Pd(OAc)2/DABCO-catalyzed Suzuki-Miyaura cross-coupling reaction in DMF

Article abstract of DOI:10.1016/j.tet.2006.08.103

The scope and limitations of the Pd(OAc)₂/DABCO (1,4-diaza-bicyclo[2.2.2]octane)-catalyzed Suzuki-Miyaura cross-coupling reactions have been demonstrated. The results showed that the effect of solvent had a fundamental influence on the reaction. In the presence of Pd(OAc)₂ and DABCO, both aryl bromides and aryl chlorides all worked well with arylboronic acids to form biaryls, heteroaryl-aryls, and biheteroaryls in moderate to excellent yields using DMF as the solvent. Additionally, the reactions of aryl bromides were conducted under relatively mild conditions.

Full text of DOI:10.1016/j.tet.2006.08.103

Tetrahedron 62 (2006) 10888–10895
Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura
cross-coupling reaction in DMF
*
Jin-Heng Li, Qi-Ming Zhu and Ye-Xiang Xie
Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education),
College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, China
Received 5 June 2006; revised 28 August 2006; accepted 30 August 2006
Available online 18 September 2006
Abstract—The scope and limitations of the Pd(OAc)2/DABCO (1,4-diaza-bicyclo[2.2.2]octane)-catalyzed Suzuki–Miyaura cross-coupling
reactions have been demonstrated. The results showed that the effect of solvent had a fundamental influence on the reaction. In the presence of
Pd(OAc)2 and DABCO, both aryl bromides and aryl chlorides all worked well with arylboronic acids to form biaryls, heteroaryl-aryls, and
biheteroaryls in moderate to excellent yields using DMF as the solvent. Additionally, the reactions of aryl bromides were conducted under
relatively mild conditions.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
DABCO, only aryl iodides and bromides were coupled with
arylboronic acids efficiently using acetone as the solvent,6a
whereas the scope was extended to the activated aryl chlo-
rides when PEG-4006b or H2O6c was used as the media. Fur-
thermore, the deactivated aryl chlorides could be coupled
smoothly with PEG-400 to afford moderate yields with the
aid of TBAB (tetrabutylammonium bromide). The results
encouraged us to further explore the effects of the solvents
on the scope and limitations of the Pd(OAc)2/DABCO-cata-
lyzed Suzuki–Miyaura cross-coupling reactions.2 We were
happy to discover that the scope of the protocol could be ex-
tended to aryl chlorides to construct biaryls, heteroaryl-aryl,
and biheteroaryls when DMF was employed as the media.
Moreover, the couplings of aryl bromides in DMF could be
conducted under relatively mild conditions. Here, we wish to
report the results of this methodology in detail (Eq. 1).
Palladium-catalyzed cross-coupling of aryl halides with or-
ganoboronic acids, namely Suzuki–Miyaura cross-coupling
reaction, is a versatile and utilized reaction for the selective
formation of carbon–carbon bonds, in particular for the syn-
thesis of biaryls.1–7 Recently, efforts have been focused on
the development of efficient and selective catalytic systems
for the Suzuki–Miyaura reaction. However, many catalytic
systems are limited to the couplings of aromatic iodides
and bromides.2 In recent years, employing readily available
aryl chlorides in these transformations have received
increasing attention, and a number of effective catalytic
systems have been developed for this purpose.2–4 In these
processes, the use of sterically hindered and electron-rich
ligands played crucial roles in the coupling of these chal-
lenging substrates. One of the notable examples is the use
of bulky trialkylphosphines.4 However, many of those phos-
phine ligands are sensitive to air and/or moisture besides
expensive, which place significant limits on their synthetic
applications. Very recently, we have reported that DABCO
(1,4-diaza-bicyclo[2.2.2]octane) was an inexpensive, stable,
and highly efficient ligand for the palladium-catalyzed
Suzuki–Miyaura cross-coupling reaction.6 After checking
our previous results carefully, we found that the scopes of
the Suzuki–Miyaura reactions catalyzed by our catalytic sys-
tem relied on the solvents. In the presence of Pd(OAc)2 and
Pd(OAc)2/DABCO
+
Ar
X
Ar' B(OH)2
Ar Ar'
(1)
Cs2CO3, DMF
Ar, Ar' = aryl, heteroaryl
X = Br, Cl
2. Results and discussion
2.1. Effect of solvents on the Pd(OAc)2/DABCO-
catalyzed Suzuki–Miyaura reaction
The Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura reaction
between 1-chloro-4-nitro-benzene (1a) and phenylboronic
acid (2a) was chosen as a model reaction to evaluate the
effects of the solvents, and the results are summarized in
Keywords: Pd(OAc)2/DABCO; Suzuki–Miyaura cross-coupling reaction;
Aryl halide; Arylboronic acids.
* Corresponding author. Tel.: +86 731 8872530; fax: +86 731 8872531;
e-mail: jhli@hunnu.edu.cn
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.08.103

J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
10889
Table 1. Effect of solvents on Pd(OAc)2/DABCO-catalyzed Suzuki–
Miyaura cross-coupling reaction of 1-chloro-4-nitrobenzene with phenyl-
boronic acida
Table 2. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura cross-coupling
reaction of aryl chlorides with arylboronic acids in DMF a
3 mol% Pd(OAc)2
6 mol% DABCO
base, DMF, 110 °C
Pd(OAc)2/DABCO
Cl
B(OH)2
+
+
Cl
O2N
B(OH)2
NO2
R
R'
R
R'
Yield (%)b
1
2
1a
2a
3
Entry
1
ArX
ArB(OH)2
Entry Solvent
Time (h) Isolated yield (%)
1
Acetone (5 mL)
Acetone (5 mL)
PEG-400 (2 g)
PEG-400 (2 g)
Dioxane (3 mL)
H2O (5 mL)
2
2
3
3
19
24
18 (Ref. 6a)
40
60 (Ref. 6b)
92 (Ref. 6b)
45
Trace (Ref. 6c)
50 (Ref. 6c)
100
100
94
(1a)
(2b)
B(OH)2
99 (4)
52 (5)
93 (6)
O2N
Cl
F
2b
3
Me
B(OH)2 (2c)
Me
4c
5
2
3
(1a)
(1a)
6b
7b
8
CH3CH2OH/H2O (1:4; 5 mL) 24
(2d)
B(OH)2
DMF (3 mL)
DMF (3 mL)
DMF (3 mL)
DMF (3 mL)
19
17
33
42
MeO
9d
10d,e
11d,f
4c
5
(1b)
(2a)
100 (7)
65 (8)
72
Cl
B(OH)2
O
a
Reaction conditions: 1 (0.5 mmol), 2 (0.7 mmol), Pd(OAc)2 (3 mol %),
DABCO (6 mol %), and K2CO3 (3 equiv) at 110 ꢀC.
