Improved procedure for palladium-catalyzed Hiyama cross-coupling reaction of aryl halides with aryltrimethoxysilanes under solvent-free conditions

Article abstract of DOI:10.1055/s-2006-926364

An improved palladium-catalyzed Hiyama cross-coupling reaction is reported. In the presence of PdCl₂(MeCN)₂, P(o-tol)₃ and TBAF, a number of ArX (X = I, Br, Cl) were coupled with ArSi(OMe)₃ efficiently to afford the desired cross-coupled products in moderate to excellent yields. It is noteworthy that this protocol is conducted under relatively low Pd loadings and solvent-free conditions. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-926364

PAPER
969
Improved Procedure for Palladium-Catalyzed Hiyama Cross-Coupling
Reaction of Aryl Halides with Aryltrimethoxysilanes under Solvent-Free
Conditions
C
J
ross-Cou
i
pling R
n
eaction of
A
-
r
yl Hali
H
de
s
w
ith Aryltrime
e
thoxysilan
n
e
s
g Li,* Chen-Liang Deng, Ye-Xiang Xie
Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education), College of Chemistry and
Chemical Engineering, Hunan Normal University, Changsha 410081, China
Fax +86(731)8872531; E-mail: jhli@hunnu.edu.cn
Received 6 September 2005; revised 18 October 2005
As shown in Table 1, the PdCl (MeCN) /P(o-tol) /TBAF
system was efficient for the palladium-catalyzed Hiyama
cross-coupling reaction of p-bromotoluene (1a) with
2
2
3
Abstract: An improved palladium-catalyzed Hiyama cross-cou-
pling reaction is reported. In the presence of PdCl (MeCN) , P(o-
2
2
tol) and TBAF, a number of ArX (X = I, Br, Cl) were coupled with
3
ArSi(OMe) efficiently to afford the desired cross-coupled products phenyltrimethoxysilane (2a). Compared with DeShong’s
3
5a
in moderate to excellent yields. It is noteworthy that this protocol is results, the reaction performed under solvent-free condi-
conducted under relatively low Pd loadings and solvent-free condi-
tions.
tions was more effective than in DMF. Without the aid of
any ligands, the coupling of 1a with silane 2a gave a 67%
Key words: PdCl (MeCN) , Hiyama cross-coupling reaction, aryl yield of the corresponding product 3 in the presence of 3
2
2
halide, arylsiloxane
mol% of Pd(OAc) and 6 equivalents of TBAF, whereas
2
the yield of 3 was enhanced sharply when a phosphine
ligand [P(o-tol) ) or PPh , 6 mol%] was added [(P(o-tol) :
3
3
3
The Hiyama cross-coupling reaction attracts much atten- 94% yield; PPh : 90% yield] (entries 1–3). However, De-
3
5
a
tion because its products, biaryls, are useful intermediates Shong’s results showed that only 78% [P(o-tol) )] or
3
in organic synthesis as well as a recurring functional 82% [PPh ] yield of 3 was observed even in the presence
3
group in a wide range of natural products and other bio- of 10 mol% of Pd(OAc) , 20 mol% of the phosphine
2
1
–8
logically active compounds. Besides these, the silicon- ligand and 2 equivalents of TBAF when DMF was used as
derived compounds as alternative reagents are easily the medium (entries 2 and 3). Other ligands such as Ph PO
3
9
available and/or less toxic. Consequently, many efficient and DABCO were also investigated, and they were less
and selective palladium catalytic systems for the reactions effective than either P(o-tol) or PPh (entries 2–5). A se-
3
3
4
–8
have been described. However few efficient catalytic ries of Pd catalysts including Pd(OAc) , Pd(dba) and
2
2
systems have been developed for the palladium-catalyzed PdCl (MeCN)2 were then examined. PdCl (MeCN)2
2
2
Hiyama cross-coupling reaction. Generally, the Hiyama turned out to be the best catalyst in term of yields and re-
reaction is carried out under both high Pd catalyst and action rates using P(o-tol) as the ligand (entries 3, 6 and
3
phosphine loadings, resulting in high yields for unactivat- 7). In the presence of PdCl (MeCN) (3 mol%), P(o-tol)
2
2
3
5
ed aryl halides. For example, 5 to 20 mol% of Pd cata- (6 mol%) and TBAF (6 equiv), quantitative yield of 3 was
lysts are usually required (often 10 mol% Pd) for the obtained in 40 minutes (entry 7). Identical results were ob-
coupling of aryl halides with arylsiloxanes when phos- served when the amount of TBAF was reduced to 3 equiv-
phines were used as the ligands. Thus, the development of alents (entry 8). It is noteworthy that higher yields of 3 can
efficient Hiyama cross-coupling reaction is still signifi- be achieved smoothly at a loading of 1 mol% Pd. Thus, in
cant. Here, we wish to report that the combination of the presence of 1 mol% of PdCl (MeCN) , 2 mol% of P(o-
2
2
PdCl (MeCN) /P(o-tol) /TBAF is an efficient system for tol) and 3 equivalents of TBAF, a high yield of 3 was still
2
2
3
3
10
the Hiyama cross-coupling reactions of aryl halides with isolated after 40 minutes (92% yield, entry 9). However,
aryltrimethoxysilanes under solvent-free conditions further decreasing loadings of Pd to 0.1 mol% resulted in
(
Equation 1).
