Air-stable imidazole-imine palladium complexes for Suzuki-Miyaura coupling: Toward an efficient, green synthesis of biaryl compounds

Article abstract of DOI:10.1016/j.jorganchem.2013.12.015

New imidazole-imine ligands have been developed for the air and moisture stable Pd-catalyzed Suzuki-Miyaura cross-coupling reaction. Under optimized reaction conditions, coupling products from a wide range of aryl halides and aryl boronic acids were obtained in excellent yields.

Full text of DOI:10.1016/j.jorganchem.2013.12.015

Journal of Organometallic Chemistry 752 (2014) 161e170
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Air-stable imidazole-imine palladium complexes for SuzukieMiyaura
coupling: Toward an efficient, green synthesis of biaryl compounds
Jadsada Ratniyom, Thanawat Chaiprasert, Songyos Pramjit, Sirilata Yotphan,
Preeyanuch Sangtrirutnugul, Pailin Srisuratsiri, Palangpon Kongsaeree,
*
Supavadee Kiatisevi
Center for Alternative Energy, Department of Chemistry and Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol
University, 272 Rama 6 Road, Ratchthewee, Bangkok, Thailand
a r t i c l e i n f o
a b s t r a c t
Article history:
New imidazole-imine ligands have been developed for the air and moisture stable Pd-catalyzed Suzuki
eMiyaura cross-coupling reaction. Under optimized reaction conditions, coupling products from a wide
range of aryl halides and aryl boronic acids were obtained in excellent yields.
Ó 2013 Elsevier B.V. All rights reserved.
Received 18 October 2013
Received in revised form
29 November 2013
Accepted 5 December 2013
Keywords:
Imidazole-imine ligand
Air-stable palladium complex
SuzukieMiyaura cross-coupling reaction
1. Introduction
Our effort to develop an improved Suzuki reaction protocol
has centered on the search for a catalytic system consisting of
Many important reactions for carbonecarbon bond formation
have been continuously developed over the past four decades.
Among these, SuzukieMiyaura cross-coupling reaction is one of the
most effective methods for constructing biaryl structures which are
wide-spread in many naturally occurring bioactive products [1e4].
This reaction has two significant advantages over other cross-
coupling processes. Aryl boronic acid reactants are readily avail-
able and react under mild conditions. In addition, the inorganic by-
products are usually easy to remove. However, several existing
SuzukieMiyaura cross-coupling methods generally employ palla-
dium complexes supported by phosphine ligands [5e7], which are
often sensitive to air oxidation and require air-sensitive handling.
This oxygen sensitivity of catalyst is one of the crucial limitations
that hamper the development of practical biaryl synthesis. There-
fore, air- and moisture-stable ligands, which are easily prepared
from inexpensive, commercially available starting materials, are
needed for the improvement of Pd-catalyzed cross coupling
reaction.
rigid phosphine-free ligands. The ligands with nitrogen-based
frameworks such as, N-heterocyclic carbenes [8e12], nitrogen-
acyclic carbenes [13], cyclometalated imine [14], diazabutadiene
[15], and guanidines [16] have been reported. Despite the
achievements of modest to high yields of products, the systems
require high reaction temperatures under an inert atmosphere.
In our studies, we selected the new imidazole-imine backbone
due to its structural rigidity, strong s-donating property and low-
cost. In addition, compared to phosphine ligands, the imidazole-
imine ligands are easier to prepare and more resistant to air.
Substituents on the nitrogen atom of the imine moiety also play
important roles in tuning steric and electronic properties of the
molecule. Furthermore, no catalytic study of transition metal
complexes supported by the bidentate, imidazole-imine based
ligands has previously been investigated. Only structural, spec-
troscopic and water relaxivity properties of manganese(II) com-
plexed with tetradentate imidazole-imine ligands have been
reported [17].
Herein, we wish to report the synthesis of a series of new, air-
and moisture-stable palladium complexes with imine ligands
based on N-arylated imidazoles (Scheme 1) and their application in
SuzukieMiyaura cross-coupling reactions.
* Corresponding author. Tel.: þ66 2 201 5131; fax: þ66 2 354 7151.
E-mail address: supavadee.mon@mahidol.ac.th (S. Kiatisevi).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.12.015

162
J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
2. Results and discussion
shown in Fig. 2. Similarly, in case of the free imine ligand 2h, the
protons also resonated as the doublet signals at 7.33 ppm and
6.94 ppm (J ¼ 0.8 Hz) (see Supporting information for the NMR
data of the isolated ligand 2h). The appearance of a cross-peak
signal of complex 3h in a 1H-COSY spectrum indicated the cor-
relation between these imidazole protons. The outcome of this
study was also supported by the NOEDIFF results. Inspection of
the NOEDIFF spectrum revealed the presence of NOE contacts
which allow us to define the spatial relationship between the
ligand protons, H-4 and H-5, as well as between the imine and H-
16 methylene protons (Fig. 1). Moreover, the 1H NMR data was
also used to confirm the coordination of complex 3h. The upfield
shift of the characteristic singlet signal of the imine proton, H-6,
2.1. Synthesis and X-ray crystal structure
As an access to imidazole-imine Pd complexes 3, compound 1
was first prepared from a four-component condensation of the
corresponding amine with formaldehyde, ammonium chloride, and
glyoxal [18]. The 1-(2,6-diisopropylphenyl)-1H-imidazole com-
pound was deprotonated by n-butyl lithium at ꢀ30 ꢁC, and reacted
with N,N-dimethylformamide to afford 1 in a quantitative yield.
Compound 2 was obtained via the condensation of 1 with corre-
sponding primary amines and used, without further purifications,
to react with (COD)PdCl2 to afford complexes 3ae3h in good yields
(Scheme 1).
with respect to the free ligand (dcoord
ꢀ dfree ¼ ꢀ0.8 ppm) was
The structural characterization of the ligands and complexes
was carried out by 1H, 13C NMR spectroscopy, elemental analysis
and HRMS. The 1H NMR spectrum of the starting material 1 showed
a signal of the aldehyde proton at 9.80 ppm and two singlet signals
of imidazole protons at 7.51 ppm and 7.11 ppm which can be
ascribed to H-4 and H-5, respectively. The NMR data are consistent
with those of similar compounds described in the literature [18,19].
These imidazole protons also gave 3J cross peaks with C-2 on the
basis of HMBC correlation. In addition, only H-5 exhibited HMBC
cross peaks with C-7, leaving the position of this proton at C-5. This
result was confirmed by the signal enhancement of H-5 that was
observed upon irradiation of methyl protons (H-12 and H-13) in an
NOEDIFF experiment. According to the 1H-COSY NMR spectral data,
H-4 and H-5 appeared as distinct singlet signals and no cross-peak
signal was found, suggesting no correlation between these two
protons. However, the NOE enhancement of H-4 was detected upon
irradiation of H-5 as shown in Fig. 1. Based on the HMBC and
NOEDIFF results, H-4 and H-5 were attached on the neighboring
carbon atoms and could thus be assigned as vicinal protons.
The structures of the imidazole-imine palladium complexes
3aeh which were readily prepared from the reaction of ligands
with (COD)PdCl2 in chloroform also exhibited some characteristic
1H NMR data and multiplicity of the two protons on the imidazole
ring. Interestingly, their equivalent resonances were observed as
doublet signals with low coupling constants ranging from 1.2 Hz
to 1.6 Hz. For instance, the protons, H-4 and H-5, of complex 3h
appeared at 7.79 ppm and 7.07 ppm (J ¼ 1.6 Hz), respectively, as
observed.
