Evidences of release and catch mechanism in the Heck reaction catalyzed by palladium immobilized on highly cross-linked-supported imidazolium salts

Article abstract of DOI:10.1016/j.molcata.2014.02.025

Palladium (10 wt%) on a highly cross-linked imidazolium-based material was used as catalyst in 0.1 mol% in the Heck reaction between several alkenes and aryl iodides. Products were obtained from good to high yields. Deeper investigations showed a release of Pd species in solution and their capture by the imidazolium-based support. When a sixfold amount of support was employed the re-captured Pd species (0.5-0.6 wt%) were not anymore catalytically active. This result represents a new interesting aspect of this work since the highly cross-linked imidazolium-based material can act also as Pd scavenger avoiding the release of the metal in solution. Important differences between Heck and Suzuki reactions have been evidenced when the reactions were carried out in the presence of the scavenging support.

Full text of DOI:10.1016/j.molcata.2014.02.025

Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Evidences of release and catch mechanism in the Heck reaction
catalyzed by palladium immobilized on highly
cross-linked-supported imidazolium salts
Cinzia Paviaa, Francesco Giacalonea, Lucia Anna Bivonaa,b, Anna Maria Pia Salvoa, Chiara
Petruccic, Giacomo Strappavecciac, Luigi Vaccaroc, Carmela Aprileb, Michelangelo
Gruttadauriaa,∗
a Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, Viale delle Scienze s/n, Ed. 17, I-90128
Palermo, Italy
b Laboratory of Applied Material Chemistry (CMA), University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium
c Laboratory of Green Synthetic Organic Chemistry, CEMIN – Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto, 8, Perugia, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Palladium (10 wt%) on a highly cross-linked imidazolium-based material was used as catalyst in 0.1 mol%
in the Heck reaction between several alkenes and aryl iodides. Products were obtained from good to
high yields. Deeper investigations showed a release of Pd species in solution and their capture by the
imidazolium-based support. When a sixfold amount of support was employed the re-captured Pd species
(0.5–0.6 wt%) were not anymore catalytically active. This result represents a new interesting aspect of
this work since the highly cross-linked imidazolium-based material can act also as Pd scavenger avoiding
the release of the metal in solution. Important differences between Heck and Suzuki reactions have been
evidenced when the reactions were carried out in the presence of the scavenging support.
© 2014 Elsevier B.V. All rights reserved.
Received 31 October 2013
Received in revised form 22 February 2014
Accepted 24 February 2014
Available online 4 March 2014
Keywords:
C
C cross-coupling
Heterogeneous catalysis
Ionic liquids
Heck reaction
Suzuki reaction
1. Introduction
involve ionic liquids as solvents suffer from severe problems related
with high cost as well as high viscosity of ionic liquids. To over-
Heck coupling reaction has become a mainstay of modern syn-
thetic organic chemistry for the formation of the carbon–carbon
bonds [1–5]. The importance of coupling products from Suzuki,
Heck and other C C coupling reactions as components of many
kinds of compounds, mainly pharmaceuticals and natural products
[6,7], as well as in the field of engineering materials, such as con-
ducting polymers [8–10] has attracted enormous interest from the
chemistry community. A plethora of palladium-based catalytic sys-
tems have been developed with the aim of obtaining new catalysts
displaying increased activity and selectivity [11–16].
The Heck reaction has been one of the Pd-catalyzed processes
extensively investigated in ionic liquids (ILs). As reaction media
have been used onium salts, pyridinium and imidazolium salts
[17–21] and more recently supported ILs and the so-called task-
specific ionic liquids, TSILs [22–25]. However, the reactions which
come these drawbacks, adsorbed ionic liquids or covalently linked
ionic liquids to several supports have been developed. These mate-
rials have found interesting applications for both metal catalyzed
and organocatalyzed reactions [26]. Imidazolium-based networks
serve as the reaction phase in which the homogeneous catalyst is
dissolved. This class of advanced materials shares the properties of
true ionic liquids, behaving as bulk ionic liquids and the advantages
of a solid support. In several cases the Heck reaction, takes place
through the formation of soluble complexes/Pd clusters formed
from supported PdNPs containing ILs moieties either deposited on
a solid support as a thin film [27] or covalently attached to the solid
(organic and inorganic) [28,29]. In most instances, the release of sol-
uble species has been observed [30]. The most important question
is if such soluble species are recaptured at the end of the reaction
[31–33]. Although the recapture of Pd-based catalytic species has
already been described it is important to get further evidences of
such “release and catch” mechanism [34] in order to fully under-
stand the general applicability of this phenomenon.