a rather low yield (entry 10). The results also demonstrat-
ed that the reaction could be carried out at room tempera-
PdCl2(MeCN)2
(
o-tol)3P
X
+
Si(OMe)3
R
R'
TBAF⋅3H O, 80 °C
R
2
R'
X = I, Br, Cl
Equation 1
SYNTHESIS 2006, No. 6, pp 0969–0974
x
x
.
x
x
.2
0
0
6
Advanced online publication: 27.02.2006
DOI: 10.1055/s-2006-926364; Art ID: F15005SS
Georg Thieme Verlag Stuttgart · New York
©

9
70
J.-H. Li et al.
PAPER
ture, and a moderate yield of 3 was obtained after yields of the corresponding coupled products 4 and 5 in
prolonged reaction time (54% yield, entry 11). It is inter- the presence of 1 mol% of PdCl (MeCN) , 2 mol% of P(o-
2
2
esting to note that excellent yield of 3 is still obtained in tol) and 3 equivalents of TBAF (entries 1 and 2). The re-
3
1
1
20 min when 5 mol of 1a was treated with 10 mol of 2a, action of 1c with silane 2a performed at room temperature
mol% of PdCl (MeCN) , 2 mol% of P(o-tol) and 3 was also tested, and a moderate yield was still isolated
2
2
3
equiv of TBAF (entry 12). Attempts to use KF or CsF in (49% yield after 180 min, entry 3). Under the same reac-
place of TBAF gave rather low yields (entries 13 and 14).
tion conditions, the couplings of aryl bromides 1a and 1d–
f with silanes 2a–d were also proceeded efficiently to give
the corresponding cross-coupled products in good to ex-
cellent yields (entries 4–10). The efficiency of the
PdCl (MeCN) /P(o-tol) /TBAF system for the reactions
of the deactivated aryl bromides 1g–j were decreased to
some extent, and 3 mol% Pd was required to produce high
yields (entries 11–16). It is noteworthy that the couplings
of activated aryl chlorides 1k and 1l with silanes, respec-
tively, proceed smoothly in the presence 1 to 3 mol%
The Hiyama reactions of various aryl halides 1a–l with si-
lanes 2a–c were carried out smoothly to afford moderate
to excellent yields of the corresponding biaryls 4–14 in
the presence of PdCl (MeCN) , P(o-tol) and TBAF, and
2
2
3
2
2
3
the results are summarized in Table 2. The results showed
that the palladium-catalyzed Hiyama reactions tolerated a
variety of functional groups, and the yields and rates were
based on the substrates. Treatment of aromatic iodides 1b
and 1c with silane 2a, respectively, afforded quantitative
Table 1 Palladium-Catalyzed Hiyama Cross-Coupling Reaction of p-Bromotoluene (1a) with Phenyltrimethoxysilane (2a)a
[
Pd]
Me
Br
+
Si(OMe)3
Me
1a
2a
3
Entry
[Pd]
Ligand
Present work
Time (min)
DeShong’s workc
Yield (%)b
Yield (%)b
67
1
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(dba)2
–
540
240
240
240
90
–
2
PPh3
P(o-tol)3
90
82
78
–
3
94
4
Ph PO
85
3
5
DABCO
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
P(o-tol)3
41
–
6
30
95
–
7
PdCl (MeCN)
40
>99
>99
92
–
2
2
2
2
2
2
2
2
2
8d
9d,e
PdCl (MeCN)
40
–
2
PdCl (MeCN)
40
–
2
1
1
1
1
0d,f
1d,g
2d,h
3d,i
4d,j
PdCl (MeCN)
40
12
–
2
PdCl (MeCN)
720
120
120
120
54
–
2
PdCl (MeCN)
98
–
2
PdCl (MeCN)
13
–
2
1
PdCl (MeCN)
18
–
2
a
Unless otherwise indicated, the reaction conditions were as follows: 1a (1 mmol), 2a (2 mmol), Pd (3.0 mol%), ligand (6.0 mol%), and
TBAF·3H O (6 equiv) at 80 °C under N .
