Efficient Suzuki coupling of aryl chlorides catalyzed by tricyclohexylphosphine adducts of cyclopalladated ferrocenylimines

Article abstract of DOI:10.1016/j.jorganchem.2005.05.038

The air and moisture stable tricyclohexylphosphine (PCy₃) adducts of dimeric cyclopalladated ferrocenylimines 5 and 6 have been easily synthesized and successfully used in palladium-catalyzed Suzuki cross-coupling of aryl chlorides. Using 0.1 mol% of 6 in the presence of 2 equivalent of Cs₂CO₃ as base in dioxane at 100 °C provided coupled products in excellent yields in the reaction of non-activated and deactivated aryl chlorides with phenylboronic acid. For activated chlorides such as 4-chloronitrobenzene and 4-chloroacetophenone, the catalyst loadings could be lowered to 0.01 mol% without loss of activity.

Full text of DOI:10.1016/j.jorganchem.2005.05.038

Journal of Organometallic Chemistry 690 (2005) 3963–3969
www.elsevier.com/locate/jorganchem
Efficient Suzuki coupling of aryl chlorides catalyzed by
tricyclohexylphosphine adducts of cyclopalladated ferrocenylimines
*
Junfang Gong, Guangyu Liu, Chenxia Du, Yu Zhu, Yangjie Wu
Department of Chemistry, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry
of Henan Universities, Zhengzhou University, Zhengzhou 450052, PR China
Received 23 February 2005; received in revised form 5 May 2005; accepted 19 May 2005
Available online 5 July 2005
Abstract
The air and moisture stable tricyclohexylphosphine (PCy3) adducts of dimeric cyclopalladated ferrocenylimines 5 and 6 have
been easily synthesized and successfully used in palladium-catalyzed Suzuki cross-coupling of aryl chlorides. Using 0.1 mol% of
6 in the presence of 2 equivalent of Cs2CO3 as base in dioxane at 100 ꢀC provided coupled products in excellent yields in the reaction
of non-activated and deactivated aryl chlorides with phenylboronic acid. For activated chlorides such as 4-chloronitrobenzene and
4-chloroacetophenone, the catalyst loadings could be lowered to 0.01 mol% without loss of activity.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Suzuki coupling; Cyclopalladated ferrocenylimines; Tricyclohexylphosphine adducts; Aryl chlorides; Phenylboronic acid
1. Introduction
oximes or thioethers have been synthesized and used
in the Suzuki reaction. The advantages of such pallada-
cyclic catalysts include their ease of synthesis, facile
modification and convenience of handling (insensitivity
to air or moisture). Most of the palladacycles show con-
siderable activity with activated aryl chlorides but only
limited activity with deactivated substrates [3b]. It was
recently reported, however, that isolated or in situ
formed secondary [10] or tertiary phosphine [11] adducts
(L = HP(tBu)2, HPCy2 or PCy3, PtBu3, e.g.) of dimeric
phosphorus- or nitrogen-containing palladacycles (Fig.
1) efficiently promote the Suzuki coupling of both acti-
vated and deactivated aryl chlorides.
Our work had focused on cyclometallation of ferroce-
nylimines and applications of these systems [12]. We
have found that cyclopalladated ferrocenylimines 4 are
effective for the Heck reaction [13] and the dimerization
of arylmercurials [14]. They also showed good activity in
the Suzuki coupling reaction of aryl iodides and bro-
mides. In contrast, only activated aryl chlorides gave
good results [15]. We thought it interesting to study
whether the activity of palladacycles 4 with aryl
Palladium-catalyzed reactions are widely used in or-
ganic synthesis for formation of carbon–carbon and car-
bon–heteroatom bonds [1]. The Suzuki reaction of aryl
halides/triflates with boronic acids has been one of the
most widely studied owing to its applicability and the
low toxicity of the reagents [2]. There is currently much
interest in development of catalysts that can activate
aryl chlorides since these substrates are cheaper and
more readily available than the corresponding bromides
and iodides [3]. Substantial progress has been made by
using catalysts with bulky, electron-rich phosphines [2–
7] and N-heterocyclic carbenes [2,3,8]. Moreover, palla-
dacyclic catalysts are amongst the most active catalysts
for forming carbon–carbon and carbon–heteroatom
bonds [2b,3b,7c,8c–9]. A large number of phosphorus,
nitrogen or sulfur based palladacycles derived from
phosphines, phosphites, phosphinites, amines, imines,
*
Corresponding author: Tel./fax: +86 371 797 9408.