∗
Corresponding author. Tel.: +39 091 23897534; fax: +39 091596825.
E-mail addresses: luigi@unipg.it (L. Vaccaro), carmela.aprile@fundp.ac.be (C.
Recently, we have prepared several supported imidazolium
salts on silica gel by using a new approach, i.e. the thiol-ene
Aprile), michelangelo.gruttadauria@unipa.it (M. Gruttadauria).
http://dx.doi.org/10.1016/j.molcata.2014.02.025
1381-1169/© 2014 Elsevier B.V. All rights reserved.

58
C. Pavia et al. / Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
Scheme 1. Heck reaction between 4-vinyltoluene and 1-(bromomethyl)-4-iodobenzene catalyzed by 1a.
reaction between a mercaptopropyl-modified silica gel and bis-
vinylimidazolium salts. These materials have been employed for
the non-covalent immobilization of organic molecules, such as a
ionic liquid-tagged proline [35] or TEMPO catalysts [36]. On the
other hand, the same supports have been successfully employed for
palladium nanoparticles immobilization. The latter materials have
been used in the Suzuki–Miyaura reaction between arylboronic
acids and arylhalides to give biaryls in high yields both under
batch [37,38] and continuous-flow conditions [39]. The interest-
ing aspect of these materials is the high imidazolium salt content
which allows a high Pd content (10 wt%). Since these catalysts
were used in only 0.1 mol%, only 1 mg of catalytic material was
needed per mol of substrate. Moreover, the Suzuki–Miyaura reac-
tion under flow conditions was carried out by placing catalyst
and solid base (K2CO3) in two separate columns. Here we report
preliminary observation about the use of our catalytic materials
toward the Heck reaction under batch conditions as a first step
for a study under flow conditions, exploring scope and limitations
and trying to get evidences of a “release and catch” mechanism
[34]. Moreover, the ability of highly cross-linked imidazolium-
based material to act as Pd scavenger from its solutions or
from Suzuki reactions [39,40] could be extended to Heck reac-
tions allowing the obtainment of products with a minimal metal
contamination.
Fig. 1. Structure of catalysts 1a and b.
plug of silica under vacuum using petroleum ether/ethyl acetate as
eluent.
3. Results and discussion
As catalyst we have employed material 1a (Fig. 1) which has
been prepared as previously reported [37]. As a first approach, we
have investigated the reaction between styrene and iodobenzene
(Table 1). Two different bases, namely triethylamine and potassium
carbonate, and several solvents were preliminarily screened. The
best reaction condition was found when a 4:1 DMF/water solvent
mixture in the presence of triethylamine as base was employed.
The presence of water increased the yield (Table 1, entries 1–2). No
product was isolated when other solvents (isopropanol/water 4:1,
dioxane, ethanol, water) were used under the same conditions. Also
the use of potassium carbonate as base had a detrimental effect
on the yield (entries 3–4). In each case the reaction afforded the
expected trans-alkene with small amount of the gem-alkene.
Then we employed the optimized conditions for a set of
reactions between styrene or styrene derivatives and several arylio-
dides (Table 2).