2
2
b
c
Isolated yield.
DeShong’s reaction conditions: 1a (5.425 mmol), 2a (10.983 mmol), Pd (10 mol%), ligand (20 mol%), TBAF·3H O (2 equiv), and DMF (40
2
mL) at 85 °C under N for 1–5 h.
2
d
TBAF·3H O (3 equiv).
PdCl (MeCN) (1 mol%).
PdCl (MeCN) (0.1 mol%).
At room temperature.
a (5 mmol) and 2a (10 mmol).
2
e
2
2
f
2
2
g
h
i
1
KF (3 equiv) instead of TBAF for 6 h.
CsF (3 equiv) instead of TBAF for 6 h.
j
Synthesis 2006, No. 6, 969–974 © Thieme Stuttgart · New York

PAPER
Cross-Coupling Reaction of Aryl Halides with Aryltrimethoxysilanes
971
6
PdCl (MeCN) . For example, the reaction of chloride 1k dicated in the earlier report, CuI might be another better
2
2
with silane 2a or 2b afforded the corresponding biaryls 4 promoter for the Hiyama reaction. However, the yield of
and 15 in 90% and 98% yields, respectively, at a loading 5 was decreased to 10% in the presence of PdCl (MeCN)2
2
of 1 mol% Pd (entries 17 and 19). Unfortunately, the cou- (10 mol%), P(o-tol) (20 mol%), CuI (0.5 equiv) and
3
plings of the deactivated aryl chlorides 1m and 1n gave TBAF (3 equiv) (entry 25).
low yields in the presence of 3 mol% Pd (entries 21 and
2
3). Moderate yields were obtained when the loadings of
Pd were increased to 10 mol% (entries 22 and 24). As in-
a
3
Table 2 Palladium-Catalyzed Hiyama Cross-Coupling Reactions in the Presence of PdCl (MeCN) and P(o-tol)
2
2
Entry
1
Aryl halide
R¢Si(OMe)3
Pd (mol%)
1
Time (min)
45
Productb
Yield (%)c
>99
4
O2N
I
Si(OMe)3
1
b
2a
2a
2
1
45
5
>99
MeO
I
1
1c
c
3d
4
2a
1
1
180
40
5
6
49
79
Me
Br
Me
Si(OMe)3
Si(OMe)3
Si(OMe)3
1a
2b
5
6
7
1a
1
1
3
60
60
45
7
8
4
81
90
90
MeO
2
c
1a
O2N
2
d
2a
O2N
Br
1d
8
9
1d
2a
2a
1
1
120
45
4
9
91
88
Br
O
1e
1
1
0
1
2a
2b
1
1
50
10
11
>99
85
Br
1f
120
Br
Me
1g
1
1
1
2
3
4
Me
2a
2a
2a
3
3
3
35
45
35
12
13
5
98
88
96
Br
Me
1
h
i
Me
Br
Me
1
MeO
Br
1j
1
1
5
6
1j
2b
2c
3
3
45
60
7
83
80
1j
14
Synthesis 2006, No. 6, 969–974 © Thieme Stuttgart · New York

9
72
J.-H. Li et al.
