Highly efficient and expeditious PdO/SBA-15 catalysts for allylic oxidation of cyclohexene to cyclohexenone

Article abstract of DOI:10.1039/c2cy20627g

A series of four PdO/SBA-15 catalysts with 1, 2, 4, 5% (by weight) loading of PdO have been prepared by a conventional impregnation method and are characterized by N₂-adsorption, low-angle and wide-angle XRD, XPS and TEM techniques. The catalys

Full text of DOI:10.1039/c2cy20627g

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Highly efficient and expeditious PdO/SBA-15 catalysts
for allylic oxidation of cyclohexene to cyclohexenone
Cite this: Catal. Sci. Technol., 2013,
3, 409
Saidulu Ganji, Padma Bukya, Venkateswarlu Vakati, Kamaraju Seetha Rama Rao
and David Raju Burri*
Received 7th September 2012,
Accepted 22nd November 2012
DOI: 10.1039/c2cy20627g
www.rsc.org/catalysis
A series of four PdO/SBA-15 catalysts with 1, 2, 4, 5% (by weight) on the catalytic methods for allylic oxidation including Cr/MCM-41,
loading of PdO have been prepared by a conventional impregnation Cr/MCM-48,7 Co/Al2O3,8 Ti/MCM-41,9 Co/SBA-15,10 cobalt resinate,11
method and are characterized by N2-adsorption, low-angle and wide- and Cu-amp.12 However, these methods have poor conversion and
angle XRD, XPS and TEM techniques. The catalysts exhibited very high selectivities, and new catalytic systems are still desired.
conversion of cyclohexene and high selectivity of cyclohexenone with
Recently, there have been reports on high activity/selectivity/
70% t-BuOOH in CH3CN. The structural and textural characteristics of olefin/cyclohexene oxidations. Wang et al. reported that the
catalysts play a crucial role in high conversion and selectivity.
SBA-15 supported Au nanoparticles are catalytically active and
efficiently recyclable catalysts in olefin oxidations.13 Ghiaci et al.
reported that Ru/Co/Ce trimetallic hybrid mixed oxide nano-particles
are efficient for cyclohexene oxidation.14 Zhu and Diao developed
CuO nanorods for the oxidation of cyclohexene.15 None of these
methods meet the requirement of 100% conversion and 99%
selectivity.
During the past decades, palladium-mediated catalysis has
been recognized as one of the most powerful synthetic tools
and as a fascinating area in organic transformations for both
academic research and industrial processes.16–20 It has also
been recognized that Pd(II) systems were efficient catalysts for
oxidation reactions.21–27
Introduction
Allylic oxidation of olefins to a,b-unsaturated ketones, particularly
cyclohexene to cyclohexenone, is an important and useful trans-
formation in both chemical and pharmaceutical industries.1–6
However, the present commercial processes rely on the age-old
environmentally harmful technologies. With the emergent
trepidation for environmental pollution and ever escalating
stringent specification for effluents, there has been a pressing
need to curtail the formation of unwanted by-products. The
conversion and selectivity are the two sides of a coin. Augmenting
the selectivity without foregoing the conversion is a challenge to
the scientific society, particularly in the hydrocarbon oxidation
processes. For instance, in the oxidation of cyclohexene the
formation of several oxygenated products like cyclohexenone,
cyclohexenol, cyclohexene epoxide, di-(2-cyclohexenyl) ether and
cyclohexane-1,2-diol is reported and furthermore, cyclohexanol
and cyclohexane are the two main products of the Whacker
process from cyclohexene. Hence, selectivity control by ceasing
all of these by-products is a key issue, overcoming of this
barrier resolves the problem of separation of cyclohexenone
from the product mixture as well as its further purification for a
particular application.
So far, no heterogeneous catalyst for the complete conversion
of cyclohexene into cyclohexenone with 99% selectivity has been
reported. Hence, herein for the first time, a highly efficient and
expeditious PdO/SBA-15 catalyst for the selective allylic oxidation
of cyclohexene with t-BuOOH has been delineated.
