Highly efficient cyclopalladated ferrocenylimine catalyst for Suzuki cross-coupling reaction of 3-pyridylboronic pinacol ester with aryl halides

Article abstract of DOI:10.1016/j.jorganchem.2005.11.027

The Suzuki cross-coupling reaction of 3-pyridylboronic pinacol ester with aryl iodides, bromides and chlorides was carried out in DMF/H₂O (3/1, v/v) at 110 °C in the presence of cyclopalladated ferrocenylimine I and K₂CO₃ or CsCO₃ (1.0 equiv.) without the protection of inert gas. By using this method the synthesis of 3-pyridyl biaryl compounds could be readily achieved.

Full text of DOI:10.1016/j.jorganchem.2005.11.027

Journal of Organometallic Chemistry 691 (2006) 1301–1306
www.elsevier.com/locate/jorganchem
Note
Highly efficient cyclopalladated ferrocenylimine catalyst for
Suzuki cross-coupling reaction of 3-pyridylboronic pinacol
ester with aryl halides
*
Jinli Zhang, Liang Zhao, Maoping Song, Thomas C.W. Mak, Yangjie Wu
Chemistry Department, Key Laboratory of Chemical Biology and Organic Chemistry of Henan, Key Laboratory of Applied Chemistry of Henan Universities,
Zhengzhou University, Zhengzhou 450052, PR China
Received 24 June 2005; received in revised form 2 November 2005; accepted 9 November 2005
Available online 19 December 2005
Abstract
The Suzuki cross-coupling reaction of 3-pyridylboronic pinacol ester with aryl iodides, bromides and chlorides was carried out in
DMF/H2O (3/1, v/v) at 110 ꢀC in the presence of cyclopalladated ferrocenylimine I and K2CO3 or CsCO3 (1.0 equiv.) without the pro-
tection of inert gas. By using this method the synthesis of 3-pyridyl biaryl compounds could be readily achieved.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Cyclopalladated ferrocenylimine; Suzuki reaction; 3-Pyridylboronic pinacol ester; 3-Pyridyl biaryl system
1. Introduction
C–H activation process, and most of them are air and
moisture stable. When they become catalytically active
(usually above 100 ꢀC), high turnover numbers (TONs)
could be obtained. A recent review on palladacycles has
reported that the palladacycles can be also used in the fields
of photoluminescent, liquid crystal, supramolecules and
dendrimers [11]. Therefore, an increasing research interests
are focusing on the palladacycles.
Some progresses have been made in palladacycle-cata-
lyzed Suzuki reaction. Beller et al. [12] and Bedford [13]
reported that phosphorus-based palladacycles could be
used to catalyze the cross-coupling of a large range of sub-
strates with aryl boronic acid under an inert atmosphere.
Gibson et al. [14] reported the use of orthopalladated ben-
zylphosphine complex in Suzuki reaction. However, inert
atmosphere was also required. Phosphine-free N-heterocy-
clic carbenes (NHC) [15], oxime, imine, and sulphur-based
palladacycles are also found to be good candidates for
Suzuki reaction [15e,16]. But the disadvantage of them
are being either air sensitive or catalytically inactive
towards aryl chlorides [15e,17].
As one of the most powerful methods for the formation
of biaryl Compounds [1], palladium-catalyzed Suzuki reac-
tion has attracted a lot research interest. A large number of
palladium catalysts derived from phosphines, phosphites,
phosphinites, amines, imines, oximes and thioethers were
employed in Suzuki reaction. Among them, palladium–
phosphine complexes are the most commonly employed
catalysts [2,3]. This type of catalyst is sensitive to moisture
and air. Therefore it requires air-free condition to minimize
the ligand oxidation [4–6]. Recently, some papers on the
Miyaura–Suzuki coupling under aerobic conditions have
appeared [7–9]. They reported their research results by
using Pd(OAc)2/phosphine-free ligands such as DAPCy,
Dabco or Bis(N-methyl-N-phenyl-hydrazone) as efficient
air-stable catalytic system for mild Suzuki reaction.
Palladacycles are now emerging as a new family of pal-
ladium catalysts for hosting the cross-coupling reactions
[10]. Usually, they are prepared in high yields through a
*
Ten years ago, we found that cyclopalladated ferroce-
nylimine [18] is a kind of phosphine-free compounds and
Corresponding author.