PEG-400 (0.2 equiv).
TBAB (0.1 equiv).
Cs2CO3 (3 equiv).
(1c)
(2a)
(2a)
(2a)
Cl
b
c
d
e
f
6
7
(1d)
Cl
53 (9)
Me
Pd(OAc)2 (1 mol %) and DABCO (2 mol %).
Pd(OAc)2 (0.1 mol %) and DABCO (0.2 mol %).
Me
Cl
(1e)
64 (10)
Me
Table 1. In our initial communication,6a acetone was used as
the media. Unfortunately, only an 18% yield of the target
product 3 was isolated in acetone when 1-chloro-4-nitro-
benzene (1a) was treated with phenylboronic acid (2a),
Pd(OAc)2 (3 mol %), DABCO (6 mol %), and K2CO3
(3 equiv) at 110 ꢀC (entry 1). We found that the yield of 3
was enhanced to 40% when 0.2 equiv of PEG-400 was added
(entry 2). Thus, PEG-400 employed as the medium was
tested, and a 60% yield was provided (entry 3).6b It was in-
teresting to observe that the yield of 3 was increased sharply
to 92% using PEG-400 as the media and TBAB as an addi-
tional promoter (entry 4). Dioxane, the reported excellent
solvent by Tao and Boykin,5 gave only a 45% yield of 3
(entry 5). The reaction performed in aqueous media was
also investigated.6c Trace amount of 3 was isolated in water
(entry 6), but the yield was increased to 50% when ethanol
was used as the co-solvent (entry 7). We were happy to see
that the quantitative yield of 3 was obtained when the
reaction was carried out in DMF (entry 8). The results also
indicated that effects of bases could affect the reaction to
some extent. Cs2CO3 in place of K2CO3 as the base could
shorten the reaction time (entries 8 and 9). It is noteworthy
that the reaction performed in DMF can be conducted at
0.1 mol % loading Pd together with a good yield after pro-
longed reaction time (94% yield at 1 mol % Pd and 72%
yield at 0.1 mol % Pd; entries 10 and 11).
Cl
Me
8
9
(1f)
(2a)
(2d)
60 (11)
58 (12)
(1f)
10
11
12
13
(1g)
(2a)
(2b)
(2c)
(2d)
61 (13)
71 (14)
MeO
Cl
(1g)
(1g)
(1g)
Trace (15)
52 (16)
MeO
Cl
14
(1h)
(2a)
(2a)
63 (17)
— (18)
OMe
1-Iododecane (1i)
15
a
Unless otherwise indicated, the reaction conditions were as follows: 1
(0.5 mmol), 2 (0.7 mmol), Pd(OAc)2 (3 mol %), DABCO (6 mol %),
and Cs2CO3 (3 equiv) in DMF (3 mL) at 110 ꢀC for 19 h.
Isolated yield.
b
c
For 17 h.
rings could also be tolerated as well, leading to the corre-
sponding hindered coupling products in moderate yields.
As shown in Table 2, the Pd(OAc)2/DABCO/DMF system
was proved exceptionally active for the couplings of the
activated chlorides 1a and 1b, but the yields relied on aryl-
boronic acids. For example, treatment of 1a with boronic
acid 2b or 2d afforded the target products in excellent yields
(a 99% yield for 2b and a 93% yield for 2d; entries 1 and 3),
whereas only a moderate yield was observed when 1a re-
acted with the hindered boronic acid 2c (entry 2). Although
the efficiency of the Pd(OAc)2/DABCO/DMF system was
also decreased for more challenging deactivated aryl
chlorides, moderate yields of the corresponding hindered
coupling products were still achieved (entries 7–9 and 14).
Unfortunately, an attempt to coupling of the deactivated
2.2. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura
reaction to synthesize biaryls
The coupling reaction between a range of substrates and
several arylboronic acids was then conducted to explore
the general effectiveness of the Pd(OAc)2/DABCO/DMF
system (Table 2). Under the above optimized reaction condi-
tions, a wide range of aryl chlorides 1a–h, whether electron-
rich or electron-deficient, all worked well with arylboronic
acids 2a–d. Moreover, ortho-substituents on the aromatic

10890
J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
chloride 1g with the bulky boronic acid 2c was unsuccessful
(entry 12). Finally, we also screened the reaction between
1-iododecane (1i) and phenylboronic acid (2a), but no target
product was obtained (entry 15).
Only a 40% yield of the target product 10 was isolated
from the reaction of 1n with 1a at 40 ꢀC, but the yield of
10 was enhanced to 92% when the reaction was performed
at 80 ꢀC (entries 9 and 10). The couplings of the substrates
1j and 1o with the other boronic acids were also examined.
The results demonstrated that the yields of the desired prod-
ucts were varied with different boronic acids (entries 3–5 and
12–15). The bromide 1j treated with 2b–d, Pd(OAc)2,
DABCO, and Cs2CO3 at 40 ꢀC to offer the corresponding
products in 81%, trace, and 90% yields, respectively (entries
3–5). We also observed that bromide 1o with the other
boronic acid 2b or 2d required the couplings performing at
higher temperature to produce good results (entries 12–15).
For example, the reaction of bromide 1o with 2b provided
only 37% of the desired coupled product 14 at 40 ꢀC
(entry 12). However, the yield was increased to 82% when
the reaction was carried out at 80 ꢀC (entries 13).
With the excellent reaction conditions in hand, we then
decided to explore the couplings of aryl bromides again.
Gratifyingly, the reactions between aryl bromides and aryl-
boronic acids were able to conduct under mild conditions
(Table 3). At 40 ꢀC, aryl bromides 1j–m and 1o reacted
well with 2a to afford the corresponding cross-coupling
products in excellent yields (entries 2–8 and 11). The hin-
dered bromide 1n required higher reaction temperature.