To further confirm the structure of the Pd complexes, crystals
suitable for X-ray diffraction studies of 3b and 3h were obtained by
slow diffusion of hexane into a chloroform solution. As shown in
Figs. 3 and 4, the solid state of both palladium complexes revealed a
distorted square planar geometry around Pd(II) center with the
angle sum of approximately 360ꢁ. The imidazole-imine ligand co-
ordinates to Pd(II) in a bidentate binding mode through imidazole
and imine nitrogen atoms as expected. The closest C/C distances
between isopropyl aryl substituents on imidazole and imine sub-
stituents (2,6-iPrC6H3 and 1-adamantyl) are 3.993(13) A (for 3b)
ꢀ
ꢀ
and 5.117(8) A (for 3h). The PdeN1(imine) bond distances are
ꢀ
slightly more than the expected range [20e22] and about 0.1 A
longer than those of PdeN2(imidazole) [23]. All PdeCl bond
ꢀ
lengths are similar and in the range of 2.26e2.27 A, indicating
comparable trans influence of imidazole and imine ligands. The
N1ePdeN2 bite angles of 3b and 3h are 80.00(13)ꢁ and 80.04(9)ꢁ,
respectively (Table 1). Based on crystal data, 1-adamantyl substit-
uent appears to be more sterically hindered than 2,6-iPrC6H3, as
evidenced by the unusually long PdeN1 bond, larger N1ePdeCl2
angle of 101.33(7)ꢁ for 3h [cf. 95.04(10)ꢁ for 3b], and smaller Cl1e
PdeCl2 angle of 88.45(3)ꢁ [cf. to 92.26(5)ꢁ for 3b].
2.2. SuzukieMiyaura cross-coupling catalyzed by imidazole-imine
Pd complexes
To evaluate the catalytic activity of 3ae3h for the palladium-
catalyzed SuzukieMiyaura cross-coupling, a reaction between
phenyl boronic acid and p-bromoanisole was used as the model
reaction at room temperature under aerobic conditions (Table 2).
Interestingly, quantitative yields of the coupling product were ob-
tained when catalysts 3b and 3d were used. However, compared to
3b, palladium complexes of the more sterically hindered imine li-
gands 3g and 3h afforded only moderate product yields (entries 7
and 8). We also found that ligands 3eeh which were prepared with
the alkyl substituents tend to result in lower yields than those with
the aromatic ones. Moreover, appropriated steric bulks at the imine
moiety are crucial to achieve good catalytic activities, as very large
substituents such as tert-butyl and 1-adamantyl only showed low
activities. In comparison, the catalytic activity of palladium com-
plexes containing our imidazole-imine ligands are superior to those
with commercially available ligands including pyridine, phenan-
throline, BINAP, and in the absence of ligand (Supporting
information; Table S1).
Despite the fact that both catalysts 3b and 3d exhibited similar
catalytic properties, we chose 3b as the control catalyst for deter-
mining optimal conditions for palladium-catalyzed cross-coupling
reaction of p-bromoanisole with phenyl boronic acid due to the
more complicated preparation of 3d. We then began to optimize
reaction conditions by examining the catalyst loading and found
that highly efficient catalysis could still be maintained even at
Scheme 1. Synthesis of imidazole-imine Pd complexes.

J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
163
Fig. 1. Double arrows show the NOE contacts in aldehyde 1 and complex 3h.
Fig. 2. 1H NMR spectra of (a) aldehyde 1; (b) ligand 2h and; (c) complex 3h.
Fig. 3. ORTEP diagram of 3b with 30% probability ellipsoids and partial labeling
Fig. 4. ORTEP diagram of 3h with 30% probability ellipsoids and partial labeling
scheme. Hydrogen atoms and a molecule of CHCl3 are omitted for clarity.
scheme. Hydrogen atoms are omitted for clarity.

164
J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
Table 1
We also probed the effect of solvent and observed that aprotic
solvents such as THF, DMF, acetonitrile, toluene, chloroform,
acetone, and DMSO afforded low product yields in the range of 2e
27%. On contrary, higher coupling product yields were obtained in
methanol. Interestingly, although the coupling reaction in H2O
resulted in a low product yield, a small percentage of water in
methanol has a beneficial effect on the reaction rate as found with
other catalytic systems [27e29] (Supporting information; Tables S3
and S4). It was found that a 4:1 mixture of CH3OH:H2O at the p-
bromoanisole concentration of 0.2 M provided the biaryl product in
a quantitative yield. Next, we sought to determine which base
offered the best result of the coupling reaction under the optimized
conditions: 0.15 mol% of 3b in the 4:1 CH3OH:H2O solvent. As a
result, p-bromoanisole was successfully coupled with phenyl
boronic acid in the highest product yield when K2CO3 was used as a
base (Supporting information; Table S5).
Under the optimized reaction conditions, a wide variety of aryl
halide substrates were highly reactive, generally giving the desired
coupling products in good to quantitative yields (Table 4). The
substrate scope was found to be remarkably broad, as the reaction
tolerated both electron-donating and electron-withdrawing sub-
stituents. For example, with the exception of ortho-methoxy sub-
stituent, the electron-donating methoxy groups at meta and para
positions gave the corresponding coupling products in quantitative
yields (entries 2e5). Most aryl halides with an electron-
withdrawing substituent resulted in excellent product yields i.e.,
ꢁ
ꢀ
Selected bond lengths (A) and bond angles ( ) for 3b and 3h.
Bond angle (ꢁ)
ꢀ
Bond length (A)
3b
3h
3b
3h
80.04(9)
PdeN1
PdeN2
PdeCl1
PdeCl2
2.073(3)
2.007(3)
2.273(1)
2.258(1)
2.120(2)
2.002(2)
2.270(1)
2.272(1)
N1ePdeN2
Cl1ePdeCl2
N1ePdeCl2
N2ePdeCl1
80.00(13)
92.26(5)
95.04(10)
92.71(9)
88.45(3)
101.33(7)
90.60(7)
catalyst loading as low as 0.15 mol% with a TON up to 666 (highest
TON up to 12,000 with 0.001 mol % catalyst loading) (Table 3).
Complex 3b also exhibited higher efficiencies in terms of yields/
TONs than the majority of those reported for the similar N,N-
bidentate palladium catalysts with 4-MeOC6H4Br as substrate. For
example, the catalytic systems consisting of Pd(OAc)2/hydrazone
[24] and Pd(OAc)2/guadinine [16] were reported to have TONs up to
44.5 and 180, respectively. Also, the procedure using pyridyl-
triazole ligands resulted in a TON up to 180 [25]. Another pyridyl-
triazole based catalytic system recently reported by some of us
exhibited a comparable activity (yields up to 85% with 0.1 mol %
catalyst loading and a TON up to 850) [26]. An additional experi-
ment under ambient conditions was carried out by varying the
reaction time. The quantitative yield of 4-methoxybiphenyl could
be achieved with the shortest reaction time of 4 h (Supporting
information; Table S2).
Table 2
Ligand screening for SuzukieMiyaura cross-coupling reaction between p-bromoanisole and phenyl boronic acid.a
Entry
1
Complexes
R
Yield (%)b
91
3a
2
3b
>99
3
4
3c
82
3d
>99
5
6
3e
3f
88
83
7
3g
3h
73
69
8
a
Reaction condition: 1.5 mol% of Pd catalyst, 0.5 mmol of p-bromoanisole, 0.6 mmol of phenyl boronic acid, 1.1 mmol of K2CO3, 2 mL of MeOH, 0.5 mL of H2O, rt, 24 h. All
reactions were carried out in air.
b
The yield was determined by GC analysis using hexamethylbenzene as a calibrated internal standard.