Preparation of catalysts
All the reagents and chemicals were obtained commercially and
used without further purification. The siliceous SBA-15 was synthe-
sized in accordance with the literature procedures.28 A solution of
EO20PO70EO20 : 2M HCl : TEOS : H2O = 2 : 60 : 4.25 : 15 (mass
ratio) was prepared, stirred for 12 h at 40 1C and then hydro-
thermally treated at 100 1C under static conditions for 12 h,
subsequently filtered, dried at 100 1C and calcined at 550 1C for
8 h, the yielded white powder is mesoporous silica SBA-15,
which is used as a support, it is also known as a parent SBA-15.
To prepare mesoporous SBA-15 supported palladium catalysts
(PdO/SBA-15), the SBA-15 support was dried at 120 1C for 6 h
and cooled to room temperature and divided into four parts
Development of oxidizing methods requiring only a catalytic
amount of metal reagent in combination with an appropriate
stoichiometric oxidant is a subject of interest. There are reports
Catalysis Laboratory, Indian Institute of Chemical Technology, Hyderabad-500607,
India. E-mail: david@iict.res.in; Fax: +91-40-27160921; Tel: +91-40-27191712
c
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and the requisite amounts of aqueous PdCl2 solution were added to
each part of the SBA-15 support to be around 1, 2, 4 and 5 wt% as
palladium oxide (PdO). These catalyst samples were dried at 100 1C
for 12 h and calcined at 500 1C for 6 h and denoted PdO/SBA-15
and the number prefixed to PdO/SBA-15 indicates the percentage
loading of PdO on the SBA-15 support by weight.
Characterization of catalysts
The X-ray diffraction (XRD) patterns were recorded at room tem-
perature using an X-ray diffractometer (Multiflex, M/s. Rigaku,
Japan) with a nickel filtered CuKa radiation. N2 adsorption–
desorption isotherms were recorded on a N2 adsorption unit
at ꢀ196 1C (Quadrasorb-SI V 5.06, M/s. Quantachrome Instruments
Corporation, USA). The samples were outgassed at 200 1C for 4 h
before the measurement. Transmission electron microscopic (TEM)
analysis was made using a Philips Tecnai G2 FEI F12 at an
accelerating voltage of 80–100 kV. The XPS analysis was made
using a photoelectron spectrometer (KRATOS Axis 165, Shimadzu,
Japan) with Mg Ka radiation (1253.6 eV).
Fig. 1 Low-angle XRD patterns of PdO/SBA-15 catalysts.
Liquid-phase oxidation of cyclohexene
In a typical experiment, 50 mg of PdO/SBA catalyst were
dispersed in 3 ml of acetonitrile in a 10 ml capacity round
bottom flask fitted with a water condenser, which is open to air.
Subsequently, 1 mmol of cyclohexene and 2 mmol of oxidant
were added and the reaction was conducted at 85 1C under
constant stirring. The product analysis was made using a gas
chromatograph (GC-17A, M/s. Shimadzu Instruments, Japan)
with an OV-1 capillary column (0.53 mm ꢁ 30 m). The products
were identified using a GC-MS (QP-5050 model, M/s. Shimadzu
Instruments, Japan) equipped with a DB-5 capillary column
(0.32 mm dia. and 25 m long, M/s. J & W Scientific, USA).
Fig. 2 N2 adsorption–desorption isotherms of PdO/SBA-15 catalysts and their
Results and discussion
pore size distribution curves are shown in the inset.
A series of four SBA-15 supported palladium oxide catalysts,
such as 1PdO/SBA-15(0.81%), 2PdO/SBA-15(2.14%), 4PdO/SBA- with the IUPAC classification,29 which indicates that the parent
15(4.18%) and 5PdO/SBA-15(5.20%), were prepared by a con- SBA-15 mesoporous structure was well maintained during the
ventional impregnation method. The percentage (by weight) stages of catalyst preparation.
given in the parentheses is the loading of PdO determined from
atomic absorption spectroscopy.