Alkenes were obtained in high yields and high selectivity, being
the expected trans isomer the major product. Only in one case the
reaction was carried out using a larger amount of catalyst (0.4 mol%,
entry 9). In this case the use of 0.1 mol% of catalyst gave the alkene
in 39% yield and 92/8 2/3 ratio. When the Heck reaction was carried
out using 1-(bromomethyl)-4-iodobenzene we directly isolated the
corresponding quaternary ammonium salt 2q in excellent yield
2. Experimental
2.1. General
The NMR spectra were recorded on a Bruker 300 MHz spectrom-
eter. Mass spectra were recorded on a Shimadzu GCMS-QP2010.
Carbon and nitrogen contents were determined by combustion
analysis in a Fisons EA 1108 elemental analyzer. EDX values are
an average of several measures, at least 10 per sample. XPS values
are the average of three different points.
2.2. General procedure for the Heck reaction
To a round-bottom flask catalyst 1a (0.1 mol%, 1 mg), alkene
(1.5 mmol), aryliodide (1 mmol), triethylamine (2 mmol) and
DMF/H2O (4 mL + 1 mL) were added. The reaction mixture was
heated at 90 ◦C for 21 h. Then, the reaction mixture was cooled
at room temperature, diluted with water and extracted with
dichloromethane. The organic phase is evaporated under reduced
pressure and the residue purified with a short plug of silica under
vacuum using petroleum ether/ethyl acetate as eluent.
Table 1
Effect of the solvent and base on the Heck reaction between styrene and
iodobenzene.a
2.3. General procedure for the Suzuki reaction
Entry
Solvent
Base
Yield (%)b
2a/3a ratio
1
2
3
4
DMF:H2O (4:1)
DMF
DMF:H2O (4:1)
DMF:H2O (4:1)
NEt3
NEt3
K2CO3
K2CO3/NEt3
89
71
21
27
>99/1
95/5
96/4
95/5
To
a round-bottom flask catalyst 1a (0.1 mol%, 1 mg), 4-
formylphenyl boronic acid (1.13 mmol), 4-bromobenzaldehyde
(1 mmol), K2CO3 (1.2 mmol) and EtOH/H2O (5 mL, 1:1) were added.
The reaction mixture was heated at 50 ◦C for 19 h. Then, the reac-
tion mixture was cooled at room temperature, diluted with water
and extracted with dichloromethane. The organic phase is evapo-
rated under reduced pressure and the residue purified with a short
c
a
Reaction conditions: styrene (1.5 mmol), iodobenzene (1 mmol), base (2 mmol),
1a (0.1 mol%, 1 mg), solvent (5 mL), 90 ◦C, 21 h.
b
Isolated product.
c
1:1 ratio.

C. Pavia et al. / Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
59
Table 2
Table 4
Heck reaction between styrenes and aryliodides.a
Filtration tests on Heck reaction between methyl acrylate and 4ꢀ-
iodoacetophenone.a
Yield (%)b
2/3 ratio
Entry
1st step
2nd step
Entry
2 or 3
Compound
R1
Yield (%)b
t (h)
Yield (%)b
R2
t (h)
1
2
3
4
0.5
0.5
1.0
1.0
0.5
1.0
0.5
–
5c
–
69
–
–
–
–
–
–
–
21
–
21
21
21
21
21
21
–
99
–
99
5[c]
75
99
99
99
1
2
3
4
5
6
7
8
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
H
H
H
H
H
H
CH3
CH3
CH3
Cl
Cl
Cl
Cl
Cl
CHO
CHO
H
89
88
73
96
97
96
91
82
85
89
85
75
93
97
72
62
>99/1
92/8
92/8
99/1
98/2
99/1
99/1
97/3
86/14
98/2
98/2
98.5/1.5
97/3
99/1
>99/1
>99/1
4-OCH3
3-OCH3
4-Br
5d
6d
7e
8f
9g
4-COCH3
4-COOCH3
4-COOCH3
4-COCH3
4-OCH3
4-COOCH3
4-OCH3
3-OCH3
H
9c
10
11
12
13
14
15
16
–
a
Reaction conditions (1st step): methyl acrylate (1.5 mmol), 4-iodo-
acetophenone (1 mmol), TEA (2 mmol), catalyst 1a (0.1 mol% 1 mg), DMF/H2O
(5 mL, 4:1) 90 ◦C; (2◦ step): 21 h, 90 ◦C.
b
Isolated yield.