PAPER
a
Table 2 Palladium-Catalyzed Hiyama Cross-Coupling Reactions in the Presence of PdCl (MeCN) and P(o-tol) (continued)
2
2
3
Productb
4
Entry
Aryl halide
R¢Si(OMe)3
Pd (mol%)
1
Time (min)
90
Yield (%)c
1
7
2a
90
O2N
Cl
1k
1
1
2
8
9
0
1k
2a
2b
2a
0.1
1
420
40
4
15
8
trace
98
1k
3
90
72
Cl
O
1l
2
1
2a
3
120
3
19
Me
Cl
1m
2
2
2
3
1m
2a
2a
10
3
1320
1320
3
5
51
trace
MeO
Cl
1n
2
4
1n
2a
2a
10
10
1320
1320
5
5
40
10
2
5e
1n
a
Unless otherwise indicated, the reaction conditions were as follows: 1 (1 mmol), 2 (2 mmol), PdCl (MeCN) /P(o-tol) (1:2), and TBAF·3H O
2
2
3
2
(
3 equiv) at 80 °C under N2.
Products are described in the experimental section.
Isolated yield.
At room temperature.
CuI (0.5 equiv).
b
c
d
e
In summary, an improved procedure for the palladium- starting material as monitored by TLC analysis. After the mixture
was diluted with brine, it was extracted with Et O. The Et O extract
catalyzed Hiyama cross-coupling reaction has been devel-
oped. In the presence of 1 to 3 mol% of PdCl (MeCN) , 2
2
2
was dried (Na SO ) and evaporated. The residue was purified by
flash column chromatography (hexane or hexane–EtOAc) to afford
2
4
2
2
to 6 mol% of P(o-tol) , and 3 equivalents of TBAF, the
3
4–6,11
the desired coupled products 3–14.
couplings of a variety of aryl halides with aryltrimethoxy-
silanes were carried out smoothly to afford moderate to
-Methylbiphenyl (3)5
4
1
excellent yields of the corresponding biaryls. Compared
H NMR (400 MHz, CDCl ): d = 7.58 (t, J = 7.6 Hz, 2 H), 7.49 (d,
with the previous results, several interesting features are J = 8.0 Hz, 2 H), 7.42 (t, J = 7.6 Hz, 2 H), 7.31 (t, J = 7.6 Hz, 1 H),
3
5
7
.24 (d, J = 8.0 Hz, 2 H), 2.38 (s, 3 H).
apparent for the present results: First, the reaction is effi-
cient for the deactivated chlorides (entries 14–17, 19 and
1
3
C NMR (100 MHz, CDCl ): d = 141.1, 138.3, 137.0, 129.5, 128.7,
3
1
27.3, 127.2, 127.0, 21.1.
2
0, Table 2). Second, the reaction works well aryl halides
bearing different substitutions. Third, the protocol is gen-
eral because it not only can be conducted under a relative-
ly low palladium catalyst loading (1 to 3 mol% Pd) for
aryl iodides, bromides and activated chlorides, but also
can be extended to the coupling of deactivated aryl chlo-
rides despite the requirement of high Pd loadings. Finally,
no harmful organic solvents such as DMF as the media
were required. Further efforts to extend the application of
4
-Nitrobiphenyl (4)5
1
H NMR (400 MHz, CDCl ): d = 8.30 (d, J = 8.8 Hz, 2 H), 7.74 (d,
J = 8.8 Hz, 2 H), 7.64 (d, J = 6.9 Hz, 2 H), 7.52–7.44 (m, 3 H).
3
1
3
C NMR (100 MHz, CDCl ): d = 147.6, 147.2, 138.8, 129.2, 128.9,
27.8, 127.4, 124.1.
3
1
-Methoxybiphenyl (5)5
4
1
H NMR (300 MHz, CDCl ): d = 7.54 (t, J = 8.4 Hz, 4 H), 7.41 (t,
3
the system to other coupling transformations are under- J = 7.2 Hz, 2 H), 7.31 (t, J = 7.2, 1 H), 6.98 (d, J = 6.7, 2 H), 3.85
(
s, 3 H).
way in our laboratory.