J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
165
Table 3
Catalytic activity of complex 3b on the SuzukieMiyaura cross-coupling reaction of p-bromoanisole with phenyl boronic acid.a
Entry
n mol%
Yield (%)b
TON
1
2
3
4
5
6
7
8
0.0001
0.001
0.01
0.1
0.15
0.2
0.3
0.4
0.75
1.5
3
0
12
85
0
12,000
8500
990
666
500
333
250
133
66
99
>99
>99
>99
>99
>99
>99
>99
9
10
11
33
a
Reaction condition: 0.5 mmol of p-bromoanisole 0.6 mmol of phenyl boronic acid, 1.1 mmol of K2CO3, 2 mL of MeOH, 0.5 mL of H2O, rt, 24 h.
The yield was determined by GC analysis using hexamethylbenzene as a calibrated internal standard.
b
more than 90% (entries 6e11), except for para-fluoro (65%), hy-
catalyst system is wide in substrate scope, uses low catalyst loading,
and generates water-soluble by-products. These are consistent with
characteristics of green chemistry.
droxyl (84%), and phenyl (86%) groups (entries 12e14). When
heterocyclic halides were used as substrates, moderate yields of the
coupling products were obtained (entries 15e17), presumably due
to nitrogen coordination and subsequent inactivation of the palla-
dium catalyst. Based on the results thus far, no significant effect on
product yields was observed from varying aryl bromide substrates,
suggesting relatively fast oxidative addition. Moreover, no reaction
was observed when p-chloroanisole was used as a substrate (Data
not shown).
In Table 5, CeC coupling between the electron-rich 4-
methoxyphenyl boronic acid and bromobenzene gave products in
high yields (entries 1e3). However, the yields decreased with the
electron-withdrawing 4-acetylphenyl boronic acid substrate (en-
tries 4 and 5). Furthermore, an electron-deficient acetyl substituent
on aryl bromide afforded an increase in product yields, from 80% to
90% (entries 1 and 6). It seems that although electronic properties
of aryl halides do not significantly affect the reaction rates, the
presence of electron-withdrawing substituent on phenyl boronic
acid apparently decreases product yields.
It should be noted that, formation of palladium black was not
observed with catalyst 3b during the course of the reactions. In
order to elucidate whether Pd(0) nanoparticles are involved in the
reaction, we have also carried out a mercury poisoning test with 3b.
A coupling reaction between p-bromoanisole and PhB(OH)2 in the
presence of excess Hg (Hg:Pd ¼ 400:1) under the reaction condi-
tions described for entry 2 (Table 4) showed a decrease of product
yield (down to 33%). The drop in the coupling product yield implies
that the cross-coupling reactions were catalyzed, to some extent, by
heterogeneous Pd(0) nanoparticles [30,31]. Furthermore, a previ-
ous study on the catalytic activity of Pd(0) species in the Suzukie
Miyaura cross-coupling reaction has shown that O2 can prevent
Pd(0) nanoparticle aggregation [32], probably by inhibiting the
formation of PdePd bonds through the adsorption of O2 [33,34].
This could be a reason why our catalytic system can operate in air.
4. Experimental
4.1. General information
All reagents were purchased from commercial sources and used
without further purification. n-BuLi was titrated with diphenyl-
acetic acid to confirm the correct concentration. The (COD)PdCl2
was prepared following the literature procedure [35]. DMF was
ꢀ
distilled from CaH2, stored over 4 A molecular sieves, and handled
under argon atmosphere. Thin layer chromatography (TLC) was
purchased on Merck silica gel 60 F254 aluminum sheets. Column
chromatography was performed using Merck silica gel 60 (70e
230 mesh.). NMR spectra were recorded on Bruker DPX-300
(300 MHz) and Bruker AscendÔ 400 (400 MHz) spectrometers.
The chemical shifts (
the residual proton signal of the deuterated solvent. The chemical
shifts (
) for 13C are referenced relative to the signal from the car-
d
) for 1H are given in ppm and referenced to
d
bon of the deuterated solvent. The high resolution mass spectra
were recorded on HR-TOF-MS Micromass model VQ-TOF2 spec-
trometer. The elemental analyses were performed by Perkin Elmer
Elemental Analyzer 2400 CHN. Gas chromatography analysis was
performed on Agilent Technologies 6890N with FID detector and
HP-1 capillary column (polymethylsiloxane, 25 m, 0.32 mm,
0.17
mm film thickness). Gas chromatography-mass analysis was
performed on Agilent Technologies 7890A with 5975C inert XL
MSD with Triple-Axis detector and HP-5 capillary column (poly-
dimethylsiloxane with 5% phenyl group, 20 m, 0.25 mm, 0.25 mm
film thickness) using helium as a carrier gas.
4.2. X-ray crystallography
Crystallographic analyses of complexes 3b and 3h were carried
out at the Mahidol crystallographic facility. Diffraction measure-
ments were made on a 4 K Bruker SMART [36] CCD area detector
3. Conclusion
In summary, an efficient, air-stable protocol for the palladium-
catalyzed SuzukieMiyaura cross-coupling reaction has been
developed. The use of imidazole-imine supporting ligands offers
substantial catalyst improvements with regard to air-stability and
catalytic efficiency. The catalytic studies have also shown that our
diffractometer using graphite-monochromated Mo Ka radiation
ꢀ
(l
¼ 0.71073 A). Crystals were mounted in paratone oil and held at
room temperature during data collection. Cell constants and an
orientation matrix for data collection were obtained from a least-
square refinement using the measured positions of reflections in

166
J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
Table 5
Study of substrate scopes for SuzukieMiyaura cross-coupling reaction between aryl
halides and aryl boronic acids.a
Table 4
Study of substrate scopes for SuzukieMiyaura cross-coupling reaction between aryl
halides and phenyl boronic acid.a
Entry
ArX
Ar0B(OH)2
Product Yieldb (%)
Entry
ArX
Product
Yieldb (%)
1
2
4b
4c
80
75
1
2
3
4a
4b
4c
95
>99c
>99
3
4d
4g
85c
64c
4
5
4
4d
68
4q
4q
68c
90c
5
4b
4e
4f
95c
92
6
6
a
Reaction condition: 0.15 mol% of Pd catalysts, 0.5 mmol of aryl halide, 0.6 mmol
of phenyl boronic acid, 1.1 mmol of K2CO3, 2 mL of MeOH, 0.5 mL of H2O, rt, 24 h. All
reactions were carried out in air.
7
>99
>99
91
b
Isolated yield.
1.5 mol% catalyst loading.
c
8
4g
4h
4i
the range 0.998ꢁ < < 28.4ꢁ (for 3b) and 0.998ꢁ < < 29.1ꢁ (for 3h).
q q
The frame data were integrated by the program SAINT [37] and
corrected for Lorentz and polarization effects. The structure was
solved by the maXus crystallographic software package [38], using
9
10
11
12
13
14
15
97
Table 6
Crystal data for 3b and 3h.
4j
98
3bꢂCHCl3
3h
4k
4l
65
Empirical formula
FW
Cryst color, habit
Cryst size (mm)
Cryst system
Space group
a (A)
b (A)
c (A)
C29H37Cl5N3Pd
711.27
C26H35Cl2N3Pd
566.87
Orange, cube
0.35 ꢃ 0.25 ꢃ 0.20
Orthorhombic
Pbca (#61)
13.6508(2)
21.1682(4)
23.4645(4)
90.00
90.00
90.00
6780.50(2)
0.998e26.4
8
Orange, cube
0.30 ꢃ 0.25 ꢃ 0.20
Monoclinic
P21/c (#14)
14.2165(6)
11.9991(3)
18.7543(7)
90.00
125.0801(14)
90.00
2618.09(16)
0.998e29.1
4
84
4m
4n
86
ꢀ
ꢀ
ꢀ
60d
a
b
g
(deg)
(deg)
(deg)
3
ꢀ
Volume (A )
q
16
4o
4p
41d
45d
range (deg)
Z
T/K
298
1.392
0.963
298
1.438
0.931
Dcalc (g/cm3)
17
m
(mmꢀ1
)
No. of reflns
6914
353
19.6
0.0557; 0.1852
1.331
7035
289
24.3
0.0478; 0.1126
0.987
a
Reaction condition: 0.15 mol% of Pd catalysts, 0.5 mmol of aryl halide, 0.6 mmol
of phenyl boronic acid, 1.1 mmol of K2CO3, 2 mL of MeOH, 0.5 mL of H2O, rt, 24 h. All
reactions were carried out in air.