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.2005.11.027

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J. Zhang et al. / Journal of Organometallic Chemistry 691 (2006) 1301–1306
Table 1
almost behaves all the properties of palladacycles catalysts.
The synthetic convenience, facile modification and air,
moisture stability made them easily to be handled. Subse-
quently, we discovered their wide applications such as the
resolution of racemates, the determination of amino acids
[19], the homogeneous catalysis in Heck reaction [20] both
in organic solvent and in neat water, the dimerization of
ArHgCl [21] and recently the catalyst in Suzuki reaction
of arylboronic acid with aryl halides [22].
Herein, we reported the extension of our work in cyclo-
palladated ferrocenylimine catalyzed Suzuki cross-coupling
reaction by using 3-pyridyl boronic pinacol ester with aryl
iodides, bromides and even aryl chlorides to synthesize the
hetero-biaryls compounds.
Suzuki cross-coupling of 3-pyridyl boronic pinacol ester with aryl iodides
catalyzed by I
Entrya
ArI
T(h)
4
Coupling product
No. of products,
yield %
mol%
of Pd
1
2
1
3a, 97c
3b, 99b
I
I
N
COCH3
COCH3
1
10
N
N
3
4
5
6
7
1
1
1
1
1
4
10
6
3c, 96 c
3d, 88b
3e, 89c
3f, 87c
3g, 84c
I
I
N
OCH3
OCH3
Compared with boronic acids, the boronic esters are
more stable in the presence of a wide variety of functional
groups, non-hygroscopic and easy to be handled [23].
I
I
N
N
OCH3
CH3
OCH3
2. Results and discussion
CH3
6
The catalyst I was prepared in high yield from the cyclo-
palladation of the corresponding ferrocenylimine with
Li2PdCl4 in MeOH in the presence of NaOAc at room tem-
perature [18].
I
I
N
N
10
CH3
CH3
At the very beginning, to develop our methodology, we
ran our first Suzuki cross-coupling reaction of 3-pyridyl
boronic pinacol ester with iodobenzene catalyzed by I.
Based on our previous results, we chose DMF as the sol-
vent and potassium carbonate as the base [22]. However,
we did not obtain the desired product. After a quick
search of the literature, we found that OꢀShea [24] and
Cioffi [25] had reported the hydrolysis of boroxins or
boronic esters to form boronic acid in situ. The formation
of active boronate species does not readily occur under
anhydrous conditions.
We then re-examined the coupling of iodobenzene with
1.0 equiv. of 3-pyridyl boronic pinacol ester at the similar
condition in DMF/H2O (3:1) other than anhydrous
DMF. The reaction took place smoothly in the presence
of 1 mol% palladium catalyst I and potassium carbonate
as the base at 110 ꢀC to give the desired product 3-phenyl
pyridine in 97% yield after 4 h (Table 1, Entry 1).
Under the similar condition, we studied the activity of
catalyst I towards different aryl halides. As expected, cyclo-
palladated ferrocenylimine I was found to efficiently cata-
lyze the coupling of 3-pyridylboronic pinacol ester with a
wide range of aryl iodides, bromides (Scheme 1). Good
to excellent yields were obtained regardless of the substitu-
ents of aryl halides. The experiment result is listed in
Tables.
a Reaction conditions: ArI 0.5 mmol, 3-pyridylboronic pinacol ester
0.5 mmol, K2CO3 0.5 mmol (Entry 3, 1.0 mmol), solvent DMF/H2O
(2.1 mL/0.7 mL), catalyst I, reaction temperature 110 ꢀC.
b Average results of two runs determined by HPLC based on ArI.
c
Isolated yields based on ArI. The compounds were purified by pre-
parative TLC on silica gel.
O
B
X
O
Cat. I, DMF / H2O(3:1)
K2CO3 , refiux (110oC)
+
N
R
N
R
1
3
2
X = I
CH3
5
R = H(a), 4-CH3CO(b), 3-I(c), 4-CH3O(d),
3-CH3O(e), 4-CH3(f), 3-CH3(g)
X = Br
R = H(a),4-CH3CO(b), 4-CH3O(d), 4-CH3(f),
2-CH3(h), 4-CF3(i), 4-CN(j), 4-NO2(k),
2,6-dimethyl(l), 1-naphthyl(m), 3-pyridyl(n)
C
4
N
CH3
3
Fe
Cat.