1
3
C NMR (100 MHz, CDCl ): d = 159.1, 140.8, 133.7, 128.7, 128.1,
26.7, 126.6, 114.2, 55.3.
3
1
Palladium-Catalyzed Hiyama Cross-Coupling Reaction; Gen-
eral Procedure
,4¢-Dimethylbiphenyl (6)5
4
1
H NMR: (400 MHz, CDCl ): d = 7.46 (d, J = 8.0 Hz, 4 H), 7.22 (d,
3
A mixture of aryl halide 1 (1 mmol), aryltrimethoxysilane 2 (2
mmol) PdCl (MeCN) (the indicated amount, Table 2), P(o-tol)
3
J = 7.6 Hz, 4 H), 2.37 (s, 6 H).
2
2
1
3
C NMR (100 MHz, CDCl ): d = 138.3, 136.7, 129.4, 126.8, 21.0.
(
the indicated amount, Table 2), and TBAF (3 equiv) was stirred un-
3
der N at 80 °C for desired time until complete consumption of
2
Synthesis 2006, No. 6, 969–974 © Thieme Stuttgart · New York

PAPER
-Methyl-4¢-methoxybiphenyl (7)5,6
Cross-Coupling Reaction of Aryl Halides with Aryltrimethoxysilanes
973
4
References
1
H NMR (400 MHz, CDCl ): d = 7.50 (d, J = 8.8 Hz, 2 H), 7.44 (d,
3
(
1) Bringmann, G.; Gunther, C.; Ochse, M.; Schupp, O.; Tasler,
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2) Hegedus, L. S. Organometallics in Synthesis; Schlosser, M.,
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J = 8.4 Hz, 2 H), 7.22 (d, J = 8.0 Hz, 2 H), 6.95 (d, J = 8.8 Hz, 2
H), 3.83 (s, 3 H), 2.37 (s, 3 H).
1
3
C NMR (100 MHz, CDCl ): d = 158.9, 137.9, 136.3, 133.7, 129.4,
3
1
27.9, 126.5, 114.1, 55.3, 21.0.
(
4
-Methyl-4¢-nitrobiphenyl (8)5,6
(
3) For selected Ullmann coupling reactions, see:
1
H NMR (400 MHz, CDCl ): d = 8.27 (d, J = 8.8 Hz, 2 H), 7.71 (d,
J = 8.8 Hz, 2 H), 7.53 (d, J = 8.4 Hz, 2 H), 7.30 (d, J = 7.8 Hz, 2 H),
3
(
a) Brongmann, G.; Walter, R.; Weirich, R. Angew. Chem.,
Int. Ed. Engl. 1990, 29, 977. (b) Zhang, S.; Zhang, D.;
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H.; Xie, Y.-X.; Yin, D.-L. J. Org. Chem. 2003, 68, 9867; and
references cited therein.
2
.42 (s, 3 H).
1
3
C NMR (100 MHz, CDCl ): d = 147.5, 146.7, 139.0, 135.7, 129.8,
3
1
27.4, 127.1, 124.0, 21.2.
(
(
4) For selected reviews on the Hiyama cross-coupling reaction,
see: (a) Diederich, F.; Stang, P. J. Metal-Catalyzed Cross-
Coupling Reactions; Wiley-VCH: Weinheim, 1998.
(b) Miyaura, N. Cross-Coupling Reaction; Springer: Berlin,
2002. (c) Chuit, C.; Corriu, R. J. P.; Reye, C.; Young, J. C.
Chem. Rev. 1993, 93, 1317. (d) Horn, K. A. Chem. Rev.
1
-Biphenyl-4-ylethanone (9)5,6
1
H NMR (300 MHz, CDCl ): d = 8.04 (d, J = 8.4 Hz, 2 H), 7.69 (d,
J = 8.4 Hz, 2 H), 7.64 (d, J = 7.6 Hz, 2 H), 7.50–7.40 (m, 3 H), 2.64
3
(
m, 3 H).
1
3
C NMR (75 MHz, CDCl ): d = 197.8, 145.8, 139.9, 135.8, 128.9,
3
1995, 95, 1317.