Table 3. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura cross-coupling
reactions of aryl bromides with arylboronic acids in DMFa
Pd(OAc)2/DABCO
Br
B(OH)2
+
Cs2CO3 (3 equiv)
DMF, 40 °C
R
R'
R
2.3. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura
reaction to synthesize heteroaryl-aryls and
biheteroaryls
R'
1
2
Entry
1c
ArX
ArB(OH)2
Yield (%)b
Construction of biaryl containing heteroaryl rings via the
palladium-catalyzed Suzuki–Miyaura reaction is another
interesting area.2,7 There are a few transformations for
general cross-coupling reactions of both aryl halides and
heteroaryl halides with arylboronic acids including hetero-
arylboronic acids to synthesize biaryls containing heteroaryl
rings. However, most of the transformations required the
phosphine ligands to improve them as well as limited to aryl
bromides. To our delight, the Pd(OAc)2/DABCO/DMF sys-
tem was also effective for the reactions of aryl halides with
heteroarylboronic acids (Table 4). Solvent was also found to
play a crucial role in the reaction (entries 1–4). In acetone,
treatment of 1p with 2a, Pd(OAc)2, DABCO, and Cs2CO3
afforded a 34% yield of the target product 19 in 48 h. In
dioxane, the yield of 19 was increased slightly to 49% for
48 h (entry 2). We were happy to find that the yield of 19
was enhanced to 66% for 22 h when the reaction was
conducted in DMF. Under the same optimized reaction con-
ditions, the other heteroaryl bromides 1q–v, including nitro-
gen- or sulfur-containing heteroaryl bromides, coupled with
arylboronic acids were carried out efficiently to produce
the corresponding products in moderate to excellent yields
(entries 4–12). For example, 5-bromopyrimidine 1t reacted
with three kinds of arylboronic acids, including a challenging
boronic acid 2d, smoothly to give the corresponding desired
products 23–25 in 98, 50, and 98% yields, respectively
(entries 7–9). The sulfur-containing substrate 1v coupled
with 2a offered a moderate yield of the target product 27
under the same reaction conditions (entry 11). It was pleased
to find that the yield of 27 was increased sharply to
98% when K2CO3 was employed as the base (entry 12).
However, the best base for the couplings of heteroaryl
chlorides 1w–y was KOH (entries 13–17). Treatment of
chloride 1w with 2a, Pd(OAc)2, DABCO, and Cs2CO3 pro-
vided a 40% of the desired product 19 (entry 13), whereas
the yield of 19 was enhanced dramatically to 58% using
KOH as the base (entry 14). In the presence of Pd(OAc)2,
DABCO, KOH, and DMF, the other chlorides 1x and 1y
underwent the coupling with 2a smoothly to afford the
corresponding products in moderate yields (entries 15
and 16).
(1j)
(2a)
Trace (3)
100 (3)
81 (3)
O2N
Br
B(OH)2
2
3
(1j)
(1j)
(2a)
(2b)
B(OH)2
F
Me
B(OH)2 (2c)
Me
4
(1j)
(1j)
Trace (5)
90 (3)
5
(2d)
B(OH)2
MeO
Br
6
(1k)
(2a)
96 (7)
O
7
(1l)
(2a)
(2a)
(2a)
(2a)
94 (8)
Br
8
(1m)
Br
89 (9)
Me
Me
9
Br (1n)
40 (10)
92 (10)
Me
10d
(1n)
11
12
13d
14
(1o)
Br
(2a)
(2b)
(2b)
(2d)
(2d)
90 (13)
37 (14)
82 (14)
30 (16)
96 (16)
MeO
(1o)
(1o)
(1o)
(1o)
15d,e
a
Unless otherwise indicated, the reaction conditions were as follows: 1
(0.5 mmol), 2 (0.7 mmol), Pd(OAc)2 (3 mol %), DABCO (6 mol %),
and Cs2CO3 (3 equiv) in DMF (3 mL) at 40 ꢀC for 16 h.
b
c
d
e
Isolated yield.
At room temperature.
At 80 ꢀC.
For 25 h.

J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
Table 4. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura cross-coupling
Table 4. (continued)
reaction of aryl halides with heteroarylboronic acids to synthesize hetero-
10891
Entry
ArX
ArB(OH)2
Time Yield
(h) (%)b
aryl-arylsa
Entry
ArX
ArB(OH)2
Time Yield
(h) (%)b
22
(1c)
(2e)
(2f)
24
24
88 (27)
74 (31)
Cl
(1c)
23
1c
2d
3
(1p)
(1q)
48
48
22
34 (19)
(2a)
B(OH)2
a
N
N
Br
(1p)
Unless otherwise indicated, the reaction conditions were as follows: 1
(0.5 mmol), 2 (0.7 mmol), Pd(OAc)2 (3 mol %), DABCO (6 mol %),
and Cs2CO3 (3 equiv) in DMF (3 mL) at 110 ꢀC.
Isolated yield.
In acetone (3 mL).
In dioxane (3 mL).
(2a)
(2a)
49 (19)
66 (19)
b
c
d
e
f
(1p)
Br
K2CO3 (3 equiv) instead of Cs2CO3.
KOH (3 equiv) instead of Cs2CO3.
4
5
(2a)
(2a)
22
21
81 (20)
65 (21)
Br
(1r)
N
OMe
Br
Subsequently, the couplings between aryl halides and hetero-
arylboronic acids were conducted under the same optimized
conditions. The results indicated that the reactions of aryl
bromides 1j or 1l with heteroarylboronic acid 2e produced
the corresponding products in excellent yields using
Pd(OAc)2/DABCO as the catalytic system and DMF as the
solvent (entries 17 and 18). Moderate to good yields were still
achieved when aryl chlorides 1a or 1c were treated with
heteroarylboronic acids under the same reaction conditions
(entries 19–23). For example, the reaction of substrate 1a
with 2e–g afforded the corresponding products 28–30 in
93, 90, and 58%, respectively, in the presence of Pd(OAc)2,
DABCO, Cs2CO3, and DMF (entries 19–21).