E-mail address: wyj@zzu.edu.cn (Y. Wu).
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.038

3964
J. Gong et al. / Journal of Organometallic Chemistry 690 (2005) 3963–3969
L
Y
O PR
tBu
tBu
2
Pd
Cl
X
Pd
L
Pd Cl
NMe
2
L
1
L = PR
Y = NR , =NR L = PR
3
2
3
2
3
L = HPR or PCy
2 3
X = TFA, OTf, Cl, etc.
Fig. 1. Examples of adducts resulting from the corresponding dimeric palladacycles with phosphines.
chlorides could be enhanced with the corresponding tri-
cyclohexylphosphine adduct 5. Novel palladacycle 6 was
also prepared for comparison. The results of this study
are presented below.
ladium in CH2Cl2 at room temperature produced the
corresponding tricyclohexylphosphine adduct 5 or 6 as
red crystals after recrystallization from CH2Cl2–petro-
leum ether in 53.4% and 57.0% yield, respectively. Both
5 and 6 are air and moisture stable both in the solid state
and in solution.
CH
CH
3
3
The new compounds 5 and 6 were characterized by
1H NMR, IR and high resolution mass spectrometry.
The structure of 5 was determined by X-ray single crys-
tal analysis. The molecule is shown in Fig. 2. Crystallo-
graphic and data collection parameters for 5 Æ CH2Cl2
N
N
CH
3
R
Fe
Pd
Cl
Fe
Pd Cl
PCy
2
3
R = p-CH (a), p-OCH (b),
3
3
˚
5
are summarized in Table 1. Selected bond length (A)
p-Cl(c), o-Cl(d), m-Cl(e)
and angles (ꢀ) are given in Table 2. As depicted in Fig.
2, the palladium adopts an approximately square planar
configuration defined by the P, N, Cl(1) and C(6) atoms.
The N–Pd–C(6) bond angle (80.5(2)ꢀ) is essentially
identical to the corresponding values in PPh3 adducts
of cyclopalladated ferrocenylimines 4 [16,17]. The coor-
4
H
N
Fe
Pd Cl
PCy
3
6
2. Results and discussion
2.1. Synthesis and characterization of complexes 5 and 6
The reaction of chloride-bridged palladacyclic dimers
4a or 7 (Scheme 1) with 1.2 equivalent of PCy3 per pal-
CH3
CH3
PCy3
CH3
N
N
CH3
CH2Cl2, r.t.
Fe
Fe
Pd
Pd Cl
PCy
Cl
2
3
4a
5
H
H
N
N
PCy3
Fe
Pd Cl
PCy
Fe
Pd Cl
CH2Cl2, r.t.
2
3
6
7
Scheme 1.
Fig. 2. Molecular structure of 5 Æ CH2Cl2.

J. Gong et al. / Journal of Organometallic Chemistry 690 (2005) 3963–3969
3965
Table 2
dinated PCy3 is trans to the imino nitrogen with a
P–Pd–N angle of 172.25(14)ꢀ. The Pd–C(6) (2.019(6)
A), Pd–N (2.170(5) A) and Pd–P (2.2833(16) A) bond
˚
Selected bond lengths (A) and angles (ꢀ) for 5 Æ CH2Cl2
˚
˚
˚
Pd(1)–C(6)
Pd(1)–P(1)
Pd(1)–Cl(1)
N(1)–C(13)
C(10)–C(11)
Pd(1)–N(1)
Pd(1)–Cl(10)
N(1)–C(11)
C(6)–C(10)
2.019(6)
2.2833(16)
2.530(3)
1.444(8)
1.441(10)
2.170(5)
2.426(3)
1.299(8)
1.441(9)
˚
lengths in 5 are longer than those of 8 (1.998(3) A,
˚
˚
2.136(3) A, 2.2371(10) A, respectively) [17] possibly
due to the steric bulk of the PCy3 ligand.
