Palladium/tetraphosphine catalyzed suzuki cross-coupling of heteroarylboronic acids with aryl halides

Article abstract of DOI:10.1002/jhet.5570450109

(Chemical Equation Presented) cis,cis,cis-1,2,3,4- Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H ₅)]₂ efficiently catalyses the Suzuki reaction of heteroarylboronic acids with aryl bromides and also the coupling of arylboronic acids with heteroaryl bromides. The coupling of thiophene- or benzothiopheneboronic acids, furan- or benzofuranboronic acids and 3-pyridineboronic acid with a variety of aryl bromides gave the corresponding coupling products in good yields. However, in most cases, better results in terms of ratio substrate/catalyst were obtained for the reverse reaction using heteroaryl bromides with arylboronic acids.

Full text of DOI:10.1002/jhet.5570450109

Jan-Feb 2008
109
Palladium/Tetraphosphine Catalyzed Suzuki Cross-Coupling of
Heteroarylboronic Acids with Aryl Halides.
Isabelle Kondolff,a Henri Doucet,b* Maurice Santellia*
aUMR 6180 CNRS and Université d'Aix-Marseille III: "Chirotechnologies: catalyse et biocatalyse",
Laboratoire de Synthèse Organique, Faculté des Sciences de Saint Jérôme, Université d'Aix-Marseille III,
Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France, FAX: (33) 4 91 98 91 12; E-mail:
m.santelli@univ-cezanne.fr
bInstitut Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes "Catalyse et
Organometalliques", Campus de Beaulieu, 35042 Rennes, France. Fax: 02-23-23-69-39; Tel: 02-23-23-62-80;
E-mail: henri.doucet@univ-rennes1.fr.
Received January 29, 2007
1/2 [Pd(C3H5)Cl]2/
R
R
R
Ph2P
Ph2P
PPh2
PPh2
X
+ Heteroarylboronic acids
or
S (O)
or
R
xylene, K2CO3
B(OH)2 + Heteroaryl bromides
N
cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C3H5)]2 efficiently catalyses
the Suzuki reaction of heteroarylboronic acids with aryl bromides and also the coupling of arylboronic
acids with heteroaryl bromides. The coupling of thiophene- or benzothiopheneboronic acids, furan- or
benzofuranboronic acids and 3-pyridineboronic acid with a variety of aryl bromides gave the
corresponding coupling products in good yields. However, in most cases, better results in terms of ratio
substrate/catalyst were obtained for the reverse reaction using heteroaryl bromides with arylboronic acids.
J. Heterocyclic Chem., 45, 109 (2008).
with 2,6-dimethylbromobenzene [16]. PdCl2(ethylene-
diamine-N,N,N',N'-tetraacetic acid) is also an efficient
catalyst for the arylation of 3-thiopheneboronic acid [17].
A palladium–metalla-macrocycle supported by an amino-
functionalised ferrocene was used for the coupling of 3-
thiophene-boronic acid with 4-bromobenzophenone [18].
A few other coupling reactions using these heteroaryl-
boronic acids have also been described in the presence of
palladium nanoparticles, supported catalysts, in ionic
liquids as solvent or using microwaves [19-25].
In order to obtain stable and efficient palladium
catalysts, we have prepared the tetraphosphine ligand,
cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)-
cyclopentane or Tedicyp [26] (Scheme 1). The presence
of four phosphines close to the metal center seems to
increase the stability of the catalyst. The palladium is
shown by NMR to circulate around the 4 phosphorous
atoms under the “pressure to coordinate” of the 4 phos-
phino groups maintained in a half-space. This “pressure
to coordinate” in a half space might be responsible for
easy reductive elimination step for several cross-coupling
reactions. We have already reported several results
obtained in allylic substitution, [27] for Heck, [28]
Sonogashira, [29] Suzuki [30] or Negishi [31]. reactions
and also for C–H activation/arylation of furans [32] using
this ligand. We have also described several results for the
Suzuki coupling of heteroaryl halides with arylboronic
acids [33]. Recently, we have described preliminary
results, for the reverse reaction using heteroarylboronic
acids with aryl halides [34]. In order to further establish
INTRODUCTION
Due to their important biological properties, the
preparation of heterobiaryls is an important industrial
goal. The palladium-catalysed Suzuki cross-coupling
reaction between heteroaryl halides and arylboronic acids
provides a very efficient method for the preparation of
heterobiaryl derivatives [1,2]. On the other hand, the
reverse reaction using heteroarylboronic acids and aryl
halides has attracted much less attention, and most of the
results have been described with Pd(PPh3)4 as catalyst
[3–6]. But this ligand can be labile under coupling
conditions especially at elevated temperature and gave
palladium black which is generally completely inactive
for cross-coupling reactions. In recent years, a few other
catalysts have been tested on the Suzuki coupling of these
heteroarylboronic acid derivatives [7–15]. For example,
Fu et al. have reported the coupling of 2-thiopheneboronic
acid with 4-bromo-N,N-dimethylaniline using 0.5%
Pd2(dba)3 and 1.2% P(t-Bu)3 as catalyst [7]. Two dialkyl-
biphenylphosphino ligands with 1–3% Pd2(dba)3 are also
efficient catalysts for the coupling of pyridineboronic
acids with aryl halides [8,9]. Dppf as ligand gave
satisfactory results for the arylation of thiophene, benzo-
furan and pyridineboronic acids [10-14]. A palladium
complex with a di(norbornyl)phosphine and a 2-phenyl-
pyridine ligand catalyses the arylation of 3-furan- and 3-
thiopheneboronic acid derivatives using 5 mol % catalyst
[15]. Recently, diaminocarbenes were also found to be
useful ligands for the coupling of 3-pyridineboronic acid

110
I. Kondolff, H. Doucet, M. Santelli
Vol 45
the requirements for successful Suzuki coupling reactions
for the synthesis of arylthiophene, arylfuran or
arylpyridine derivatives with our catalyst, we herein
report on the coupling of heteroarylboronic acids such as
thiophene-, benzothiophene-, dibenzothiophene-, furan-,
benzofuran-, or pyridineboronic acids with aryl bromides.
We have also compared in several cases the relative
reaction rates for the coupling of heteroarylboronic acids
and aryl bromides with the reverse combination of
reactants.
were performed at 130°C under argon in the presence of a
1:2 ratio of [Pd(C3H5)Cl]2/Tedicyp as catalyst (Scheme 1).
The coupling of 2-thiopheneboronic acid with
iodobenzene, bromobenzene, 4-bromoacetophenone, 4-
bromoanisole or 2-bromotoluene gave the expected 2-
arylthiophenes 1–5 in good yields in the presence of 1–
5% catalyst (Table 1, entries 1, 2, 4, 5, 7–9, 11 and 12).
Similar reaction rates were observed with electron-poor
and electron-rich aryl bromides indicating that with this
heteroarylboronic acid, the oxidative addition of the aryl
bromide to palladium is not rate-limiting. The reverse
reaction using 2-bromothiophene and arylboronic acids
led to much faster reactions and very high substrate/
catalyst ratios of 1000–1,000,000 have been successfully
employed (Table 1, entries 3, 6, 10 and 13). These results
seem to indicate that the catalyst might be partially
RESULTS AND DISCUSSION
Palladium chemistry involving heterocycles has its
unique characteristics stemming from the heterocycles'
inherently different structural and electronic properties in
comparison to the corresponding carbocyclic aryl
compounds. Furthermore, palladium(II) possesses strong
thiophilicity. Therefore, when using thiophene deriva-
tives for some palladium-catalysed reactions, a poisoning
effect of the sulphur atom can be observed. This
poisoning effect has also been observed in the presence of
nitrogen atom. For these reasons, the position of the
halide on a heteroaromatic ring and the nature of the
heteroatom have important effects on the reactions rates.
We first studied the reactivity of 2-thiopheneboronic
acid with a range of aryl bromides (Scheme 1, Table 1).
For this study, based on previous results [33], xylene was
used as the solvent and K2CO3 as the base. The reactions
poisoned by 2-thiopheneboronic acid.
