Palladium-catalyzed Mizoroki-Heck-type reactions using telluronium salts

Article abstract of DOI:10.1246/cl.2004.1280

A Mizoroki-Heck-type reaction of telluronium iodides with olefins proceeded under mild conditions to produce substituted olefins in high yields. The reaction required a catalytic amount of palladium(II) species and a stoichiometric amount of silver(I) acetate as an additive.

Full text of DOI:10.1246/cl.2004.1280

1280
Chemistry Letters Vol.33, No.10 (2004)
Palladium-Catalyzed Mizoroki–Heck-type Reactions Using Telluronium Salts
Kazunori Hirabayashi, Yoshiko Nara, Toshio Shimizu, and Nobumasa KamigataÃ
Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University,
Minami-ohsawa, Hachioji, Tokyo 192-0397
(Received July 21, 2004; CL-040854)
A Mizoroki–Heck-type reaction of telluronium iodides with
Table 1. Reaction of dimethylphenyltelluronium iodide (1a)
with butyl acrylate in the presence of palladium catalysta
olefins proceeded under mild conditions to produce substituted
olefins in high yields. The reaction required a catalytic amount
of palladium(II) species and a stoichiometric amount of silver(I)
acetate as an additive.
[Pd] (10 mol %)
AgOAc (4 mmol)
Ph
+
-
+
PhTe Me I
R
2
R
solvent, 50 °C
R : CO Bu
1a
2a
2
Carbon–carbon bond-forming reactions using palladium cat-
alysts are useful means of synthesizing natural products and ma-
terials.1 It is well known that the Mizoroki–Heck (MH) reactions
of organic halides with olefins in the presence of palladium cat-
alyst afford substituted olefins.2 Recently, it was found that orga-
nometallic compounds, such as boron,3 silicon,4 tin,5 and other
organometallic reagents,6 instead of organic halides also reacted
with olefins to produce the same products as obtained by the MH
reaction. These reactions are called MH type reactions.
Entry
[Pd]
Solvent
Time/h
Yield/%b
1
2
3
4
5
6
7
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
PdCl2
CH3CN
THF
DMF
toluene
hexane
CH3CN
CH3CN
6
8
24
48
48
1
99
93
97
77
67
97
56
PdCl2(PPh3)2
24
Various organometallic reagents have been investigated to
use palladium-catalyzed coupling reactions. Tellurium com-
pounds can be also used as organometallic reagents, because tel-
lurium atom possesses metallic properties. However, to the best
of our knowledge, only organic tellurides or organotelluriu-
m(IV) compounds (R2TeCl2 or RTeCl3) were used in palladi-
um-catalyzed coupling reactions.8 On the other hand, we have
been studying the synthesis and stereochemistry of telluronium
salts.7 In the course of our studies, we focused on the application
of telluronium salts to organic synthesis because, until now, tel-
luronium salts have not been used in transition-metal-catalyzed
reactions. Telluronium salts are more stable compounds and
can be stored for a few months in the air, therefore telluronium
salts can be used as convenient organometallic reagents. We in-
vestigated the palladium-catalyzed MH type reaction using tel-
luronium salts, and the results are described herein.
When the reaction of dimethylphenyltelluronium iodide
(1a) with butyl acrylate was carried out in the presence of a cat-
alytic amount of Pd(OAc)2 (10 mol %) in CH3CN at 50 ꢀC for
24 h, (E)-butyl 3-phenylpropenoate (2a) was produced. Howev-
er, the amount of product was almost the same as the amount of
palladium catalyst employed (7%). On the other hand, palladi-
um(0) catalyst, such as Pd(PPh3)4, was not effective in this reac-
tion. Thus, the reaction requires a Pd(II) complex. Next, when
4.0 equiv. of AgOAc was used as an additive, 2a formed in ex-
cellent yield even though a catalytic amount of Pd(OAc)2 was
used (Table 1, Entry 1). When the reaction was carried out in
THF, 2a was also produced in high yield (Entry 2). Although
the reaction proceeded using a more polar solvent such as
DMF or nonpolar solvent such as toluene or hexane, the reaction
required a longer reaction time for completion (Entries 3–5). The
reaction also occurred using PdCl2 to produce 2a in excellent
yields after 1 h (Entry 6). When the reaction was carried out us-
ing other palladium catalysts possessing phosphine ligands, such
as PdCl2(PPh3)2, longer reaction time was required (24 h) and
aAll reactions were carried out using 1a (1.0 mmol), butyl ac-
rylate (1.0 mmol), [Pd] (10 mol %), and AgOAc (4.0 mmol).