No. of params refined
Refln/param ratio
Final residuals R1a; wR2
b
b
Goodness of fit indicatorc
Isolated yield.
GC yield.
1.5 mol% catalyst loading.
c
Max. shift/error in final LS cycle
0.001
0.001
d
a
R ¼ SjjFoj ꢀ jFcjj/SjFoj.
P
P
wR2 ¼ ½ ½wðFo2 ꢀ Fc2Þ2ꢄ= ½wðFo2Þ2ꢄꢄ1=2
;
where w ¼ ½s2ðFo2Þ þ ðaPÞ2 þ bPꢄꢀ1
:
b
c
GOF ¼ [Sw(jFoj ꢀ jFcj)2/(Nobs ꢀ Nparam)]1/2
.

J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
167
direct methods (SIR97) [39] and refined by full-matrix least-
refluxed for 16 h and concentrated under reduced pressure to
afford the target imine ligand (the imine ligand was used in the
next step without further purification) (Note: If the starting ma-
terial is p-nitroaniline, a DeaneStark trap will be used and the re-
action mixture will be refluxed for 48 h). In a 10 mL vial equipped
with magnetic stir bar was charged with (COD)PdCl2 (1.0 equiv) and
the corresponding imine ligand (1.0 equiv) under air condition.
Chloroform (0.05 M) was added as solvent into the reaction vial.
The reaction mixture was stirred at room temperature for 1 h. The
solvent was evaporated. The crude product was recrystallized three
times by using chloroform and hexane to give pure palladium
complexes.
2
squares method on (Fobs
) using the SHELXTL-PC V 6.12 software
package [40] (Table 6).
X-ray quality crystals of 3b and 3h were grown by layer diffusion
of hexane onto the CHCl3 solution of the palladium complexes at
room temperature.
Complex 3b crystallizes in the orthorhombic Pbca space group
with each asymmetric unit cell containing one molecules of 3b and
one distorted CHCl3 molecule. The CHCl3 molecule was modeled
with Cl5 and Cl6 atoms each occupying a half-occupancy with no
hydrogen. Large thermal ellipsoids were observed for isopropyl
groups. All non-hydrogen atoms were refined anisotropically while
the hydrogen atoms were placed in calculated positions and not
refined.
Complex 3h crystallized in the monoclinic P21/c space group
with each asymmetric unit containing one molecule of 3h. Large
thermal ellipsoids were observed for isopropyl groups. All non-
hydrogen atoms were refined anisotropically while the hydrogen
atoms were placed in calculated positions and not refined.
4.5.1. Synthesis of palladium complex (3a)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)ani-
line ligand was prepared from 1 (76.9 mg, 0.3 mmol, 1.0 equiv) and
aniline (27.4 mL, 0.3 mmol, 1.0 equiv) in MeOH (6 mL, 0.05 M). The
crude imine ligand was reacted with (COD)PdCl2 (86.2 mg,
0.3 mmol, 1.0 equiv) in chloroform (6 mL, 0.05 M) following the
general procedure for the preparation of palladium complexes to
afford complex 3a as a red crystalline (124 mg, 81%). 1H NMR
4.3. Synthesis of 1-(2,6-diisopropylphenyl)-1H-imidazole
(400 MHz, CDCl3):
d
7.84 (d, J ¼ 1.4 Hz, 1H), 7.59 (t, J ¼ 8.0 Hz, 1H),
The 1-(2,6-diisopropylphenyl)-1H-imidazole was prepared ac-
cording to the literature procedure [18]. The crude product was
purified by column chromatography (SiO2, EtOAc). The NMR
spectra agree with published data [18]. 1H NMR (300 MHz, CDCl3):
7.49 (s,1H), 7.40e7.36 (m, 5H), 7.30e7.27 (m, 2H), 7.25 (d, J ¼ 1.4 Hz,
1H), 2.35 (sept, J ¼ 6.9 Hz, 2H), 1.21 (d, J ¼ 6.9 Hz, 6H), 1.19 (d,
J ¼ 6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3):
d 151.5, 147.5, 146.7, 145.8,
132.2, 130.3, 129.6, 129.5, 128.7, 126.0, 124.9, 123.7, 28.6, 24.6, 24.2.
HRMS (ESI): calcd. for C22H25Cl2N3Pd [M þ Na]þ 532.0351, Found:
532.0352.
d
7.48 (s, 1H), 7.46 (t, J ¼ 7.9 Hz, 1H), 7.28 (s, 1H), 7.27 (d, J ¼ 7.4 Hz,
2H), 6.96 (s, 1H), 2.41 (sept, J ¼ 6.9 Hz, 2H), 1.15 (d, J ¼ 6.9 Hz, 12H).
13C NMR (75 MHz, CDCl3):
d
¼ 146.5,138.5,132.8,129.8,129.3,123.7,
121.5, 28.1, 24.4, 24.3. HRMS (ESI): calcd. for C15H20N2 [M þ H]þ
4.5.2. Synthesis of palladium complex (3b)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)-2,6-
diisopropylaniline ligand was prepared from 1 (76.9 mg, 0.3 mmol,
229.1705; Found: 229.1727.
4.4. Synthesis of 1-(2,6-diisopropylphenyl)-1H-imidazole-2-
carboxaldehyde (1)
1.0 equiv) and 2,6-diisopropylamine (56.6 mL, 0.3 mmol, 1.0 equiv)
in MeOH (6 mL, 0.05 M). The crude imine ligand was reacted with
(COD)PdCl2 (86.2 mg, 0.3 mmol, 1.0 equiv) in chloroform (6 mL,
0.05 M) following the general procedure for the preparation of
palladium complexes to afford complex 3b as a red crystalline
In a 100 mL round-bottomed flask equipped with a magnetic stir
bar was charged with 1-(2,6-diisopropylphenyl)-1H-imidazole
(855 mg, 3.74 mmol, 1.0 equiv), closed with three-way, evacuated
and backfilled with argon (this procedure was repeated three
times). The dried THF (20 mL) was added by syringe then n-BuLi
(1.17 M in hexane, 3.9 mL, 4.48 mmol, 1.2 equiv) was slowly added
at ꢀ30 ꢁC. The reaction mixture was allowed to warm to room
temperature and stirred for 3 h. Dried DMF (0.45 mL, 5.61 mmol,
1.5 equiv) was added under argon atmosphere and continually
stirred for 16 h. The saturated NH4Cl solution was added to reaction
flask and poured into the separatory funnel. The aqueous phase was
extracted with CH2Cl2 (3 ꢃ 10 mL), washed with brine (1 ꢃ 10 mL)
and dried with Na2SO4. The combined organic phase was concen-
trated under vacuum. The crude product was purified by column
chromatography (SiO2, CH2Cl2) to afford the pure product 1
(127 mg, 71%). 1H NMR (300 MHz, CDCl3):
d
7.88 (d, J ¼ 1.2 Hz, 1H),
7.57 (t, J ¼ 7.9 Hz, 1H), 7.47 (s, 1H), 7.35e7.26 (m, 3H), 7.14 (d,
J ¼ 7.9 Hz, 2H), 3.27 (sept, J ¼ 6.9 Hz, 2H), 2.34 (sept, J ¼ 6.7 Hz, 2H),
1.42 (d, J ¼ 6.9 Hz, 6H),1.21 (d, J ¼ 6.7 Hz, 6H),1.18 (d, J ¼ 6.7 Hz, 6H),
1.06 (d, J ¼ 6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3):
d
¼ 207.0, 153.8,
146.8, 145.7, 142.6, 140.6, 132.3, 130.3, 129.6, 128.9, 126.3, 124.8,
123.3, 28.7, 24.7, 24.2, 23.8, 23.2. HRMS (ESI): calcd. for
C
28H37Cl2N3Pd [M þ Na]þ 616.1291; Found: 616.1291. Anal. Calcd.
for C28H37Cl2N3Pd: C, 56.72; H, 6.29; N, 7.09. Found: C, 56.85; H,
6.74; N, 7.15.