Using the
functionalised 2-acetyl-5-thiopheneboronic acid we also
obtained the arylation product 6 in good yield (Scheme 2).
It should be noted that such 2-arylthiophenes can also be
prepared directly by palladium catalysed C–H activation/
fonctionalisation using simple thiophenes and aryl halides
[36]. Therefore, the coupling reaction using 2-thiophene-
boronic acid is probably not economically attractive
compared to the Suzuki arylation reaction of 2-bromothio-
phene which proceeds at high substrate/catalyst ratios or
to the C–H activation/functionalisation of thiophene
which does not require the use of an arylboronic acid.
Scheme 1
Ph2P
Ph2P
Ph2P
PPh2
PPh2
PPh2
Tedicyp
Ph2P
PPh2
R
R
Tedicyp
B(OH)2
X
S
R
[Pd(C3H5)Cl]2
[Pd(C3H5)Cl]2
+
+
xylene, K2CO3, 130 °C
xylene, K2CO3, 130 °C
1-5
B(OH)2
Br
S
S
X = I, Br
R = H, Me, OMe, MeCO, PhCO
Table 1
Suzuki reaction with 2-thiopheneboronic acid catalysed by the Tedicyp-palladium complex (Scheme 1).
Entry
1
2
3
4
5
6
7
8
Aryl halide
Arylboronic acid
Ratio substrate/catalyst
100
50
100000
100
250
1000
50
20
50
Product
Yield (%)a
82 (96)
(47)
Iodobenzene
Bromobenzene
2-Thiopheneboronic acid
2-Thiopheneboronic acid
Benzeneboronic acid
1
1
1
2
2
2
3
4
4
4
5
5
5
2-Bromothiophene
4-Bromoacetophenone
4-Bromoacetophenone
2-Bromothiophene
4-Bromobenzophenone
4-Bromoanisole
88
2-Thiopheneboronic acid
2-Thiopheneboronic acid
4-Acetylphenylboronic acid
2-Thiopheneboronic acid
2-Thiopheneboronic acid
2-Thiopheneboronic acid
4-Methoxyphenylboronic acid
2-Thiopheneboronic acid
2-Thiopheneboronic acid
2-Methylphenylboronic acid
80 (86)
(64)
90
39 (44)
(100)
81
9
4-Bromoanisole
10
11
12
13
2-Bromothiophene
2-Bromotoluene
2-Bromotoluene
2-Bromothiophene
1000000
20
50
85
87 (100)
(40)
89
100000
Conditions: catalyst [Pd(C H )Cl] / Tedicyp 1:2, see ref. 26, ArX (1 equiv.), arylboronic acid (2 equiv.), K CO (2 equiv.), xylene, 20 h, 130 °C,
3
5
2
2
3
under argon, isolated yields, ratio substrate/catalyst based on the aryl halide. a Yields in parenthesis correspond to GC and NMR yields.

Jan-Feb 2008
Palladium/Tetraphosphine Catalyzed Suzuki Cross-Couplilng of Heteroarylboronic Acids
111
Scheme 2
cross-coupling reactions remain the most powerful
method for their preparation. We observed that higher
reactions rates were observed for the coupling reactions
in the presence of 3-thiopheneboronic acid than with 2-
thiopheneboronic acid. Using 4-bromoacetophenone, 4-
[Pd(C3H5)Cl]2 5% / Tedicyp 10%
xylene, K2CO3, 130 °C
+
I
(HO)2B
S
S
O
6
O
74%
bromobenzaldehyde,
4-bromobenzophenone
or
4-bromoanisole the reactions were performed using as
little as 0.4–0.1% catalyst. Employing these reaction
conditions, the products 11–14 were obtained in high
yields (Table 3, entries 1–4, 6–13). The sterically
congested aryl bromides 2-bromotoluene and bromo-
mesitylene were also found to be suitable reactants for
coupling with 3-thiopheneboronic acid (Table 3, entries
15, 17 and 18). However, the coupling with bromo-
mesitylene required the presence of 5 mol % catalyst.
Again, in order to determine the most powerful method
for the synthesis of these compounds via Suzuki
coupling, we determined the reactions rates for the
coupling reactions using 3-bromothiophene with 4-
acetylphenylboronic acid (Table 3, entry 5). For this
reaction a TON of 215 was obtained, which is quite
similar to the TON of 550 obtained for the coupling of
3-thiopheneboronic acid with 4-bromoacetophenone.
On the other hand, the coupling of 3-bromothiophene
with 4-methoxy- or 2-methylphenylboronic acids led to
a very high TONs of 750000 and 930000, respectively,
and the reverse reactions to TONs of 420 and 900
(Table 3, entries 11 and 14–16). In fact, the functions
on the arylboronic acid have an important influence on
the reactions rates of the coupling reactions.
2-Benzothiopheneboronic acid was found to be less
reactive than 2-thiopheneboronic acid (Scheme 3, Table
2). Using iodobenzene or 4-bromoacetophenone, low
yields of 2-arylbenzothiophenes 7 and 8 have been
obtained. With this heteroarylboronic acid, the best result
was obtained using the sterically congested and electron-
rich 2-bromotoluene (Table 2, entry 4). Again, for the
cross-coupling reactions with 2-benzothiopheneboronic
acid, the oxidative addition of the aryl bromide to
palladium is certainly not the rate-limiting step of the
catalytic cycle.
Scheme 3
[Pd(C3H5)Cl]2 / Tedicyp
+
Br
(HO)2B
S
R
xylene, K2CO3, 130 °C
R
S
7-10
Table 2
Suzuki reaction with 2-benzothiopheneboronic acid catalysed by the
Tedicyp-palladium complex (Scheme 3).
Entry
Aryl halide
Ratio
Product
Yield (%)a
substrate/
catalyst
20
1
2
3
4
Iodobenzene
7
8
9
10
26 (34)
6 (10)
41 (53)
92 (100)
4-Bromoacetophenone 20
In some cases, coupling reactions at elevated
temperatures are not suitable due to the decomposition of
the substrates or products. So, we performed a few
4-Bromobenzonitrile
2-Bromotoluene
100
50
Conditions: catalyst [Pd(C3H5)Cl]2 / Tedicyp 1:2, see ref. 26, ArX (1
equiv.), 2-benzothiopheneboronic acid (2 equiv.), K2CO3 (2 equiv.),
xylene, 20 h, 130 °C, under argon, isolated yields, ratio substrate/catalyst
based on the aryl halide. Yields in parenthesis correspond to GC and
NMR yields.
reactions with 3-thiopheneboronic acid at
a lower
temperature (90°C). The reactions were slower, but
satisfactory TONs of 300 and 225 were obtained with 4-
bromoacetophenone and 4-bromoanisole (Table 1, entries
3, 4, 12 and 13).
a
The Suzuki reaction with 3-thiopheneboronic acid is
not limited to the reaction with aryl bromides. A benzyl
bromide has also been successfully used as coupling
partner (Scheme 5). Moreover, this reaction proceeds in
good yield using as little as 0.1 mol % catalyst.
Then we examined the coupling of 3-thio-
pheneboronic acid with several aryl bromides to give
3-arylated thiophenes (Scheme 4, Table 3). These
compounds can not be obtained by palladium catalysed
C–H activation of thiophene. Therefore, the classical
Scheme 4
R
R
B(OH)2
Br
R
[Pd(C3H5)Cl]2 / Tedicyp
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 130 °C
+
Br
+
S
xylene, K2CO3, 90 or
130 °C
B(OH)2
11-16
S
S
R = Me, OMe, MeCO, CHO, PhCO

112
I. Kondolff, H. Doucet, M. Santelli
Vol 45
Table 3
Suzuki reaction with 3-thiopheneboronic acid catalysed by the Tedicyp-palladium complex (Scheme 4).
