Di- and tri-nuclear-palladium complexes bearing piperidoimidazolin-2-ylidenes: Synthesis, characterization, and catalytic applications

Article abstract of DOI:10.1016/j.tet.2015.05.059

A series of di- and tri-nuclear Pd(II) complexes with piperidoimidazolin-2-ylidenes anchored to benzene ring via methylene spacers were synthesized. The obtained complexes were fully characterized by IR, ¹H NMR, ¹³C NMR spectroscopy

Full text of DOI:10.1016/j.tet.2015.05.059

Tetrahedron 71 (2015) 4770e4778
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Di- and tri-nuclear-palladium complexes bearing
piperidoimidazolin-2-ylidenes: synthesis, characterization, and
catalytic applications
a
a
b
a,
*
€
€
€
Guls¸ ah Turkmen , Aylin Atik , Zarife Sibel S¸ ahin , Hayati Turkmen
a Department of Chemistry, Ege University, 35100 Bornova-Izmir, Turkey
b Department of Energy Systems Engineering, Faculty of Engineering and Architecture, Sinop University, 57000 Sinop, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of di- and tri-nuclear Pd(II) complexes with piperidoimidazolin-2-ylidenes anchored to benzene
ring via methylene spacers were synthesized. The obtained complexes were fully characterized by IR, 1H
NMR, 13C NMR spectroscopy and elemental analysis. Molecular structures of two of the products have
been determined by means of X-ray crystallography. Their catalytic performances in Suzuki-Miyaura and
Mizoroki-Heck cross-coupling reactions were thoroughly investigated. The catalytic reactivity of new di-
and tri-metallic complexes was compared with the monometallic systems. It is observed that the ac-
tivities of the tri-nuclear Pd(NHC) complexes were higher than the corresponding mono- and di-nuclear
complexes under the same conditions.
Received 9 February 2015
Received in revised form 9 May 2015
Accepted 18 May 2015
Available online 23 May 2015
Keywords:
Palladium
Carbene ligands
Cross-coupling
Ó 2015 Elsevier Ltd. All rights reserved.
Piperidoimidazolin-2-ylidene
Polynuclear complexes
1. Introduction
both the nitrogen atoms and the backbone of NHCs. The variation of
substituents bound to the nitrogen atoms or to the backbone of
Recently, PdeNHC complexes stabilized by ancillary nitrogen
ligands have been the focus of intense research in organometallic
chemistry and homogenous catalysis.1e5 Due to a combination of
their versatility and efficiency, the nitrogen family appears the
popular family of nitrogen-stabilized PdeNHC complexes. Organ
and co-workers reported a combination of Pd(NHC) with PEPPSI
(PEPPSI¼Pyridine Enhanced Precatalysts Preparation, Stabilization
and Initiation) and successfully applied as the cross coupling cat-
alysts.2 Different examples of L (L¼3-Cl-pyridine,1 Et3N4a, Et2NH,4b
1-methylimidazol,5 in the [Pd(NHC)(L)Cl2] type complexes were
employed as dissociable (throw-away) ligands. In our previous
studies, we have also focused on hydrophilic dissociable ligands
(L¼2,6-(HOOC)2-pyridine,6a HO(CH2)2)2NH6b). On the other hand,
the electronic and steric parameters of NHC complexes can be
modified easily, and they have greater stability toward air, moisture
and heating when compared with phosphine analogues.7 Therefore
catalysis under phosphine-free conditions represents a challenge of
high importance. The electronic properties can be modified by
varying the number, nature and position of the substituents on
NHC directly influence the catalyst’s performance and they have
become highly popular in catalysis owing to their ability to stabilize
transition metals. More recent studies have shown that the annu-
lations of the 1,5- or 3,4-position of the imidazole ring also in-
fluence the electronic and steric properties of the resulting
complexes.8e15 Furthermore, the development of potent polytopic
NHCs, anchoring on aromatic ring or connected by
rigid systems for transition metal coordination, has been re-
ported.16 However, to date only
few examples of poly-
p-delocalized
a
topiceNHCemetal complexes have been prepared and investigated
in homogenous catalysis.17 Nonrigid poly-NHCs have also allowed
the preparation of polymetallic NHC complexes, when the NHCs are
a sufficient distances to avoid chelation.18 It is well known that
catalysts containing poly-metal centers in complexes can lead to
better reactivity in comparison to that for the related monometallic
systems, in particular for second-order kinetic dependence on the
catalyst.19
Inspired by these considerations, the synthesis and charac-
terization of new di-, and tri-nuclear PdNHC complexes were
described. All of the complexes synthesized were investigated in
the Suzuki-Miyaura under air atmosphere and Mizoroki-Heck
coupling reaction under argon atmosphere with low catalyst
loading.
* Corresponding author. Tel.: þ90 232 311 1713; fax: þ90 232 388 8264; e-mail
€
address: hayatiturkmen@hotmail.com (H. Turkmen).
http://dx.doi.org/10.1016/j.tet.2015.05.059
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
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2. Results and discussion
2c are those assigned to the metalated carbene carbons, at 178.2
and 177.9 ppm. In the 13C NMR spectrum, two carbene signals of 2c
with an approximate intensity ratio 50/50 were observed. Similar
observations were made for other carbon signals. We explain this
by assuming that rotation around an acyclic CeN bond allows for-
mation of two rotamers, which do not interconvert rabidly at RT
and exhibit slightly different NMR spectra (Scheme 4). Consistent
with this suggestion is the observation that when the 13C NMR
spectrum was run at 60 ꢀC the two signals at 178.2 and 177.9 ppm
2.1. Synthesis of NHC-palladium complexes
The preliminary work was initiated with the synthesis of bis-,
and tris-piperidine fused imidazolinium salts (1a, 1d, 1e, 1f).20 We
have also prepared the related new salts 1b and 1c (which is an
isomer of 1b) (Scheme 1). The 1H NMR spectrum of 1b and 1c
showed the resonance for C2eH protons of imidazolinium salts as
a singlet at
protons become diastereotopic upon complex formation and two
doublets are observed at
¼5.11 and 4.75 ppm for 1c.
d
¼9.07 ppm for 1b; 9.52 ppm for 1c. The bridged CH2
had coalesced to afford a single peak at 178.2 ppm (See
Supplementary data). Additionally, the molecular structure of 2c
was unambiguously confirmed by means of X-ray analysis.
d
Br
N
N
Br
N
N
Br
Br
2Br
2Br
N
N
N
N
N
N
1c
1b
A
Scheme 1. Synthesis of ligands (1b and 1c).
Once the synthesis of imidazolinium salts was complete, we
directed the preparation of novel potentially di- and tri-nuclear
palladium(II) complexes (Schemes 2 and 3). A more general and
cleaner synthetic procedure for metal NHC complexes is the metal
acetate protocol. For this reason, direct reaction between imida-
zolium salt and Pd(OAc)2 (1:2 for 2aed and 1:3 for 3eef molar
ratio) in pyridine at 90 ꢀC for 24 h was carried out. After removal of
the solution and washing the residue with water, a light yellow
powder was isolated. The complexes were purified by chromatog-
raphy on silica gel. Yellow crystals suitable for X-ray crystallo-
graphic structure analysis were grown by slow diffusion of ether
into a concentrated CH2Cl2 solution of the complex at room tem-
perature. The complexes 2aed and 3eef are readily soluble in most
organic solvents (CH2Cl2, CHCl3, MeOH, EtOH, EtOAc, DMSO and
acetone). As a solid, they are stable to air and moisture for weeks
without decomposition.
Py
N
N
Br Pd Br
Br
Br
N
N
Br
N
N
N
Pd
N
N
N
Py
Br
N
Br
Br
N
Py
Br
3e-f
1e-f
=
e
f
Br
Br
N
N
N
N
Br
Br
Pd
Py Pd
Py
Scheme 3. Synthesis of trinuclear complexes (3eef).