1
28.9, 128.2, 127.3, 127.2, 26.7.
5) For selected papers on palladium-phosphine catalytic
systems for the Hiyama cross-coupling reaction of siloxanes,
see: (a) Mowery, M. E.; DeShong, P. Org. Lett. 1999, 1,
Biphenyl (10)5
1
H NMR (300 MHz, CDCl ): d = 7.59 (d, J = 8.4 Hz, 4 H), 7.43 (t,
3
2137. (b) Mowery, M. E.; DeShong, P. J. Org. Chem. 1999,
J = 7.2 Hz, 4 H), 7.36 (t, J = 7.8 Hz, 2 H).
64, 1684. (c) McElroy, W. T.; DeShong, P. Org. Lett. 2003,
1
3
C NMR (75 MHz, CDCl ): d = 141.6, 129.1, 127.6, 127.5.
3
5, 4779. (d) Lee, J.-Y.; Fu, G. C. J. Am. Chem. Soc. 2003,
25, 5616. (e) Koike, T.; Mori, A. Synlett 2003, 1850.
f) Wolf, C.; Lerebours, R. Org. Lett. 2004, 6, 1147.
(g) Seganish, W. M.; DeShong, P. J. Org. Chem. 2004, 69,
137. (h) Lerebours, R.; Wolf, C. Synthesis 2005, 2287.
1
(
2
-Methyl-4¢-methoxybiphenyl (11)5,6
1
H NMR (400 MHz, CDCl ): d = 7.26–7.22 (m, 6 H), 6.95 (d,
J = 8.4 Hz, 2 H), 3.85 (s, 3 H), 2.28 (s, 3 H).
3
1
1
3
(6) For selected papers on palladium-phosphine catalytic
systems for the Hiyama cross-coupling reaction of other
silanes, see: (a) Hatanaka, Y.; Fukushima, S.; Hiyama, T.
Chem. Lett. 1989, 1711. (b) Hatanaka, Y.; Gouda, Y.;
Okahara, T.; Hiyama, T. Tetrahedron 1994, 50, 8301.
C NMR (100 MHz, CDCl ): d = 158.5, 141.5, 135.5, 134.3, 130.3,
3
1
30.2, 129.9, 127.0, 125.8, 113.5, 55.3, 20.6.
,5-Dimethylbiphenyl (12)11
3
1
H NMR (400 MHz, CDCl ): d = 7.59 (d, J = 8.4 Hz, 2 H), 7.44–
7
3
(c) Gouda, K.; Hagiwara, E.; Hatanaka, Y.; Hiyama, T. J.
.40 (m, 2 H), 7.31–7.28 (m, 1 H), 7.19 (d, J = 8.4 Hz, 2 H), 6.98
Org. Chem. 1996, 61, 7232. (d) Hagiwara, E.; Gouda, K.;
Hatanaka, Y.; Hiyama, T. Tetrahedron Lett. 1997, 38, 439.
(
d, J = 9.2 Hz, 1 H), 2.35 (d, J = 8.6 Hz, 6 H).
1
3
C NMR (100 MHz, CDCl ): d = 141.5, 138.1, 128.9, 128.7, 127.9,
3
(e) Denmark, S. C.; Choi, J. U. J. Am. Chem. Soc. 1999, 121,
1
27.2, 127.1, 125.1, 21.4.
5821. (f) Mowery, M. E.; DeShong, P. J. Org. Chem. 1999,
6
4, 3266; and references cited therein. (g) Hirabayashi, K.;
2
,6-Dimethylbiphenyl (13)11
Kawashima, J.; Nishihara, Y.; Mori, A.; Hiyama, T. Org.
Lett. 1999, 1, 299. (h) Denmark, S. C.; Wu, Z. Org. Lett.
1
H NMR (400 MHz, CDCl ): d = 7.43 (t, J = 7.6 Hz, 2 H), 7.36–7.30
3
(
m, 1 H), 7.15–7.11 (m, 5 H), 2.03 (s, 6 H).