Pd Cl
2
I
Scheme 1. Suzuki cross-coupling reaction of 3-pyridyl boronic pinacol
ester with aryl halides (I, Br) catalyzed by I.
2.2. Reaction with aryl bromides
To evaluate the scope and limitation of this procedure,
we performed a number of coupling reactions of 3-pyridyl
boronic pinacol ester with several aryl bromides (Scheme 1,
Table 2). The results show that in this case the coupling
reaction could be applied to aryl bromides bearing various
functional groups: cyano, carbonyl, nitro, methoxyl,
methyl, etc. Furthermore, 3-bromopyridine could also be
2.1. Reaction with aryl iodides
In the palladium-catalyzed Suzuki coupling with aryl
halides, the order of reactivity is usually I > Br ꢀ Cl. The
results of Suzuki cross-coupling of 3-pyridyl-boronic pina-
col ester with some aryliodides are listed in Table 1.

J. Zhang et al. / Journal of Organometallic Chemistry 691 (2006) 1301–1306
1303
Table 2
Table 3
Suzuki cross-coupling reaction of 3-pyridyl boronic pinacol ester with aryl
Influence of base on the Suzuki coupling
bromides catalyzed by I
Entrya
Base
Yieldb (%)
Entrya ArBr
mol%
T(h)
6
Coupling product
No. of products,
yield %
1
2
3
4
5
a
Cs2CO3
K2CO3
K3PO4
KOAC
i-Pr2NEt
69
58
22
22
<2
of Pd
1
2
3
1
3a, 87c
3b, 83b
3d, 68b
Br
Br
N
COCH3
Reaction conditions: 4-chloroanisole 0.2 mmol, 3-pyridylboronic
pinacol ester 0.2 mmol, base 0.2 mmol, solvent DMF/H2O (0.84 mL/
0.28 mL), catalyst I, reaction temperature 110 ꢀC.
COCH3
1
1
6
6
N
b
Average results of two runs, isolated yields based on ArCl.
OCH3
OCH3
Br
Br
N
2.3. Reaction with arylchlorides
CH3
CH3
4
5
6
1
13
10
10
3f, 73c
3h, 70c
3i, 84c
Bedford and Fu reported that the dioxane/Cs2CO3 sys-
tem is efficient for the coupling of aryl chlorides with aryl-
boronic acids [26]. We investigated the effect of the base in
the cross-coupling reaction with 4-chloroanisole (Table 3).
By alternating the base K2CO3, Cs2CO3, K3PO4, KOAC
and i-Pr2NEt. It was found that Cs2CO3 is much better
than the others (isolated yield was 69%). Then, we exam-
ined the same reaction in dioxane by using 1% catalyst I
and Cs2CO3 as the base. We found that DMF/H2O is bet-
ter than dioxane (In dioxane, the yield is only 35%) (see
Schemes 2 and 3).
Under the optimized reaction conditions for aryl chlo-
rides, we investigated the reactivity of various aryl chlo-
rides. The electronic effect of substituent was observed
but not very significant. However, the steric factor has a
great influence on the reaction. The coupling with 2-chloro-
toluene and 2-chloroanisole only gave isolated yields 29%
and 35% in the presence of 1.5% catalyst I, respectively
(Table 4, Entries 6 and 9).
N
CH3
Br
CH
3
N
1
CF3
CF3
CN
0.5
Br
N
CN
7
8
9
0.5
1
5
5
3j, 100b
3k, 92c
3l, 71c
Br
Br
N
NO2
NO2
N
CH3
Br
CH3
1
10
N
CH3
CH3
N
Br
10
11
1
1
10
5
3m, 83c
3n, 87c
Br
N
N
3. Experimental
N
a
Reaction conditions: ArBr 0.5 mmol, 3-pyridylboronic pinacol ester
3.1. General
0.5 mmol, K2CO3 0.5 mmol, solvent DMF/H2O (2.1 mL/0.7 mL), catalyst
I, reaction temperature 110 ꢀC.
b Average results of two runs determined by HPLC based on ArBr.
c Isolated yields based on ArBr. The compounds were purified by pre-
parative TLC on silica gel.