However, there is a gradual decrease in the surface area and
total pore volume as the PdO loading increases on the surface
To assess the structural integrity of the catalysts, low-angle of the SBA-15 support (Table 1), which suggests that as the PdO
XRD patterns of PdO/SBA-15 catalysts including parent SBA-15 loading increases the agglomeration of PdO particles increases
were recorded and the resultant patterns are shown in Fig. 1. (the particle size of PdO with increased loading is as follows: 38,
The parent SBA-15 and PdO/SBA-15 catalysts with various PdO 40, 42 and 48 nm, calculated by Scherrer’s equation) leading
loadings exhibited well-resolved peaks with a sharp peak at about to partial blockage of pores.30,31 As shown in Table 1, no
0.911 and two weak peaks at about 1.561 and 1.791. Similar to that substantial variation in the structural parameters, like d spacing,
of parent silica SBA-15 the calcined PdO/SBA-15 catalysts also unit cell length and pore wall thickness, implies the retention of
exhibited three diffraction peaks positioned at 0.91–0.961, 1.57– the parent SBA-15 mesophase structure in all the PdO/SBA-15
1.621, and 1.81–1.851 on the 2y scale, revealing the retention of catalysts.
mesoporous structural ordering. The position of diffraction peaks
is well matched with the reported XRD patterns of SBA-15.28
To evaluate the crystalline behavior of palladium oxide
species that dispersed on the surface of SBA-15 support X-ray
Fig. 2 shows the N2 adsorption–desorption isotherms of diffraction analysis was made in the 2y range of 5–801 (Fig. 3).
PdO/SBA-15 catalysts together with the parent SBA-15. The The XRD reflections that appear at 2y = 33.69, 41.8, 54.5, 60.69
isotherms obtained for parent SBA-15 and Pd/SBA-15 are of and 71.281 for the respective crystal planes (101), (110), (112),
type IV and exhibited a hysteresis loop of H1 type in accordance (200) and (202) reveal the presence of palladium oxide species
c
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Table 1 Textural and structural parameters of PdO/SBA-15 catalysts obtained
from N2 sorption data and low-angle XRD analysis respectively
Catalyst
SBA-15
1PdO/SBA-15 652
2PdO/SBA-15 611
4PdO/SBA-15 589
5PdO/SBA-15 560
SBETa/m2 gꢀ1 Vtb/cm3 gꢀ1 Dc/nm d1ood/nm aoe/nm tf/nm
689
1.08
1.01
0.94
0.91
0.84
6.3
6.2
6.1
6.2
6.0
9.65
9.41
9.09
9.33
9.45
11.1
10.9
10.5
10.8
10.9
4.9
4.7
4.4
4.6
4.9
a
b
c
BET surface area. Total pore volume. BJH pore diameter.
d
e
Periodicity of SBA-15 derived from low angle XRD. Unit cell length
f
(a0 = 2d100/O3). Pore wall thickness (t = a0 ꢀ D).
Fig. 3 Wide-angle XRD patterns of PdO/SBA-15 catalysts.
as the tetragonal form of PdO according to card no. JCPDS 43-
1024. A broad peak that appears in all the patterns at 2y =
21.51–21.851 is responsible for the SiO2 phase of SBA-15. As the
loading of PdO increases the intensity of the main peak (2y =
33.691) also increases in order, which implies the increment in
size of crystalline PdO particles.
Fig. 4 XPS spectra of (a) 1PdO/SBA-15, (b) 2PdO/SBA-15, (c) 4PdO/SBA-15 and
The X-ray photoelectron spectra obtained for PdO/SBA-15 cata-
lysts are depicted in Fig. 4, in which the Pd3d5/2 binding energy of
337.4 eV is attributed to bulk and dispersed PdO.32,33 The higher
(d) 5PdO/SBA-15 catalysts.
Pd3d3/2 binding energy at 342.8 eV can be assigned to extremely of oxidizing cyclohexene completely into cyclohexenone alone,
small PdO particles with a chemical shift of 1.2 eV for Pd2+–Pd0.