Entry
Aryl bromide
Arylboronic acid
Ratio substrate/catalyst
250
1000
250
1000
250
250
1000
50
1000
250
1000
250
Product
11
11
11
11
11
12
12
13
13
14
14
14
14
14
15
15
Yield (%)a
77 (82)
(55)
(84) b
(30) b
86
81 (90)
(45)
91 (97)
(60)
84 (97)
(42)
(90) b
0 b
75
84 (90)
93
74 (78)
(56)
1
2
3
4
5
6
7
8
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
3-Bromothiophene
4-Bromobenzaldehyde
4-Bromobenzaldehyde
4-Bromobenzophenone
4-Bromobenzophenone
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
3-Bromothiophene
2-Bromotoluene
3-Bromothiophene
2,4,6-Trimethylbromobenzene
2,4,6-Trimethylbromobenzene
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
4-Acetylphenylboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
4-Methoxyphenylboronic acid
3-Thiopheneboronic acid
2-Methylphenylboronic acid
3-Thiopheneboronic acid
3-Thiopheneboronic acid
9
10
11
12
13
14
15
16
17
18
1000
1000000
1000
1000000
20
16
16
100
Conditions: catalyst [Pd(C H )Cl] / Tedicyp 1:2, see ref. 26, ArBr (1 equiv.), arylboronic acid (2 equiv.), K CO (2 equiv.), xylene, 20 h,
3
5
2
2
3
130 °C, under argon, isolated yields, ratio substrate/catalyst based on the aryl halide. a Yields in parenthesis correspond to GC and NMR yields.
b Reaction temperature: 90 °C.
Scheme 5
Scheme 7
[Pd(C3H5)Cl]2 0.05% /
Tedicyp 0.1%
S
B(OH)2
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 130 °C
Br
+
Br
+
S
R
R
xylene, K2CO3, 130 °C
(HO)2B
90%
S
S
20-22
17
Then, we examined the reactivity of 2-formyl-3-thio-
pheneboronic acid (Scheme 6). Even if this function-
alised arylboronic acid is less reactive than 3-thiophene-
boronic acid, the products 18 and 19 were obtained in
good yields using 1–2 mol % catalyst.
Table 4
Suzuki reaction with 2-dibenzothiopheneboronic acid catalysed by the
Tedicyp-palladium complex (Scheme 7).
Entry Aryl bromide
Ratio
Product Yield
(%)a
substrate/
catalyst
100
Scheme 6
1
2
3
4
Bromobenzene
20
21
21
22
93 (100)
89 (100)
(67)
4-Bromoacetophenone 1000
4-Bromoacetophenone 10000
2-Bromobenzaldehyde 100
(HO)2B
[Pd(C3H5)Cl]2 / Tedicyp
92 (100)
+
X
H
S
xylene, K2CO3, 130 °C
Conditions: catalyst [Pd(C3H5)Cl]2 / Tedicyp 1:2, see ref. 26, ArBr (1
equiv.), 2-dibenzothiopheneboronic acid (2 equiv.), K2CO3 (2 equiv.),
xylene, 20 h, 130 °C, under argon, isolated yields, ratio substrate/catalyst
S
R
R
O
H
O
18, 19
a
based on the aryl halide. Yields in parenthesis correspond to GC and
NMR yields.
R = H and X = I: catalyst 1 mol % yield of 18: 90%
R = OMe and X = Br: catalyst 2 mol % yield of 19: 75%
The reactions rates using 3-furanboronic acid and aryl
halides were quite similar to those obtained with 3-thio-
pheneboronic acid (Scheme 8, Table 5). With this hetero-
arylboronic acid, iodobenzene, 4-bromoaceto-phenone, 4-
bromobenzonitrile or 2-bromotoluene gave the arylfuran
derivatives 23–26 in good yields in the presence of 0.4–
0.1% catalyst (Table 5, entries 1, 2, 4, 5, 7–11). The
reverse reaction using 3-bromofuran and arylboronic
acids also gave the expected 3-arylfuranes in the presence
of 0.4–0.1% catalyst (Table 5, entries 3, 6 and 13).
The Suzuki reaction with 2-dibenzothiophene-
boronic acid gave the expected 2-aryldibenzothio-
phene derivatives 20–22 in high yields (Scheme 7,
Table 4). This reaction led to a higher TON of 6700
using the electron-deficient 4-bromoacetophenone
than with bromobenzene. With this substrate, the
oxidative addition of the aryl bromide to palladium
might be rate-limiting.

Jan-Feb 2008
Palladium/Tetraphosphine Catalyzed Suzuki Cross-Couplilng of Heteroarylboronic Acids
113
Scheme 8
R
R
B(OH)2
Br
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 130 °C
R
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 90 °C
+
Br
+
O
B(OH)2
23-26
O
O
23-26
R = H, Me, MeCO, CN
Table 5
Suzuki reaction with 3-furanboronic acid catalysed by the Tedicyp-palladium complex (Scheme 8).
Entry
1
2
3
4
5
6
7
8
Aryl halide
Arylboronic acid
Ratio substrate/catalyst
250
1000
1000
250
1000
250
100
250
100
250
1000
100
Product
23
23
23
24
24
24
25
25
26
26
26
26
Yield (%)a
83 (100)
(68)
91 (100) b
81 (98)
(84)
87 (94) b
(98)
68
(100)
81 (90)
(28)
0 b
70 b
Iodobenzene
Iodobenzene
3-Bromofuran
3-Furanboronic acid
3-Furanboronic acid
Benzeneboronic acid
3-Furanboronic acid
3-Furanboronic acid
4-Acetylphenylboronic acid
3-Furanboronic acid
3-Furanboronic acid
3-Furanboronic acid
3-Furanboronic acid
3-Furanboronic acid
3-Furanboronic acid
2-Methylphenylboronic acid
4-Bromoacetophenone
4-Bromoacetophenone
3-Bromofuran
4-Bromobenzonitrile
4-Bromobenzonitrile
2-Bromotoluene
2-Bromotoluene
2-Bromotoluene
2-Bromotoluene
3-Bromofuran
9
10
11
12
13
250
26
Conditions: catalyst [Pd(C3H5)Cl]2 / Tedicyp 1:2, see ref. 26, ArX (1 equiv.), 3-furanboronic acid (2 equiv.), K2CO3 (2 equiv.), xylene, 20 h,
130 °C, under argon, isolated yields, ratio substrate/catalyst based on the aryl halide. a Yields in parenthesis correspond to GC and NMR yields.
b Reaction temperature: 90 °C.
However, these reactions were performed at a lower
temperature (90 °C) due to the low boiling point of
3-bromofuran. In order to compare the respective rates of
the reactions, a coupling was also performed with
3-furanboronic acids and 2-bromotoluene at 90 °C but, the
aryl bromide was recovered unreacted (Table 5, entry 12).
We had previously reported that the coupling of 5-bromo-
2-furaldehyde with arylboronic acids proceeds in very
high TONs [33].
oxidative addition is not the rate limiting-step of the
catalytic cycle.