Melting points were measured on a WC-1 microscopic
apparatus and uncorrected. HPLC analyses were carried
out on a Waters 600E type instrument equipped with a
˚
Nava-Pak (R) C8 60A HPLC Cartridge column
(3.9 · 150 mm, 4 lm), and UV detector for determination
of the products. 1H NMR were recorded on a Bruker
DPX 400 instrument using CDCl3 as the solvent and tetra-
methylsilane as the internal standard. API mass spectro-
scopic analyses were performed using atmospheric
pressure chemical ionization (APCI). Elemental analyses
were determined with a VARIO EL apparatus. Preparative
coupled in good yield (Table 2, Entry 11). We also investi-
gated the steric effect. As shown in Table 2, aryl bromides
with ortho substituents, such as 2-bromotoluene and 2-
bromo-m-xylene, gave the corresponding products in good
yields (Table 2, Entries 5 and 9).
O
B
O
Cat. I, DMF / H2O(3:1)
base, reflux
OCH3
Cl
+
H3CO
N
N
Scheme 2. Effect of base on the Suzuki cross-coupling of 3-pyridyl boronic pinacol ester with 4-chloroanisole catalyzed by I.

1304
J. Zhang et al. / Journal of Organometallic Chemistry 691 (2006) 1301–1306
Cl
condenser was charged with 3-pyridylboroxin Æ 0.5H2O
O
B
Cat. I, DMF / H2O(3:1), 24h
O
(10.0 g, 30.8 mmol), pinacol (13.5 g, 114 mmol), and toluene
(400 mL). The solution was heated to reflux in a 120 ꢀC oil
bath using a Dean–Stark apparatus for 2.5 h. The reaction
was completed when the reaction solution changed from
cloudy white to clear. The solution was then concentrated
in vacuo to provide a solid. This crude solid was transferred
to cyclohexane (50 mL) and crystallized by holding the sus-
pension at 85 ꢀC for 30 min and then allowing the tempera-
ture to slowly return to room temperature. The slurry was
filtered, and the solid was washed with cyclohexane
(10 mL) and dried under vacuum to afford 15.39 g of 3-pyr-
idylboronic pinacol ester as a white solid. Yield: 72%. M.p.:
+
Cs2CO3 , reflux (110oC)
N
R
N
3
R
3
1
4
CH3
R = H(a), 4-CH3O(d), 4-CH3(f),
2-CH3(h), 4-NO2(k), 3-pyridyl(n),
2-pyridyl(o), 2-CH3O(p)
5
C
4
N
CH3
Fe
Cat.
Pd Cl
2
I
Scheme 3. Suzuki cross-coupling of 3-pyridyl boronic pinacol ester with
aryl chlorides.
Table 4
Suzuki cross-coupling reaction of 3-pyridyl boronic pinacol ester with aryl
chlorides catalyzed by I
1
104–105 ꢀC. H NMR (400 MHz, CDCl3) d 8.95 (br, 1H),
8.67 (dd, 1H, J = 1.8, 4.9 Hz), 8.06 (dt, 1H, J = 1.8,
7.5 Hz), 7.29–7.26 (m, 1H), 1.36 (s, 12H).
Entrya
Aryl halides
mol%
of Pd
Coupling
product
No. of products,
yieldb %
O2N
O2N
Cl
Cl
1
1
3k, 77
3.3. General procedure of Suzuki coupling reaction of
3-pyridylboronic pinacol ester with aryl halides
N
NC
NC
2
1
3j, 80
A 5 mL round-bottom flask was charged with aryl
halides (0.5 mmol), 3-pyridylboronic pinacol ester
(0.5 mmol, 0.1024 g), potassium carbonate (0.5 mmol,
0.079 g) and catalyst I in DMF/H2O (2.1 mL/0.7 mL) at
room temperature. The reaction mixture was stirred at
reflux temperature (110 ꢀC) in air and the reaction progress
was monitored by TLC. After the completion of the reac-
tion, the mixture was quenched by 5 mL water and then
extracted with CH2Cl2 (3 · 10 mL). The combined organic
layer was dried over Na2SO4. After removal of the solvent
in vacuo, the product was obtained by preparative TLC,
eluting with acetic ether/petroleum ether (1:1–1: 5) and
the yield was calculated based on ArX or determined by
N
Cl
3
4
5
1
1
1
3a, 66
3d, 69
3f, 76
N
H3CO
H3CO
H3C
Cl
N
H3C
Cl
N
CH3
CH3
Cl
6
3h, 29
1.5
N
Cl
7
8
3n, 64
3o, 74
1
1
N
N
N
N
Cl
N
N
1
HPLC. Final products were characterized by H NMR,
OCH3
OCH3
LC/MS/MS and elemental analysis.