4.5.3. Synthesis of palladium complex (3c)
(955 mg, 99%) as a white solid. 1H NMR (400 MHz, CDCl3):
d
¼ 9.80
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)-4-
methoxyaniline ligand was prepared from 1 (76.9 mg, 0.3 mmol,
1.0 equiv) and p-anisidine (36.9 mg, 0.3 mmol, 1.0 equiv) in MeOH
(6 mL, 0.05 M). The crude imine ligand was reacted with (COD)
PdCl2 (86.2 mg, 0.3 mmol, 1.0 equiv) in chloroform (6 mL, 0.05 M)
following the general procedure for the preparation of palladium
complexes to afford complex 3c as a red crystalline (124 mg, 77%).
(s,1H), 7.51 (s,1H), 7.49 (t, J ¼ 7.7 Hz,1H), 7.28 (d, J ¼ 7.7 Hz, 2H), 7.11
(br s, 1H), 2.21 (sept, J ¼ 6.8 Hz, 2H), 1.12 (d, J ¼ 6.8 Hz, 6H), 1.08 (d,
J ¼ 6.8 Hz, 6H). 13C NMR (75 MHz, CDCl3):
d
¼ 180.2, 145.1, 144.6,
132.5, 132.0, 130.0, 127.4, 123.9, 28.3, 24.6, 23.3. HRMS (ESI): calcd.
for C16H20N2O [M þ H]þ 257.1654, Found: 257.1631.
4.5. General procedure for the preparation of palladium complexes
(3aeh)
1H NMR (300 MHz, CDCl3):
d
¼ 7.82 (d, J ¼ 1.3 Hz, 1H), 7.60 (t,
J ¼ 7.8 Hz, 1H), 7.41 (s, 1H), 7.37 (d, J ¼ 7.8 Hz, 2H), 7.29e7.26 (m,
2H), 7.22 (d, J ¼ 1.3 Hz, 1H), 6.87 (d, J ¼ 9.0 Hz, 2H), 3.81 (s, 3H), 2.35
(sept, J ¼ 6.9 Hz, 2H), 1.21 (d, J ¼ 6.9 Hz, 6H), 1.18 (d, J ¼ 6.9 Hz, 6H).
In a 50 mL round-bottomed flask equipped with a magnetic stir
bar and
a
reflux condenser was charged with 1-(2,6-
13C NMR (75 MHz, CDCl3):
d
¼ 160.7, 149.7, 147.7, 145.8, 140.0, 132.1,
diisopropylphenyl)-1H-imidazole-2-carboxaldehyde (1.0 equiv)
and the corresponding primary amine (1.0 equiv). Then, MeOH
(6 mL) was added into the reaction vial. The reaction mixture was
130.0, 129.7, 125.5, 125.3, 124.9, 113.8, 55.6, 28.6, 24.5, 24.2. HRMS
(ESI): calcd. for C23H27Cl2N3OPd [M þ Na]þ 562.0457; Found:
562.0457.

168
J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
4.5.4. Synthesis of palladium complex (3d)
4.5.8. Synthesis of palladium complex (3h)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)-4-
nitroaniline ligand was prepared from 1 (76.9 mg, 0.3 mmol,
1.0 equiv) and p-nitroaniline (41.4 mg, 0.3 mmol, 1.0 equiv) in
MeOH (6 mL, 0.05 M). The crude imine ligand was reacted with
(COD)PdCl2 (86.2 mg, 0.3 mmol, 1.0 equiv) in chloroform (6 mL,
0.05 M) following the general procedure for the preparation of
palladium complexes to afford complex 3d as an orange solid
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene) ada-
mantylamine ligand was prepared from 1 (89.7 mg, 0.35 mmol,
1.0 equiv) and 1-adamantylamine (52.9 mg, 0.35 mmol, 1.0 equiv)
in MeOH (7 mL, 0.05 M). The crude imine ligand was reacted with
(COD)PdCl2 (100 mg, 0.35 mmol, 1.0 equiv) in chloroform (7 mL,
0.05 M) following the general procedure for the preparation of
palladium complexes to afford complex 3h as a red microcrystalline
(110 mg, 66%). 1H NMR (300 MHz, CDCl3):
d
¼ 8.21 (d, J ¼ 9.0 Hz,
(86.7 mg, 87%). 1H NMR (400 MHz, CDCl3):
d
¼ 7.79 (d, J ¼ 1.6 Hz,
2H), 7.85 (d, J ¼ 1.2 Hz, 1H), 7.62e7.57 (m, 2H), 7.49 (d, J ¼ 9.0 Hz,
1H), 7.61 (t, J ¼ 7.7 Hz, 1H), 7.37 (d, J ¼ 7.7 Hz, 2H), 7.20 (s, 1H), 7.07
2H), 7.37 (d, J ¼ 7.8 Hz, 2H), 2.41 (sept, J ¼ 6.8 Hz, 2H), 1.22e1.18 (m,
(d, J ¼ 1.6 Hz, 1H), 2.27 (sept, J ¼ 7.0 Hz, 2H), 2.18 (m, 3H), 2.09 (m,
12H). 13C NMR (75 MHz, CDCl3):
d
¼ 153.1, 150.9, 147.6, 147.3, 146.0,
6H), 1.70 (m, 6H), 1.20 (d, J ¼ 7.0 Hz, 6H), 1.14 (d, J ¼ 7.0 Hz, 6H). 13
C
132.3, 130.9, 129.9, 129.6, 126.9, 125.1, 125.0, 124.1, 28.6, 24.8, 24.3.
HRMS (ESI): calcd. for C22H24Cl2N4O2Pd [M þ Na]þ 577.0202,
Found: 577.0202.
NMR (75 MHz, CDCl3):
d
¼ 147.9, 147.7, 145.8, 132.1, 129.7, 129.5,
124.9, 124.1, 67.0, 42.1, 35.5, 29.5, 28.5, 24.31, 24.30. Anal. Calcd. for
26H35Cl2N3Pd; C, 55.09; H, 6.22; N, 7.41. Found: C, 55.16; H, 6.59; N,
C
7.31.
4.5.5. Synthesis of palladium complex (3e)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)
methylamine ligand was prepared from 1 (64 mg, 0.25 mmol,
4.6. General procedure for screening of palladium complexes for
SuzukieMiyaura cross coupling reaction (Table 1)
1.0 equiv) and 40 %w/w methylamine solution (22 mL, 0.25 mmol,
In the air condition, a 10 mL vial equipped with a magnetic stir
bar was charged with Pd complexes (1.5 mol%), hexame-
thylbenzene (0.05 mmol, 0.0081 g, 0.1 equiv) phenyl boronic acid
(0.6 mmol, 0.073 g, 1.2 equiv), K2CO3 (1.1 mmol, 0.153 g, 2.2 equiv)
and p-bromoanisole (0.5 mmol, 0.062 mL, 1.0 equiv). MeOH (2 mL)
and water (0.5 mL) were mixed and added to the reaction mixture.