N
N
N
N
Br
Br
1a-d
2a-d
Br
Br
Br
N
Br
Pd
Br
Py
Py
Py
Py
N
N
Pd
Br
N
N
Pd
Br
Pd
N
Br
N
N
=
a
b
c
d
Scheme 4. Rotamers of complex (2c) in CDCl3.
Scheme 2. Synthesis of dinuclear complexes (2aed).
In this study, our aim was to compare the structural features and
the catalytic properties of 2aed and 3eef with monometallic
counterparts, we prepared the NHCePd-Py complex (1).21
The IR spectra of 2aed, 3e,f showed many bands of varying in-
tensities within 4000e400 cmꢁ1. The assignment of each individual
band to a specific vibration has not been attempted. The presence of
the eC]N- group in complexes was verified with ʋ (C]N) vibra-
tions between 1605 and 1448 cmꢁ1 (Supplementary data).
All complexes were characterized by means of spectroscopy and
elemental analysis. The NMR spectra of di-nuclear (2aed) and tri-
nuclear (3eef) complexes are consistent with the symmetry of
their structure. The 13C NMR spectra display the resonances to the
metalated carbene carbon atom in the range
178.6 ppm (for di-nuclear 2a, b, d, respectively) and
d
¼178.9; 179.0;
d
¼178.7 and
179.4 ppm (for tri-nuclear 3e and 3f, respectively). The most sig-
nificant resonances in the 13C NMR spectra of di-nuclear complex

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
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2.2. Crystal structures
z) acts as hydrogen-bond donors to the Cg(7) benzene rings in the
molecules at (x-1, ꢁyþ1/2, z-1/2) and (xþ1, ꢁyþ1/2, zþ1/2), so
The molecular structures of 1 and 2c have been further char-
acterized by single-crystal X-ray diffraction studies. As shown in
Fig. 1, palladium center was coordinated by an NHC ligand, a pyri-
dine and two bromo ions in a trans-arrangement, giving rise to
a four coordinate environment.
forming C(11) chains running parallel to the [101] direction (Fig. 3).
In 1, molecules are linked into sheets by combination of CeH/
p
and interactions. Atom C(11) in the molecule at (x, y, z) acts as
p
/p
hydrogen-bond donor to the Cg(2) pyridine ring in the molecule at
(x-1, y, z), so forming C(7) chains running parallel to the [100] di-
rection. Similarly, atom C(23) in the molecule at (x, y, z) acts as
hydrogen-bond donor to the Cg(4) benzene ring in the molecule at
(1ꢁx, 2ꢁy, 1ꢁz), so forming centrosymmetric R22(8) ring. Adjacent
R22(8) rings are connected by
network (Fig. 4).
p/p interactions to forming 1D
2.3. Catalytic tests
The palladium-catalyzed Suzuki-Miyaura cross-coupling re-
action is one of the most powerful methods for the preparation of
biaryl derivatives. A great deal of effort has been directed towards
the development of efficient catalytic systems for the Suzuki-
Miyaura reaction.24 Recently, Pd(NHC) complexes with PEPPSI
have been used in the Suzuki-Miyaura coupling reaction with high
activities.25 In our previous study, it has been shown that the pre-
catalyst 1 is effective in Suzuki-Miyaura cross-coupling.21 The
complexes were tested in Suzuki-Miyaura cross-coupling reaction
of chloroacetophenone. In order to evaluate the differences be-
tween the mono-, di- and tri-metallic complexes, we applied a low
catalyst loading at 353 K, 6 h (Fig. 5). The mol % of palladium is an
important parameter so it should be kept constant while carrying
out these catalytic reactions (1 mol % for mononuclear com-
plexes(1), 0.5 mol % for dinuclear complexes(2aed) and 0.33 mol %
for trinuclear complexes (3eef). In the course of the Suzuki-
Miyaura coupling reaction, black particles appear, which suggest
that catalysts (1, 2aed and 3eef) are probably precursors to a cat-
alytically active complex, which is formed during the reaction. A
direct comparison between dinuclear (2aed) and trinuclear com-
plexes (3eef) was performed by GC analysis, which revealed nearly
identical catalytic behavior for complexes (Fig. 5). A short induction
period was present for 3eef relative to 2aed, which may be related
to the reduction to the active Pdꢀ species. The observance of higher
catalytic activity for the trinuclear complexes(3eef) possibly in-
dicates the existence of cooperative effects during catalysis in these
systems. They are also somewhat rich in Pd.
Fig. 1. Molecular structure of complex 1.
There are two independent molecules in a unit cell of the solvate
2c.CH2Cl2. The molecular structure of complex 2c (Fig. 2) confirms
that the xylyl-bridged bis-NHC is two palladium fragments, each of
which complete their coordination spheres with two bromides and
a pyridine ligand.
The complex 3f was determined as the most active of the seven
tested so this complex was investigated in all subsequent reactions
in an attempt to optimize the solvent, base and temperature con-
ditions in Suzuki-Miyaura cross-coupling reaction. Initial studies
aimed at optimizing the solvent in the coupling of chlor-
oacetophenone and phenylboronic acid (Table 1). n-Propanol
resulted in a better yield than methanol and ethanol(entries 1e3).
Different bases (NaOH, Na2CO3, Cs2CO3, K3PO4, Pyridine) were ap-
plied instead of KOH. Significant variation in activity was observed
with different bases, highlighting the importance of the base, with
the inorganic bases consistently leading to higher yields than or-
ganic bases. The effect of temperature was investigated (entries
9e11). Decreasing the reaction temperature from 353 K to 323 K
and 298 K at a catalyst loading of 0.33 mol % of 3f led to an decrease
of yield from 99% to 67% and 38% respectively, after 2 h. With
a lower catalyst loading of 0.033 mol % of 3f, the product, 4-
acetylbiphenyl, was obtained with lower efficiency (51%, 2 h). The
coupling activity is highly solvent, base, temperature, and catalyst
loading dependent. We also performed an additional experiment to
assess whether the reaction system is homogeneous or heteroge-
neous, mercury was carried out (entry 13). The suppression of ca-
talysis by Hg(0) is evidence for a heterogeneous catalyst; if Hg(0)
does not suppress catalysis that is, evidence for a homogeneous
catalyst.26 As can be seen from a comparison of the results shown in
Fig. 2. Molecular structure of complex 2c.
The detailed X-ray structural analysis indicates that the struc-
tural parameters around the palladium centers, such as the bond
angles and bond distances, are in a range similar to those for
mononuclear NHC-palladium complexes. The PdeCcarbene bonds
ꢀ
ꢀ
[1.961(8) A for 1, 1.941(14), 1.964(12) A for 2c] and PdeN bonds
ꢀ
ꢀ
[2.108(6) A for 1, 2.157(9), 2.149(10) A for 2c] are comparable to
those found in mononuclear pyridine/NHC palladium complexes,
PdCl2(NHC)(L) [e.g., PdeCcarbene
: 1.990(3) for PdCl2(SIPr)(L),
(SIPr¼N,N0-bis(2,6-diisopropylphenylimidazolidin-2-ylidene, L¼3-
chloro-pyridine);22 PdeCcarbene: 1.953(4) for PdBr2(iPr-Bimy)(L),
(iPr-Bimy¼N,N0-diisopropylbenzimidazolidin-2-ylidene,
L¼pyridine)23].
Molecules of 2c are linked into sheets by a combination of
CeH/p interactions. Atoms C(3) and C(36) in the molecule at (x, y,

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
4773
ꢀ
Fig. 3. Crystal structure of 2c, showing the formation of CeH/
p
interactions. CeH/
p
interactions distances (A) and angles (deg). H(3)/Cg(7) 2.8623, C(3)-H(3)/Cg(7) 3.72(3),
C(3)/Cg(7) 155, H(36)/Cg(7) 2.9048, C(36)-H(36)/Cg(7) 3.75(3), C(36)/Cg(7) 151.