CH3
N
Pd Cl
PPh3
CH3
Fe
C(6)–Pd(1)–N(1)
N(1)–Pd(1)–P(1)
P(1)–Pd(1)–Cl(10)
P(1)–Pd(1)–Cl(1)
C(11)–N(1)–Pd(1)
C(6)–Pd(1)–P(1)
N(1)–Pd(1)–Cl(10)
N(1)–Pd(1)–Cl(1)
Cl(10)–Pd(1)–Cl(1)
N(1)–C(11)–C(10)
80.5(2)
172.25(14)
93.38(10)
92.29(8)
114.0(4)
96.81(18)
89.56(17)
91.76(16)
9.41(11)
114.7(6)
8
2.2. Suzuki coupling reaction
Initially, a quick survey of solvents, including diox-
ane, toluene and THF, with phenyl chloride and phen-
ylboronic acid as the coupling partners (using
0.1 mol% of 6 and Cs2CO3 as the base) revealed that
dioxane gave the fastest reaction (data not shown). We
further investigated the effect of the base in the same
reaction (Table 3), examining K2CO3, Cs2CO3, K3PO4,
KF Æ 2H2O and t-BuONa. It was found that Cs2CO3
Table 3
Influence of base on the Suzuki coupling of phenyl chloride with
phenyl boronic acid
Cat. 5/dioxane/100 oC
B(OH)2
Cl
+
Base/10h
Table 1
Crystallographic and data collection parameters for 5 Æ CH2Cl2
Entry
Base
K2CO3
Cs2CO3
% Yielda
1
2
3
4
5
24.2 (20.2)
76.4 (66.2)
38.7 (35.0)
35.6 (32.5)
13.9 (12.6)
Empirical formula
Formula weight
Temperature (K)
C37H51ClFeNPPd Æ CH2Cl2
823.38
291(2)
K3PO4
KF Æ 2H2O
t-BuONa
˚
Wavelength (A)
0.71073
Monoclinic
P212121
Crystal system
Space group
Unit cell dimensions
Reaction conditions: catalyst 5 (0.1 mol%), PhCl (1 mmol), PhB(OH)2
(1.5 mmol), base (2 mmol), dioxane (6 mL), 100 ꢀC, 10 h.
Determined by GC (undecane standard), based on PhCl, average of
˚
a
a (A)
12.003(2)
15.614(3)
˚
b (A)
two runs. Yields in parentheses refer to isolated yields, average of two
runs.
˚
c (A)
20.924(4)
90
a (ꢀ)
b (ꢀ)
c (ꢀ)
90
90
3
˚
was much better than others (with 0.1 mol% 5, 100 ꢀC,
10 h, GC yield was 76.4%). Therefore, Cs2CO3 was ulti-
mately chosen as the base for this system.
Volume (A )
3921.8(14)
4
1.395
Z
Calculated density (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
1.100
1704
With the appropriate solvent (dioxane) and base
(Cs2CO3) in hand, the relative activities of several palla-
dacycles (Table 4) for the same model reaction were then
studied. When the reaction was carried out at 100 ꢀC for
10 h, both 5 and 6 exhibited high activity with catalyst
loadings as low as 0.1 mol%. Catalyst 6 was slightly
more active (76.4% versus 82.6% GC yield, respectively,
entries 1 and 2), while dimeric complex 4a and the cor-
responding PPh3 adduct 8 were almost inactive under
the same reaction conditions (entries 3 and 4). The nota-
bly high efficiency of 5 and 6 (relative to 4a and 8) is
attributed to electronic effects of the coordinated
PCy3, suggesting that PCy3 participates in the catalytic
cycles. The isolated yield of biphenyl could reach
100% by prolonging the reaction time from 10 to 15 h
(entry 5). The reaction also proceeded well when the
Crystal size (mm)
Theta range for data collection (ꢀ)
Index ranges
0.20 · 0.18 · 0.17
1.63—25.00
ꢀ14 6 h 6 14, 0 6 k 6 18,
ꢀ24 6 l 6 24
11325/6429 [0.0433]
96.2%
Reflections collected/unique [R(int)
Completeness to 2h = 25.00
Absorption correction
]
None
Maximum and minimum transmission
Refinement method
0.8351 and 0.8100
Full-matrix least-squares
on F2
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
6429/0/413
1.008
R1 = 0.0461, wR2 = 0.0973
R1 = 0.0669, wR2 = 0.1036
0.50(3)
Absolute structure parameter
Extinction coefficient
Largest difference peak and hole (e A
0.00057(16)
0.631 and ꢀ0.384
ꢀ3
˚
)

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J. Gong et al. / Journal of Organometallic Chemistry 690 (2005) 3963–3969
Table 4
Relative activities of palladacycles for the Suzuki coupling of phenyl
chloride with phenyl boronic acid
and 6 are efficient catalysts for the Suzuki coupling of
aryl chlorides with phenylboronic acid. A diverse array
of aryl chlorides, including sterically hindered, electron-
ically deactivated and some heteroaryl chlorides, have
been successfully coupled using this system. Applica-
tions involving these adducts in other palladium-
catalyzed reactions are currently under investigation in
our laboratory.