6
(1s)
(2a)
(2a)
22
94 (22)
N
N
7
8
(1t)
4
98 (23)
50 (24)
N
Br
Me
B(OH)2
Me
(1t)
(2c)
12
9
(1t)
(2d) 10
B(OH)2
98 (25)
94 (26)
MeO
N
N
10
(1u)
(1v)
(2a)
46
The reactions of heteroaryl halides with heteroarylboronic
acids were also performed smoothly under the Pd(OAc)2/
DABCO/DMF system and the results are summarized in
Table 5. In the presence of Pd(OAc)2 and DABCO, a number
of heteroaryl bromides reacted with sulfur- and oxygen-
containing heteroarylboronic acids to afford the correspond-
ing products in high yields using KOH or K2CO3 as the base
and DMF as the solvent (entries 1–6), but with nitrogen-
containing heteroarylboronic acid (2g) provided a moderate
yield (entry 7). For example, the reaction of substrate 1u
with 2e gave the desired product 37 in a 98% yield, whereas
treatment of 1u with 2g, a nitrogen-containing heteroaryl-
boronic acid, produced only a 65% yield of the target prod-
uct 38 (entries 6 and 7). To our surprise, only a 16% yield of
the desired coupled product 32 was isolated together with
a 56% yield of 2-(pyridin-2-yl)pyridine, a homocoupling
product of 2-bromopyridine (1p) (entry 1). Under the same
reaction conditions, the reaction of 2-chloropyridine 1w
was also unsuccessful (entry 8). However, another chloride
1y coupled with 2e was carried out smoothly to offer the
desired product 37 in a moderate yield (entry 9).
Br
11
(2a)
(2a)
22
22
65 (27)
98 (27)
Br
S
12e
(1v)
13
(1w)
(2a)
(2a)
48
46
40 (19)
58 (19)
N
Cl
14f
(1w)
N
15f
16f
17
18
19
20
(1x)
(1y)
(2a)
(2a)
46
46
10
12
19
19
52 (23)
54 (26)
98 (28)
95 (27)
93 (28)
90 (29)
N
Cl
Cl
N
N
(1j)
(2e)
O2N
O2N
Br
B(OH)2
S
(1l)
(2e)
Br
3. Conclusion
(1a)
(2e)
Cl
In summary, we have discussed the effect of solvents on the
scope and limitations of the Pd(OAc)2/DABCO-catalyzed
Suzuki–Miyaura cross-coupling reaction. On the base of
the results, several features are established: (1) the effect
of the solvents has a fundamental influence on the scope
and limitations of the current reaction, and the results dem-
onstrate the broad substrate scope of the Pd(OAc)2/DABCO/
DMF system for the Suzuki–Miyaura coupling. In acetone,
(1a)
(1a)
(2f)
B(OH)2
O
21
(2g)
24
58 (30)
N
B(OH)2
(continued)

10892
J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
Table 5. Pd(OAc)2/DABCO-catalyzed Suzuki–Miyaura cross-coupling
reactions of heteroaryl halides with heteroarylboronic acids to provide
biheteroarylsa
consumption of starting material as monitored by TLC. Af-
ter the mixture was poured into diethyl ether, then washed
with water, extracted with diethyl ether, dried by anhydrous
Na2SO4, and evaporated under vacuum, the residue was
purified by flash column chromatography (hexane or
hexane/ethyl acetate) to afford the desired coupled products
3–14, 16, 17, and 19–38.
Entry
ArX
ArB(OH)2
B(OH)2
(2e)
Time (h) Yield (%)b
1
(1p)
(2e) 39
16 (32)
S
N
Br
Br
4.1.1. 4-Nitro-biphenyl (3).3 Yellow solid; 1H NMR
(400 MHz, CDCl3) d: 8.30 (d, J¼8.8 Hz, 2H), 7.74 (d,
J¼8.8 Hz, 2H), 7.64 (d, J¼6.9 Hz, 2H), 7.52–7.44 (m,
3H); 13C NMR (100 MHz, CDCl3) d: 147.6, 147.1, 138.8,
129.2, 128.91, 127.8, 127.4, 124.1; LRMS (EI, 20 eV) m/z
(%): 199 (M+, 100).
2
3
(1s)
23
93 (33)
98 (34)
N
(1s)
(2f) 21
B(OH)2
O
N
4c
5c
(1t)
(2e)
(2f)
17
22
96 (35)
93 (36)
N
Br
(1t)
4.1.2. 4-Nitro-40-fluorobiphenyl (4).3 Yellow solid; 1H
NMR (400 MHz, CDCl3) d: 8.30 (d, J¼8.8 Hz, 2H), 7.70
(d, J¼8.8 Hz, 2H), 7.59 (dd, J¼5.6 Hz, 5.6 Hz, 2H), 7.20
(t, J¼8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3) d: 164.6,
162.1, 146.5, 134.9, 129.1 (d, J¼8.6 Hz, 1C), 127.6,
124.2, 116.2 (d, J¼21.7 Hz, 1C); LRMS (EI, 20 eV) m/z
(%): 217 (M+, 100).
N
N
6
7
8
(1u)
(2e)
23
(2g) 23
41
98 (37)
65 (38)
Br
(1u)
N
B(OH)2
(1w)
(1y)
(2e)
Trace (32)
N
N
Cl
Cl
1
4.1.3. 4-Nitro-20,60-dimethylbiphenyl (5).3 Yellow oil; H
9
(2e)
38
50 (37)
NMR (300 MHz, CDCl3) d: 8.31 (d, J¼9.0 Hz, 2H), 7.35
(d, J¼8.7 Hz, 2H), 7.25–7.20 (m, 1H), 7.15–7.13 (m, 2H),
2.02 (s, 6H); 13C NMR (75 MHz, CDCl3) d: 148.4, 146.8,
139.5, 135.3, 130.7, 128.0, 127.6, 123.8, 20.7; LRMS (EI,
20 eV) m/z (%): 227 (M+, 100).
N
a
Unless otherwise indicated, the reaction conditions were as follows: 1
(0.5 mmol), 2 (0.7 mmol), Pd(OAc)2 (3 mol %), DABCO (6 mol %),
and KOH (3 equiv) in DMF (3 mL) at 110 ꢀC.
Isolated yield.
b
c
K2CO3 (3 equiv) instead of KOH.