Scheme 9
[Pd(C3H5)Cl]2 / Tedicyp
+
Br
(HO)2B
O
xylene, K2CO3, 130 °C
R
R
O
27-32
The direct arylation of benzofuran via C–H function-
alisation has been reported by Ohta in 1990, but the yields
were low (12–50%) [36]. To our knowledge, high yield
arylations of benzofuran via C–H activation have not been
reported so far. Therefore, the arylation of 2-benzofuran-
boronic acid remains a simple process for the formation of
2-arylbenzothiophenes. We found that 2-benzofuran-
boronic acid is less reactive than 3-furanboronic acid
(Scheme 9, Table 6). However, with electron-deficient
aryl bromides such as 4-bromo-benzophenone, 4-bromo-
benzaldehyde or 4-bromo-benzonitrile high yields of
products 27–30 were obtained using 1–5 mol % catalyst
(Table 6, entries 1–6). With the electron-excessive or the
sterically congested aryl bromides, 4-bromoanisole or 2-
bromotoluene, similar results were obtained (Table 6,
entries 7–10). These results indicate that for the reaction
with 2-benzofuranboronic acid and aryl bromides, the
Finally, we studied the synthesis of 3-arylpyridines by
coupling of 3-pyridineboronic acid with several aryl
bromides and also by reaction of 3-bromopyridine with
arylboronic acids (Scheme 10, Table 7). Relatively slow
reactions were observed with 3-pyridineboronic acid, and
2–10% catalyst had to be used in order to obtain high
yields of adducts (Table 7, entries 1, 3, 4, 6, 8, 10, 11, 13,
14, 16 and 18). The results unfold a minor substituent
effect of the aryl bromide on the reaction rate, indicating
that again, with 3-pyridineboronic acid as coupling
partner, the rate-limiting step of the reaction is not the
oxidative addition of the aryl bromide. The reverse
coupling reactions using 3-bromopyridine and arylboronic
acids gave much more satisfactory results in terms of ratio
substrate/catalyst. The reactions were performed using
0.1–0.001% catalyst (Table 7, entries 2, 5, 7, 9, 12, 15, 17
and 18). For example, a TON of 8 was obtained for the

114
I. Kondolff, H. Doucet, M. Santelli
Vol 45
Table 6
Suzuki reaction with 2-benzofuraneboronic acid catalysed by the Tedicyp-palladium complex (Scheme 9).
Entry
Aryl halide
Ratio substrate/catalyst
20
100
250
20
20
100
20
Product
27
28
28
29
30
30
31
31
Yield (%)a
66 (81)
95 (100)
(27)
85 (92)
88 (100)
(52)
62 (80)
(60)
75 (88)
(34)
1
2
3
4
5
6
7
8
4-Bromoacetophenone
4-Bromobenzaldehyde
4-Bromobenzaldehyde
4-Bromobenzophenone
4-Bromobenzonitrile
4-Bromobenzonitrile
4-Bromoanisole
4-Bromoanisole
2-Bromotoluene
2-Bromotoluene
100
20
100
9
10
32
32
Conditions: catalyst [Pd(C3H5)Cl]2 / Tedicyp 1:2, see ref. 26, ArX (1 equiv.), 2-Benzofuraneboronic acid (2 equiv.), K2CO3 (2 equiv.), xylene, 20 h,
130 °C, under argon, isolated yields, ratio substrate/catalyst based on the aryl halide. a Yields in parenthesis correspond to GC and NMR yields.
coupling of 3-pyridineboronic acid with 1-bromo-napht-
halene; and a TON of 56000 for the reaction of
3-bromopyridine with 1-naphthaleneboronic acid (Table
7, entries 16 and 18).
In summary, in the presence of the Tedicyp/palladium
complex, the Suzuki cross-coupling of heteroarylboronic
acids such as 3-thiopheneboronic acid or 3-furanboronic
acid with aryl bromides can be performed with as little as
0.1% catalyst. On the other hand, with 2-thiophene-, 2-
benzothiophene-, 2-benzofuran- and 3-pyridineboronic
acids, the reactions are quite slow and were generally
performed with 1–10% catalyst. Pyridines are ꢀ-electron
deficient heterocycles. Thiophenes or furans are ꢀ-
electron excessive. These results seem to demonstrate
that the electron-density on the heteroarylboronic acid is
not a determining factor for the success of such couplings.
On the other hand, palladium(II) possesses strong
thiophilicity. This is reflected in the poisoning effects of
Scheme 10
R
R
B(OH)2
Br
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 130 °C
[Pd(C3H5)Cl]2 / Tedicyp
xylene, K2CO3, 130 °C
R
+
+
N
Br
B(OH)2
33-42
N
N
Table 7
Suzuki reaction with pyridine derivatives catalysed by the Tedicyp-palladium complex (Scheme 10).
Entry
1
2
3
4
5
6
7
8
Aryl bromide
Arylboronic acid
Ratio substrate/catalyst
33
1000000
20
20
100
10
100000
20
100000
20
50
1000
10
20
10000
10
10000
100000
20
Product
Yield (%)a
75
Bromobenzene
3-Pyridineboronic acid
Benzeneboronic acid
33
33
34
35
35
36
36
37
37
38
38
38
39
40
40
41
41
41
42
3-Bromopyridine
4-Bromobenzophenone
3-Bromobenzaldehyde
3-Bromopyridine
4-Fluorobromobenzene
3-Bromopyridine
4-Bromoanisole
3-Bromopyridine
2-Bromoacetophenone
2-Bromoacetophenone
3-Bromopyridine
2-Bromoanisole
98b,c
3-Pyridineboronic acid
3-Pyridineboronic acid
3-Formylphenylboronic acid
3-Pyridineboronic acid
4-Fluorophenylboronic acid
3-Pyridineboronic acid
4-Methoxyphenylboronic acid
3-Pyridineboronic acid
3-Pyridineboronic acid
2-Acetylphenylboronic acid
3-Pyridineboronic acid
3-Pyridineboronic acid
2-Methylphenylboronic acid
3-Pyridineboronic acid
1-Naphthaleneboronic acid
1-Naphthaleneboronic acid
3-Pyridineboronic acid
82 (100)
84 (100)
87 (100)
84
96b,d
80
82b
80 (100)
(49)
77
61 (70)
85 (100)
87b
84
77
(56)
85 (98)
9
10
11
12
13
14
15
16
17
18
19
2-Bromotoluene
3-Bromopyridine
1-Bromonaphthalene
3-Bromopyridine
3-Bromopyridine
2,6-Dimethylbromobenzene
Conditions: catalyst [Pd(C3H5)Cl]2 / Tedicyp 1:2, see ref. 26, ArBr (1 equiv.), arylboronic acid (2 equiv.), K2CO3 (2 equiv.), xylene, 20 h, 130
a
°C, under argon, isolated yields, ratio substrate/catalyst based on the aryl halide. Yields in parenthesis correspond to GC and NMR yields.
b Ref. 33b. c PhB(OH)2 1.5 equiv., 115 h. d PhB(OH)2 1.5 equiv., 90 h.

Jan-Feb 2008
Palladium/Tetraphosphine Catalyzed Suzuki Cross-Couplilng of Heteroarylboronic Acids
115
mL), Tedicyp-palladium complexe (10 μmol) gave 2 in 80%
(162 mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.59 (s,
3H), 7.11 (dd, J = 5.1, 3.6 Hz, 1H), 7.36 (d, J = 5.1 Hz, 1H),
7.42 (d, J = 3.6 Hz, 1H), 7.68 (d, J = 8.3 Hz, 2H), 7.95 (d, J =
8.3 Hz, 2H).
the sulphur atom on some palladium-catalysed reactions.
This poisoning effect has also been observed in the
presence of nitrogen atoms. For this reason, the halide
position on the heteroaroaryl boronic acid has an
important effect on the reactions rates. This could
partially explain the differences of reactivity between
4-(Thiophen-2-yl)benzophenone (3). (Table 1, entry 7) 4-
Bromobenzophenone (261 mg, 1 mmol), 2-thiopheneboronic
acid (256 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (20 μmol) gave 3 in 39%
these heteroarylboronic acids.
With most of these
heteroarylboronic acid derivatives similar reaction rates
were generally observed in the presence of 4-bromo-
acetophenone or 4-bromoanisole indicating that the rate-
limiting step of these reactions does not seem to be the
oxidative addition of the aryl halides to palladium. In
order to obtain higher TONs for the synthesis of these
products, we also studied the reverse reactions using
arylboronic acids and heteroaryl bromides. We observed
that, in most cases, much higher reaction rates were
obtained for the coupling of bromothiophenes or 3-
bromopyridine with arylboronic acids. For this reason,
for the synthesis of arylthiophene or arylpyridine
derivatives, the boronic acid function should preferably be
located on the aryl and the halide on the heteroaryl rather
than the reverse.