The reaction vial was capped and vigorously stirred at room tem-
perature for 24 h. The reaction mixture was extracted with CH2Cl2
(3 ꢃ 10 mL), washed with water (2 ꢃ 10 mL), brine (1 ꢃ10 mL) and
dried over Na2SO4. Solvent was then evaporated. The reaction was
monitored by GC-FID to determine the yield of the product based
on integration relative to hexamethylbenzene as an internal
standard.
1.0 equiv) in MeOH (4 mL, 0.05 M). The crude imine ligand was
reacted with (COD)PdCl2 (71.8 mg, 0.25 mmol, 1.0 equiv) in chlo-
roform (5 mL, 0.05 M) following the general procedure for the
preparation of palladium complexes to afford complex 3e as a
yellow solid (99.3 mg, 89%). 1H NMR (300 MHz, CDCl3):
d
¼ 7.68 (d,
J ¼ 1.4 Hz,1H), 7.59 (t, J ¼ 7.8 Hz,1H), 7.45 (m,1H), 7.37 (d, J ¼ 7.8 Hz,
2H), 7.14 (d, J ¼ 1.4 Hz, 1H), 3.70 (s, 3H), 2.31 (sept, J ¼ 6.8 Hz, 2H),
1.20e1.16 (m, 12H). 13C NMR (75 MHz, CDCl3):
d
¼ 152.8, 147.2,
145.8, 132.1, 129.7, 129.6, 124.8, 49.1, 28.5, 24.7, 24.1. Anal. Calcd. for
17H23Cl2N3Pd: C, 45.71; H, 5.19; N, 9.41. Found: C, 45.77; H, 5.21; N,
C
9.22.
4.5.6. Synthesis of palladium complex (3f)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)
cyclohexylamine ligand was prepared from 1 (128 mg, 0.3 mmol,
1.0 equiv) and cyclohexylamine (34.4 mL, 0.3 mmol, 1.0 equiv) in
MeOH (6 mL, 0.05 M). The crude imine ligand was reacted with
(COD)PdCl2 (86.2 mg, 0.3 mmol, 1.0 equiv) in chloroform (5 mL,
0.05 M) following the general procedure for the preparation of
palladium complexes to afford complex 3f as a red crystalline
4.7. General procedure for the investigation of the effect of catalyst
loading, base, solvent, time and substrate scopes on Suzukie
Miyaura cross coupling reaction (Tables S1eS5, Tables 4 and 5)
In the air condition, hexamethylbenzene (0.05 mmol, 0.0081 g,
0.1 equiv), aryl halide (0.5 mmol, 1 equiv), aryl boronic acid
(0.6 mmol, 1.2 equiv), base (1.1 mmol, 2.2 equiv) and solvent was
subsequently added into a 10 mL vial equipped with a magnetic
stir bar. The 5 mM Pd catalyst solution in MeOH was added as
indicated in the table. The reaction vial was capped and vigorously
stirred at room temperature for desired time as indicated. The
reaction mixture was extracted with CH2Cl2 (3 ꢃ 10 mL), washed
with water (2 ꢃ 10 mL), brine (1 ꢃ 10 mL) and dried over Na2SO4.
The combined organic phase was then concentrated to afford the
crude coupling product. The reaction was monitored by GC-FID
based on integration relative to hexamethylbenzene as an inter-
nal standard. The crude product was finally isolated by column
chromatography (0e10%: EtOAc/hexane) to afford the desired
product.
(149.9 mg, 97%). 1H NMR (300 MHz, CDCl3):
d
¼ 7.69 (d,
J ¼ 1.4 Hz, 1H), 7.60 (t, J ¼ 7.8 Hz, 1H), 7.36 (d, J ¼ 7.8 Hz, 2H), 7.28
(m, 1H), 7.14 (d, J ¼ 1.4 Hz, 1H), 4.29 (m, 1H), 2.30e2.20 (m, 4H),
1.81e1.65 (m, 4H), 1.41 (m, 2H), 1.19e1.10 (m, 12H), 1.04e0.99 (m,
2H). 13C NMR (75 MHz, CDCl3):
129.6, 129.4, 124.9, 124.6, 65.5, 33.8, 28.4, 25.1, 25.0, 24.2. HRMS
(ESI): calcd. for C22H31Cl2N3Pd [M þ Na]þ 538.0820, Found:
538.0820.
d
¼ 148.7, 147.9, 145.6, 132.1,
4.5.7. Synthesis of palladium complex (3g)
((1-(2,6-Diisopropylphenyl)-1H-imidazol-2-yl)methylene)-tert-
butylamine ligand was prepared from 1 (64 mg, 0.25 mmol,
1.0 equiv) and tert-butylamine (26.4 mL, 0.25 mmol, 1.0 equiv) in
MeOH (4 mL, 0.05 M). The crude imine ligand was reacted with
(COD)PdCl2 (71.8 mg, 0.25 mmol, 1.0 equiv) in chloroform (5 mL,
0.05 M) following the general procedure for the preparation of
palladium complexes to afford complex 3g as a red crystalline
4.8. Analytical data of coupling products (4aeq)
4.8.1. Biphenyl (4a, Table 4, entry 1)
1H NMR (300 MHz, CDCl3):
d
¼ 7.65 (d, J ¼ 7.7 Hz, 4H), 7.49 (t,
(93.9 mg, 75%). 1H NMR (300 MHz, CDCl3):
d
¼ 7.78 (d, J ¼ 1.4 Hz,
J ¼ 7.7 Hz, 4H), 7.37 (m, 2H). EI-MS (m/z, relative intensity): 155
1H), 7.61 (t, J ¼ 7.8 Hz, 1H), 7.37 (d, J ¼ 7.8 Hz, 2H), 7.26 (m, 1H), 7.11
(d, J ¼ 1.4 Hz, 1H), 2.26 (sept, J ¼ 6.7 Hz, 2H), 1.54 (s, 9H), 1.19 (d,
J ¼ 6.7 Hz, 6H), 1.12 (d, J ¼ 6.7 Hz, 6H). 13C NMR (75 MHz, CDCl3):
(14), 154 (Mþ, 100), 153 (42), 152 (29). CAS Number: 92-52-4.
4.8.2. 4-Methoxybiphenyl (4b, Table 4, entries 2 and 5; Table 5,
d
¼ 147.7, 147.6, 145.6, 132.2, 129.6, 129.5, 124.9, 124.4, 66.7, 29.6,
entry 1)
28.4, 24.3, 24.2. Anal. Calcd. for C20H29Cl2N3Pd: C, 49.14; H, 5.98; N,
8.60. Found: C, 49.28; H, 6.03; N, 8.48.
1H NMR (300 MHz, CDCl3):
J ¼ 7.5 Hz, 2H), 7.35e7.28 (m, 1H), 7.00 (d, J ¼ 8.7 Hz, 2H), 3.88 (s,
d
¼ 7.57 (t, J ¼ 8.7 Hz, 4H), 7.44 (t,

J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
169
3H). EI-MS (m/z, relative intensity): 185 (14), 184 (Mþ, 100), 169
(46), 141 (45), 115 (33). CAS Number: 613-37-6.
4.8.13. p-Terphenyl (4m, Table 4, entry 14)
1H NMR (300 MHz, CDCl3):
d
¼ 7.73e7.71 (m, 4H), 7.69 (d,
J ¼ 7.4 Hz, 4H), 7.51 (t, J ¼ 7.4 Hz, 4H), 7.41 (t, J ¼ 7.4 Hz, 2H). EI-MS
(m/z, relative intensity): 231 (19), 230 (Mþ, 100), 228 (13). CAS
Number: 92-94-4.