1
4.1.4. 4-Nitro-40-methoxybiphenyl (6).3 Yellow solid; H
only aryl iodides and bromides were coupled with aryl-
boronic acids efficiently,6a whereas in PEG-4006b or PEG-
400/H2O6c the scope was extended to the activated aryl
chlorides. In addition, some deactivated aryl chlorides could
be coupled smoothly when TBAB was added to PEG-400.6b
However, DMF was proved here to be the more effective sol-
vent for a wide range of aryl halides including the deacti-
vated aryl chlorides and heteroaryl halides. Moreover, the
couplings of aryl bromides in DMF were conducted under
mild conditions. The reason that DMF is the most effective
medium here may be that DMF is a highly polar solvent
and may play as a ligand to promote the reaction.2 (2) The
reaction showed excellent substituent tolerance on the aro-
matic rings. (3) DABCO is considerably inexpensive and
readily available, which emerged as an attractive alternative
to the phosphine ligand for the Suzuki–Miyaura cross-
coupling reaction. Given these advantage, design, and appli-
cation of these ligands on the base of the DABCO skeleton in
other palladium-catalyzed cross-coupling transformations
should be attractive.
NMR (300 MHz, CDCl3) d: 8.25 (d, J¼9.0 Hz, 2H), 7.68
(d, J¼9.0 Hz, 2H), 7.57 (d, J¼9.0 Hz, 2H), 7.02 (d,
J¼8.7 Hz, 2H); 13C NMR (75 MHz, CDCl3) d: 160.4,
147.2, 146.5, 131.0, 128.5, 127.0, 124.1, 114.6, 55.4;
LRMS (EI, 20 eV) m/z (%): 229 (M+, 100).
4.1.5. 1-Biphenyl-4-yl-ethanone (7).3 White solid; 1H
NMR (300 MHz, CDCl3) d: 8.04 (d, J¼8.4 Hz, 2H), 7.69
(d, J¼8.4 Hz, 2H), 7.64 (d, J¼7.6 Hz, 2H), 7.50–7.40 (m,
3H), 2.64 (s, 3H); 13C NMR (75 MHz, CDCl3): d 198.1,
146.1, 140.2, 136.2, 130.1, 129.2, 128.6, 127.6, 118.5,
27.0; LRMS (EI, 20 eV) m/z (%): 196 (M+, 100).
4.1.6. Biphenyl (8).3 White solid; 1H NMR (300 MHz,
CDCl3) d: 7.59 (d, J¼8.4 Hz, 4H), 7.43 (t, J¼7.2 Hz, 4H),
7.36 (t, J¼7.8 Hz, 2H); 13C NMR (75 MHz, CDCl3) d:
141.6, 129.1, 127.6, 127.5; LRMS (EI, 20 eV) m/z (%):
154 (M+, 100).
4.1.7. 4-Methyl-biphenyl (9).3 White solid; 1H NMR
(400 MHz, CDCl3) d: 7.59 (t, J¼7.6 Hz, 2H), 7.49 (d,
J¼8.0 Hz, 2H), 7.42 (t, J¼7.6 Hz, 2H), 7.31 (t, J¼7.6 Hz,
1H), 7.24 (d, J¼8.0 Hz, 2H), 2.38 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 141.1, 138.3, 137.0, 129.5, 128.7,
127.3, 127.2, 127.0, 21.1; LRMS (EI, 20 eV) m/z (%): 168
(M+, 100).
4. Experimental
4.1. Typical experimental procedure for the palladium-
catalyzed Suzuki–Miyaura cross-coupling reaction
in DMF
4.1.8. 3,5-Dimethyl-biphenyl (10).3 Colorless oil; 1H NMR
(400 MHz, CDCl3) d: 7.59 (d, J¼8.4 Hz, 2H), 7.44–7.40 (m,
2H), 7.31–7.28 (m, 1H), 7.19 (d, J¼8.4 Hz, 2H), 6.98 (d,
J¼9.2 Hz, 1H), 2.35 (s, 3H), 2.37 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 141.5, 138.1, 128.9, 128.7, 127.9,
A mixture of aryl halide 1 (0.5 mmol), arylboronic acid 2
(0.7 mmol), Pd(OAc)2 (3 mol %), DABCO (6 mol %), base
(3 equiv), and DMF (3 mL) was stirred at the indicated reac-
tion temperature for the desired time until complete

J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
10893
127.2, 127.1, 125.1, 21.4; LRMS (EI, 20 eV) m/z (%): 182
(M+, 100).
7.35 (t, J¼7.6 Hz, 1H), 6.82 (d, J¼8.8 Hz, 1H), 3.98 (s,
3H); 13C NMR (100 MHz, CDCl3) d: 163.6, 145.0, 137.9,
137.4, 130.1, 128.9, 127.3, 126.7, 110.8, 53.5; LRMS (EI,
20 eV) m/z (%): 185 (M+, 100); HRMS (EI) for C12H11NO
(M+): calcd, 185.0841; found, 185.0840.
4.1.9. 2-Methyl-biphenyl (11).3 Colorless oil; 1H NMR
(400 MHz, CDCl3) d: 7.40 (t, J¼7.2 Hz, 2H), 7.32 (t,
J¼6.8 Hz, 3H), 7.25–7.23 (m, 4H), 2.27 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 141.9, 135.3, 130.3, 129.8, 129.2,
128.0, 127.2, 126.7, 125.7, 125.6, 20.4; LRMS (EI, 20 eV)
m/z (%): 168 (M+, 100).
4.1.18. 3-Phenylquinoline (22).8 Yellow oil; 1H NMR
(400 MHz, CDCl3) d: 9.19 (s, 1H), 8.30 (s, 1H), 8.15 (d,
J¼8.8 Hz, 1H), 7.88 (d, J¼8.0 Hz, 1H), 7.72 (d, J¼7.2 Hz,
3H), 7.60–7.51 (m, 3H), 7.44 (t, J¼7.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d: 149.9, 147.3, 137.8, 133.8, 133.2,
129.4, 129.2, 129.1, 128.1, 128.0 (2C), 127.4, 127.0;
LRMS (EI, 20 eV) m/z (%): 205 (M+, 100).
4.1.10. 2-Methyl-40-methoxy-biphenyl (12).3 Colorless oil;
1H NMR (400 MHz, CDCl3) d: 7.26–7.22 (m, 6H), 6.95
(d, J¼8.4 Hz, 2H), 3.85 (s, 3H), 2.28 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 158.5, 141.5, 135.5, 134.3, 130.3,
130.2, 129.9, 127.0, 125.8, 113.5, 55.3, 20.6; LRMS (EI,
20 eV) m/z (%): 198 (M+, 100).