ꢀ
Fig. 4. Crystal structure of 1, showing the formation of CeH/
p
and
p/
p
interactions. CeH/
p
and
p/
p
interactions distances (A) and angles (deg). H(11)/Cg(2) 2.9084, C(11)/
Cg(2) 3.761(12), C(11)-H(11)/Cg(2) 146, H(23A)/Cg(4) 2.9028, C(23)/Cg(4) 3.840(15), C(23)-H(23A)/Cg(4) 165, Cg(4)/Cg(4) 3.629.
Fig. 5. The Suzuki-Miyaura reaction of 4-chloroacetophenone (1.0 mmol), and phenylboronic acid(1.5 mmol), KOH (2.0 mmol), 1 mol % for (1), 0.5 mol % for (2aed) and 0.33 mol %
for (3eef), diethyleneglycol-di-n-butylether (0.6 mmol, internal standard), solvent 2-propanol (4 mL), T¼353 K, 6 h.
Table 2 (compare entries 9 and 13). The homogeneous nature of
catalysis is supported as inferred on the basis of the Hg test. This
observation suggests the formation of fine palladium(0) particles.
Trzeciak and Albrecht clearly demonstrated that the PEPPSI-like
catalysts used in their detailed study of the Suzuki-Miyaura re-
action decomposed to Pd-nanoparticles.27 With these optimized
conditions, the Suzuki-Miyaura reaction catalyzed by 3f (0.33 mol
%) was tested on a series aryl chloride (from reactive (electron-

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
4774
Table 1
nuclear complexes (3eef) were the most active at 373 K, pro-
Screening of bases and reaction conditions
moting the formation of (E)e1-(4-styrylphenyl)ethanone in yields
of 93 and 89%, respectively (entries 5 and 6), compared to 67, 63, 65
and 62% for 2aed. Di- and tri-nuclear complexes were more active
than mono-nuclear complex under the condition employed. When
the deactivated aryl bromide (4-bromoanisole) was used as the
substrate, tri-nuclear complexes (3e, f) were again the most active
complexes, promoting the formation (E)-4-styrylanisole in a 71 and
73% yield.
When complex 3f was used, quantitative yields of 4-
bromobenzaldehyde, 4-bromoacetophenone, 4-bromonitrobenzene
were obtained in Table 4 (entries 1, 2 and 5). However, the yields of
2-bromoanisole, 4-bromotoluene and 3-bromopyridine were mod-
erate in this condition.
B(OH)
H COC
3
Cl
2
COCH
+
3
Entry
Base
Solvent
Temperature(K)
Yield (%)
1
2
3
4
5
6
7
8
KOH
KOH
KOH
NaOH
Na2CO3
Cs2CO3
K3PO4
Pyridine
KOH
KOH
KOH
KOH
KOH
EtOH
MeOH
n-PrOH
IPA
353
353
353
353
353
353
353
353
353
323
298
353
353
65
61
68
69
45
69
52
38
99
67
38
51a
98b
IPA
IPA
IPA
IPA
IPA
IPA
IPA
IPA
9
10
11
12
13
Table 4
IPA
Palladium-catalyzed CeC coupling reaction of styrene with aryl halides
The Suzuki-Miyaura reaction of 4-chloroacetophenone (1.0 mmol), and phenyl-
boronic acid (1.5 mmol), base (2.0 mmol), diethyleneglycol-di-n-butylether
(0.6 mmol, internal standard), solvent (4 mL), 0.33 mol % of cat. (3f), T¼353 K.
Ar-Br
+
Ar
a
Cat. loading was decreased to 0.033 mol %.
b
The reaction was carried out in the presence of a drop of Hg(0).
Entry
AreBr
Yield (%)a
1
2
3
4
5
6
7
CH3(O)CeC6H4-4-Br
NO2eC6H4-4-Br
MeeC6H4-4-Br
CH3OeC6H4-4-Br
OHCeC6H4-4-Br
CH3OeC6H4-2-Br
C5H3N-3-Br
93
91
53
52
75
53
58
Table 2
Suzuki-Miyaura reaction of aryl chlorides
Entry
AreCl
ArePh
Yield (%)
Reagents: Aryl halide (0.50 mmol), styrene (0.75 mmol), Na2CO3 (1.50 mmol),
diethyleneglycol-di-n-butylether (0.6 mmol, internal standard), 3f (0,3% mol) and
DMF (6 mL).
1
2
3
4
5
6
7
CH3(O)CeC6H4-4-Cl
CH3(O)CeC6H4-2-Cl
MeeC6H4-4-Cl
CH3OeC6H4-4-Cl
OHCeC6H4-4-Cl
CH3OeC6H4-2-Cl
NO2eC6H4-4-Cl
CH3(O)CeC6H4-4-Ph
CH3(O)CeC6H4-2-Ph
MeeC6H4-4-Ph
CH3OCeC6H4-4-Ph
OHCeC6H4-4-Ph
CH3OeC6H4-2-Ph
NO2eC6H4-4-Ph
99
88
80
82
97
74
85
a
Yields were determined by gas chromatography for an average of 2 runs.
3. Conclusion
The Suzuki-Miyaura reaction of Aryl chlorides (1.0 mmol), and phenylboronic acid
(1.5 mmol), KOH (2.0 mmol), diethyleneglycol-di-n-butylether (0.6 mmol, internal
standard), IPA (4 mL), 0.33 mol % of cat. (3f), T¼353 K, 2 h.
The piperidoimidazolium ligands anchored to benzene ring via
methylene spacers have been synthesized and metalated with
palladium precursors in pyridine to give the corresponding di- and
tri-nuclear palladium N-heterocyclic carbene complexes. All of the
complexes were isolated as air- and moisture-stable solids and
were characterized using a variety of spectroscopic techniques.
They were found to exhibit from moderate to excellent catalytic
activity in Suzuki-Miyaura and Mizoroki-Heck cross-coupling re-
action. The tri-nuclear complexes display better activities com-
pared to the mono- and di-nuclear derivatives, thus proposing that
an increase in metal moieties leads to an increase in activity in
cross-coupling reaction. The most active complex in the di-nuclear
Pd(NHC) complexes was 2c. This activity of 2c may be a conse-
quence of steric effects. In view of the modular synthesis for in-
troducing piperidoimidazolin-2-ylidene units anchored to benzene
ring via methylene spacers and the lability of pyridine ligands in
these PEPPSI complexes, the systems reported here are likely to be
appropriate synthons for generating supramolecular assemblies
and catalytic properties. Current research in our laboratory is fo-
cused in the different cross-coupling reactions.
deficient) to unreactive (electron rich)) with phenyl boronic acid in
IPA, shown in Table 2.
The same palladium complexes were also tested in the
Mizoroki-Heck cross-coupling reaction of the activated aryl bro-
mide (4-bromoacetophenone or 4-bromoanisole) and styrene us-
ing Na2CO3 as the base in DMF at 373 K (Table 3). The reaction
mixture was degassed and refilled with argon. The progress of the
reaction was monitored by TLC and GC. It was found that the tri-
Table 3
Palladium-catalyzed CeC coupling reaction of styrene with aryl halides
Entry
Catalyst
Cat. loading (mol %)
Yield (%)a/(%)b
1
2
3
4
5
6
7
2a
2b
2c
2d
3e
3f
1
0.50
0.50
0.50
0.50
0.33
0.33
1.00
67/56
63/55
65/62
62/55
89/71
93/73
46/22
4. Experimental section
4.1. General information
Unless otherwise noted, all operations were performed without
taking precautions to exclude air and moisture. All solvents and
chemicals were used as received without any further treatment if
not noted otherwise. Starting compounds and reagents were ob-
tained from Merck, Fluka, Alfa Aesar and Acros Organics; pyridine,
The aryl bromide (1.0 mmol), styrene (1.2 mmol), Na2CO3 (1.5 mmol), dieth-
yleneglycol-di-n-butylether (0.6 mmol, internal standard), solvent DMF (2 mL),
T¼373 K, 4 h.
a
4-bromoacetophenone was used as the aryl bromide.