4.8.3. 3-Methoxybiphenyl (4c, Table 4, entry 3; Table 5, entry 2)
1H NMR (300 MHz, CDCl3):
d
¼ 7.62 (d, J ¼ 7.5 Hz, 2H), 7.47 (t,
J ¼ 7.5 Hz, 2H), 7.42e7.36 (m, 2H), 7.22 (d, J ¼ 8.1 Hz, 1H), 7.16 (m,
1H), 6.94 (d, J ¼ 8.1 Hz, 1H), 3.90 (s, 3H). EI-MS (m/z, relative in-
tensity): 185 (15), 184 (Mþ, 100), 154 (23), 153 (20), 141 (32), 115
(30). CAS Number: 2113-56-6.
4.8.14. 3-Phenylpyridine (4n, Table 4, entry 15)
1H NMR (300 MHz, CDCl3):
1H), 7.91 (d, J ¼ 8.0 Hz, 1H), 7.61 (d, J ¼ 7.4 Hz, 2H), 7.51 (t, J ¼ 7.4 Hz,
2H), 7.46e7.37 (m, 2H). EI-MS (m/z, relative intensity): 155 (Mþ,
100), 154 (50), 127 (14), 102 (11). CAS Number: 1008-88-4.
d
¼ 8.88 (s, 1H), 8.62 (d, J ¼ 4.4 Hz,
4.8.4. 2-Methoxybiphenyl (4d, Table 4, entry 4; Table 5, entry 3)
1H NMR (300 MHz, CDCl3):
J ¼ 7.4 Hz, 2H), 7.42 (t, J ¼ 7.3 Hz, 3H), 7.15e7.06 (m, 2H), 3.89 (s, 3H).
EI-MS (m/z, relative intensity): 185 (14), 184 (Mþ, 100), 183 (21), 169
(54), 168 (15), 141 (37), 139 (17), 115 (37). CAS Number: 86-26-0.
d
¼ 7.64 (d, J ¼ 7.2 Hz, 2H), 7.51 (t,
4.8.15. 3-Phenylquinoline (4o, Table 4, entry 16)
1H NMR (300 MHz, CDCl3):
J ¼ 8.3 Hz, 1H), 7.90 (d, J ¼ 8.3 Hz, 1H), 7.77e7.22 (m, 3H), 7.62e7.52
(m, 3H), 7.46 (t, J ¼ 7.2 Hz, 1H). EI-MS (m/z, relative intensity): 206
(16), 205 (Mþ, 100), 204 (53), 176 (14). CAS Number: 1666-96-2.
d
¼ 9.21 (s, 1H), 8.32 (s, 1H), 8.18 (d,
4.8.5. 4-Nitrobiphenyl (4e, Table 4, entry 6): 1H NMR (300 MHz,
CDCl3)
d
¼ 8.33 (d, J ¼ 9.0 Hz, 2H), 7.76 (d, J ¼ 9.0 Hz, 2H), 7.67e7.64 (m,
4.8.16. 5-Phenylpyrimidine (4p, Table 4, entry 17)
1H NMR (300 MHz, CDCl3):
d
¼ 9.23 (s, 1H), 8.98 (s, 2H), 7.62e
2H), 7.56e7.47 (m, 3H). EI-MS (m/z, relative intensity): 200 (13), 199
(Mþ, 97), 169 (35), 153 (28), 152 (100), 151 (30), 141 (28). CAS
Number: 92-93-3.
7.49 (m, 5H). EI-MS (m/z, relative intensity): 157 (12), 156 (Mþ, 100),
155 (17), 102 (64). CAS Number: 34771-45-4.
4.8.6. 4-(Trifluoromethyl)biphenyl (4f, Table 4, entry 7)
4.8.17. 1-(40-Methoxybiphenyl-4-yl)ethanone (4q, Table 5, entries 5
and 6)
1H NMR (300 MHz, CDCl3):
d
¼ 7.61e7.55 (m, 4H), 7.49 (m, 2H),
7.39e7.27 (m, 3H). EI-MS (m/z, relative intensity): 223 (13), 222
1H NMR (300 MHz, CDCl3):
d
¼ 8.02 (d, J ¼ 8.2 Hz, 2H), 7.66 (d,
(Mþ, 100), 201 (10), 151 (20). CAS Number: 398-36-7.
J ¼ 8.2 Hz, 2H), 7.60 (d, J ¼ 8.9 Hz, 2H), 7.02 (d, J ¼ 8.4 Hz, 2H), 3.87
(s, 3H), 2.64 (s, 3H). EI-MS (m/z, relative intensity): 226 (Mþ, 66),
212 (18), 211 (100), 183 (11), 168 (19), 139 (25). CAS Number: 13021-
18-6.
4.8.7. 4-Acetylbiphenyl (4g, Table 4, entry 8; Table 5, entry 4)
1H NMR (300 MHz, CDCl3):
J ¼ 8.6 Hz, 2H), 7.66 (d, J ¼ 8.1 Hz, 2H), 7.50 (t, J ¼ 7.2 Hz, 2H), 7.43 (t,
J ¼ 7.2 Hz, 1H), 2.66 (s, 3H). EI-MS (m/z, relative intensity): 196 (Mþ,
50), 181 (100), 153 (35), 152 (58), 151 (16). CAS Number: 92-91-1.
d
¼ 8.06 (d, J ¼ 8.6 Hz, 2H.), 7.71 (d,
4.9. Hg poisoning test
The reaction vial charged with an excess of Hg (Hg:Pd ¼ 400:1)
was added hexamethylbenzene (0.05 mmol, 0.0081 g, 0.1 equiv),
phenyl boronic acid (0.6 mmol, 0.073 g, 1.2 equiv), K2CO3 (1.1 mmol,
4.8.8. 4-Biphenylcarboxaldehyde (4h, Table 4, entry 9)
1H NMR (300 MHz, CDCl3):
d
¼ 10.09 (s, 1H), 7.98 (d,
J ¼ 8.2 Hz, 2H), 7.77 (d, J ¼ 8.2 Hz, 2H), 7.66 (d, J ¼ 6.8 Hz, 2H),
7.54e7.44 (m, 3H). EI-MS (m/z, relative intensity): 183 (13), 182
(Mþ, 96), 181 (100), 153 (38), 152 (63), 151 (18). CAS Number:
3218-36-8.
0.153 g, 2.2 equiv), p-bromoanisole (0.5 mmol, 0.062 mL, 1.0 equiv),
MeOH (2 mL) and water (0.5 mL), followed by 0.00075 mmol of Pd
catalyst 3b (0.15 mol%). After 24 h, the mixture was extracted by
CH2Cl2 (3 ꢃ 10 mL), washed with water (2 ꢃ 10 mL), brine
(1 ꢃ 10 mL), dried over Na2SO4, and solvent was concentrated to
afford the crude 4-methoxybiphenyl product. The yield was
determined by GC method. A 33% yield was obtained in the pres-
ence of excess of Hg.
4.8.9. Methyl biphenyl-4-carboxylate (4i, Table 4, entry 10)
1H NMR (300 MHz, CDCl3):
d
¼ 8.14 (d, J ¼ 8.2 Hz, 2H), 7.69 (d,
J ¼ 8.4 Hz, 2H), 7.65 (d, J ¼ 7.5 Hz, 2H), 7.50 (t, J ¼ 7.3 Hz, 2H), 7.42 (t,
J ¼ 7.1 Hz, 1H), 3.97 (s, 3H). EI-MS (m/z, relative intensity): 212 (Mþ,
65), 182 (13), 181 (100), 153 (28), 152 (60), 151 (17). CAS Number:
720-75-2.
Acknowledgments
This work was supported by the Department of Chemistry,
Faculty of Science, Mahidol University and the Center of Excellence
for Innovation in Chemistry (PERCH-CIC). The authors would like to
thank Mrs. Suttiporn Pikulthong and Mr. Samran Prabpai for their
experimental help. We also would like to thank Department of
Chemistry and Center of Instrumental Facility (CIF) at Faculty of
Science, Mahidol University for facilities.