4-COCH3
4-OCH3
4-Br
c
determined by 1H NMR.
2nd step: after filtration, support 6 has been added (6 mg).
2nd step: after filtration, support 6 has been added (2 mg).
No filtration, support 6 has been added (6 mg) in the starting reaction mixture.
d
e
f
a
Reaction conditions: styrene derivative (1.5 mmol), aryliodide (1 mmol), TEA
g
(2 mmol), 1a (0.1 mol%, 1 mg), DMF/H2O (5 mL, 4:1), 90 ◦C, 21 h.
No filtration, support 6 has been added (12 mg) in the starting reaction mixture.
b
Isolated product.
catalyst 1 (0.4 mol%).
c
employed, the corresponding disubstituted compounds were
detected in only 4% and 3% respectively (entries 7–8). Also 2-iodo-
thiophene gave the corresponding acrylate 5i in high yield (entry
9).
It has been proposed that when high loading supported ionic
liquid-like phase (SILLP) materials at high temperatures were used,
the Heck reaction takes place through a leaching mechanism in
which soluble Pd(II) species are the molecular catalysts [33]. Evi-
dences of leached active Pd species have been reported in other
cases [41–44]. Therefore we investigated if a leaching occurs dur-
ing the Heck reaction between 4ꢀ-iodoacetophenone and methyl
acrylate catalyzed by material 1a (Table 4).
(Scheme 1). In this case the triethylamine (2 equiv.) acted both as
base and as nucleophile.
In place of styrene derivatives we also investigated the use of
other starting alkene compounds. Reaction between iodobenzene
and methyl vinyl ketone gave (E)-4-phenylbut-3-en-2-one 4 in
good yield using catalyst 1a in 0.1 mol% (Scheme 2).
Reaction between several aryliodides and methyl acrylate gave
compounds 5a–i in high yields and excellent selectivity (Table 3).
When 1-bromo-4-iodobenzene or 1-bromo-3-iodobenzene were
The model reaction was carried out in parallel in different flasks.
Two reaction mixtures were quenched after 0.5 h and 1 h respec-
tively (Table 4, entries 1 and 3). Other two reactions were filtered
after 0.5 h or after 1 h and the resulting filtrates were heated at 90 ◦C
for further 21 h (Table 4, entries 2 and 4). After 0.5 h only a minor
conversion was observed (ca. 5%, entry 1), however, after catalyst
removal a complete conversion was obtained (entry 2). When the
filtration was carried out after 1 h a higher conversion was observed
(69%, entry 3) and, again, complete conversion was reached after
21 h (entry 4).
Scheme 2. Heck reaction between methyl vinyl ketone and iodobenzene catalyzed
by 1a.
Table 3
Heck reaction between methyl acrylate and aryliodides.a
These observations are in agreement with the fact that the
leached Pd species actively catalyzed the Heck reaction. At this
stage, we wondered if under the reaction conditions, the supported
imidazolium network used for the preparation of Pd-catalyst 1a is
able to re-capture the leached Pd species as observed in the case of
Suzuki reaction under flow condition [39].
In order to verify this hypothesis, two runs of the model reac-
tions were additionally performed. In these cases, after filtrating
the reaction mixtures after 0.5 h and 1 h respectively, imidazolium-
modified silica 6 (Fig. 2) was added in sixfold the amount of
Pd-catalyst 1a normally used to run the experiments. In both cases,
the process was quenched (entries 5 and 6). Only a minor increase
in conversion, from 69% to 75%, was observed in the case of the
reaction filtered after 1 h (entry 6). These findings allow us to
hypothesize that the reaction is catalyzed by leached Pd species
and that such soluble Pd species were re-captured on the support 6
becoming not catalytically active. The latter result could be ascribed
Entry
5
Ar
Yield (%)b
1
2
3
4
5
6
A
B
C
D
E
F
G
H
I
Ph
74
92
99
97
94
84
92
94
80
4-NO2-Ph
4-COCH3-Ph
4-COOCH3-Ph
4-CH3O-Ph
3-CH3O-Ph
4-Br-Ph
7c
8d
9
3-Br-Ph
2-thienyl
a
Reaction conditions: methyl acrylate (1.5 mmol), aryliodide (1 mmol), TEA
(2 mmol), catalyst 1a (0.1 mol% 1 mg), 90 ◦C, 16 h.
b
Isolated product.