4-bromoanisole was used as the aryl bromide.
b

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4775
2-aminomethylpiperidine, Pd(OAc)2 were obtained from Alfa Aesar
and solvents like dichloromethane, acetonitrile, ethanol, diethyl
ether, toluene, pyridine were obtained from Merck and Ridel de
Haen. The compound A8a and salts (1b, 1c)11 were prepared
according to literature procedure. Elemental analysis data were
recorded with CHNS Elemental Analysis. 1H NMR and 13C NMR
spectra were recorded on a Varian AS 400 Mercury instrument. As
solvents CDCl3 was employed. FTIR spectra were recorded on
a Perkin Elmer Spectrum 100 series.
d
¼178.9 (Ccarbene), 152.6 (Py-C), 139.3, 138.9 (NCH2C6H(CH3)3CH2N),
137.9 (Py-C), 130.9, 130.0 (NCH2C6H(CH3)3CH2N), 124.6 (Py-C), 59.4
(NCH2CH), 54.4 (NCH2C6H(CH3)3CH2N), 49.3, 49.2, 32.1, 25.6, 23.3
(piperidine-C), 21.3, 17.8 (NCH2C6H(CH3)3CH2N). IR, ʋmax (CH2Cl2):
3054, 2987, 2947, 2861, 2370, 2308, 1605, 1448, 1308, 1266, 1071,
687 cmꢁ1. Anal. Calcd for C35H46Br4N6Pd2 (M¼1083.24): C, 38.81; H,
4.28; N, 7.76; Found C, 38.61; H, 4.29; N, 7.62%.
4.1.4. Compound 2b. This complex was prepared by same method
as for 2a starting from 1b (298.3 mg, 0.5 mmol) and Pd(OAc)2
(224.5 mg, 1.0 mmol). Yield: 355 mg, 63%, mp¼285e286 ꢀC. 1H
NMR (400 MHz, CDCl3, TMS, 25 ꢀC, ppm): 9.06 (d, J¼5.2 Hz, 4H,
Py-Ho), 7.76e7.70 (m, 2H, Py-Hp), 7.38e7.29 (m, 4H, Py-Hm), 7,03
4.1.1. Compound 1b. The salt (1b) was prepared according to the
literature procedure.11 2,4-bis(bromomethyl)-1,3,5-triethyl benzene
(348 mg, 1.0 mmol), 1,5,6,7,8,8a-hexahydroimidazo[1,5-a]pyridine
(248 mg, 2.0 mmol) were refluxed in toluene (10.0 mL) for 4 h. The
volume of the solution was reduced to 5 mL under vacuum. Diethyl
ether was added to the solution and vigorously shaken and then
decanted. The solid residue was washed with diethyl ether. Yield:
578 mg, 97%, mp¼175e176 ꢀC.1H NMR (400 MHz, CDCl3, TMS, 25 ꢀC,
(s,
1H,
NCH2C6H(CH2CH3)3CH2N),
5.40e5.36
(m,
4H,
NCH2C6H(CH2CH3)3CH2N), 5.13e5.09 (m, 2H, piperidine-H),
3.69e3.64 (m, 2H, piperidine-H), 3.35e3.26 (m, 4H, NCH2CH),
2.98e2.86 (m, 2H, piperidine-H), 2.79e2.75 (m, 6H,
NCH2C6H(CH2CH3)3CH2N), 1.95e1.87 (m, 4H, piperidine-H),
1.80e1.73 (m, 4H, piperidine-H), 1.46e1.40 (m, 4H, piperidine-H)
1.38e1.23 (m, 9H, NCH2C6H(CH2CH3)3CH2N). 13C NMR (100.6 MHz,
ppm):
d
¼9.07 (s, 2H, NCHN), 7.06 (s, 1H, NCH2C6H(CH2CH3)3CH2N),
4.54e4.20 (m, 6H, NCH2C6H(CH2CH3)3CH2N, piperidine-H),
3.76e3,72 (m, 2H, NCH2), 3.72e3,66 (m, 2H, NCH2), 3.41e3,37 (m,
2H, piperidine-H), 2.69e2.65 (m, 2H, CH2CH3), 2.56e2.48 (m, 4H,
CH2CH3), 2.09e2,05 (m, 4H, piperidine-H), 1.78e1.73 (m, 4H, piper-
idine-H),1.64e1.50 (m, 6H, piperidine-H),1.20e1,16 (m, 9H, CH2CH3).
CDCl3, TMS, 25 ꢀC, ppm):
139.0 (NCH2C6H(CH2CH3)3CH2N), 138.1 (Py-C), 128.5, 128.4
(NCH2C6H(CH2CH3)3CH2N), 124.6 (Py-C), 59.6 (NCH2CH), 54.2
(NCH2C6H(CH2CH3)3CH2N), 48.5, 48.0, 32.0, 26.7, 25.6 (piperidine-
d¼179.0 (Ccarbene), 154.5 (Py-C), 139.6,
13C NMR (100.6 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d¼154.3 (NCHN),
C),
23.3,
23.1
(NCH2C6H(CH2CH3)3CH2N),
16.3,
15.6
145.9, 137.7, 128.9, 125.9 (NCH2C6H2(CH(CH3)2)2CH2N), 59.8
(NCH2CH), 55.9 (NCH2C6H2(CH(CH3)2)2CH2N), 45.9, 31.7, 26.0, 25.5,
24.0 (piperidine-C), 22.1 (CH2eCH3), 16.7 (CH2eCH3). Anal. Calcd for
(NCH2C6H(CH2CH3)3CH2N). IR, ʋmax (CH2Cl2): 3055, 2987, 2685,
2306, 1605, 1521, 1448, 1422, 1285, 1071, 771 cmꢁ1. Anal. Calcd for
C
38H52Br4N6Pd2 (M¼1125.32): C, 40.56; H, 4.66; N, 7.47; Found C,
C
28H44Br2N4 (M¼596.48): C, 56.38; H, 7.44; N, 9.39; Found C, 56.45;
40.84; H, 4.96; N, 7.58%.
H, 7.57; N, 9.32%.
4.1.5. Compound 2c. This complex was prepared by same method
as for 2a starting from 1c (298.3 mg, 0.5 mmol) and Pd(OAc)2
(224.5 mg, 1.0 mmol). Yield: 366 mg, 65%, mp¼288e289 ꢀC. 1H
4.1.2. Compound 1c. This complex was prepared by same method
as for 1b11 starting from 2,4-bis(bromomethyl)-1,3,5-triisopropyl
benzene (348 mg, 1 mmol), 1,5,6,7,8,8a-hexahydroimidazo[1,5-a]
pyridine (248 mg, 2.0 mmol). Yield: 525 mg, 88%; mp¼171e172 ꢀC.