1
4.1.19. 5-Phenylpyrimidine (23).3 White solid; H NMR
(400 MHz, CDCl3) d: 9.21 (s, 1H), 8.96 (s, 2H), 7.58 (d,
J¼8.8 Hz, 2H), 7.53 (t, J¼8.8 Hz, 2H), 7.47 (t, J¼7.2 Hz,
1H); 13C NMR (100 MHz, CDCl3) d: 157.3, 154.8, 134.2,
134.1, 129.3, 128.9, 126.7; LRMS (EI, 20 eV) m/z (%):
156 (M+, 100).
1
4.1.11. 4-Methoxy-biphenyl (13).3 White solid; H NMR
(300 MHz, CDCl3) d: 7.54 (t, J¼8.4 Hz, 4H), 7.42 (t,
J¼7.8 Hz, 2H), 7.31 (t, J¼7.5 Hz, 1H), 6.98 (d, J¼9.0 Hz,
2H), 3.86 (s, 3H); 13C NMR (100 MHz, CDCl3) d: 159.1,
140.8, 133.7, 128.7, 128.1, 126.7, 126.6, 114.2, 55.3;
LRMS (EI, 20 eV) m/z (%): 184 (M+, 100).
4.1.20. 5-(2,6-Dimethylphenyl)pyrimidine (24). White
solid, mp 50–52 ꢀC (uncorrected); 1H NMR (400 MHz,
CDCl3) d: 9.23 (s, 1H), 8.60 (s, 2H), 7.26 (t, J¼8.0 Hz,
1H), 7.17 (d, J¼8.4 Hz, 2H), 2.06 (s, 6H); 13C NMR
(100 MHz, CDCl3) d: 157.3, 157.1, 136.4, 134.6, 133.8,
128.7, 127.8, 21.0; LRMS (EI, 20 eV) m/z (%): 184 (M+,
100); HRMS (EI) for C12H12N2 (M+): calcd, 184.1001;
found, 184.1000.
4.1.12. 4-Fluoro-40-methoxy-biphenyl (14).3 White solid;
1H NMR (300 MHz, CDCl3) d: 7.50–7.45 (m, 4H), 7.09 (t,
J¼8.4 Hz, 2H), 6.96 (d, J¼8.7 Hz, 2H), 3.83 (s, 3H); 13C
NMR (100 MHz, CDCl3) d: 163.7, 160.4, 159.0, 132.7,
128.2 (d, J¼9.3 Hz, 1C), 128.0, 115.5 (d, J¼28.2 Hz, 1C),
114.2, 55.3; LRMS (EI, 20 eV) m/z (%): 202 (M+, 100).
4.1.21. 5-(4-Methoxyphenyl)pyrimidine (25). White solid,
mp 91–93 ꢀC (uncorrected); 1H NMR (400 MHz, CDCl3) d:
9.16 (s, 1H), 8.92 (s, 2H), 7.53 (d, J¼8.4 Hz, 2H), 7.05 (d,
J¼8.4 Hz, 2H), 3.88 (s, 3H); 13C NMR (100 MHz, CDCl3)
d: 160.3, 156.8, 154.3, 133.8, 128.0, 126.4, 114.8, 55.3;
LRMS (EI, 20 eV) m/z (%): 186 (M+, 100); HRMS (EI) for
C11H10N2O (M+): calcd, 186.0793; found, 186.0791.
4.1.13. 4,40-Dimethoxy-biphenyl (16).3 White solid; 1H
NMR (300 MHz, CDCl3) d: 7.48 (d, J¼8.4 Hz, 4H), 6.95
(d, J¼8.87 Hz, 4H), 3.84 (s, 6H); 13C NMR (100 MHz,
CDCl3) d: 158.7, 133.5, 127.7, 114.1, 59.3; LRMS (EI,
20 eV) m/z (%): 214 (M+, 100).
1
4.1.14. 2,4-Dimethoxy-biphenyl (17).3 Colorless oil; H
NMR (300 MHz, CDCl3) d: 7.53 (d, J¼8.1 Hz, 2H), 7.40
(t, J¼7.5 Hz, 2H), 7.34 (t, J¼9.0 Hz, 1H), 6.95–6.82 (m,
3H); 13C NMR (75 MHz, CDCl3) d: 153.6, 138.3, 129.4,
128.0, 127.0, 116.6, 116.0, 113.0, 112.8, 112.5, 56.2, 55.8;
LRMS (EI, 20 eV) m/z (%): 214 (M+, 100).
4.1.22. 2-Phenylpyrazine (26).9 White solid; 1H NMR
(400 MHz, CDCl3) d: 9.04 (d, J¼1.6 Hz, 2H), 8.65 (s,
1H), 8.52 (d, J¼2.4 Hz, 1H), 8.02 (d, J¼8.0 Hz, 2H), 7.51
(t, J¼7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3) d: 152.8,
144.2, 142.9, 142.2, 136.3, 129.9, 129.0, 126.9; LRMS
(EI, 20 eV) m/z (%): 156 (M+, 100).
4.1.15. 2-Phenylpyridine (19).3 White solid; 1H NMR
(400 MHz, CDCl3) d: 8.59 (d, J¼4.8 Hz, 1H), 7.99 (d,
J¼6.8 Hz, 2H), 7.78–7.71 (m, 2H), 7.48 (t, J¼8.8 Hz, 2H),
7.42 (t, J¼7.2 Hz, 1H), 7.26–7.21 (m, 1H); 13C NMR
(100 MHz, CDCl3) d: 157.4, 149.6, 139.3, 136.7, 128.9,
128.7, 126.9, 122.1, 120.5; LRMS (EI, 20 eV) m/z (%):
155 (M+, 100).
4.1.23. 2-Phenylthiophene (27).10 Yellow oil; 1H NMR
(400 MHz, CDCl3) d: 7.61–7.57 (m, 2H), 7.35 (t,
J¼7.6 Hz, 2H), 7.29–7.23 (m, 2H), 7.05 (t, J¼4.0 Hz, 1H);
13C NMR (100 MHz, CDCl3) d: 144.4, 134.3, 128.8,
127.9, 127.4, 125.9, 124.7, 123.0; LRMS (EI, 20 eV) m/z
(%): 160 (M+, 100).