Disubstituted compound 4%.
Disubstituted compound 3%.
c
d

60
C. Pavia et al. / Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
Fig. 2. Structure of support 6.
Table 5
Pd content in materials 7 and 1b.
Entry
Material
Pd (mass%)a
Pd(II) (%)b
100
100
88
Pd(0) (%)b
1
7
7
1b
0.5
0.6
1.3
–
–
12
2c
3
a
Determined by EDX.
Determined by XPS.
Duplicated experiment.
b
c
Scheme 4. Heck reaction between methyl acrylate and aryl iodides catalyzed by
material 1a.
to the very low Pd loading on the surface of the new material (vide
infra). We repeated the reaction by using a lower amount of support
6 (twofold amount, entry 7). In the latter case, the lower amount of
support 6 did not quench the reaction and it was completed after
21 h.
Table 6
Suzuki reaction in the presence of variable amount of support 6.a
We verified our hypothesis that support 6 is able to re-capture
leached Pd species. We carried out the reaction between 4ꢀ-
iodoacetophenone and methyl acrylate on larger scale (5 mmol).
After 1 h catalyst 1a was removed by filtration and support 6 (six-
fold, 30 mg) was added. After 21 h the support 6 was recovered by
filtration and characterized. This experiment was duplicated. EDX
measurements showed the presence of Pd on material 7 (Fig. 3),
then, demonstrating that support 6 was able to capture the leached
Pd species. Moreover, XPS data indicated mainly the presence of
Pd(II) species, whereas Pd(0) species were not detected probably
because of the not good resolution of XPS spectra due to the very
low Pd content (Table 5, entries 1–2 and figures at pages S42–S43).
In order to test if catalyst 1 having a low content of Pd is catalyt-
ically active, we prepared a new material 1b containing palladium
in 1.3 wt% (determined by EDX). We used such material in the Heck
reaction between methyl acrylate and 4ꢀ-iodoacetophenone but no
reaction occurred (Scheme 3).
Entry
1
ArX
Cat.1a/Supp. 6 (wt./wt.) Conv. (%) Yield (%)b
1/0
1/2
1/3
1/4
1/6
1/6
>99
>99
27
4
99
91
20
4
2
3
4
5
0
0
6
0
0
We also carried out the reaction between methyl acrylate and
4ꢀ-iodoacetophenone by adding the sixfold or 12-fold amount of
support 6 in the starting reaction mixture (Table 4, entries 8–9).
In these cases, the reactions were complete. Since the leached Pd
species are re-captured by the support (becoming not catalytically
active) the completion of the reaction could be explained consid-
ering that a heterogeneous catalysis pathway promoted by the
starting material 1a could be also active.
In Scheme 4 is described the plausible reaction pathway. Mate-
rial 1a releases Pd species in solution. The leached Pd catalyzes
the Heck reaction. Addition of support 6 captures Pd in solution to
give material 7 that is not catalytically active because of the very
low Pd content. Only a minor amount of the starting Pd is leached
a
Reaction conditions: 4-formylphenyl boronic acid (1.13 mmol), 4-
bromobenzaldehyde (1 mmol), K2CO3 (1.2 mmol), catalyst 1a (0.1 mol% 1 mg),
EtOH/H2O (5 mL, 1:1) 50 ◦C.
b
Isolated yield.
(see Table 5, entries 1–2) then, an active role of material 1a in the
catalytic process could be taken into account.