Cat. /dioxane
B(OH)2
Cl
+
Cs2CO3
Entry
Catalyst (mol%)
T (ꢀC)
Time (h)
% Yielda
1
2
3
4
5
6
7
8
9
5 (0.1)
6 (0.1)
4a (0.1)
8 (0.1)
6 (0.1)
5 (1.0)
6 (1.0)
6 (0.05)
6 (0.01)
100
100
100
100
100
80
10
10
10
10
15
5
76.4 (66.2)
82.6 (76.1)
1.1
0.8
100 (100)
96.1
<1
3. Experimental
60
5
3.1. General
100
100
20
15
(66.2)
28.3 (25.9)
All reactions were carried out under a dry nitrogen
atmosphere using standard Schlenk techniques. 1,4-
Dioxane was dried over sodium benzophenone and dis-
tilled under nitrogen prior to use. The chloride-bridged
palladacyclic dimer 4a, 7 [13a] and PCy3 [18] were pre-
pared according to published procedures. All other
chemicals were used as purchased. Melting points were
measured using a WC-1 microscopic apparatus and were
uncorrected. IR spectra were collected on a Bruker VEC-
TOR22 spectrophotometer in KBr pellets. 1H and
31P{1H} NMR spectra were recorded on a Bruker
DPX-400 spectrometer in CDCl3 with TMS as an inter-
nal standard. GC analysis was performed on Agilent
4890D gas chromatograph. High-resolution mass spectra
were measured on a Waters Q-Tof Microe spectrometer.
Reaction conditions: PhCl (1 mmol), PhB(OH)2 (1.5 mmol), Cs2CO3
(2 mmol), dioxane (6 mL).
a
Determined by GC (undecane standard), based on PhCl, average of
two runs. Yields in parentheses refer to isolated yields, average of two
runs.
reaction temperature was decreased from 100 to 80 ꢀC
when 1 mol% of 5 was used for 5 h (96.1% GC yield, en-
try 6). Further decrease in temperature to 60 ꢀC, how-
ever, led to loss of the activity of the catalyst (entry 7).
In terms of reduction of catalyst loading, palladacycle
6 was still efficient at 0.05 mol% level (entry 8), although
at 0.01 mol% it gave biphenyl product in only 25.9% iso-
lated yield (entry 9).
The scope of the Suzuki coupling was investigated by
varying the aryl chloride under the optimized reaction
conditions (Cs2CO3, dioxane, 100 ꢀC) (Table 5). A
variety of electronically and structurally diverse aryl
chlorides including 3-chloropyridine could be cross-cou-
pled very efficiently with phenylboronic acid. ortho-Sub-
stituents were tolerated and even the very sterically
hindered 2-chloro-m-xylene provided the biaryl product
in 98.7% isolated yield using 0.1 mol% of 6 (entries 1–
4). A strongly electron-donating group such as methoxy
led to a certain drop in isolated yield under the same
reaction conditions (88.1%, entry 5). For activated chlo-
rides such as 4-chloronitrobenzene and 4-chloroaceto-
phenone, the catalyst loadings could be lowered to
0.01 mol% without loss of activity (entries 8–10). Cou-
pling of heteroaryl chlorides with phenylboronic acid
with this catalyst system was also studied. In case of 2-
chloropyridine, using only 0.01 mol% of 6 afforded the
corresponding product in 74.6% isolated yield (entry
11). For 3-chloropyridine only 22.7% yield was obtained
under the low catalyst loading conditions as those of 2-
chloropyridine (entry 12), but the yield was improved
to 62.1% in the presence of 0.1 mol% of 6 (entry14). Fi-
nally, 2-chlorothiophene was found to be a poor cou-
pling partner in this system giving only 24.4% yield
with 0.1 mol% of 6 (entry 15).