9
3p, 35
Cl
1.5
N
a Reaction conditions: arylchlorides 0.2 mmol, 3-pyridylboronic pinacol
ester 0.2 mmol, Cs2CO3 0.2 mmol, solvent DMF/H2O (0.84 mL/0.28 mL),
catalyst I.
b Isolated yields based on ArCl. The compounds were purified by pre-
parative TLC on silica gel.
3.3.1. 3-Phenyl pyridine (3a) [28]
Colourless oil, nD20 1.6150. APCI MS: m/z 156
1
[C11H9N + H]+. H NMR (CDCl3) d 8.86 (1H, s), 8.60
(1H, J = 4.0 Hz, d), 7.87 (1H, J = 8.0 Hz, d), 7.35–7.60
(6H, m).
3.3.2. 1-(4-Pyridin-3-ylphenyl) ethanone (3b) [29]
1
TLC was performed on dry silica gel plates developed with
acetic ether/petroleum ether.
White plates, m.p. 81–83 ꢀC. H NMR (CDCl3) d 8.89
(1H, s), 8.64 (1H, J = 4.0 Hz, m), 8.09 (2H, J = 8.4 Hz,
J = 6.4 Hz, dd, Ar H), 7.92 (1H, m), 7.02 (2H,
J = 8.4 Hz, J = 6.4 Hz, dd, Ar H), 7.39 (1H, m), 2.65
(3H, s, CH3).
Cyclopalladated ferrocenylimine
I was synthesized
according to the literature procedures [18]. All solvents were
dried according to the standard methods. The aryl halides
were obtained from commercial sources and were generally
used without further purification. The biaryls for HPLC
external standard were prepared via Suzuki reaction and
characterized by comparison of the melting points to the lit-
3.3.3. 1,3-Bis(3-pyridyl) benzene (3c) [30]
1
White needles, m.p. 84–86 ꢀC H NMR (CDCl3) d 8.91
1
(2H, s), 8.65 (2H, J = 4.0 Hz, J = 1.2 Hz, dd), 7.96 (2H,
J = 8.4 Hz, J = 1.6 Hz, dd, Py-H), 7.77 (1H, s), 7.65 (3H,
J = 4.8 Hz, m), 7.44 (2H, J = 4.8 Hz, d, Ar H).
APCI MS: m/z 233 [C16H12N2 + H]+. Anal. Calc. for
C16H12N2: C, 82.73; H, 5.21; N, 12.06. Found: C, 82.74;
H, 5.22; N, 12.09%.
eratures, by elemental analysis or by H NMR.
3.2. Preparation of 3-pyridylboronic pinacol ester [27]
A 0.5 L three-necked flask equipped with a stir bar, a
nitrogen inlet adapter, and a Dean-Stark trap with a

J. Zhang et al. / Journal of Organometallic Chemistry 691 (2006) 1301–1306
1305
3.3.4. 3-(4-Methoxyphenyl) pyridine (3d) [29]
1
3.3.14. 3,30-Bipyridine (3n) [37]
White solid, m.p. 55–57 ꢀC. H NMR (CDCl3) d 8.83
Yellow oil, APCI MS: m/z 157 [C10H8N2 + H]+. 1H
NMR (CDCl3) d 8.54 (2H, s), 8.66 (2H, J = 4.0 Hz, d),
7.90 (2H, J = 8.0 Hz, J = 4.0 Hz, dt), 7.43 (2H,
J = 4.8 Hz, J = 8.0 Hz, m).
(1H, s), 8.60 (1H, d), 7.87 (1H, J = 8.0, d), 7.53 (2H,
J = 8.4 Hz, d, Ar H), 7.38 (1H, m), 7.02 (2H, J = 8.4 Hz,
d, Ar H), 3.87 (3H, s, CH3).
3.3.5. 3-(3-Methoxyphenyl) pyridine (3e) [31]
White solid, m.p. 119–120 ꢀC. APCI MS: m/z 186
[C12H11NO + H]+.
3.3.15. 2,30-Bipyridine (3o) [29]
1H NMR (CDCl3, 400 MHz), d 9.21 (1H, s), 8.74 (dt,
J = 8.4 Hz, J = 4.0 Hz, 1H), 8.60 (d, J = 4.0 Hz, 1H),
8.55 (dt, J = 8.0 Hz, J = 6.0 Hz, 1H), 7.83-7.75 (m, 2H),
7.44 (m, 1H), 7.30 (m, 1H).