In order to get more insight on the behavior of material 7 and
1b, we carried out EDX and XPS experiments. First, freshly prepared
catalyst 1b with low Pd content showed about 12% of Pd(0) (Table 5,
entry 3). By contrast, a Pd catalyst having the same Pd(0)/Pd(II)
ratio and a high Pd amount (10 wt%) was highly active [39]. In our
opinion, material 7 and 1b are not catalytically active because the
Pd species are strongly bound into the inner surface of the support.
Probably, the high imidazolium loading and its multilayer nature,
well stabilize the Pd species.
Since catalytic material 1a has been recently employed by us
in the heterogeneous Suzuki–Miyaura reaction, we verified if the
addition of support 6 can change the course of such reaction
(Table 6). Both mechanisms at the NPs surface [45–49] and involv-
ing homogeneous molecular Pd(II) catalysts [32,50–54] have been
suggested for the Suzuki reaction. Increasing amount of support
Scheme 3. Heck reaction between methyl acrylate and 4ꢀ-iodoacetophenone in the
presence of material 1b.

C. Pavia et al. / Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
61
Fig. 3. EDX mapping of material 7.
6 in the starting reaction mixture quenched the Suzuki reaction
between 4-formylphenyl boronic acid and 4-bromobenzaldehyde
(Table 6, entries 1–5). When a sixfold amount of support 6 was
employed no biaryl compound was obtained. The same result was
observed when a different aryl halide was used (4-iodotoluene,
entry 6). These results are in sharp contrast with the Heck reaction
between methyl acrylate and 4ꢀ-iodoacetophenone (Table 4, entry
6). In the latter case, the addition of a sixfold or even 12-fold amount
of support 6 did not quench the reaction, demonstrating that two
different mechanisms are operative. In the case of the Suzuki reac-
tion, the reaction takes place with the leached Pd species and the
reaction is quenched when a large amount of support is added. The
captured Pd species gave a non-catalytically active supported Pd
material. On the other hand, in the case of Heck reaction, the reac-
tion could be catalyzed by both leached and supported Pd species.
A similar hypothesis was given when a supported Pd catalyst on
high loading SILLP material was used in the Heck reaction between
iodobenzene and methylacrylate [33]. The accepted mechanism of
the Heck reaction involves the presence of soluble anionic inter-
mediate that can operate via a homeopathic catalytic Pd(0)–Pd(II)
cycle [55,56]. ESI-MS studies confirmed the presence of [PhPdI2]−
anionic species in solution and also [PdI3]− and its dimer [Pd2I6]2−
[33]. Such anionic species can be exchanged with bromide anion of
support 6 and then efficiently removed, as confirmed by XPS, when
a sixfold amount of support is added to the reaction mixture.
Pd catalyst (1.3 wt%). The non-catalytic activity of low loaded
Pd material can be explained assuming that such Pd species are
strongly bound in the inner surface of the multilayered structure
of the high loading silica gel-supported imidazolium salt. A sim-
ilar behavior was observed in the case of the Suzuki reaction.
These results constitute the basis for the development of an effi-
cient flow approach for the Heck reaction in which the released Pd
species could be recaptured giving a product with a minimal metal
contamination.
Acknowledgements
We gratefully acknowledge the Università degli Studi di
Palermo, the Università degli Studi di Perugia, the University of
Namur for financial support and the “Centro Grandi Apparecchia-
ture – UniNetLab – Università di Palermo funded by P.O.R. Sicilia
2000–2006, Misura 3.15 Quota Regionale”.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.molcata.2014.02.025.
References
[1] I.P. Beletskaya, A.V. Cheprakov, Chem. Rev. 100 (2000) 3009–3066.
[2] N.J. Whitcombe, K.K. Hii, S.E. Gibson, Tetrahedron 57 (2001) 7449–7476.
[3] L. Yin, J. Liebscher, Chem. Rev. 107 (2006) 133–173.
4. Conclusions
[4] L. Yin, J. Liebscher, Chem. Rev. 107 (2007) 133–173.
[5] D. Astruc, Inorg. Chem. 46 (2007) 1884–1894.