3.2. Synthesis of tricyclohexylphosphine adducts 5 and 6
A solution of chloride-bridged palladacyclic dimer 4a
(0.084 g, 0.092 mmol) and PCy3 (0.061 g, 0.22 mmol) in
dichloromethane (10 mL) was stirred at room tempera-
ture for 30 min. The solution was filtered through Celite
and evaporated to dryness. The crude product was
recrystallized from dichloromethane–petroleum ether
to afford red crystals of 5 (0.081 g, 53.4%); m.p. 163–
165 ꢀC. IR (KBr pellet): 3434, 2926, 2852, 1626, 1582,
1508, 1451, 1108, 1006 cmꢀ1 1H NMR (CDCl3): d
.
1.27 (m, 9H, PCy3), 1.76 (m, 15H, PCy3), 1.98 (s, 3H,
CH3), 2.05 (m, 6H, PCy3), 2.33 (m, 3H, CH3), 2.54 (m,
3H, PCy3), 4.26 (s, 5H, C5H5), 4.47 (m, 2H, C5H3),
4.54 (m, 1H, C5H3), 5.30 (s, 2H, CH2Cl2), 6.81 (m,
2H, Ar-H), 7.15 (m, 2H, Ar-H). 31P{1H} NMR
(CDCl3): d 46.78, 48.24. HRMS (positive ESI) calc.
for C37H51ClFeNPPd: 737.1832, found: 737.1840.
Adduct 6 was prepared by a similar procedure: Dimer
7 (0.086 g, 0.11 mmol) reacted with PCy3 (0.073 g,
0.26 mmol) in DCM to produce 0.084 g (57.0%) of 6
as red crystals after recrystallization from CH2Cl2–
petroleum ether; m.p. 199–201 ꢀC. IR (KBr pellet):
3442, 2928, 2852, 1611, 1449, 1302, 1171, 1117,
1
1002 cmꢀ1. H NMR (CDCl3): d 1.32 (m, 15H, PCy3,
In summary, we have demonstrated that novel, sim-
ple PCy3 adducts of cyclopalladated ferrocenylimines 5
CH(CH3)2), 1.78 (m, 15H, PCy3), 2.07 (m, 6H, PCy3),

J. Gong et al. / Journal of Organometallic Chemistry 690 (2005) 3963–3969
3967
Table 5
Suzuki coupling of aryl chlorides with phenyl boronic acid
Cat. /dioxane/100 oC
Cs2CO3/10-15h
Ar
B(OH)2
+
ArCl
Entry
1
Aryl halide
Catalyst (mol%)
Time (h)
15
Product
% Yielda
6 (0.1)
100
Cl
CH3
Cl
CH3
2
3
6 (0.1)
6 (0.1)
15
15
100
100
H3C
H3C
Cl
CH3
Cl
CH3
4
6 (0.1)
15
98.7
CH
CH3
3
OCH
OCH3
3
5
6
6 (0.1)
6 (0.5)
15
12
88.1
93.5
Cl
H3CO
H3CO
O2N
H3CO
H3CO
O2N
Cl
7
8
5 (0.5)
6 (0.1)
12
10
10
10
87.4
Cl
100
Cl
9
6 (0.01)
6 (0.01)
93.6
98.7
O2N
O2N
Cl
O
O
10
H3CC
Cl
H3CC
11
12
6 (0.01)
6 (0.01)
15
15
74.6
22.7
N
N
Cl
Cl
N
N
N
Cl
Cl
13
6 (0.05)
15
55.4
N
14
15
6 (0.1)
6 (0.1)
15
15
62.1
24.4
N
S
N
Cl
S
Reaction conditions: ArCl (1 mmol), PhB(OH)2(1.5 mmol), Cs2CO3 (2 mmol), dioxane (6 mL), 100 ꢀC.
Isolated yields, based on ArCl, average of two runs.
a

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J. Gong et al. / Journal of Organometallic Chemistry 690 (2005) 3963–3969
2.54 (m, 3H, PCy3), 4.21 (s, 5H, C5H5), 4.41 (m, 2H,
C5H3), 4.53 (m, 1H, C5H3), 4.81 (m, 1H, CHMe2),
8.09 (m, 1H, N@CH). 31P{1H} NMR (CDCl3): d
45.57, 46.92. HRMS (positive ESI) calc. for
C32H49ClFeNPPd: 675.1675, found: 675.1670.
3.4. Structure determination
Crystals of 5 were obtained by recrystallization from
CH2Cl2–petroleum ether solution at 0 ꢀC. A single crys-
tal suitable for X-ray analysis was mounted on a glass
fiber. All measurements were made on a Rigaku-IV
imaging plate area detector with graphite monochro-
3.3. General procedure for the coupling reactions
˚
mated Mo Ka radiation (k = 0.71073 A). The data
A Schlenk tube was charged with the appropriate aryl
chloride (1.0 mmol), phenyl boronic acid (0.183 g,
1.5 mmol) and base (2.0 mmol) under nitrogen. The
were corrected for Lorentz and polarization factors.