4.1.16. 3-Phenylpyridine (20).3 White solid; 1H NMR
(400 MHz, CDCl3) d: 8.85 (s, 1H), 8.59 (d, J¼6.4 Hz,
1H), 7.88 (d, J¼12.0 Hz, 1H), 7.60 (d, J¼8.4 Hz, 2H),
7.49 (t, J¼7.2 Hz, 2H), 7.43–7.35 (m, 2H); 13C NMR
(100 MHz, CDCl3) d: 148.4, 148.3, 137.8, 136.6, 134.3,
129.0, 128.1, 127.1, 123.5; LRMS (EI, 20 eV) m/z (%):
155 (M+, 100).
4.1.24. 2-(4-Nitrophenyl)thiophene (28).11 Yellow solid;
1H NMR (400 MHz, CDCl3) d: 8.23 (d, J¼8.8 Hz, 2H),
7.74 (d, J¼9.6 Hz, 2H), 7.48 (d, J¼4.0 Hz, 1H), 7.44 (d,
J¼5.2 Hz, 1H), 7.15 (t, J¼4.4 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d: 146.6, 141.6, 140.6, 128.7, 127.7,
126.0, 125.7, 124.4; LRMS (EI, 20 eV) m/z (%): 205
(M+, 100).
4.1.17. 2-Methoxy-5-phenylpyridine (21). Colorless oil;
1H NMR (400 MHz, CDCl3) d: 8.39 (s, 1H), 7.79 (d,
J¼2.8 Hz, 1H), 7.54–7.52 (m, 2H), 7.46 (t, J¼7.2 Hz, 2H),
4.1.25. 2-(4-Nitrophenyl)furan (29).11 Yellow solid;
1H NMR (400 MHz, CDCl3) d: 8.24 (d, J¼8.8 Hz, 2H),
7.78 (d, J¼7.8 Hz, 2H), 7.57 (d, J¼1.2 Hz, 1H), 6.87

10894
J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
(d, J¼2.4 Hz, 1H), 6.55 (t, J¼3.6 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d: 151.7, 146.4, 144.1, 136.4, 124.3,
123.3,112.4,108.6;LRMS(EI,20 eV)m/z(%): 189 (M+,100).
1H), 8.64 (s, 1H), 7.93 (d, J¼6.4 Hz, 2H); 13C NMR
(100 MHz, CDCl3) d: 150.7, 150.1, 144.7, 144.6, 143.5,
142.3, 120.9; LRMS (EI, 20 eV) m/z (%): 157 (M+, 100);
HRMS (EI) for C9H7N3 (M+): calcd, 157.0640; found,
157.0640.
4.1.26. 4-(4-Nitrophenyl)pyridine (30). Yellow solid, mp
128.4–129.4 ꢀC (uncorrected); 1H NMR (400 MHz,
CDCl3) d: 8.75 (d, J¼6.0 Hz, 2H), 8.36 (d, J¼8.8 Hz, 2H),
7.81 (d, J¼8.8 Hz, 2H), 7.55 (d, J¼6.0 Hz, 2H); 13C NMR
(100 MHz, CDCl3) d: 150.6, 148.1, 145.7, 144.4, 127.9,
124.3, 121.7; LRMS (EI, 20 eV) m/z (%): 200 (M+, 100).
Acknowledgements
We thank the National Natural Science Foundation of China
(nos. 20572020 and 20202002), the Key Project of Chinese
Ministry of Education (no. 206102), Scientific Research
Fund of Hunan Provincial Education Department (no.
05B038), Hunan Provincial Natural Science Foundation of
China (no. 05JJ1002), and Fok Ying Dong Education Foun-
dation (no. 101012) for financial support.
4.1.27. 2-Phenylfuran (31).12 White solid; 1H NMR
(300 MHz, CDCl3) d: 7.67 (d, J¼8.8 Hz, 1H), 7.60 (d,
J¼8.8 Hz, 2H), 7.46–7.34 (m, 5H); 13C NMR (75 MHz,
CDCl3) d: 142.0, 128.7, 128.6, 127.3, 127.2, 127.1, 123.7,
111.6; LRMS (EI, 20 eV) m/z (%): 144 (M+, 100).
4.1.28. 3-(Thiophen-2-yl)quinoline (33). White solid, mp
1
73.4–73.9 ꢀC (uncorrected); H NMR (400 MHz, CDCl3)
Supplementary data
d: 9.18 (s, 1H), 8.21 (s, 1H), 8.08 (d, J¼8.0 Hz, 1H), 7.77
(d, J¼8.4 Hz, 1H), 7.66 (t, J¼7.6 Hz, 1H), 7.51 (t,
J¼7.6 Hz, 1H), 7.45 (s, 1H), 7.35 (d, J¼4.8 Hz, 1H), 7.12
(t, J¼4.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 148.5,
147.1, 140.6, 131.2, 129.2, 129.1, 128.3, 127.8, 127.7,
127.4, 127.1, 126.0, 124.3; LRMS (EI, 20 eV) m/z (%):
211 (M+, 100); HRMS (EI) for C13H9NS (M+): calcd,
211.0456; found, 211.0455.
Supplementary data associated with this article can be found
in the online version, at doi:10.1016/j.tet.2006.08.103.
References and notes
1. Bringmann, G.; Gunther, C.; Ochse, M.; Schupp, O.; Tasler, S.
Progress in the Chemistry of Organic Natural Products; Herz,
W., Falk, H., Kirby, G. W., Moore, R. E., Eds.; Springer: New
York, NY, 2001; Vol. 82, pp 1–293.
4.1.29. 3-(Furan-2-yl)quinoline (34). Pale solid, mp 81.7–
82.0 ꢀC (uncorrected); 1H NMR (400 MHz, CDCl3) d:
9.21 (s, 1H), 8.33 (s, 1H), 8.07 (d, J¼8.4 Hz, 1H), 7.81 (d,
J¼8.0 Hz, 1H), 7.66 (t, J¼8.8 Hz, 1H), 7.56–7.51 (m, 2H),
6.85 (d, J¼3.2 Hz, 1H), 6.54 (d, J¼5.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d: 151.3, 147.1, 143.1, 129.3, 129.2,
129.0, 127.9, 127.8, 127.1, 124.0, 111.9, 106.7; LRMS
(EI, 20 eV) m/z (%): 195 (M+, 100); HRMS (EI) for
C13H9NO (M+): calcd, 195.0684; found, 195.0684.