1
(103 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.12
(dd, J = 5.0, 3.7 Hz, 1H), 7.37 (d, J = 5.0 Hz, 1H), 7.44 (d, J =
3.7 Hz, 1H), 7.48 (t, J = 7.7 Hz, 2H), 7.58 (t, J = 7.7 Hz, 1H),
7.71 (d, J = 8.5 Hz, 2H), 7.80 (d, J = 7.7 Hz, 2H), 7.83 (d, J =
8.5 Hz, 2H). 13C nmr (300 MHz, CDCl3): ꢀ = 124.5, 125.4,
126.4, 128.3, 128.4, 129.9, 130.9, 132.3, 136.1, 137.7, 138.3,
143.0, 195.9. MS (EI, 70 eV): m/z (%) = 264 (100) [M+]. Anal.
Calcd. for C17H12OS, C, 77.24; H, 4.58; found C, 77.42; H, 4.42.
White solid mp = 127 °C.
2-(4-Methoxyphenyl)thiophene (4). (Table 1, entry 9) 4-
Bromoanisole (187 mg, 1 mmol), 2-thiopheneboronic acid (256
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (20 μmol) gave 4 in 81% (154 mg)
isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 3.83 (s, 3H), 6.91
(d, J = 8.9 Hz, 2H), 7.04 (dd, J = 5.1, 3.7 Hz, 1H), 7.19 (d, J =
3.7 Hz, 1H), 7.21 (d, J = 5.1 Hz, 1H), 7.54 (d, J = 8.9 Hz, 2H).
2-(2-Methylphenyl)thiophene (5). (Table 1, entry 11) 2-
Bromotoluene (171 mg, 1 mmol), 2-thiopheneboronic acid (256
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (50 μmol) gave 5 in 87% (151 mg)
EXPERIMENTAL
General. All reactions were run under argon using vacuum
lines in Schlenk tubes in oven-dried glassware. Xylene was not
distilled before use. Commercial arylboronic acids and aryl
halides were used without purification. 1H (300 MHz) and 13C
(75 MHz) spectra were recorded in CDCl3 solutions. Chemical
shift (ꢀ) are reported in ppm relative to CDCl3. Flash
chromatographies were performed on silica gel (230–400 mesh).
Preparation of the Pd-Tedicyp Catalyst [26]. An oven-dried
40-mL Schlenk tube equipped with a magnetic stirring bar,
under argon atmosphere, was charged with [Pd(C3H5)Cl]2 (4.2
mg, 11.6 μmol) and Tedicyp (20 mg, 23.2 μmol). 2.5 mL of
anhydrous DMF were added then the solution was stirred at
room temperature for 10 min. The appropriate amount of
catalyst (see tables) was transferred to the mixture of aryl halide,
arylboronic acid and base in xylene.
1
isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 2.42 (s, 3H),
7.04–7.11 (m, 2H), 7.15–7.25 (m, 3H), 7.33 (dd, J = 5.0, 1.3 Hz,
1H), 7.40 (dd, J = 5.7, 2.7 Hz, 1H).
2-Acetyl-5-phenylthiophene (6). (Scheme 2) Iodobenzene
(204 mg, 1 mmol), 2-acetyl-5-thiopheneboronic acid (340 mg, 2
mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-
palladium complexe (100 μmol) gave 6 in 74% (150 mg)
isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.56 (s, 3H), 7.32
(d, J = 4.2 Hz, 1H), 7.38 (d, J = 4.2 Hz, 1H), 7.40 (t, J = 7.1 Hz,
2H), 7.63–7.65 (m, 1H), 7.66 (d, J = 7.1 Hz, 2H).
2-Phenylbenzothiophene (7). (Table 2, entry 1) Iodoben-
zene (204 mg, 1 mmol), 2-benzothiopheneboronic acid (356 mg,
2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-
palladium complexe (50 μmol) gave 7 in 26% (55 mg) isolated
1
yield. H nmr (300 MHz, CDCl3): ꢀ = 7.27–7.38 (m, 3H), 7.41
Catalytic procedure for Suzuki reactions. As a typical
experiment, the reaction of the arylboronic acid (2 mmol), aryl
bromide (1 mmol) and K2CO3 (276 mg, 2 mmol) at 130 °C over
20 h in xylene (3 mL) in the presence of cis,cis,cis-1,2,3,4-
tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C3H5)]2
complex under argon afforded the corresponding products after
addition of water, extraction with dichloromethane, separation,
drying (MgSO4), evaporation and chromatography on silica gel.
2-Phenylthiophene (1). (Table 1, entry 1) Iodobenzene (204
mg, 1 mmol), 2-thiopheneboronic acid (256 mg, 2 mmol),
K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium
(t, J = 7.6 Hz, 2H), 7.54 (s, 1H), 7.71 (d, J = 7.6 Hz, 2H), 7.77
(d, J = 6.8 Hz, 1H), 7.85 (d, J = 7.1 Hz, 1H).
2-(4-Acetylphenyl)benzothiophene (8). (Table 2, entry 2)
4-Bromoacetophenone (199 mg, 1 mmol), 2-benzothiophene-
boronic acid (356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (50 μmol) gave 8
1
in 6% (15 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
2.62 (s, 3H), 7.35 (ddd, J = 6.0, 4.2, 3.2 Hz, 2H), 7.66 (s, 1H),
7.78 (d, J = 8.5 Hz, 2H), 7.80–7.86 (m, 2H), 8.00 (d, J = 8.5 Hz,
2H).
1
2-(4-Benzonitrile)benzothiophene (9). (Table 2, entry 3) 4-
Bromobenzonitrile (182 mg, 1 mmol), 2-benzothiopheneboronic
acid (356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (10 μmol) gave 9 in 41% (96
complexe (10 μmol) gave 1 in 82% (131 mg) isolated yield. H
nmr (300 MHz, CDCl3): ꢀ = 7.08 (dd, J = 5.1, 3.6 Hz, 1H), 7.19
(d, J = 5.1 Hz, 1H), 7.25–7.34 (m, 2H), 7.38 (t, J = 7.5 Hz, 2H),
7.62 (dd, J = 7.5, 1.5 Hz, 2H).
4-(Thiophen-2-yl)acetophenone (2). (Table 1, entry 4) 4-
Bromoacetophenone (199 mg, 1 mmol), 2-thiopheneboronic
acid (256 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
1
mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.37 (t, J =
4.5 Hz, 2H), 7.64 (s, 1H), 7.68 (d, J = 8.6 Hz, 2H), 7.79 (d, J =
8.6 Hz, 2H), 7.80–7.86 (m, 2H).

116
I. Kondolff, H. Doucet, M. Santelli
Vol 45
1
2-(2-Methylphenyl)benzothiophene (10). (Table 2, entry 4)
mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.22 (d, J =
4.9 Hz, 1H), 7.43–7.50 (m, 5H), 7.73 (dd, J = 4.9, 1.3 Hz, 1H),
9.88 (d, J = 1.3 Hz, 1H).
2-Bromotoluene (171 mg, 1 mmol), 2-benzothiopheneboronic
acid (356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (20 μmol) gave 10 in 92%
(206 mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.48 (s,
3H), 7.27–7.50 (m, 7H), 7.79 (d, J = 7.2 Hz, 1H), 7.85 (d, J = 8.1
Hz, 1H).
3-(4-Acetylphenyl)thiophene (11). (Table 3, entry 1)
4-Bromoacetophenone (199 mg, 1 mmol), 3-benzothiophene-
boronic acid (356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (4 μmol) gave 10
in 77% (0.156 g) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ =
2.61 (s, 3H), 7.39–7.44 (m, 2H), 7.56 (t, J = 2.1 Hz, 1H), 7.67
(d, J = 8.5 Hz, 2H), 7.98 (d, J = 8.5 Hz, 2H).
2-Formyl-3-(2-methoxyphenyl)thiophene (19): (Scheme 6)
2-Bromoanisole (187 mg,
boronic acid (312 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (20 μmol) gave 19
1 mmol), 2-formyl-3-thiophene-
1
in 75% (164 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
3.79 (s, 3H), 6.95–7.10 (m, 2H), 7.18 (d, J = 5.0 Hz, 1H), 7.25–
7.30 (m, 1H), 7.40 (td, J = 7.5, 4.4 Hz, 1H), 7.68 (dd, J = 5.0, 1.1
Hz, 1H), 9.71 (d, J = 1.1 Hz, 1H).