[6] J.G. De Vries, Can. J. Chem. 79 (2001) 1086–1092.
We have demonstrated that palladium (10 wt%) on a highly
cross-linked imidazolium-based material is an efficient catalyst
when used in 0.1 mol%, for the Heck reaction between aryl iodides
and alkenes (styrene derivatives, methyl vinylketone and methyl
acrylate) in DMF/H2O in the presence of TEA at 90 ◦C. Under
these conditions such catalyst released Pd species in solution and
the leached Pd species catalyzed the reaction, but in the pres-
ence of a sixfold amount of the imidazolium-based support they
were very efficiently scavenged. The new supported Pd species
(0.5–0.6 wt%) were not catalytically active as well as a low loading
[7] C. Torborg, M. Beller, Adv. Synth. Catal. 351 (2009) 3027–3043.
[8] Z. Peng, A.R. Gharavi, L. Yu, J. Am. Chem. Soc. 119 (1997) 4622–4632.
[9] F. Babudri, G.M. Farinola, F. Naso, J. Mater. Chem. 14 (2004) 11–34.
[10] Y. Lim, Y.S. Park, Y. Kang, D.Y. Jang, J.H. Kim, J.J. Kim, A. Sellinger, D.Y. Yoon, J.
Am. Chem. Soc. 133 (2011) 1375–1382.
[11] W.A. Herrmann, V.P.W. Böhm, C.P. Reisinger, J. Organomet. Chem. 576 (1999)
23–41.
[12] V. Farina, Adv. Synth. Catal. 346 (2004) 1553–1582.
[13] R.B. Bedford, C.S.J. Cazin, D. Holder, Coord. Chem. Rev. 248 (2004) 2283–2321.
[14] N. Marion, S.P. Nolan, Acc. Chem. Res. 41 (2008) 1440–1449.

62
C. Pavia et al. / Journal of Molecular Catalysis A: Chemical 387 (2014) 57–62
[15] Á. Molnár, Chem. Rev. 111 (2011) 2251–2320.
[16] Palladium-Catalyzed Coupling Reactions: Practical Aspects and Future Devel-
opments, Wiley-VCH, Weinheim, Germany, 2013.
[17] A.J. Carmichael, M.J. Earle, J.D. Holbrey, P.B. McCormac, K.R. Seddon, Org. Lett.
1 (1999) 997–1000.
[18] H. Zhao, S.V. Malhotra, Aldrichim. Acta 35 (2002) 75–83.
[19] C.C. Cassol, A.P. Umpierre, G. Machado, S.I. Wolke, J. Dupont, J. Am. Chem. Soc.
127 (2005) 3298–3299.
[36] H.A. Beejapur, F. Giacalone, R. Noto, P. Franchi, M. Lucarini, M. Gruttadauria,
ChemCatChem 5 (2013) 2991–2999.
[37] M. Gruttadauria, L.F. Liotta, A.M.P. Salvo, F. Giacalone, V. La Parola, C. Aprile, R.
Noto, Adv. Synth. Catal. 353 (2011) 2119–2130.
[38] M. Gruttadauria, L.A. Bivona, P. Lo Meo, S. Riela, R. Noto, Eur. J. Org. Chem. 2012
(2012) 2635–2642.
[39] C. Pavia, E. Ballerini, L.A. Bivona, F. Giacalone, C. Aprile, L. Vaccaro, M. Grut-
tadauria, Adv. Synth. Catal. 355 (2013) 2007–2018.
[20] V.I. Pârvulescu, C. Hardacre, Chem. Rev. 107 (2007) 2615–2665.
[21] F. Bellina, C. Chiappe, Molecules 15 (2010) 2211–2245.
[22] J.C. Xiao, B. Twamley, J.M. Shreeve, Org. Lett. 6 (2004) 3845–3847.
[23] L. Zhou, L. Wang, Synthesis (2006) 2653–2658.
[24] Y. Liu, S.S. Wang, W. Liu, Q.X. Wan, H.H. Wu, G.H. Gao, Curr. Org. Chem. 13
(2009) 1322–1346.