The structure was solved by direct methods [20] and
expanded using Fourier techniques and refined by full-
matrix least-squares methods. The non-hydrogen atoms
were refined anisotropically, and the hydrogen atoms
were included but not refined. All calculations were per-
formed using the TEXSAN [21] crystallographic software
package of Molecular Structure corporation.
catalyst was introduced as
a
dioxane solution
(0.001 mmol/mL) via syringe, and additional dioxane
was added to obtain a total volume of 6 mL. The reac-
tion mixture was then placed in an oil bath and heated
at 60–100 ꢀC for a certain time, cooled and quenched
with water. The organic layer was separated and the
aqueous layer was extracted with dichloromethane, then
the combined organic layers were washed with water,
dried over MgSO4, filtered, and the solvent was removed
on a rotary evaporator. The residue was analyzed by GC
(dissolved in dioxane, undecane as internal standard) or
purified by column chromatography on silica gel (the
purified products were identified by comparison of melt-
ing points with the literature values [19] or by 1H NMR
spectra).
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 262129. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK,
fax: +44 1223 336 033, e-mail: deposit@ccdc.cam.ac.uk
or on the web www: http://www.ccdc.cam.ac.uk.
2,6-Dimethylbiphenyl. Colorless oil. 1H NMR
(CDCl3): d 2.02 (s, 3H, CH3), 2.03 (s, 3H, CH3), 7.12
(m, 5H, Ar-H), 7.32 (m, 1H, Ar-H), 7.39 (m, 2H, Ar-H).
2-Methoxybiphenyl. Colorless oil. 1H NMR (CDCl3):
d 3.81 (s, 3H, OCH3), 6.98 (m, 1H, Ar-H), 7.03(t,
J = 7.6 Hz, 1H, Ar-H), 7.32 (m, 3H, Ar-H), 7.40 (t,
J = 7.6 Hz, 2H, Ar-H), 7.52 (d, J = 7.2 Hz, 2H, Ar-H).
Acknowledgments
We are grateful to the National Natural Science
Foundation of China (Project 20472074) and Education
Ministry of China for their financial support. We thank
Dr. Jared Cumming and Dr. Yusheng Wu for comments
on this paper.
1
2-Phenylpyridine. Colorless oil. H NMR (CDCl3): d
7.24 (m, 1H, Py-H), 7.46 (m, 3H, Ar-H), 7.74 (m, 2H,
Py-H), 8.00 (d, J = 7.2 Hz, 2H, Ar-H), 8.70 (d,
J = 4.4 Hz, 1H, Py-H).
1
3-Phenylpyridine. Colorless oil. H NMR (CDCl3): d
7.45 (m, 4H, Py-H, Ar-H), 7.59 (d, J = 7.4 Hz, 2H, Ar-
H), 7.90 (d, J = 7.8 Hz, 1H, Py-H), 8.60 (s, 1H, Py-H),
8.86 (s, 1H, Py-H).
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2.27 (s, 3H, CH3), 7.25 (m, 4H, Ar-H), 7.33 (m, 3H, Ar-
H), 7.40 (m, 2H, Ar-H).
(b) F. Diederich, P.J. Stang (Eds.), Metal-Catalyzed Cross-
Coupling Reactions, Wiley-VCH, Weinheim, 1998.
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2-Phenylthiophene. White solid; m.p. 39–41 ꢀC (lit.
40–41 ꢀC). 1H NMR (CDCl3): d 7.09 (t, J = 4.2 Hz,
1H, C4H3S), 7.29 (m, 3H, C4H3S, Ar-H), 7.38 (t,
J = 7.6 Hz, 2H, Ar-H), 7.62 (d, J = 7.6 Hz, 2H, Ar-H).
4-Methoxybiphenyl. White solid; m.p. 88–90 ꢀC (lit.
91–92 ꢀC).
4-Methylbiphenyl. White solid; m.p. 47–49 ꢀC (lit. 48–
50 ꢀC).
4-Acetylbiphenyl. White solid; m.p. 117–119 ꢀC (lit.
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(b) H.N. Nguyen, X.H. Huang, S.L. Buchwald, J. Am. Chem.
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