4-Phenyldibenzothiophene (20). (Table 4, entry 1) Bromo-
benzene (157 mg, 1 mmol), 2-dibenzothiopheneboronic acid (456
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-
palladium complexe (10 μmol) gave 20 in 93% (242 mg) isolated
yield. 1H nmr (300 MHz, CDCl3): ꢀ = 7.45–7.61 (m, 7H), 7.77 (d,
J = 7.0 Hz, 2H), 7.85 (m, 1H), 8.13-8.22 (m, 2H).
4-(4-Acetylphenyl)dibenzothiophene (21). (Table 4, entry
2) 4-Bromoacetophenone (199 mg, 1 mmol), 2-dibenzothio-
pheneboronic acid (456 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (1 μmol) gave 21
4-Thiophen-3-yl-benzaldehyde (12). (Table 3, entry 6)
4-Bromobenzaldehyde (185 mg, 1 mmol), 3-benzothiophene-
boronic acid (356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (4 μmol) gave 12
1
in 81% (152 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
7.40–7.47 (m, 2H), 7.61 (t, J = 2.2 Hz, 1H), 7.75 (d, J = 8.1 Hz,
2H), 7.91 (d, J = 8.1 Hz, 2H), 10.02 (s, 1H).
1
Phenyl-(4-thiophen-3-yl-phenyl)-methanone (13). (Table 3,
entry 8) 4-Bromobenzophenone (261 mg, 1 mmol), 3-benzo-
thiopheneboronic acid (356 mg, 2 mmol), K2CO3 (276 mg, 2
mmol), xylene (3 mL), Tedicyp-palladium complexe (20 μmol)
in 89% (269 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
2.67 (s, 3H), 7.45–7.52 (m, 3H), 7.58 (t, J = 7.6 Hz, 1H), 7.83–
7.86 (m, 1H), 7.84 (d, J = 8.2 Hz, 2H), 8.11 (d, J = 8.2 Hz, 2H),
8.16–8.21 (m, 2H). 13C nmr (300 MHz, CDCl3): ꢀ = 26.7, 121.2,
121. 8, 122.6, 124.5, 125.2, 126.9, 127.0, 128.5, 128.9, 135.6,
135.8, 136.5, 138.4, 139.4, 145.3, 197.7. Anal. Calcd. For
C20H14OS: C, 79.44; H, 4.67, found C, 79.57; H, 4.84. MS (EI,
70 eV): m/z (%) = 302 (81) [M+]. White solid mp = 129 °C.
2-Dibenzothiophen-4-ylbenzaldehyde (22). (Table 4, entry
4) 2-Bromobenzaldehyde (185 mg, 1 mmol), 2-dibenzothio-
pheneboronic acid (456 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (10 μmol) gave 22
1
gave 13 in 91% (240 mg) isolated yield. H nmr (300 MHz,
CDCl3): ꢀ = 7.40–7.46 (m, 2H), 7.48 (t, J = 8.0 Hz, 2H), 7.55–
7.60 (m, 2H), 7.69 (d, J = 8.7 Hz, 2H), 7.80 (d, J = 8.0 Hz, 2H),
7.85 (d, J = 8.7 Hz, 2H). 13C nmr (300 MHz, CDCl3): ꢀ = 121.9,
126.1, 126.2, 126.7, 128.3, 129.9, 130.9, 132.3, 135.9, 137.8,
139.7, 141.1, 196.1. MS (EI, 70 eV): m/z (%) = 264 (100) [M+].
Anal. Calcd. For C17H12OS: C, 77.24; H, 4.58, found C, 76.96;
H, 4.82. White solid mp = 155 °C.
1
3-(4-Methoxyphenyl)thiophene (14). (Table 3, entry 10)
4-Bromoanisole (187 mg, 1 mmol), 3-benzothiopheneboronic acid
(356 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (4 μmol) gave 14 in 84% (160 mg)
in 92% (265 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
7.39 (dd, J = 7.4, 1.2 Hz, 1H), 7.47 (ddd, J = 6.5, 4.3, 2.2 Hz,
2H), 7.55–7.63 (m, 3H), 7.68–7.81 (m, 2H), 8.13 (dd, J = 8.5,
1.9 Hz, 1H), 8.17–8.25 (m, 2H), 9.81 (s, 1H).
3-Phenylfuran (23). (Table 5, entry 1) Iodobenzene (204
mg, 1 mmol), 3-furanboronic acid (224 mg, 2 mmol), K2CO3
(276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium complexe
1
isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 3.82 (s, 3H), 6.92
(d, J = 8.9 Hz, 2H), 7.30–7.36 (m, 3H), 7.51 (d, J = 8.9 Hz, 2H).
3-(2-Methylphenyl)thiophene (15). acid (356 mg, 2 mmol),
K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium
1
(4 μmol) gave 23 in 83% (120 mg) isolated yield. H nmr (300
1
complexe (1 μmol) gave 15 in 84% (146 mg) isolated yield. H
MHz, CDCl3): ꢀ = 6.70 (dd, J = 1.3, 0.9 Hz, 1H), 7.25–7.30 (m,
1H), 7.37 (t, J = 7.6 Hz, 2H), 7.46 (t, J = 1.3 Hz, 1H), 7.49 (d, J
= 7.6 Hz, 2H), 7.72 (bs, 1H).
nmr (300 MHz, CDCl3): ꢀ = 2.37 (s, 3H), 7.16 (dd, J = 4.9, 1.4
Hz, 1H), 7.21–7.28 (m, 4H), 7.30 (m, 1H), 7.36 (dd, J = 4.9, 3.0
Hz, 1H).
1-(4-Furan-3-ylphenyl)-ethanone (24). (Table 5, entry 4) 4-
Bromoacetophenone (199 mg, 1 mmol), 3-furanboronic acid
(224 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (4 μmol) gave 24 in 81% (151 mg)
isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.60 (s, 3H), 6.74
(dd, J = 1.8, 0.9 Hz, 1H), 7.50 (t, J = 1.8 Hz, 1H), 7.56 (d, J =
8.3 Hz, 2H), 7.82 (bs, 1H), 7.96 (d, J = 8.3 Hz, 2H). 13C NMR
(300 MHz, CDCl3): ꢀ = 26.5, 108.6, 125.7, 129.0, 135.6, 137.2,
139.6, 144.1, 197.4. MS (EI, 70 eV): m/z (%) = 186 (53) [M+].
Anal. Calcd. For C12H10O2: C, 77.40; H, 5.41, found C, 77.23; H,
5.36. White solid mp = 96 °C.
4-Furan-3-ylbenzonitrile (25). (Table 5, entry 8) 4-Bromo-
benzonitrile (182 mg, 1 mmol), 3-furanboronic acid (224 mg, 2
mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-
palladium complexe (4 μmol) gave 25 in 68% (115 mg) isolated
yield. H nmr (300 MHz, CDCl3): ꢀ = 6.70 (dd, J = 1.9, 0.9 Hz,
1H), 7.51 (t, J = 1.9 Hz, 1H), 7.56 (d, J = 9.6 Hz, 2H), 7.64 (d, J
= 9.6 Hz, 2H), 7.81 (t, J = 0.9 Hz, 1H).
3-(2,4,6-Trimethylphenyl)thiophene (16): (Table 3, entry
17) 2,4,6-Trimethylbromobenzene (199 mg, 1 mmol), 3-benzo-
thiopheneboronic acid (356 mg, 2 mmol), K2CO3 (276 mg, 2
mmol), xylene (3 mL), Tedicyp-palladium complexe (50 μmol)
1
gave 16 in 74% (150 mg) isolated yield. H nmr (300 MHz,
CDCl3): ꢀ = 2.04 (s, 6H), 2.30 (s, 3H), 6.86–6.93 (m, 3H), 7.00–
7.04 (m, 1H), 7.36–7.40 (m, 1H).
