl sulfides and selenides
*
V. Prakash Reddy, K. Swapna, A. Vijay Kumar, K. Rama Rao
Organic Chemistry Division-I, Indian Institute of Chemical Technology, Hyderabad 500 607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Lanthanum oxide/TMEDA-catalyzed cross-coupling of vinyl halides with thiols/diphenyl diselenide in
anhydrous DMSO and KOH is reported. Utilizing this protocol various vinyl sulfides and selenides were
synthesized in excellent yields with retention of the stereochemistry. The catalyst was recyclable.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 9 September 2009
Revised 27 October 2009
Accepted 2 November 2009
Available online 5 November 2009
Vinyl sulfides and selenides are valuable compounds found in
manybiologicallyactive molecules witha broad range ofapplications
in organic synthesis.1 They can be used as equivalents of carbonyl
compounds2 and Michael acceptors,3 and as key intermediates in
the stereoselective synthesis of functionalized alkenes.4
For the past several years, transition metal catalysts such as pal-
ladium, nickel, and copper-based catalysts were explored for the
synthesis of vinyl sulfides and selenides. However, until now there
has been no report on lanthanum-catalyzed cross-coupling reac-
tions. In continuation of our interest in the field of cross-coupling
reactions,8 we wish to report, herein, the synthesis of vinyl sulfides
and selenides in a very efficient manner by the cross-coupling of
vinyl halides with thiols or diphenyl diselenides in the presence
of lanthanum oxide as a recyclable catalyst. To the best of our
knowledge, this is the first lanthanum-catalyzed coupling of vinyl
halides with thiols or diphenyl diselenide to form vinyl sulfides
and selenides (Scheme 1). This novel method is economically
attractive since the catalyst will be recyclable, inexpensive, and
the reaction can be performed in the absence of co-catalyst.
In the first instance, the reaction conditions were optimized
using trans-b-iodostyrene and benzene thiol as model substrates,
to observe the effect of the base, solvent, ligand, and catalyst on
this cross-coupling reaction. Initially, we examined the effect of
different ligands L1–L5 with the combination of La(OTf)3 in differ-
Various processes have been reported for the synthesis of these
vinyl sulfides and selenides. The most commonly employed strat-
egy involves the reaction of vinyl halides with thiols or diphenyl
diselenide,5 and different protocols have been developed for the
synthesis of vinyl sulfides and selenides.6,7 Notable amongst them
is the well defined catalytic systems such as, copper complex [Cu(-
phen)(PPh3)2]NO3 system,5c CuI/l-proline in ionic liquids,5f and
CuI/ cis-1,2-cyclohexanediol in DMF.5g However, most of these me-
tal-catalyzed reactions involve expensive and moisture-sensitive
catalysts/co-catalysts causing major problems in purification of
the product, separation of metal catalysts, and stereocontrol of
double bond geometry. Thus, it is desirable to develop an inexpen-
sive, environmentally benign, and recyclable catalytic system for
an efficient access to such biologically important compounds.
Scheme 1.
* Corresponding author.
E-mail address: kakulapatirama@gmail.com (K.R. Rao).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.11.004

294
V. P. Reddy et al. / Tetrahedron Letters 51 (2010) 293–296
Table 1
ent solvent and base combinations. Among the bases screened KOH
Optimized conditions for the synthesis of vinyl sulfidesa
has shown the best efficiency with DMSO as the solvent and 90 °C
as the optimum temperature. L3 was found to be the efficient li-
gand giving the coupling product in 79% yield (Table 1, entry 8).