bDetermined by GC analysis.
the yield decreased (Entry 7). Thus, phosphine ligands inhibit
the reaction.
The reaction of 1a with butyl acrylate was carried out in
CH3CN at 50 ꢀC in the presence of various amounts of AgOAc.
When 3.0 equiv. of AgOAc were used, the reaction proceeded
successfully to give 2a in 94% yield after 1 h, however, when
2.0 or 1.0 equiv. of AgOAc were used, the yields decreased even
though after 24 h (45%, 19%). These results indicate that this re-
action requires at least 3.0 equiv. of AgOAc.9
The MH type reactions of various aryltelluronium iodides
with olefins were studied under the optimized conditions
(Table 2). Telluronium salt 1a reacted with various olefins pos-
sessing electron-withdrawing or neutral groups to give the corre-
sponding products in good yields. The reactions of telluronium
salts 1b and 1c, which possess an electron-donating group at
the 4-position of the aryl group, proceeded to give the products
in high yields (Entries 6 and 7), whereas, the reaction using tel-
luronium salts 1d afforded the product in a slightly lower yield
(Entry 8). In the case of telluronium salts possessing methyl or
methoxy group at the 2-position, such as 1e and 1f, longer reac-
tion times were required (Entries 9 and 10). The reactions of tel-
luronium salts 1g and 1h afforded the corresponding products in
72% and 66% yields, respectively (Entries 11 and 12). These re-
sults indicated that, at least, two phenyl groups on telluronium
salts were used in the present reaction. On the other hand, when
alkenyltelluronium salts such as dimethylstyryltelluronium io-
dide was used, homocoupling reaction instead of the MH type
reaction occurred and 1,4-diphenyl-1,3-butadiene was given in
81% yield.
It was noteworthy that purification of this reaction product
was very easy. When the MH type reactions were carried out us-
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.10 (2004)
1281
ing organic tellurides, the crude mixture must be purified to re-
move unreacted organic telluride in some cases. On the other
hand, in the case of the present reaction using telluronium salts,
the pure product was obtained by only filtration using silica gel
to remove solids in the reaction mixture.
In summary, the palladium-catalyzed MH type reaction
of telluronium salts was achieved. Because the workup of this
reaction is very simple, and telluronium salts can be stored as
solids for a few months in the air, this reaction is convenient.
References and Notes
Table 2. The MH type reaction of aryltelluronium iodides 1a
1
a) J. Tsuji, ‘‘Palladium Reagents and Catalysts. Innovations
in Organic Synthesis,’’ Wiley-VCH, New York (1995).
b) J. Tsuji, ‘‘Transition Metal Reagents and Catalysts.
Innovations in Organic Synthesis,’’ Wiley-VCH, New York
(2000).
PdCl (10 mol %)
2
AgOAc (3 mmol)
Ar
+
-
Ar Te Me
I +
(3-n)
n
R
R
CH CN, 50 °C
3
1
2
2
3
a) T. Mizoroki, K. Mori, and A. Ozaki, Bull. Chem.
Soc. Jpn., 44, 581 (1971). b) R. F. Heck and J. P. Nolley,
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and M. Kosugi, Org. Lett., 3, 3313 (2001). b) C. S. Cho and
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Jung, R. K. Mishra, C. H. Yoon, and K. W. Jung, Org. Lett.,
5, 2231 (2003).