3-Benzylthiophene (17). (Scheme 5) Benzyl bromide (171
mg, 1 mmol), 3-thiopheneboronic acid (256 mg, 2 mmol),
K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium
1
complexe (1 μmol) gave 17 in 90% (157 mg) isolated yield. H
nmr (300 MHz, CDCl3): ꢀ = 4.02 (s, 2H), 7.24–7.40 (m, 6H),
7.95 (m, 2H).
2-Formyl-3-phenylthiophene (18). (Scheme 6) Iodo-
benzene (204 mg, 1 mmol), 2-formyl-3-thiopheneboronic acid
(312 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (10 μmol) gave 18 in 90% (169
1

Jan-Feb 2008
Palladium/Tetraphosphine Catalyzed Suzuki Cross-Couplilng of Heteroarylboronic Acids
117
3-o-Tolylfuran (26). (Table 5, entry 10) 2-Bromotoluene
(171 mg, 1 mmol), 3-furanboronic acid (224 mg, 2 mmol),
K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium
complexe (33 μmol) gave 33 in 75% (116 mg) isolated yield. 1H
nmr (300 MHz, CDCl3): ꢀ = 7.33–7.42 (m, 2H), 7.48 (t, J = 7.1
Hz, 2H), 7.58 (d, J = 7.1 Hz, 2H), 7.87 (dt, J = 8.0, 1.9 Hz, 1H),
8.58 (dd, J = 4.7, 1.9 Hz, 1H), 8.84 (d, J = 2.2 Hz, 1H).
1
complexe (4 μmol) gave 26 in 81% (128 mg) isolated yield. H
nmr (300 MHz, CDCl3): ꢀ = 2.38 (s, 3H), 6.58 (dd, J = 1.7, 0.9
Hz, 1H), 7.17–7.35 (m, 4H), 7.47 (t, J = 1.7 Hz, 1H), 7.52 (d, J =
0.9 Hz, 1H).
Phenyl-(4-pyridin-3-yl-phenyl)-methanone (34). (Table 7,
entry 3) 4-Bromobenzophenone (261 mg, 1 mmol), 3-pyridine-
boronic acid (246 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (50 μmol) gave 34
1-(4-Benzofuran-2-yl-phenyl)-ethanone (27).
(Table 6,
1
entry 1) 4-Bromoacetophenone (199 mg, 1 mmol), 2-benzo-
furanboronic acid (324 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (50 μmol) gave 27
in 82% (210 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
7.45 (dd, J = 7.9, 4.9 Hz, 1H), 7.54 (t, J = 7.1 Hz, 2H), 7.63 (t, J
= 7.1 Hz, 1H), 7.75 (d, J = 8.4 Hz, 2H), 7.88 (d, J = 8.4 Hz, 2H),
7.93–8.03 (m, 3H), 8.70 (dd, 1H, J = 4.8, 1.8 Hz, 1H), 8.95 (d, J
= 1.8 Hz, 1H).
1
in 66% (156 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
2.62 (s, 3H), 7.15 (s, 1H), 7.27 (td, J = 7.8, 1.2 Hz, 1H), 7.33 (td,
J = 7.8, 1.2 Hz, 1H), 7.53 (d, J = 7.8 Hz, 1H), 7.59 (d, J = 7.8
Hz, 1H), 7.93 (d, J = 8.4 Hz, 2H), 8.03 (d, J = 8.4 Hz, 2H).
4-Benzofuran-2-yl-benzaldehyde (28). (Table 6, entry 2)
4-Bromobenzaldehyde (185 mg, 1 mmol), 2-benzofuranboronic
acid (324 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (10 μmol) gave 28 in 95%
(211 mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 7.19 (s,
1H), 7.28 (td, J = 7.8, 1.5 Hz, 1H), 7.32 (td, J = 7.8, 1.5 Hz, 1H),
7.52 (d, J = 7.8 Hz, 1H), 7.61 (d, J = 7.8 Hz, 1H), 7.92 (d, J =
8.4 Hz, 2H), 8.01 (d, J = 8.4 Hz, 2H), 10.02 (s, 1H).
3-Pyridin-3-yl-benzaldehyde (35). (Table 7, entry 4)
3-Bromobenzaldehyde (185 mg, 1 mmol), 3-pyridineboronic
acid (246 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (50 μmol) gave 35 in 84%
1
(174 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.42
(dd, J = 7.6, 4.9 Hz, 1H), 7.66 (t, J = 7.8 Hz, 1H), 7.85 (dt, J =
7.6, 1.0 Hz, 1H), 7.93 (dd, J = 7.8, 1.3 Hz, 2H), 8.08 (s, 1H),
8.64 (bs, 1H), 8.89 (bs, 1H), 10.09 (s, 1H).
3-(4-Fluorophenyl)-pyridine (36).
(Table 7, entry 6)
4-Fluorobromobenzene (175 mg, 1 mmol), 3-pyridineboronic
acid (246 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (100 μmol) gave 36 in 84%
(4-Benzofuran-2-yl-phenyl)-phenylmethanone (29).
(Table 6, entry 4) 4-Bromobenzophenone (261 mg, 1 mmol),
2-benzofuranboronic acid (324 mg, 2 mmol), K2CO3 (276 mg, 2
mmol), xylene (3 mL), Tedicyp-palladium complexe (50 μmol)
1
(145 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.14
(dd, J = 8.8, 8.6 Hz, 2H), 7.35 (dd, J = 7.7, 4.9 Hz, 1H), 7.54
(dd, J = 8.8, 5.3 Hz, 2H), 7.83 (dt, J = 7.7, 1.4 Hz, 1H), 8.59 (bs,
1H), 8.81 (bs, 1H).
1
gave 29 in 85% (253 mg) isolated yield. H nmr (300 MHz,
CDCl3): ꢀ = 7.18 (d, J = 0.8 Hz, 1H), 7.26 (td, J = 8.0, 1.3 Hz,
1H), 7.33 (td, J = 8.0, 1.3 Hz, 1H), 7.46–7.64 (m, 5H), 7.82 (dd,
J = 7.0, 1.3 Hz, 2H), 7.90 (d, J = 8.6 Hz, 2H), 7.97 (d, J = 8.6
Hz, 2H). 13C nmr (300 MHz, CDCl3): ꢀ = 103.5, 111.4, 121.3,
123.2, 124.5, 125.1, 128.3, 128.9, 129.9, 130.7, 132.5, 134.1,
137.0, 137.6, 154.6, 155.2, 195.9. MS (EI, 70 eV): m/z (%) =
298 (100) [M+]. Anal. Calcd. For C21H14O2: C, 84.54; H, 4.73,
found C, 84.38; H, 4.84. White solid mp = 192 °C.
4-Benzofuran-2-ylbenzonitrile (30). (Table 6, entry 5)
4-Bromobenzonitrile (182 mg, 1 mmol), 2-benzofuranboronic
acid (324 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (50 μmol) gave 30 in 88%
(193 mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 7.16 (s,
1H), 7.26 (td, J = 7.8, 1.3 Hz, 1H), 7.34 (td, J = 7.8, 1.3 Hz, 1H),
7.53 (d, J = 7.9 Hz, 1H), 7.61 (d, J = 7.9 Hz, 1H), 7.71 (d, J =
8.6 Hz, 2H), 7.94 (d, J = 8.6 Hz, 2H).
2-(4-Methoxyphenyl)-benzofuran (31). (Table 6, entry 7)
4-Bromoanisole (187 mg, 1 mmol), 2-benzofuranboronic acid
(324 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (50 μmol) gave 31 in 62% (139
mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 3.85 (s, 3H),
6.88 (s, 1H), 6.97 (d, J = 9.0 Hz, 2H), 7.17–7.25 (m, 2H), 7.49
(dd, J = 7.4, 1.1 Hz, 1H), 7.55 (dd, J = 7.4, 1.1 Hz, 1H), 7.79 (d,
J = 9.0 Hz, 2H).