Encouraged by these results, we have chosen moisture stable and
inexpensive La2O3 to examine the effect with various ligands L1–
L5 in DMSO with KOH as the base at 90 °C. Among the ligands,
TMEDA (L3) was found to be the most effective for the synthesis
of vinyl sulfides (Table 1, entry 14). Then we examined the reactiv-
ity of several metal catalysts with the combination of TMEDA (L3)
as a ligand. Amongst these catalysts, La2O3 has shown better activ-
ity compared to other metal sources such as Fe2O3, In2O3, La(OTf)3,
FeCl3, InBr3, and In(OTf)3 (Table 1). But Fe2O3, and In2O3 gave com-
petitive yields after longer reaction times (Table 1, entries 19 and
23). Only a trace amount of the expected product was formed
without the metal source, (Table 1, entry 24) and moderate yields
were observed with La2O3 in the absence of ligand (Table 1, entry
25). The optimum reaction conditions for the synthesis of vinyl sul-
fides were, vinyl halide (1.0 equiv), thiol (1.0 equiv) La2O3
(0.1 equiv), TMEDA (0.2 equiv), KOH (1.5 equiv), and a reaction
temperature of 90 °C for 5 h with DMSO as the solvent.9,10
Entry
Catalyst
Ligands
Solvents
Base
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La(OTf)3
La2O3
La2O3
La2O3
La2O3
La2O3
lnBr3
ln(OTf)3
ln2O3
ln2O3
FeCl3
L1
L1
L2
L3
L3
L3
L3
L3
L3
L4
L5
L1
L2
L3
L4
L5
L3
L3
L3
L3
L3
L3
L3
L3
––
L3
DMF
K3PO4
KOH
Cs2O3
K3PO4
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
––
0
0
PhMe
DMSO
DMSO
DMF
Trace
25
51
79
40b
79c
79d
56
49
81
67
95
51
75
71
78
92e
79
69
76
93
10
51
0
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
Fe2O3
Fe2O3
––
La2O3
La2O3
a
Reaction conditions: trans-iodostyrene (1.0 mmol), benzene thiol (1.0 mmol),
catalyst (10 mol %), ligand (20 mol %), KOH (1.5 equiv), and DMSO (2.0 mL), 90 °C,
5 h.
b
At 50 °C.
At 90 °C.
At 110 °C.
After 9 h.
c
d
e
Table 2
La2O3-catalyzed stereoselective synthesis of vinyl sulfidesa
Entry
Halides
Thiol
Product
Yield (%)
1
2
95
55
3
4
91
89
5
6
91
90
7
8
9
89
92
88

V. P. Reddy et al. / Tetrahedron Letters 51 (2010) 293–296
295
Table 2 (continued)
Entry
Halides
Thiol
Product
Yield (%)
10
11
12
86
85
82
13
14
15
16
17
87
85
82
83
81
18
85
82
19
a
Reaction conditions: trans-b-iodostyrenes (1.0 mmol), thiols (1.0 mmol), La2O3 (10 mol %), TMEDA (20 mol %), KOH (1.5 equiv), and DMSO (2.0 mL), at 90 °C.
To expand the scope of this novel transformation, we examined
various vinyl halides with different thiols for cross-coupling (Table
2). This protocol efficiently cross-coupled trans-b-iodostyrene hav-
ing electron-rich, electron-neutral, and electron-poor functional-
ities with various thiols such as aromatic, acyclic, and cyclic
thiols under the optimized reaction conditions and generated the
desired products in high yields (Table 2). Fortunately, aromatic thi-
ols with both electron-donating and electron-withdrawing func-
Table 3
La2O3-catalyzed stereoselective synthesis of vinyl selenidesa
Entry
Halides
Product
Yield (%)
1
2
96
51
3
Trace
4
92
5
6
89
41
7
8
83
88
a
Reaction conditions: trans-b-iodostyrene (1.0 mmol), diphenyl diselenide (0.5 mmol), La2O3 (10 mol %), TMEDA (20 mol %), KOH (1.5 equiv), and DMSO (2.0 mL) at 90 °C.

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V. P. Reddy et al. / Tetrahedron Letters 51 (2010) 293–296
Chattopadhyay, K.; Banerjee, S. J. Org. Chem. 2006, 71, 423; (f) Wang, Z.; Mo,
Table 4
H.; Bao, W. Synlett 2007, 91; (g) Kabir, M. S.; Van Linn, M. L.; Monte, A.; Cook, J.
M. Org. Lett. 2008, 10, 3363.
Recycling of La2O3
Cycle
Catalyst recovery (%)
Yield (%)
6. (a) Zeni, G.; Stracke, M. P.; Nogueira, C. W.; Braga, A. L.; Menezes, P. H.; Stefani,
H. A. Org. Lett. 2004, 6, 1135; (b) Griesbaum, K. Angew. Chem., Int. Ed. Engl. 1970,
9, 273; (c) Benati, L.; Capella, L.; Montevecchi, P. C.; Spagnolo, P. J. Chem. Soc.,
Perkin Trans. 1 1995, 1035; (d) Benati, L.; Capella, L.; Montevecchi, P. C.;
Spagnolo, P. J. Org. Chem. 1994, 59, 2818; (e) Kataoka, T.; Yoshimatsu, M.;
Shimizu, H.; Hori, M. Tetrahedron Lett. 1990, 31, 5927.