[40] R. Buscemi, F. Giacalone, S. Orecchio, M. Gruttadauria, ChemPlusChem (2014),
http://dx.doi.org/10.1002/cplu.201300361.
[41] N.T.S. Phan, M. Van Der Sluys, C.W. Jones, Adv. Synth. Catal. 348 (2006) 609–679.
[42] M. Weck, C.W. Jones, Inorg. Chem. 46 (2007) 1865–1875.
[43] K. Yu, W. Sommer, J.M. Richardson, M. Weck, C.W. Jones, Adv. Synth. Catal. 347
(2005) 161–171.
[25] S.A. Forsyth, U. Fröhlich, P. Goodrich, H.Q.N. Gunaratne, C. Hardacre, A. McKe-
own, K.R. Seddon, New J. Chem. 34 (2010) 723–731.
[26] Y. Gu, G. Li, Adv. Synth. Catal. 351 (2009) 817–847.
[27] H. Hagiwara, Synlett 23 (2012) 837–850.
[28] V. Sans, F. Gelat, M.I. Burguete, E. Garcia-Verdugo, S.V. Luis, Catal. Today 196
(2012) 137–147.
[29] D. Elhamifar, B. Karimi, J. Rastegar, M.H. Banakar, ChemCatChem 5 (2013)
2418–2424.
[44] J.M. Richardson, C.W. Jones, J. Catal. 251 (2007) 80–93.
[45] R. Narayanan, M.A. El-Sayed, J. Am. Chem. Soc. 125 (2003) 8340–8347.
[46] C.M. Crudden, M. Sateesh, R. Lewis, J. Am. Chem. Soc. 127 (2005) 10045–10050.
[47] C.P. Mehnert, D.W. Weaver, J.Y. Ying, J. Am. Chem. Soc. 120 (1998)
12289–12296.
[48] M.T. Reetz, G. Lohmer, Chem. Commun. 0 (1996) 1921–1922.
[49] N.T.S. Phan, D.H. Brown, H. Adams, S.E. Spey, P. Styring, Dalton Trans. (2004)
1348–1357.
[30] M.H.G. Prechtl, J.D. Scholten, J. Dupont, Molecules 15 (2010) 3441–3461.
[31] V. Sans, F. Gelat, N. Karbass, M.I. Burguete, E. García-Verdugo, S.V. Luis, Adv.
Synth. Catal. 352 (2010) 3013–3021.
[32] K. Köhler, W. Kleist, S.S. Pröckl, Inorg. Chem. 46 (2007) 1876–1883.
[33] M.I. Burguete, E. García-Verdugo, I. Garcia-Villar, F. Gelat, P. Licence, S.V. Luis,
V. Sans, J. Catal. 269 (2010) 150–160.
[50] J. Hu, Y. Liu, Langmuir 21 (2005) 2121–2123.
[51] Z. Niu, Q. Peng, Z. Zhuang, W. He, Y. Li, Chem. Eur. J. 18 (2012) 9813–9817.
[52] K. Köhler, R.G. Heidenreich, S.S. Soomro, S.S. Pröckl, Adv. Synth. Catal. 350
(2008) 2930–2936.
[53] F. Zhao, M. Shirai, Y. Ikushima, M. Arai, J. Mol. Catal. A: Chem. 180 (2002)
211–219.
[34] M. Gruttadauria, F. Giacalone, R. Noto, Green Chem. 15 (2013)
2608–2618.
[54] S.S. Pröckl, W. Kleist, M.A. Gruber, K. Köhler, Angew. Chem. Int. Ed. 43 (2004)
1881–1882.
[35] E. Montroni, M. Lombardo, A. Quintavalla, C. Trombini, M. Gruttadauria, F.
Giacalone, ChemCatChem 4 (2012) 1000–1006.
[55] J.G. de Vries, Dalton Trans. 0 (2006) 421–429.
[56] D. Astruc, Inorg. Chem. 46 (2007) 1884–1894.