3-(4-Methoxyphenyl)-pyridine (37). (Table 7, entry 8)
4-Bromoanisole (187 mg, 1 mmol), 3-pyridineboronic acid (246
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (50 μmol) gave 37 in 80% (148
mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 3.85 (s, 3H),
7.00 (d, J = 8.9 Hz, 2H), 7.35 (dd, J = 7.5, 4.7 Hz, 1H), 7.50 (d, J
= 8.9 Hz, 2H), 7.82 (dt, J = 7.5, 1.5 Hz, 1H), 8.54 (dd, J = 4.7,
1.5 Hz, 1H), 8.80 (d, J = 1.5 Hz, 1H).
1-(2-Pyridin-3-ylphenyl)-ethanone (38). (Table 7, entry 10)
2-Bromoacetophenone (199 mg, 1 mmol), 3-pyridineboronic
acid (246 mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3
mL), Tedicyp-palladium complexe (50 μmol) gave 38 in 80%
(147 mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.19 (s,
3H), 7.32–7.38 (m, 2H), 7.47 (td, J = 7.6, 1.3 Hz, 1H), 7.55 (td, J
= 7.6, 1.5 Hz, 1H), 7.62–7.68 (m, 2H), 8.58 (bs, 1H), 8.62 (d, J =
3.4 Hz, 1H).
3-(2-Methoxyphenyl)pyridine (39). (Table 7, entry 13)
2-Bromoanisole (187 mg, 1 mmol), 3-pyridineboronic acid (246
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (100 μmol) gave 39 in 61% (113
mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 3.81 (s, 3H),
6.67–7.10 (m, 2H), 7.30–7.40 (m, 3H), 7.85 (dt, J = 8.0, 2.1 Hz,
1H), 8.54 (d, J = 3.7 Hz, 1H), 8.76 (bs, 1H).
2-o-Tolylbenzofuran (32). (Table 6, entry 9) 2-Bromo-
toluene (171 mg, 1 mmol), 2-benzofuranboronic acid (324 mg, 2
mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-
palladium complexe (50 μmol) gave 32 in 75% (156 mg)
isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.58 (s, 3H), 6.89
(s, 1H), 7.24–7.35 (m, 5H), 7.52 (dd, J = 7.2, 1.0 Hz, 1H), 7.61
(dd, J = 7.2, 1.0 Hz, 1H), 7.85 (m, 1H).
3-Phenylpyridine (33). (Table 7, entry 1) Bromobenzene
(157 mg, 1 mmol), 3-pyridineboronic acid (246 mg, 2 mmol),
K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-palladium
3-(2-Methylphenyl)pyridine (40).
(Table 7, entry 14)
2-Bromotoluene (171 mg, 1 mmol), 3-pyridineboronic acid (246
mg, 2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL),
Tedicyp-palladium complexe (50 μmol) gave 40 in 85% (144
mg) isolated yield. 1H nmr (300 MHz, CDCl3): ꢀ = 2.27 (s, 3H),
7.18–7.31 (m, 4H), 7.34 (dd, J = 7.8, 4.8 Hz, 1H), 7.65 (dt, J =
7.8, 1.9 Hz, 1H), 8.56 (dd, J = 4.8, 1.9 Hz, 1H), 8.59 (s, 1H).
3-(1-Naphthyl)pyridine (41). (Table 7, entry 16) 1-Bromo-
naphthalene (207 mg, 1 mmol), 3-pyridineboronic acid (246 mg,
2 mmol), K2CO3 (276 mg, 2 mmol), xylene (3 mL), Tedicyp-

118
I. Kondolff, H. Doucet, M. Santelli
Vol 45
S. L. J. Am. Chem. Soc., 2005, 127, 4685.
[9] Billingsley, K. L.; Anderson, K. W.; Buchwald, S. L. Angew.
Chem. Int. Ed., 2006, 45, 3484.
[10] Morris, G. A.; Nguyen, S. T. Tetrahedron Lett., 2001, 42,
2093.
[11] Molander, G. A.; Biolatto, B. J. Org. Chem. 2003, 68, 4302.
[12] Kuhnert, N.; Patel, C.; Jami, F. Tetrahedron Lett., 2005, 46,
7575.
palladium complexe (100 μmol) gave 41 in 84% (172 mg)
1
isolated yield. H nmr (300 MHz, CDCl3): ꢀ = 7.38–7.60 (m,
5H), 7.76–7.84 (m, 2H), 7.86–7.96 (m, 2H), 8.68 (bs, 1H), 8.75
(bs, 1H).
3-(2,6-Dimethylphenyl)pyridine (42). (Table 7, entry 19)
2,6-Dimethylbromobenzene (185 mg, 1 mmol), 3-pyridine-
boronic acid (246 mg, 2 mmol), K2CO3 (276 mg, 2 mmol),
xylene (3 mL), Tedicyp-palladium complexe (50 μmol) gave 42
[13] Wang, Z.; Elokdah, H.; McFarlane, G.; Pan, S.; Antane, M.
Tetrahedron Lett., 2006, 47, 3365.
1
in 85% (156 mg) isolated yield. H nmr (300 MHz, CDCl3): ꢀ =
2.02 (s, 6H), 7.12 (d, J = 7.3 Hz, 2H), 7.16–7.21 (m, 1H), 7.37
(dd, J = 7.6, 4.7 Hz, 1H), 7.50 (dt, J = 7.6, 1.9 Hz, 1H), 8.43 (bs,
1H), 8.60 (d, J = 4.7 Hz, 1H).
[14] Cammidge, A. N.; Goddard, V. H. M.; Gopee, H.; Harrison,
N. L.; Hughes, D. L.; Schubert, C. J.; Sutton, B. M.; Wats, G. L.;
Whitehead, A. J. Org. Lett., 2006, 8, 4071.
[15] Liu, B.; Moffett, K. K.; Joseph, R. W.; Dorsey, B. D.
Tetrahedron Lett., 2005, 46, 1779.
[16] Dhudshia, B.; Thadani, A. N. Chem. Commun., 2006, 668.
[17] Korolev, D. N.; Bumagin, N. A. Tetrahedron Lett., 2005, 46,
5751.
[18] Weng, Z.; Teo, S.; Koh, L. L.; Hor, T. S. A.
Organometallics, 2004, 23, 3603.
[19] Solodenko, W.; Wen, H.; Leue, S.; Stuhlmann, F.;
Sourkouni-Argirusi, G.; Jas, G.; Schönfeld, H.; Kunz, U.; Kirschning, A.
Eur. J. Org. Chem., 2004, 3601.
[20] Uozumi, Y.; Nakai, Y. Org. Lett., 2002, 4, 2997.
[21] Miao, W.; Chan, T. H. Org. Lett., 2003, 5, 5003.
[22] Atrash, B.; Reader, J.; Bradley, M. Tetrahedron Lett., 2003,
44, 4779.
CAS numbers: 1, 825-55-8; 2, 35294-37-2; 4, 42545-43-7; 5,
99846-56-7; 6, 1665-41-4; 7, 1207-95-0; 8, 132932-62-8; 9,
132932-64-0; 10, 55084-51-0; 11, 172035-84-6; 12, 157730-74-0;
14, 82437-75-0; 15, 16939-08-5; 16, 16939-06-3; 17, 27921-48-8;
18, 26170-85-4; 19, 666841-73-2; 20, 98251-31-1; 22, 485824-
13-3; 23, 13679-41; 25, 207119-82-2; 26, 80866-25-7; 27,
132932-61-7; 28, 53348-90-6; 30, 41013-94-9; 31, 19234-04-9;
32, 65246-39-1.; 33, 1008-88-4; 34, 159429-67-1; 35, 131231-24-
8; 36, 85589-65-7; 37, 5958-02-1; 38, 90395-44-1; 39, 5959-01-
0.; 40, 9039-49-6; 41, 189193-21-3; 42, 157402-43-2.
Acknowledegments. We thank the CNRS for providing
financial support.
[23] Tzschucke, C. C.; Markert, C.; Glatz, H.; Bannwarth, W.
Angew. Chem. Int. Ed., 2002, 41, 4500.
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