4.8.10. 4-Cyanobiphenyl (4j, Table 4, entry 11)
1H NMR (300 MHz, CDCl3):
d
¼ 7.76 (d, J ¼ 8.6 Hz, 2H), 7.71 (d,
J ¼ 8.6 Hz, 2H), 7.62 (d, J ¼ 6.9 Hz, 2H), 7.54e7.45 (m, 3H). EI-MS (m/
z, relative intensity): 179 (Mþ, 100), 178 (24), 151 (12). CAS Number:
2920-38-9.
4.8.11. 4-Fluorobiphenyl (4k, Table 4, entry 12)
1H NMR (300 MHz, CDCl3):
J ¼ 7.4 Hz, 2H), 7.40 (t, J ¼ 7.4 Hz, 1H), 7.18 (t, J ¼ 8.7 Hz, 2H). EI-MS
(m/z, relative intensity): 173 (13), 172 (Mþ, 100), 171 (36), 170 (25).
CAS Number: 324-74-3.
d
¼ 7.62e7.58 (m, 4H), 7.50 (t,
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.12.015.
4.8.12. 4-Hydroxybiphenyl (4l, Table 4, entry 13)
1H NMR (300 MHz, CDCl3):
d
¼ 7.58 (d, J ¼ 8.5 Hz, 2H), 7.52 (d,
References
J ¼ 8.5 Hz, 2H), 7.45 (t, J ¼ 7.5 Hz, 2H), 7.34 (t, J ¼ 7.5 Hz, 1H), 6.94
(d, J ¼ 8.5 Hz, 2H), 5.08 (br s, 1H). EI-MS (m/z, relative intensity):
171 (13), 170 (Mþ, 100), 141 (22), 115 (28). CAS Number: 92-69-3.
[1] N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457e2483.
[2] A. Suzuki, J. Organomet. Chem. 576 (1999) 147e168.
[3] S. Kotha, K. Lahiri, D. Kashinath, Tetrahedron 58 (2002) 9633e9695.

170
J. Ratniyom et al. / Journal of Organometallic Chemistry 752 (2014) 161e170
[4] F. Bellina, A. Carpita, R. Rossi, Synthesis (2004) 2419e2440.
[24] T. Mino, Y. Shirae, M. Sakamoto, T. Fujita, J. Org. Chem. 70 (2005) 2191e2194.
[25] E. Amadio, A. Scrivanti, G. Chessa, U. Matteoli, V. Beghetto, M. Bertoldini,
M. Rancan, A. Dolmella, A. Venzo, R. Bertani, J. Organomet. Chem. 716 (2012)
193e200.
[5] A.F. Littke, C. Dai, G.C. Fu, J. Am. Chem. Soc. 122 (2000) 4020e4028.
[6] J. Yin, M.P. Rainka, X.X. Zhang, S.L. Buchwald, J. Am. Chem. Soc. 124 (2002)
1162e1163.
[7] G. Adjabeng, T. Brenstrum, J. Wilson, C. Frampton, A. Robertson, J. Hillhouse,
J. McNulty, A. Capretta, Org. Lett. 5 (2003) 953e955.
[26] S. Jindabot, K. Teerachanan, P. Thongkam, S. Kiatisevi, T. Khamnaen,
P. Phiriyawirut, S. Charoenchaidet, T. Sooksimuang, P. Kongsaeree,
P. Sangtrirutnugul, J. Organomet. Chem. 750 (2014) 35e40.
[27] A. John, M.M. Shaikh, P. Ghosh, Inorg. Chim. Acta 363 (2010) 3113e3121.
[28] H.-S. Wang, Y.-C. Wang, Y.-M. Pan, S.-L. Zhao, Z.-F. Chen, Tetrahedron Lett. 49
(2008) 2634e2637.
[29] H. Bulut, L. Artok, S. Yilmazu, Tetrahedron Lett. 44 (2003) 289e291.
[30] G.K. Rao, A. Kumar, B. Kumar, D. Kumar, A.K. Singh, Dalton Trans. 41 (2012)
1931e1937.
[8] W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290e1309.
[9] W.A. Herrmann, V.P.W. Böhm, C.W.K. Gstöttmayr, M. Grosche, C.P. Reisinger,
T. Weskamp, J. Organomet. Chem. 617e618 (2001) 616e628.
[10] G. Altenhoff, R. Goddard, C.W. Lehmann, F. Glorius, J. Am. Chem. Soc. 126
(2004) 15195e15201.
[11] E.A.B. Kantchev, C.J. O’Brien, M.G. Organ, Angew. Chem. Int. Ed. 46 (2007)
2768e2813.
[12] L.A. Schaper, S.J. Hock, W.A. Herrmann, F.E. Kühn, Angew. Chem. Int. Ed. 52
(2013) 270e289.
[31] G.K. Rao, A. Kumar, S. Kumar, U.B. Dupare, A.K. Singh, Organometallics 32
(2013) 2452e2458.
[13] A.S.K. Hashmi, C. Lothschütz, Organometallics 30 (2011) 2411e2417.
[14] H. Weissman, D. Milstein, Chem. Commun. (1999) 1901e1902.
[15] G.A. Grasa, A.C. Hillier, S.P. Nolan, Org. Lett. 3 (2001) 1077e1080.
[16] S. Li, Y. Lin, J. Cao, S. Zhang, J. Org. Chem. 72 (2007) 4067e4072.
[17] K.S. Dube, T.C. Harrop, Dalton Trans. 40 (2011) 7496e7498.
[18] J. Liu, J. Chen, J. Zhao, Y. Zhao, L. Li, H. Zhang, Synthesis (2003) 2661e2666.
[19] H. Zhou, W.Z. Zhang, Y.M. Wang, J.P. Qu, Z.B. Lu, Macromolecules 42 (2009)
5419e5421.
[20] T.V. Laine, M. Klinga, M. Leskelä, Eur. J. Inorg. Chem. (1999) 959e964.
[21] M. Schmid, R. Eberhardt, M. Klinga, M. Leskelä, B. Rieger, Organometallics 20
(2001) 2321e2330.
[22] T.V. Laine, U. Piironen, K. Lappalainen, M. Klinga, E. Aitola, M. Leskelä,
J. Organomet. Chem. 606 (2002) 112e124.
[32] L.A. Adrio, B.N. Nguyen, G. Guilera, A.G. Livingston, K.K. Hii, Catal. Sci. Technol.
2 (2012) 316e323.
[33] A.N. Salanov, A.I. Titkov, V.N. Bibin, Kinet. Catal. 47 (2006) 430e436.
[34] A.N. Salanov, E.A. Suprun, Kinet. Catal. 50 (2009) 31e39.
[35] J. Wiedermann, K. Mereiter, K. Kirchner, J. Mol. Catal. A Chem. 257 (2006)
67e72.
[36] SMART v.5.6, Bruker AXS Inc., Madison, WI, USA, 2000.
[37] SAINT v.4, Siemens Analytical X-ray Systems, Inc., Madison, WI, USA, 1996.
[38] S. Mackay, C.J. Gilmore, C. Edwards, N. Stewart, K. Shankland, maXus Com-
puter Program for the Solution and Refinement of Crystal Structures Bruker
Nonius, The Netherlands, MacScience, Japan & The University of Glasgow.
[39] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, C. Giacovazzo, A. Guagliardi,
A.G.G. Moliterni, G. Polidori, R.J. Spagna, Appl. Crystallogr. 32 (1999) 115.
[40] G.M. Sheldrick, SHELXTL v.6.12, Siemens Analytical X-ray Systems, Inc.,
Madison, WI, USA, 1997.
[23] M.C. Done, T. Rüther, K.J. Cavell, M. Kilner, E.J. Peacock, N. Braussaud,
B.W. Skelton, A. White, J. Organomet. Chem. 607 (2000) 78e92.