NMR (400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d
¼8.98 (d, J¼7.6 Hz, 4H,
Py-Ho), 7.71 (t, J¼7.6 Hz, 2H, Py-Hp), 7.75e6.67 (m, 6H, Py-Hm,
1H NMR (400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d¼9.52 (s, 2H, NCHN),
NCH2C6H2(CH(CH3)2)2CH2N), 5.62 (d, Hz, 1H,
J¼3.9
7.56 (s, 1H, NCH2C6H2(CH(CH3)2)2CH2N), 7.21 (s, 1H,
NCH2C6H2(CH(CH3)2)2CH2N), 5.11, 4.75 (d, J¼14.8 Hz, 4H,
NCH2C6H2(CH(CH3)2)2CH2N), 4.49e4.45 (m, 2H, piperidine-H),
4.38e4.34 (m, 4H, NCH2), 3.85e3.80 (m, 2H, piperidine-H),
3.05e3.02 (m, 2H, CH(CH3)2), 2.04e1.92 (m, 4H, piperidine-H),
1.63e1.55 (m, 4H, piperidine-H), 1.57e1.52 (m, 12H, piperidine-H),
1.21e1.14 (m, 6H, CH(CH3)2). 13C NMR (100.6 MHz, CDCl3,
NCH2C6H2(CH(CH3)2)2CH2N), 5.42 (d, J¼3.9 Hz,1H, Ph-CH2), 5.20 (d,
J¼3.9 Hz, 1H, NCH2C6H2(CH(CH3)2)2CH2N), 5.10e5.06 (m, 2H, pi-
peridine-H), 5.02 (d, J¼3.9 Hz, 1H, NCH2C6H2(CH(CH3)2)2CH2N),
3.92e3.84 (m, 2H, NCH2CH), 3.71e3.66 (m, 4H, NCH2CH),
3.46e3.40 (m, 2H, piperidine-H), 3.34e3.27 (m, 2H,
NCH2C6H2(CH(CH3)2)2CH2N), 3.25e3.18 (m, 2H, piperidine-H),
3.03e2.98 (m, 2H, piperidine-H), 1.94e1.90 (m, 4H, piperidine-H),
1.78e1.72 (m, 4H, piperidine-H), 1.48e1.44 (m, 4H, piperidine-H),
1.29e1.22 (m, 12H, NCH2C6H2(CH(CH3)2)2CH2N). 13C NMR
TMS, 25 ꢀC, ppm):
d
¼155.7 (NCHN), 148.2, 130.9, 127.8,
123.4 (NCH2C6H2(CH(CH3)2)2CH2N), 59.6 (NCH2CH), 54.6,
(NCH2C6H2(CH(CH3)2)2CH2N), 48.1, 45.9, 31.5, 28.9, 25.4, (piperi-
dine-C), 23.9 (CH(CH3)2), 22.1 (CH(CH3)2). Anal. Calcd for
(100.6 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d
¼178.2, 177.9 (Ccarbene),
153.3, 151.4 (Py-C), 146.1, 145.8 (NCH2C6H2(CH(CH3)2)2CH2N), 137.3,
136.7 (Py-C),128.5,128.4,127.8,127.3 (NCH2C6H2(CH(CH3)2)2CH2N),
123.9, 123.4, 121.7, 121.6 (Py-C), 59.1, 59.0 (NCH2CH), 53.9, 53.8
(NCH2C6H2(CH(CH3)2)2CH2N), 50.9, 50.7 (piperidine-C), 47.2, 46.8
(NCH2C6H2(CH(CH3)2)2CH2N), 31.0, 30.9, 27.5, 27.3 24.4,
24.3, 23.0, 22.9, 22.8, 22.7, 22.2, 22.1 (piperidine-C,
NCH2C6H2(CH(CH3)2)2CH2N). IR, ʋmax (CH2Cl2): 3054, 2987, 2686,
2306, 1605, 1520, 1448, 1422, 1263, 773 cmꢁ1. Anal. Calcd for
C
28H44Br2N4 (M¼596.48): C, 56.38; H, 7.44; N, 9.39; Found C, 56.21;
H, 7.49; N, 9.31%.
4.1.3. Compound 2a. A schlenk tube was charged with Pd(OAc)2
(224.5 mg, 1.0 mmol), KBr (238.0 mg, 2.0 mmol), 1a (277.2 mg,
0.5 mmol). Pyridine (5.0 mL) was then added as the solvent. It was
heated at 90 ꢀC during 24 h. During this time, the reaction solution
turned orange from being initially red. The remaining pyridine was
removed in vacuo to give an orange solid. Further purification was
carried out using flash column (CH2Cl2) to get pure complexes for
analysis and catalysis. Yield: 368 mg, 68%, mp¼281e282 ꢀC. 1H NMR
C
38H52Br4N6Pd2 (M¼1125.32): C, 40.56; H, 4.66; N, 7.47; Found C,
40.67; H, 4.48; N, 7.30%.
4.1.6. Compound 2d. This complex was prepared by same method
as for 2a starting from 1d (284.2 mg, 0.5 mmol) and Pd(OAc)2
(224.5 mg, 1.0 mmol). Yield: 395 mg, 70%, mp¼275e276 ꢀC. 1H
(400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d¼9.05 (d, J¼5.2 Hz, 4H, Py-Ho),
7.74 (t, J¼5.2 Hz, 2H, Py-Hp), 7.32 (t, J¼5.2 Hz, 4H, Py-Hm), 6.95 (s,1H,
NCH2C6H(CH3)3CH2N), 5.31 (s, 4H, NCH2C6H(CH3)3CH2N), 5.10e5.07
(m, 2H, piperidine-H), 3.71e3.69 (m, 2H, piperidine-H), 3.32e3.30
(m, 4H, NCH2CH), 2.78e2.76 (m, 2H, piperidine-H), 2.55 (s, 3H,
NCH2C6H(CH3)3CH2N), 2.44 (s, 6H, NCH2C6H(CH3)3CH2N), 1.97e1.92
(m, 4H, piperidine-H),1.79e1.73 (m, 4H, piperidine-H),1.47e1.39 (m,
4H, piperidine-H). 13C NMR (100.6 MHz, CDCl3, TMS, 25 ꢀC, ppm):
NMR (400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d
¼9.02 (d, J¼5.1 Hz, 4H,
Py-Ho), 7.72 (t, J¼5.1 Hz, 2H, Py-Hp), 7.34 (t, J¼5.1 Hz, 4H, Py-Hm),
5.38e5.26 (m, 4H, NCH2C6 (CH3)4CH2N), 5.10e5.07 (m, 2H, piperi-
dine-H), 3.70e3.66 (m, 2H, piperidine-H), 3.34e3.23 (m, 4H,
NCH2CH), 2.81e2.77 (m, 2H, piperidine-H), 2.37 (s, 12H, NCH2C6
(CH3)4CH2N), 1.98e1.94 (m, 4H, piperidine-H), 1.79e1.72 (m, 4H,

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
4776
piperidine-H), 1.47e1.38 (m, 4H, piperidine-H). 13C NMR
(100.6 MHz, CDCl3, TMS, 25 ꢀC, ppm):
hydrogen bond, CeH/p and p/p interactions. The details of these
interactions are given in Figs 3 and 4.
d
¼178.6 (Ccarbene), 152.6,
137.8 (Py-C), 135.1, 131.7 (NCH2C6(CH3)4CH2N), 124.8 (Py-C), 59.3
(NCH2CH), 54.2 (NCH2C6(CH3)4CH2N), 49.6, 48.4, 31.9, 25.5, 23.2
(piperidine-C), 17.5 (NCH2C6(CH3)4CH2N). IR, ʋmax (CH2Cl2): 3054,
2987, 2947, 2306,1605,1520,1448,1422,1286,1071, 772 cmꢁ1. Anal.
Calcd for C39H56Br4N5Pd2 (M¼1127.35): C, 53.15; H, 7.06; N, 10.33;
Found C, 53.15; H, 7.12; N, 10.29%.
4.1.8.2. General procedure for the Suzuki coupling reactions. A
two-necked 25 mL flask fitted with a reflux condenser was charged
with aryl chlorides (1.0 mmol), 2 mmol KOH, phenylboronic acid
(1.5 mmol), diethyleneglycol-di-n-butylether (0.6 mmol, internal
standard), 1 mol % for 1; 0.5 mol % for 2aed; 0.33 mol % for 3eef in
4 mL of 2-propanol (IPA) was added. The flask was placed in
a preheated oil bath (353 K) under air atmosphere, temperature
353 K, and 2 h. The conversion was monitored by gas chromatog-
raphy following filtration. Yields were determined by gas chro-
matography for an average of two runs. Products were puried by
column chromatography on silica gel using a mixture of hexane and
EtOAc (4:1) as eluent.