1
2
3
4
98
95
91
91
95
91
89
84
7. (a) Aucagne, V.; Tatibouet, A.; Rollin, P. Tetrahedron 2004, 60, 1817; (b) Stephan,
E.; Olaru, A.; Jaouen, G. Tetrahedron Lett. 1999, 40, 8571; (c) Kuniyasu, H.;
Ogawa, A.; Sato, K. I.; Ryu, I.; Kambe, N.; Sonoda, N. J. Am. Chem. Soc. 1992, 114,
5902; (d) Kuniyasu, H.; Ogawa, A.; Sato, K. I.; Ryu, I.; Sonoda, N. Tetrahedron
Lett. 1992, 33, 5525; (e) Ogawa, A.; Ikeda, T.; Kimura, K.; Hirao, T. J. Am. Chem.
Soc. 1999, 121, 5108; (f) Kondoh, A.; Takami, K.; Yorimitsu, H.; Oshima, K. J. Org.
Chem. 2005, 70, 6468.
8. (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; (c)
Reddy, V. P.; Swapna, K.; Kumar, A. V.; Rao, K. R. J. Org. Chem. 2009, 74, 3189.
9. General procedure for the synthesis of vinyl sulfides: To a stirred solution of trans-
b-iodostyrene (1.0 mmol) and La2O3 (10 mol%) in DMSO (2.0 mL) was added
benzenethiol (1.0 mmol) followed by TMEDA (20 mol%) and KOH (1.5 equiv)
and stirred at 90 °C for 5 h. The progress of the reaction was monitored by TLC.
The mixture was allowed to cool to room temperature, diethyl ether (5.0 mL)
was added, and the organic phase was separated, dried over anhydrous Na2SO4,
evaporated, and the crude product was purified by chromatography on silica
gel (n-hexane as eluent) to afford the corresponding coupling product in 95%
yield.
tional groups, such as methyl and chloro groups, afforded the cor-
responding products in good yields (Table 2, entries 3, 4, 6, 7, 11,
and 13). This protocol was applied for the cross-coupling of alkyl
vinyl iodides with different thiols and the desired vinyl sulfides
were also obtained in impressive yields (Table 2, entries 18 and
19). Encouraged by these results, we tested the coupling of trans-
b-bromostyrenes with benzene thiol under the same conditions.
The reaction of trans-b-bromostyrenes with benzene thiol pro-
ceeded smoothly to afford the desired product in reasonable yield
(Table 2, entry 2). Unfortunately, the crosss-coupling of heteroaro-
matic thiols with trans-b-iodostyrene has failed.
The same catalytic system was applied for the C–Se bond for-
mation via coupling of diphenyl diselenide with trans-b-iodosty-
rene under the optimized conditions. This protocol efficiently
cross-coupled different substituted trans-b-iodostyrene with di-
phenyl diselenide and produced the vinyl selenides in high yields
(Table 3). The reaction of trans-b-bromostyrenes with diphenyl
diselenide proceeded smoothly to afford the desired product in
reasonable yield (Table 3, entries 2 and 6). Furthermore, the stereo-
chemistry of the vinyl sulfides and vinyl selenides was retained in
all the cases as determined by 1H NMR studies.
La2O3 was used directly in the next cycle. The catalyst was
found to be recyclable without the loss of catalytic activity up to
four cycles (Table 4). The structures of all the products were deter-
mined from their analytical and spectral (IR, 1H NMR, and 13C
NMR) data and by direct comparison with authentic samples.
In conclusion, La2O3 acts as an active, moisture stable, inexpen-
sive, and nontoxic catalyst for the stereo selective synthesis of vinyl
sulfides and selenides under additive-free conditions in excellent
yields. The catalyst can also be easily recovered and reused.
General procedure for the synthesis of vinyl selenides: To a stirred solution of
trans-b-iodostyrene (1.0 mmol) and La2O3 (10 mol %) in DMSO (2.0 mL) was
added diphenyl diselenide (1.0 mmol) followed by TMEDA (20 mol %) and KOH
(1.5 equiv). The reaction mixture was then stirred at 90 °C for 5 h. The progress
of the reaction was monitored by TLC. The mixture was allowed to cool to room
temperature. Diethyl ether (5.0 mL) was added, and the organic phase was
separated, dried over anhydrous Na2SO4, evaporated, and the crude product
was purified by chromatography on silica gel (n-hexane as eluent) to afford the
corresponding coupling product in 96% yield.
Recycling of the catalyst: 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 La2O3 was removed by centrifugation. After each cycle, the catalyst
was recovered by simple centrifugation, washed with deionized water
followed by acetone, and then dried in vacuo. The recovered La2O3 was used
directly in the next cycle.