Entry
Ar
n
R
Time/h Yield/%b
1
2
3
4
5
6
7
8
9
Ph (1a)
1a
1a
1a
1a
1
1
1
1
1
1
1
1
1
1
2
3
CO2Bu
CN
CHO
COMe
Ph
CO2Bu
CO2Bu
CO2Bu
CO2Bu
CO2Bu
CO2Bu
CO2Bu
3
6
7
7
6
3
3
3
12
12
120
120
94
63
82
80
86
95
95
73
55
70
72c,d
66c,e
4-MeC6H4 (1b)
4-MeOC6H4 (1c)
4-CF3C6H4 (1d)
2-MeC6H4 (1e)
2-MeOC6H4 (1f)
Ph (1g)
4
5
6
a) K. Hirabayashi, J. Ando, J. Kawashima, Y. Nishihara, A.
Mori, and T. Hiyama, Bull. Chem. Soc. Jpn., 73, 1409
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(1998).
10
11
12
Ph (1h)
aAll reactions were carried out using 1 (1.0 mmol), olefin
(1.0 mmol), PdCl2 (10 mol %), and AgOAc (3.0 mmol), unless
otherwise noted. Isolated yields. Yields were based on ole-
b
c
d
fins. 1g (0.5 mmol) was used. e1h (0.33 mmol) was used.
AgOAc
+
-
ArTe Me I
AgI
2
1
2 Ag
+
-
[ArTe Me ]AcO
2
II
Pd X
7
8
a) T. Shimizu, T. Urakubo, and N. Kamigata, Chem. Lett.,
1996, 297. b) T. Shimizu, T. Urakubo, and N. Kamigata,
J. Org. Chem., 61, 8032 (1996). c) T. Shimizu, T. Urakubo,
P. Jin, M. Kondo, S. Kitagawa, and N. Kamigata, J.
Organomet. Chem., 539, 171 (1997).
a) Y. Nishibayashi, C. S. Cho, and S. Uemura, J. Organomet.
Chem., 507, 197 (1996). b) K. Ohe, H. Takahashi, S.
Uemura, and N. Sugita, J. Org. Chem., 52, 4859 (1987). c)
Y. Nishibayashi, C. S. Cho, K. Ohe, and S. Uemura, J.
Organomet. Chem., 526, 335 (1996). d) T. Kawamura, K.
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Jpn., 50, 2021 (1977). e) S. Uemura, M. Wakasugi, and M.
Okano, J. Organomet. Chem., 194, 277 (1980). f) A. L.
2
2 AgOAc
3
II
Ar Pd
X
Pd(0)
R
+
HX
4
H
R
Ar
R
Ar
II
2
Pd X
Scheme 1.
A plausible mechanism of the MH type reaction of telluro-
nium salts is shown in Scheme 1. As mentioned above, since this
reaction only occurred when using Pd(II) catalyst, arylpalladium
species 4 will be formed by transmetallation of tellurium
compound with Pd(II) compounds. After arylpalladium species
4 is produced, the reaction proceeds in a similar manner to that
in other MH type reactions to give the product 2. Because this
reaction needs 3 equiv. of AgOAc, AgOAc plays two roles in
the present reaction. Firstly, 2 equiv. of AgOAc act as oxidant
that reproduces the Pd(II) species. Secondly, 1 equiv. of AgOAc
exchanges the counter-anions of telluronium salts from iodide to
acetate. Thus, AgOAc is converted to Ag(0) and AgI.10
Braga, D. S. Ludtke, F. Vargas, R. K. Donato, C. C. Silveira,
¨
H. A. Stefani, and G. Zeni, Tetrahedron Lett., 44, 1779
(2003). g) G. Zeni, C. W. Nogueira, D. O. Silva, P. H.
Menezes, A. L. Braga, H. A. Stefani, and J. B. T. Rocha,
Tetrahedron Lett., 44, 1387 (2003).
9
When other silver salts and copper salts were used, the yields
of the corresponding products were very low (<17%).
10 Formation of Ag(0) and AgI was identified from reaction
mixture by the X-ray diffraction (XRD). We attempted to
survey the tellurium species after the reaction, but it could
not be identified.
Published on the web (Advance View) September 4, 2004; DOI 10.1246/cl.2004.1280