4.1.7. Compound 3e. This complex was prepared by same method as
for 2a starting from 1e (254.5 mg, 0.33 mmol) and Pd(OAc)2
(224.5 mg,1.0 mmol). Yield: 362 mg, 70%, mp¼292e293 ꢀC. .1H NMR
(400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d
¼9.04 (d, J¼4.8 Hz, 6H, Py-Ho),
7.29 (t, J¼4.8 Hz, 3H, Py-Hp), 7.32 (t, J¼4.8 Hz, 6H, Py-Hm), 5.33 (s, 6H,
N(CH2)3C6(CH3)3N), 5.10e5.05 (m, 3H, piperidine-H), 3.71e3.66 (m,
3H, piperidine-H), 3.35e3.26 (m, 6H, NCH2CH), 2.80e2.75 (m, 3H,
piperidine-H), 2.42e2.36 (s, 12H, N(CH2)3C6(CH3)3N), 1.92e1.84 (m,
6H, piperidine-H),1.83e1.74 (m, 6H, piperidine-H),1.48e1.39 (m, 6H,
piperidine-H). 13C NMR (100.6 MHz, CDCl3, TMS, 25 ꢀC, ppm):
4.1.8.2.1. 4-Acetylbiphenyl.32e34 White solid, mp: 120e121 ꢀC.
1H NMR (400 MHz, CDCl3)
d
: 8.01e8.05 (m, 2H, Ph-H), 7.70e7.60
(m, 4H, Ph-H), 7.50e7.38 (m, 3H, Ph-H), 2.63 (s, 3H, COCH3); 13C
NMR (100 MHz, CDCl3) : 197.9, 146.0, 140.1, 136.1, 129.2, 129.1,
d
d
¼178.7 (Ccarbene), 152.6 (Py-C), 137.9 (N(CH2)3C6(CH3)3N),135.2 (Py-
128.5, 127.5, 127.4, 26.8 ppm.
C), 130.1 (N(CH2)3C6(CH3)3N), 124.6 (Py-C), 59.4 (NCH2CH), 54.3
(N(CH2)3C6(CH3)3N), 49.7, 49.6, 32.1, 25.7, 23.3 (piperidine-C), 17.7
(N(CH2)3C6(CH3)3N). IR, ʋmax (CH2Cl2): 3054, 2987, 2947, 2305, 1605,
1521, 1448, 1422, 1284, 772 cmꢁ1. Anal. Calcd for C48H63Br6N9Pd3
(M¼1564.76): C, 36.84; H, 4.06; N, 8.06; Found C, 36.61; H, 4.26; N,
8.15%.
4.1.8.2.2. 4-Nitrobiphenyl.33,34 Yellow solid, mp: 114e115 ꢀC. 1H
NMR (400 MHz, CDCl3)
d: 8.31e8.27 (m, 2H, Ph-H), 7.75e7.71 (m,
2H, Ph-H), 7.64e7.60 (m, 2H, Ph-H); 7.52e7.42 (m, 3H, Ph-H); 13C
NMR (100 MHz, CDCl3)
127.6, 124.3 ppm.
d: 147.9, 147.3, 139.0, 129.4, 129.1, 128.0,
4.1.8.2.3. 4-Phenylbenzaldehyde.32,33 White solid, mp: 59e60 ꢀC.
1H NMR (400 MHz, CDCl3)
d: 10.11 (s, 1H, CHO), 7.96 (d, 2H, Ph-H),
4.1.8. Compound 3f. This complex was prepared by same method as
for 2a starting from 1f (268.5 mg, 0.33 mmol) and Pd(OAc)2
(224.5 mg,1.0 mmol). Yield: 339 mg, 64%, mp¼296e298 ꢀC. . 1H NMR
7.64 (d, 2H, J¼5.6 Hz, Ph-H), 7.98 (d, J¼5.6 Hz, 2H, Ph-H), 7.51e7.42
(m, 3H, Ph-H). 13C NMR (100 MHz, CDCl3)
135.5, 130.5, 129.2, 128.7, 127.9, 127.6 ppm.
d: 192.1, 147.4, 140.0,
(400 MHz, CDCl3, TMS, 25 ꢀC, ppm):
d¼9.04 (d, J¼5.2 Hz, 6H, Py-
4.1.8.2.4. 4-Methylbiphenyl.33,34 White solid, mp: 45e46 ꢀC. 1H
Ho),7.74 (t, J¼5.2 Hz, 3H, Py-Hp), 7.33 (t, J¼5.2 Hz, 6H, Py-Hm),
5.45e5.40 (m, 6H, N(CH2)3C6(CH2CH3)3N), 5.13e5.08 (m, 3H, piperi-
dine-H), 3.66e3.60 (m, 3H, piperidine-H), 3.38e3.30 (m, 6H,
NCH2CH), 3.05e3.00 (m, 6H, N(CH2)3C6(CH2CH3)3N), 2.79e2.73 (m,
3H, piperidine-H), 2.66e2.59 (m, 3H, piperidine-H),1.95e1.88 (m, 6H,
piperidine-H), 1.82e1.70 (m, 6H, piperidine-H), 1.60e1.55 (m, 3H,
piperidine-H), 1.47e1.41 (m, 3H, piperidine-H), 1.36e1.25 (m, 9H,
N(CH2)3C6(CH2CH3)3N). 13C NMR (100.6 MHz, CDCl3, TMS, 25 ꢀC,
NMR (400 MHz, CDCl3) d: 7.67e7.26 (m, 9H, Ph-H), 2.41 (s, 3H, CH3).
13C NMR (100 MHz, CDCl3)
127.3, 21.4 ppm.
d: 141.5, 138.7, 137.3, 129.8, 129.0, 127.3,
4.1.8.2.5. 4-Methoxybiphenyl.32e34 White solid, mp: 84e85 ꢀC.
1H NMR (400 MHz, CDCl3)
d: 7.63e7.58 (m, 4H, Ph-H), 7.49e7.45 (m,
2H, Ph-H), 7.38e7.34 (m, 1H, Ph-H), 7.05e7.03 (d, 2H, Ph-H), 3.89 (s,
3H, OCH3). 13C NMR (100 MHz, CDCl3)
128.4, 127.0, 126.9, 114.5, 55.6 ppm.
d
: 159.5, 141.1, 134.1, 129.0,
ppm):
d¼179.4 (Ccarbene), 152.5 (Py-C) 146.6 (N(CH2)3C6(CH2CH3)3N),
4.1.8.2.6. 2-Methoxybiphenyl.32,34 Colorless
oil.1H
NMR
137.7 (Py-C), 129.8 (N(CH2)3C6(CH2CH3)3N), 124.5 (Py-C), 59.2
(NCH2CH), 54.3 (N(CH2)3C6(CH2CH3)3N), 48.2, 31.9, 29.7,
25.6, 23.6 (piperidine-C), 23.2 (N(CH2)3C6(CH2CH3)3N), 15.9
(N(CH2)3C6(CH2CH3)3N). IR, ʋmax (CH2Cl2): 3054, 2986, 2947, 2305,
1605,1521,1448,1285,1071, 689 cmꢁ1. Anal. Calcd forC51H69Br9N9Pd3
(M¼1606.84): C, 41.55; H, 5.01; N, 6.21; Found C, 41.51; H, 5.14; N,
6.31%.
(400 MHz, CDCl3)
d
: 7.57e7.59 (d, 2H, J¼8.6 Hz, Ph-H); 7.43e7.47 (t,
2H, J¼8.6 Hz, Ph-H); 7.34e7.38 (t, 3H, J¼5.2 Hz, Ph-H); 7.09e7.01
(m, 2H, Ph-H), 3.84 (s, 3H, OCH3). 13C NMR (100 MHz, CDCl3)
d
:156.8, 138.8, 131.2, 131.0, 129.8, 128.9, 128.2, 127.2, 121.1, 111.6,
55.8 ppm.