10. Data for the representative examples of synthesized compounds: (E)-
phenyl(styryl)sulfane (Table 2, entries
1
and 2): Colorless oil; 1H NMR
(200 MHz, CDCl3, TMS): d = 7.39 (d, 2H, J = 7.62 Hz), 7.34–7.18 (m, 8H), 6.88
(d, 1H, J = 15.25 Hz), 6.69 (d, 1H, J = 15.25 Hz); 13C NMR (100 MHz, CDCl3,
TMS): d = 135.1, 132.5, 131.7, 129.7, 129.3, 129.1, 128.6, 127.6, 127.5, 127.3,
126.9, 126.0, 123.3, 119.3
(E)-(2-(Biphenyl-4-yl)vinyl)(4-chlorophenyl)sulfane (Table 2, entry 11): white
solid, mp 132–133 °C; IR (KBr):
m 3053, 2985, 1621, 1503, 1453, 1274, 943,
756 cmÀ1 1H NMR (300 MHz, CDCl3, TMS): d = 7.58–7.52 (m, 4H), 7.44–7.27
;
(m, 9H), 6.85 (d, 1H, J = 15.38 Hz), 6.76 (d, 1H, J = 15.38 Hz) 13C NMR (100 MHz,
CDCl3, TMS): d = 140.5, 140.4, 135.2, 133.8, 132.9, 132.1, 130.9, 129.2, 128.7,
127.3, 126.8, 126.4, 122.5; Mass (ESI): m/z 345 [M+Na]; Anal. Calcd for
C20H15ClS: C, 74.40; H, 4.68; S, 9.93. Found: C, 74.31; H, 4.59; S, 9.86.
(E)-Cyclohexyl(styryl)sulfane (Table 2, entry 16): Colorless oil; 1H NMR
(300 MHz, CDCl3, TMS): d = 7.24–7.20 (m, 4H), 7.19–7.09 (m, 1H), 6.66 (d,
1H, J = 15.86), 6.44 (d, 1H, J = 15.86 Hz), 2.98–2.87 (m, 1H), 2.06–2.02 (m, 2H),
1.82–1.79 (m, 2H), 1.65–1.61(m, 1H), 1.49–1.25 (m, 5H); 13C NMR (100 MHz,
CDCl3, TMS): d = 137.1, 128.5, 126.8, 125.5, 124.0, 33.5, 29.6, 25.9, 25.6.
(Z)-Ethyl 3-(4-chlorophenylthio)acrylate (Table 2, entry 18): Light yellow solid,
Acknowledgments
V.P.R. thanks CSIR and K.S., A.V.K. thank UGC, New Delhi, for the
award of fellowships.
References and notes
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mp 64–65 °C; IR (KBr): m ;
3056, 2925, 1702, 1577, 1214, 959, 744 cmÀ1 1H NMR
(200 MHz, CDCl3, TMS): d = 7.39 (d, 2H, J = 8.49 Hz), 7.31 (d, 2H, J = 8.49 Hz),
7.11 (d, 1H, J = 10.00 Hz), 5.89 (d, 1H, J = 10.00 Hz), 4.21 (q, 2H, J = 6.98 Hz),
1.33 (t, 3H, J = 7.17 Hz); 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; Mass (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.
(E)-Phenyl(styryl)selane (Table 3, entries 1–3): yellowish oil; 1H NMR (200 MHz,
CDCl3, TMS): d = 7.54–7.49 (m, 2H), 7.31–7.18 (m, 8H), 7.13 (d, 1H, J = 15.8 Hz),
6.85 (d, 1H, J = 15.8 Hz); 13C NMR (100 MHz, CDCl3, TMS): d = 136.9, 135.0,
132.4, 130.0, 129.2, 128.6, 127.5, 127.3, 126.0, 119.3.
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(E)-(4-Fluorostyryl)(phenyl)selane (Table 3, entry 8): yellowish oil; 1H NMR
(200 MHz, CDCl3, TMS): d = 7.52–7.50 (m, 2H), 7.32–7.26 (m, 5H), 7.05 (d, 1H,
J = 16.11 Hz), 6.97 (t, 2H, J = 8.0 Hz), 6.76 (d, 1H, J = 16.11 Hz); 13C NMR
(100 MHz, CDCl3, TMS): d = 164.6, 132.9, 132.7, 130.0, 129.9, 129.3, 127.6,
121.7, 114.3, 114.0; Mass (ESI): m/z 300 [M+Na]; Anal. Calcd for C14H11FS: C,
60.66; H, 4.0. Found: C, 60.59; H, 3.96.
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