1
999, 1, 1495. (i) Hirabayashi, K.; Mori, A.; Kawashima, J.;
1
3
C NMR (100 MHz, CDCl ): d = 141.1, 136.1, 129.0, 128.8, 128.4,
Suguro, M.; Nishihara, Y.; Hiyama, T. J. Org. Chem. 2000,
65, 5342. (j) Mori, A.; Suguro, M. Synlett 2001, 845.
3
1
27.3, 127.0, 126.6, 20.9.
(
k) Hoosoi, K.; Nozaki, K.; Hiyama, T. Chem. Lett. 2002,
4
,4¢-Dimethoxybiphenyl (14)5,6
138. (l) Nakao, Y.; Oda, T.; Sahoo, A. K.; Hiyama, T. J.
Organomet. Chem. 2003, 687, 570. (m) Sahoo, A. K.; Oda,
T.; Nakao, Y.; Hiyama, T. Adv. Synth. Catal. 2004, 346,
1715. (n) Pierrat, P.; Gros, P.; Fort, Y. Org. Lett. 2005, 7,
1
H NMR (400 MHz, CDCl ): d = 7.46 (d, J = 8.8 Hz, 4 H), 6.94 (d,
J = 8.8 Hz, 4 H), 3.83 (s, 6 H).
3
1
3
C NMR (100 MHz, CDCl ): d = 158.7, 133.5, 127.7, 114.1, 59.3.
3
6
97. (o) Jayanth, T. T.; Jeganmohan, M.; Cheng, C.-H. Org.
-Methyl-4¢-nitrobiphenyl (15)5,6
Lett. 2005, 7, 2921. (p) Shindo, M.; Matsumoto, K.;
Shishido, K. Synlett 2005, 176. (q) Nakao, Y.; Imanaka, H.;
Sahoo, A. K.; Yada, A.; Hiyama, T. J. Am. Chem. Soc. 2005,
4
1
H NMR (400 MHz, CDCl ): d = 8.27 (d, J = 8.8 Hz, 2 H), 7.71 (d,
3
J = 8.8 Hz, 2 H), 7.53 (d, J = 8.4 Hz, 2 H), 7.30 (d, J = 7.8 Hz, 2 H),
127, 6952.
2
1
.42 (s, 3 H).
(
(
7) For a papers on palladium-imidazolium chloride catalytic
system for the Hiyama cross-coupling reaction, see: Lee, H.
M.; Nolan, S. P. Org. Lett. 2000, 2, 2053.
8) For a papers on b-diimine-palladium catalysts for the
Hiyama cross-coupling reaction, see: Domin, D.; Benito-
Garagorri, D.; Mereiter, K.; Fröhlich, J.; Kirchner, K.
Organometallics 2005, 24, 3957.
3
C NMR (100 MHz, CDCl ): d = 147.5, 146.7, 139.0, 135.7, 129.8,
3
1
27.4, 127.1, 124.0, 21.2.
Acknowledgment
We thank the National Natural Science Foundation of China (No.
2
0202002 and 20572020) and Hunan Provincial Natural Science
Foundation of China (No. 05JJ1002) for financial support.
Synthesis 2006, No. 6, 969–974 © Thieme Stuttgart · New York

9
74
J.-H. Li et al.
PAPER
(
9) For papers on DABCO as a ligand for the palladium-
catalyzed cross-coupling reactions, see: (a) Li, J.-H.; Liu,
W.-J. Org. Lett. 2004, 6, 2809. (b) Li, J.-H.; Zhang, X.-D.;
Xie, Y.-X. Synthesis 2005, 804. (c) Li, J.-H.; Liang, Y.;
Wang, D.-P.; Liu, W.-J.; Xie, Y.-X.; Yin, D.-L. J. Org.
Chem. 2005, 70, 2832.
(10) Only Pd(OAc) as the Pd source was examined in reference
2
5a. We also attempted to reuse the PdCl (MeCN) /P(o-tol) /
2
2
3
TBAF system, however, only a 48% yield of 3 was isolated
in the second run.
(11) Akiyama, R.; Kobayashi, S. Angew. Chem. Int. Ed. 2001, 40,
3469.
Synthesis 2006, No. 6, 969–974 © Thieme Stuttgart · New York