4.1.8.2.7. 2-Acetylbiphenyl.34 light yellow oil.1H NMR (400 MHz,
CDCl3) : 7.57e7.49 (m, 4H, Ph-H), 7.45e7.38 (m, 3H, Ph-H),
7.37e7.33 (m, 2H, Ph-H), 2.00 (s, 3H, COCH3). 13C NMR (100 MHz,
CDCl3) : 205.0.141.2, 140.9, 140.8, 130.9, 130.5, 129.1, 128.9, 128.1,
d
4.1.8.1. Crystallographic
data
collection
and
re-
d
finement. Diffraction experiments were carried out at 296 K on
a Stoe IPDS diffractometer. The structures were solved by direct
methods and refined using the programs SHELXS97 and
SHELXL97.28 All non-hydrogen atoms were refined anisotropically
by full-matrix least squares methods.28 The parameters for data
collection and structure refinement of complexes 1 and 2c are listed
in Table 1. All hydrogen atoms bonded to C atoms were refined
127.7, 30.6 ppm.
4.1.8.3. General procedure for the Heck coupling reactions. A
two-necked 25 mL flask fitted with a reflux condenser was charged
with aryl chlorides (1.0 mmol), 2 mmol Na2CO3, styrene (1.5 mmol),
diethyleneglycol-di-n-butylether (0.6 mmol, internal standard),
1 mol % for 1; 0.5 mol % for 2aed; 0.33 mol % for 3eef in 6 mL of
DMF. The flask was placed in a preheated oil bath (373 K) under
argon atmosphere for 4 h. After the required reaction time, the
solution was allowed to cool to room temperature and then
extracted with Et2O (3ꢂ5 mL). The combined organic layers were
dried over anhydrous Na2SO4 and the solvent evaporated. The
residue was puried by column chromatography on silica gel using
a mixture of hexane and EtOAc (4:1) as eluent. Yields were de-
termined by gas chromatography for an average of two runs.
using
a
riding model, with CeH¼0.93e0.98. The constraint
Uiso(H)¼1.2Ueq(C and CH2) or 1.5Ueq(CH3) was applied. The fol-
lowing procedures were implemented in our analysis: data col-
lection: X-Area, cell refinement: X-Area, data reduction: X-RED;29
program(s) used for molecular graphics were as follows: Mercury
programs;30 software used to prepare material for publication:
WinGX.31 The molecular structures of 1 and 2c with the atom
numbering schemes are shown in Figs 1 and 2. Molecules of 1 are
linked into sheets by a combination of two CeH/
p
interactions.
4.1.8.3.1. 4-Nitro-trans-stilbene.35e37 Yellow
solid,
: 8.21 (d, 2H, J¼9.2 Hz,
Molecules of 2c are linked into sheets by a combination of CeH/Br
mp¼156e157 ꢀC. 1H NMR (400 MHz, CDCl3)
d

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G. Turkmen et al. / Tetrahedron 71 (2015) 4770e4778
4777
Ph-H), 7.61 (d, 2H, J¼9.2 Hz, Ph-H), 7.52 (d, 2H, J¼7.2 Hz, Ph-H),
References and notes
7.28e7.42 (m, 3H, Ph-H), 7.24 (d, 1H, J¼16 Hz, CH), 7.12 (d, 1H,
J¼16.4 Hz, CH). 13C NMR (100 MHz, CDCl3)
d: 147.2, 143.9, 136.4,
133.5, 129.1, 129.0, 127.2, 126.9, 126.5, 124.3 ppm.
1. (a) Navarro, O.; Kelly, R. A., III; Nolan, S. P. J. Am. Chem. Soc. 2003, 125, 16194; (b)
Viciu, M. S.; Kelly, R. A., III; Stevens, E. D.; Naud, F.; Studer, M.; Nolan, S. P. Org.
Lett. 2003, 5, 1479.
2. (a) O’Brien, C. J.; Kantchev, E. A. B.; Valente, C.; Hadei, N.; Chass, G. A.;
Lough, A.; Hopkinson, A. C.; Organ, M. G. Chem.dEur. J. 2006, 12, 4743; (b)
Organ, M. G.; Abdel-Hadi, M.; Avola, S.; Hadei, N.; Nasielski, J.; O’Brien, C.
J.; Valente, C. Chem.dEur. J. 2006, 13, 50; (c) Organ, M. G.; Avola, S.; Du-
bovyk, I.; Hadei, N. E. A. B.; O’Brien, C. J.; Valente, C. Chem.dEur. J. 2006,
12, 4749.
3. (a) Kantchev, E. A. B.; Peh, G.-R.; Zhang, C.; Ying, J. Y. Org. Lett. 2008, 10, 3949;
(b) Kantchev, E. A. B.; Ying, J. Y. Organometallics 2009, 28, 289.
4. (a) Chen, M.-T.; Vicic, D. A.; Chain, D. W. J.; Turner, M. L.; Navarro, O. Organo-
metallics 2011, 30, 6770; (b) Chen, M.-T.; Vicic, D. A.; Turner, M. L.; Navarro, O.
Organometallics 2011, 30, 5052.
4.1.8.3.2. 4-Acetyl-trans-stilbene.35e37 White
solid,
: 7.92 (d, 2H, J¼8.0 Hz,
mp¼142e143 ꢀC. 1H NMR (400 MHz, CDCl3)
d
Ph-H), 7.55 (d, 2H, J¼8.0 Hz, Ph-H), 7.50 (d, 2H, J¼8.0 Hz, Ph-H),
7.24e7.38 (m, 3H, Ph-H), 7.19 (d, 1H, J¼16.4 Hz, CH), 7.04 (d, 1H,
J¼16.4 Hz, CH), 2.28 (s, 3H, COCH3). 13C NMR (100 MHz, CDCl3)
d:
196.6,142.1,136.9,136.3,131.7, 129.0,128.9,128.5,127.7, 127.0, 126.7,
26.6 ppm.
4.1.8.3.3. 4-Methoxy-trans-stilbene.35,37 White
solid,
: 7.37 (d, 2H, J¼7.2 Hz,
mp¼136e137 ꢀC. 1H NMR (400 MHz, CDCl3)
d
5. (a) Tang, Y.-Q.; Lu, J.-M.; Shao, L.-X. J. Organomet. Chem. 2011, 696, 3741; (b)
Zhou, X.-X.; Shao, L.-X. Synthesis 2011, 3138; (c) Zhu, L.; Gao, T.-T.; Shao, L.-X.
Tetrahedron 2011, 67, 5150.
Ph-H), 7.33 (d, 2H, J¼8.4 Hz, Ph-H), 7.23 (t, 2H, J¼7.2 Hz, Ph-H), 7.12
(t, 1H, J¼6.8 Hz, Ph-H), 6.95 (d, 1H, J¼16.0 Hz, CH), 6.85 (d, 1H,
€
€
J¼16.4 Hz, CH), 6.78 (d, 2H, J¼8.4 Hz, Ph-H), 3.73 (s, 3H, OCH3). 13
C
6. (a) Turkmen, H.; Can, R.; C¸ etinkaya, B. Dalton Trans. 2009, 7039; (b) Turkmen,
_
€
H.; Gok, L.; Kani, I.; C¸ etinkaya, B. Turk. J. Chem. 2013, 37, 633.
7. Tapu, D.; Dixon, D. A.; Roe, C. Chem. Rev. 2009, 109, 3385.
NMR (100 MHz, CDCl3) d: 159.4, 137.8, 130.3, 128.7, 128.4, 127.8,
€
8. (a) Turkmen, H.; Pape, T.; Hahn, F. E.; C¸ etinkaya, B. Organometallics 2008, 27,
127.2, 126.8, 126.4, 114.2, 55.2 ppm.
4.1.8.3.4. 2-Methoxy-trans-stilbene.37 White
solid,
571; (b) Wurtz, S.; Glorius, F. Acc. Chem. Res. 2008, 41, 1523.
