660 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
1999, 660^661y
A Stereoselective Synthesis of (E)-Arylvinyl
Selenides via Coupling of (E)-Vinylseleno
Zirconocenes and Diaryliodonium Saltsy
Jun-Hua Wang, Qing Xu and Xian Huang*
Department of Chemistry, Zhejiang University (Campus Xixi), Hangzhou, 310028, P. R. China
(E)-Arylvinyl selenides are prepared by coupling of (E)-vinylseleno zirconocenes and diaryliodonium salts.
Vinylic selenides are important intermediates in organic
synthesis, and their promising potential could be anticipated
by the combination of the special reactivity of selenium and
the reactivity associated with the carbon^carbon double
bond. They are particularly useful in highly stereoselective
C^C bond formation processes.1 Various preparations of
these compounds have been reported, however, most of
these methods involved the use of highly toxic selenides,
such as RSeX, RSeSeR or RSeH, furthermore, many of
these methods are not stereocontrolled and give mixtures
of isomers.1 Recently we developed a novel methodology
which involved the insertion of elemental selenium into
the C(sp2)^Zr bond of alkenylchlorozirconocenes derived
from hydrozirconation of alkynes, a¡ording vinylseleno
zirconocenes 1 as active intermediates. This method has
been applied to the stereoselective synthesis of vinylseleno
esters.2 Herein we report a stereoselective synthesis of
(E)-arylvinyl selenides via coupling of (E)-vinylseleno
zirconocenes 1 and diaryliodonium salts (Scheme 1).
Coupling of aryl halides with a variety of organometallics
has long been achieved via organopalladium chemistry.4
Initially we tried the Pd-catalyzed coupling reaction of
vinylseleno zirconocenes 1 with aryl bromides and aryl
iodides but it failed. (Scheme 2).
R
R
(i) Cp2Zr(H)Cl, THF
(ii) Se, rt
ArX, Pd(PPh3)4
RC CH
X
SeZrCp2Cl
SeAr
1
2
Scheme 2
It should be pointed out that besides the alklynes
employed in Scheme 1, various internal alkynes can undergo
the hydrozirconation reaction smoothly and stereo-
selectiely,5 moreover, all the reagents used in Scheme 1
are easily available and of low toxicity. As a result, the pre-
sent method has provided an environmentally friendly,
stereoselective route to various arylvinyl selenides.
R
R
Ar2I+X–
(i) Cp2Zr(H)Cl, THF
(ii) Se, rt
RC CH
Pd(PPh3)4, 60 ˚C
Experimental
SeZrCp2Cl
SeAr
Cp2ZrꢀHCl6 and diaryliodonium salts7 were prepared according to
literature procedures. THF was freshly distilled from sodium/
benzophenone before use. All reactions were carried out under an N2
atmosphere.
1
2
General Procedure for the Synthesis of Arylvinyl Selenides
(2a-2f).öTo a stirred suspension of Cp2ZrꢀHCl (1.2 mmol, 0.308 g)
in THF (8 ml) under an N2 atmosphere was added alkyne (1.0 mmol).
The mixture was stirred until the solution became clear and was then
transferred via syringe into a stirred suspension of selenium powder
(1.0 mmol. 0.080 g) in THF (2 ml). The mixture turned gradually from
a green suspension into a red solution during 0.5 h. Diaryliodonium
salt (1 mmol) and Pd(PPh3)4 (0.05 mmol) were added and the mixture
was left stirring at about 60 8C for 6 h. It was then diluted with light
petroleum and ®ltered through a short plug of silica gel. After
evaporation of the ®ltrate the residue was puri®ed by preparative
thin layer chromatography on silica gel (light petroleum as the eluent
for 2a^2c, light petroleum^ethyl acetate (20 : 1) for 2d^2f). Com-
pound 2a:8 dH(CCl4, HMDS) 7.50^6.90 (11H, m), 6.72 (1H, d, J
Scheme 1
The insertion of elemental selenium into the C(sp2)^Zr
bond proceeds smoothly in THF at room temperature
and is usually completed within 30 minutes, a¡ording a
red solution. The vinylseleno zirconocenes 1 produced were
trapped with diaryliodonium salts, giving arylvinyl selenides
2 in moderate yields. Catalytic amounts of Pd(0) can
e¡ectively accelerate the reaction. The results are
summarized in Table 1. It is noteworthy that arylation
of aryl selenides with diaryliodonium salts has been
reported.3
1
15.6 Hz). IR (¢lm): nmax=cm 3100, 3080, 3050, 1650, 1610, 1590,
1506, 950, 730, 690. Compound 2b:9 dH(CCl4, HMDS) 7.60^6.90
Table 1 Synthesis of (E)-vinylic selenides from alkynes, elemen-
tal selenium and diaryliodonium salts
(10H, m), 6.68 (1H, d,
J 16.4 Hz), 2.28 (3H, s). IR (¢lm):
1
n
max=cm 3100, 3060, 1610, 1494, 800, 728, 690. Compound 2c:
mp 58^60 8C (lit.8 59±60 8C). dH(CCl4, HMDS) 7.60±6.90 (10H,
RCꢀCH
Ar2I X
Ar
1
m), 6.74 (1H, d, J 15.2 Hz), IR (®lm, CCl4): nmax=cm 3042, 1612,
R
Products
Yielda(%)
1584, 1508, 950, 690. Compound 2d:8 dH(CCl4, HMDS) 7.60^6.90
(5H, m), 6.57 (1H, d, J 15.6 Hz), 5.86 (1H, dt, J 5.6 and 15.6 Hz),
Ph
Ph
Ph
Ph
2a
2b
2c
2d
2e
2f
66
72
65
69
71
62
1
3.82 (2H, d, J 5.6 Hz), 3.20 (3H, s). IR (¢lm): nmax=cm 3100, 3020,
p-MeC6H4
p-BrC6H4
Ph
p-MeC6H4
p-BrC6H4
1640, 1600, 1495, 960, 745, 700, 675. Compound 2e:8 dH(CCl4,
HMDS) 7.50^7.20 (2H, m), 7.16^6.87 (2H, m), 6.53 (1H, d, J
15.4 Hz), 5.80 (1H, dt, J 5.4 and 15.4 Hz), 3.80 (2H, d, J 5.4 Hz), 3.16
MeOCH2
MeOCH2
MeOCH2
aIsolated yields.
1
(3H, s), 2.27 (3H, s). IR (¢lm): nmax=cm 3020, 1640, 1505, 950, 810,
755. Compound 2f:8 dH(CCl4, HMDS) 7.50^7.16 (4H, m), 6.57 (1H,
d, J 15.8 Hz), 5.86 (1H, dt, J 5.2 and 15.8 Hz), 3.84 (2H, d, J 5.2 Hz),
1
3.20 (3H, s). IR (¢lm): nmax=cm 3020, 1640, 1585, 1500, 1490, 960,
920, 820, 715.
* To receive any correspondence.
y This is a Short Paper as de¢ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is
therefore no corresponding material in J. Chem. Research (M).
This work was supported by the National Natural Science
Foundation of China (Projects 29672008 and 29772007).