2. For reviews, see: (a) Bringmann, G.; Walter, R.; Weirich, R.
Angew. Chem., Int. Ed. Engl. 1990, 29, 977; (b) Hegedus,
L. S. Organometallics in Synthesis; Schlosser, M., Ed.;
Wiley: Chichester, UK, 2002; p 1123; (c) Handbook of
Organopalladium Chemistry for Organic Synthesis; Negishi,
E., Ed.; Wiley-Interscience: New York, NY, 2002; (d)
Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457; (e)
Diederich, F.; Stang, P. J. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, 1998; (f) Miyaura, N.
Cross-Coupling Reaction; Springer: Berlin, 2002; (g) de
Meijere, A.; Diederich, F. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, 2004; (h) Herrmann,
W. A. Angew. Chem., Int. Ed. 2002, 41, 1290; (i) Yong, B. S.;
Nolan, S. P. Chemtracts: Org. Chem. 2003, 205; (j) Littke,
A. F.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41, 4176; (k)
Tang, S.; Liang, Y.; Liu, W.-J.; Li, J.-H. Chin. J. Org. Chem.
2004, 24, 1133.
4.1.30. 5-(Thiophen-2-yl)pyrimidine (35). White solid, mp
77.2–78.0 ꢀC (uncorrected); 1H NMR (400 MHz, CDCl3) d:
9.13 (s, 1H), 8.96 (s, 1H), 7.46 (d, J¼6.0 Hz, 2H), 7.43 (d, J¼
5.2 Hz, 1H), 7.18 (t, J¼3.6 Hz, 1H); 13C NMR (100 MHz,
CDCl3) d: 157.2, 153.4, 136.2, 128.6 (2C), 127.3, 125.2;
LRMS (EI, 20 eV) m/z (%): 162 (M+, 100); HRMS (EI) for
C8H6N2S (M+): calcd, 162.0252; found, 162.0251.
4.1.31. 5-(Furan-2-yl)pyrimidine (36).13 Slight yellow
solid; H NMR (400 MHz, CDCl3) d: 9.10 (s, 1H), 9.01 (s
1
3. For selected recent papers on the palladium-catalyzed Suzuki–
Miyaura cross-coupling reaction of aryl chlorides, see: (a)
Willis, M. C.; Mori, L.; Yamaguchi, K.; Hara, T.; Mizugaki,
T.; Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2002, 124,
2H), 7.59 (d, J¼1.6 Hz, 1H), 6.85 (d, J¼3.6 Hz, 1H), 6.55
(t, J¼1.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 157.0,
151.3, 147.9, 144.0, 125.0, 112.1, 107.9; LRMS (EI,
20 eV) m/z (%): 146 (M+, 100).
€
€
11572; (b) Gstottmayr, C. W. K.; Bohm, V. P. W.;
Herdtweck, E.; Grosche, M.; Herrmann, W. A. Angew.
Chem., Int. Ed. 2002, 41, 1363; (c) Altenhoff, G.; Goddard,
R.; Lehmann, C. W.; Glorius, F. Angew. Chem., Int. Ed.
2003, 42, 3690; (d) Bedford, R. B.; Hazelwood, S. L.;
Limmert, M. E. Organometallics 2003, 22, 1364; (e) Powell,
H.; Claverie, C. K. Angew. Chem., Int. Ed. 2004, 43, 1249;
(f) Barder, T. E.; Buchwald, S. L. Org. Lett. 2004, 6, 2649;
(g) Colacot, T. J.; Shea, H. A. Org. Lett. 2004, 6, 3731; (h)
Walker, S. D.; Barder, T. E.; Martinelli, J. R.; Buchwald,
S. L. Angew. Chem., Int. Ed. 2004, 43, 1871; (i) Son, S. U.;
Jang, Y.; Park, J.; Na, H. B.; Park, H. M.; Yun, H. J.; Lee, J.;
4.1.32. 2-(Thiophen-2-yl)pyrazine (37).13 Slight yellow
solid; H NMR (400 MHz, CDCl3) d: 8.96 (s, 1H), 8.51 (s,
1
1H), 8.40 (s, 1H), 7.69 (d, J¼4.0 Hz, 1H), 7.49 (d, J¼5.6 Hz,
1H), 7.16 (t, J¼4.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d: 148.5, 143.9, 142.3, 141.3, 140.6, 129.0, 128.4, 125.7;
LRMS (EI, 20 eV) m/z (%): 162 (M+, 100).
4.1.33. 2-(Pyridin-4-yl)pyrazine (38). Slight yellow solid,
mp 87.6–88.4 ꢀC (uncorrected); 1H NMR (400 MHz,
CDCl3) d: 9.11 (s, 1H), 8.79 (d, J¼6.0 Hz, 2H), 8.72 (s,

J.-H. Li et al. / Tetrahedron 62 (2006) 10888–10895
10895
Hyeon, T. J. Am. Chem. Soc. 2004, 126, 5026; (j) Altenhoff, G.;
Goddard, R.; Lehmann, C. W.; Glorius, F. J. Am. Chem. Soc.
2004, 126, 15195; (k) Zapf, A.; Jackstell, R.; Rataboul, F.;
Reirmeier, T.; Monsees, A.; Fuhrmann, C.; Shaikh, N.;
Dingerdissen, U.; Beller, M. Chem. Commun. 2004, 38; (l)
Lebel, H.; Janes, M. K.; Charette, A. B.; Nolan, S. P. J. Am.
Chem. Soc. 2004, 126, 5046 and references cited therein; (m)
Barder, T. E.; Walker, S. D.; Martinelli, J. R.; Buchwald,
S. L. J. Am. Chem. Soc. 2005, 127, 4685; (n) Anderson,
K. W.; Buchwald, S. L. Angew. Chem., Int. Ed. 2005, 44,
6173; (o) Liu, D.; Gao, W.; Dai, Q.; Zhang, X. Org. Lett.
2005, 7, 4907 and references cited therein; (p) Singh, R.;
Viciu, M. S.; Kramareva, N.; Navarro, O.; Nolan, S. P. Org.
Lett. 2005, 7, 1829; (q) Navarro, O.; Marion, N.; Oonishi, Y.;
Kelly, R. Y., III; Nolan, S. P. J. Org. Chem. 2006, 71, 685; (r)
Marion, N.; Navarro, O.; Mei, J.; Stevens, E. D.; Scott,
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4. For papers on the use of bulky trialkylphosphines for the palla-
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