3.3.6. 3-(4-Tolyl) pyridine (3f) [32]
1
White solid, m.p. 39–40 ꢀC. H NMR (CDCl3) d 8.84
(1H, s), 8.57 (1H, J = 4.0 Hz, d), 7.87 (1H, J = 8.0 Hz,
d), 7.49 (2H, J = 8.0 Hz, d, Ar H), 7.36 (1H, m), 7.32
(2H, J = 8.0 Hz, d, Ar H), 2.40 (3H, s, CH3). APCI MS:
m/z 170 [C12H11N + H]+. Anal. Calc. for C12H11N: C,
85.17; H, 6.55; N, 8.28. Found C, 85.03; H, 6.56; N, 8.18%.
3.3.16. 3-(2-Methoxyphenyl) pyridine (3p) [31]
Colorless oil 1H NMR (CDCl3) d 8.81 (1H, s), 8.58 (1H,
s), 7.92 (1H, J = 8.0 Hz, d), 7.41–7.32 (3H, m), 7.09–7.01
(2H, m), 3.12 (3H, s, CH3).
4. Conclusion
3.3.7. 3-(3-Tolyl) pyridine (3g) [31]
White solid, m.p. 186–187 ꢀC. APCI MS: m/z 170
[C12H11N + H]+.
In conclusion, cyclopalladated ferrocenylimine I pro-
vides a convenient catalyst for the cross-coupling of 3-pyr-
idylboronic pinacol ester with a variety of aryl halides
(even including electron-rich aryl chlorides). Moderate to
excellent yields were obtained without the protection of
inert gas. The tolerance towards various substrates, high
stability and activity make it an excellent and practical cat-
alyst for this Suzuki cross-coupling reaction.
3.3.8. 3-(2-Tolyl) pyridine (3h) [25]
Colorless oil, 1H NMR (CDCl3) d 8.61 (2H, s), 7.69 (1H,
J = 7.6 Hz, d), 7.41–7.21 (5H, m), 2.98 (3H, s, CH3).
3.3.9. 3-(4-Trifluoroacetphenyl) pyridine (3i) [33]
1
White plates, m.p. 64–66 ꢀC. H NMR (CDCl3) d 8.90
(1H, s), 8.67 (1H, s), 7.99 (2H, J = 7.2 Hz, d, Ar H), 7.78
(2H, J = 8.0 Hz, d, Ar H), 7.72 (2H, J = 8.0 Hz, d, Ar
H), 7.52 (1H, m). APCI MS: m/z 224 [C12H8NF3 + H]+.
Anal. Calc. for C12H8NF3: C, 64.58; H, 3.61; N, 6.28.
Found: C, 64.37; H, 3.53; N, 6.07%.
Acknowledgments
We are grateful to the National Science Foundation of
China (Project 20072034) and Natural Science Foundation
of Henan Province for the financial support given to this
research. We thank Mr. Keith Eagen and Dr. Yusheng
Wu for comments on this paper.
3.3.10. 4-Pyridin-3-ylbenzonitrile (3j) [34]
White needles, m.p. 95–96 ꢀC. 1H NMR (CDCl3) d 8.87
(1H, s), 8.68 (1H, d), 7.91 (1H, J = 8.4 Hz, d), 7.79 (2H,
J = 8.4 Hz, d, Ar H),7.70 (2H, J = 8.4 Hz, d, Ar H), 7.45
(1H, m), 3.87 (3H, s, CH3). Anal. Calc. for C12H8N2 C,
79.98; H, 4.47; N, 15.55. Found: C, 80.05; H, 4.42; N,
15.74%.
References
[1] (a) N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457;
(b) A. Suzuki, in: F. Diederich, P.J. Stang (Eds.), Metal-Catalyzed
Cross-Coupling Reactions, Wiley–VCH, Weinheim, Germany, 1998
(Chapter 2);
(c) S.P. Stanforth, Tetrahedron 54 (1998) 263;
(d) A. Suzuki, J. Organomet. Chem. 576 (1999) 147;
(e) A. Suzuki, J. Organomet. Chem. 653 (2002) 83.
[2] Applications of phosphine ligands in homogeneous catalysis: (a)
G.W. Parshall, S. Ittel, Homogeneous Catalysis, Wiley, New York,
1992;
3.3.11. 3-(4-Nitrophenyl) pyridine (3k) [35]
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