9. Baskakov, D.; Herrmann, W. A.; Herdtweck, E.; Hofmann, S. D. Organometallics
2007, 26, 626.
10. (a) Cavell, K. J.; Elliott, M. C.; Nielsen, D. J.; Paine, J. S. Dalton Trans. 2006,
4922; (b) Burstein, C.; Lehmann, C. W.; Glorius, F. Tetrahedron 2005, 61,
6207.
11. Herrmann, W. A.; Baskakov, D.; Herdtweck, E.; Hofmann, S. D.; Bunlaksana-
nusorn, T.; Rampf, F.; Rodefeld, L. Organometallics 2006, 25, 2449.
12. Alcarazo, M.; Roseblade, S. J.; Cowley, A. R.; Fernandez, R.; Brown, J. M.; Las-
saletta, J. M. J. Am. Chem. Soc. 2005, 127, 3290.
mp¼62e63 ꢀC. 1H NMR (400 MHz, CDCl3)
: 7.46 (d, 1H, J¼8.0 Hz,
d
Ph-H), 7.40 (d, 2H, J¼7.2 Hz, Ph-H), 7.35 (d, 1H, J¼16.8 Hz, Ph-H),
7.21 (t, 2H, J¼7.6 Hz, Ph-H), 7.06e7.13 (m, 2H, Ph-H), 6.97 (d, 1H,
J¼16.4 Hz, CH), 6.83 (d, 1H, J¼16.4 Hz, CH), 6.74 (d, 1H, J¼8.0 Hz,Ph-
H), 3.76 (s, 3H, OCH3). 13C NMR (100 MHz, CDCl3)
d: 157.2, 138.3,
129.3, 128.8, 127.6, 126.9, 126.8, 126.7, 123.9, 121.0, 111.1, 55.6 ppm.
4.1.8.3.5. 4-Methyl-trans-stilbene.35e37 White
solid,
: 7.38 (d, 2H, J¼8.4 Hz,
13. Roseblade, S. J.; Ros, A.; Monge, D.; Alcarazo, M.; Alvarez, E.; Lasselatta, J. M.;
mp¼117e118 ꢀC. 1H NMR (400 MHz, CDCl3)
d
Fernandes, R. Organometallics 2007, 26, 2570.
14. Weiss, R.; Handke, M.; Hampel, F. Angew. Chem., Int. Ed. 1998, 371, 344.
15. Nonnenmacher, M.; Kunz, D.; Rominger, F.; Oeser, T. J. Organomet. Chem. 2005,
690, 5647.
Ph-H), 7.29 (d, 2H, J¼8.0 Hz, Ph-H), 7.23 (t, 2H, J¼7.6 Hz, Ph-H), 7.12
(t, 1H, J¼6.4 Hz, Ph-H), 7.04 (d, 2H, J¼8.0 Hz, Ph-H), 6.97 (d, 1H,
J¼16.5 Hz, CH), 6.93 (d, 1H, J¼16.3 Hz, CH), 2.27 (s, 3H, CH3). 13C
16. (a) Boydston, A. J.; Williams, K. A.; Bielawski, C. W. J. Am. Chem. Soc. 2005, 127,
12496; (b) Sanderson, M. D.; Kamplain, J. W.; Bielawski, C. W. J. Am. Chem. Soc.
2006, 128, 16514; (c) Zanardi, A.; Corberan, R.; Mata, J. A.; Peris, E. Organome-
tallics 2008, 27, 3570; (d) Zanardi, A.; Mata, J. A.; Peris, E. J. Am. Chem. Soc. 2009,
131, 14531; (e) Tennyson, A. G.; Ono, R. J.; Hudnall, T. W.; Khramov, D. M.; Er, J.
A. V.; Kamplain, J. W.; Lynch, V. M.; Sessler, J. L.; Bielawski, C. W. Chem.dEur. J.
2010, 16, 304; (f) Prades, A.; Peris, E.; Alcarazo, M. Organometallics 2012, 31,
4623; (g) Sabater, S.; Mata, J. A.; Peris, E. Nat. Commun. 2013, 4, 2553; (h) Gonell,
S.; Peris, E. ACS Catal. 2014, 4, 2811.
17. (a) Guisado-Barrios, G.; Hiller, J.; Peris, E. Chem.dEur. J. 2013, 19, 10405; (b)
Valdes, H.; Poyatos, M.; Peris, E. Organometallics 2013, 32, 6445; (c) Gonell, S.;
Poyatos, M.; Peris, E. Angew. Chem., Int. Ed. 2013, 52, 7009; (d) Gonell, S.;
Poyatos, M.; Peris, E. Chem.dEur. J. 2014, 20, 9716; (e) Mata, J. A.; Hahn, F. E.;
Peris, E. Chem. Sci. 2014, 5, 1723; (f) Ruiz-Botella, S.; Peris, E. Organometallics
2014, 33, 5509.
NMR (100 MHz, CDCl3) d: 137.7, 137.3, 134.8, 129.5, 128.8, 128.7,
127.9, 127.5, 126.6, 126.6, 21.5 ppm.
4.1.8.3.6. trans-3-Styrylpyridine.35,37 Yellow
solid,
mp¼79e80 ꢀC. 1H NMR (400 MHz, CDCl3)
d: 8.62 (s, 1H, Py-H), 8.38
(d, 1H, J¼4.8 Hz, Py-H), 7.70 (d, 1H, J¼4.8 Hz, Py-H), 7.40 (d, 2H,
J¼7.2 Hz, Ph-H), 7.26 (t, 2H, J¼7.2 Hz, Ph-H), 7.12e7.20 (m, 2H, Py-H,
Ph-H), 7.05 (d, 1H, J¼16.4 Hz, CH), 6.95 (d, 1H, J¼16.0 Hz, CH). 13
C
NMR (100 MHz, CDCl3) d: 148.7, 148.6, 136.8, 133.0, 132.6, 130.9,
128.9, 128.3, 126.8, 125.0, 123.5 ppm.
4.1.8.3.7. trans-4-Styrylbenzaldehyde.36 White
solid,
mp¼115e116 ꢀC. 1H NMR (400 MHz, CDCl3)
d: 9.94 (s, 1H, CHO),
18. (a) Rit, A.; Pape, T.; Hahn, F. E. J. Am. Chem. Soc. 2010, 132, 4572; (b) Radloff, C.;
Gong, H. Y.; Brinke, C. S. T.; Pape, T.; Lynch, V. M.; Sessler, J. L.; Hahn, F. E. Chem.
dEur. J. 2010, 16, 13077; (c) Rit, A.; Pape, T.; Hahn, F. E. Organometallics 2011, 30,
6393; (d) Ruiz-Botella, S.; Guisado-Barrios, G.; Mata, J. A.; Peris, E. Organome-
tallics 2013, 32, 6613.
7.84 (d, 2H, J¼8.0 Hz, Ph-H), 7.61 (d, 2H, J¼8.0 Hz, Ph-H), 7.52 (d, 2H,
J¼8.0 Hz, Ph-H), 7.39e7.31 (m, 3H, Ph-H), 7.22 (d, 1H, J¼16.0 Hz,
CH), 7.14 (d, 1H, J¼16.0 Hz, CH) ppm. 13C NMR (100.6 MHz, CDCl3)
d:
193.7, 143.6, 136.8, 135.6, 132.4, 130.4, 129.1, 128.7, 128.6, 128.0,
127.5, 127.1, 126.4 ppm.
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We sincerely thank to Prof. Dr. S¸ amil Is¸ ık for his help with the
data collection. We also thank Prof. Dr. Stephen T. Astley for helpful
discussion regarding the NMR spectra. Financial support from Ege
University (Project 2010-FEN-046 and 2010-Fen-076) is gratefully
acknowledged.
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data for 1 and 2c. These data can be obtained free of charge via
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