The TEM image of 2PdO/SBA-15 catalyst reveals that the PdO
various reaction parameters are systematically investigated.
It is well known that in a particular oxidation process, the
deposited on the surface of the SBA-15 support is in the form of oxidant plays a crucial role. Hence, to find a suitable oxidant for
nanorods. Similar kind of nano-rod formation in SBA-15 channels the improved selectivity, different oxidants such as aqueous
has been reported.34 The average diameter of the PdO nanorods is H2O2 (30%), aqueous t-BuOOH (70%), urea H2O2 and molecular
around 13.1 nm, which are shown in Fig. 5.
oxygen are used. Keeping the reaction vessel open to air, the
As shown in Scheme 1 and reported by several authors,35–41 the cyclohexene oxidation reactions were conducted at 85 1C for
main oxidation products of cyclohexene are (I) cyclohexane oxide, (II) 12 h using 50 mg of 2PdO/SBA-15 catalyst, 1 mmol of cyclohex-
cyclohexane-1,2-diol, (III) 3-hydroperoxycyclohex-1-ene, (IV) cyclohex- ene, 2 mmol of oxidant and 3 ml of acetonitrile. A significant
enol and (V) cyclohexenone. According to Weiner et al., selectivity of increase both in the conversion and selectivity was observed,
the above cited products varies with the catalyst, oxidant, tempera- which can be seen from Table 2. In all the cases the major
ture, time, pressure and solvent so on and so forth.42
product is cyclohexenone and the minor one is cyclohexenol
Despite the formation of several products in the cyclohexene over 2PdO/SBA-15 catalyst. Particularly, with t-BuOOH oxidant,
oxidation (shown in Scheme 1), selective formation of cyclo- the 2PdO/SBA-15 exhibited high activity with 100% conversion
hexenone is the cutting-edge of this publication. To meet the goal and 99% selectivity. To understand the catalytic behavior of
c
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t-BuOOH is an efficient oxidant for the selective conversion of
cyclohexene into cyclohexenone. The oxidation of cyclohexene
takes place via two different routes, such as allylic C–H bond
oxidation and epoxidation of the CQC bond. As reported, in
the oxidation of cyclohexene with t-BuOOH, the attack of the
C–H bond is preferred instead of the epoxidation of the CQC
bond.43,44 One of the important reasons for high selectivity in
the present study is due to preferential attack of the C–H bond
in the presence of t-BuOOH and in addition controlled transpor-
tation of reactants in the uniformly ordered pores.45 So t-BuOOH
is a best oxidant for our catalytic system.
Once it is found that the best oxidant is t-BuOOH, its optimal
amount is verified and the results are shown in Fig. 6. With an
increase in the t-BuOOH to cyclohexene molar ratio, i.e., 0.5 to 2,
the conversion increased from 92.8% to 100% and the selectivity
also increased from 81.6% to 99.8%, which may be due to higher
availability of oxidant molecules. However, with further increase
in the amount of t-BuOOH, i.e., 2 to 3, the conversion remained
almost unchanged. Hence, the optimum amount of t-BuOOH is
found to be 2 moles per mole of cyclohexene.
Fig. 5 TEM image of 2PdO/SBA-15 catalyst.
To attest to that the cyclohexene oxidation is a catalytic
process, an experiment was conducted without adding the
catalyst at 85 1C for 12 h with 1 mmol of cyclohexene, 2 mmol
of t-BuOOH in 3 ml of CH3CN solvent. No appreciable conversion
is observed (B6%), which proves that the particular oxidation
process is catalytic. Under identical conditions another experi-
ment was conducted using SBA-15 support as a catalyst and found
that SBA-15 is capable of converting cyclohexene into cyclo-
hexenone to some extent (B25.4%). To ascertain that the catalytic
process is heterogeneous, an experiment was conducted, wherein
the catalyst was separated by centrifugation after 6 h of reaction
and the reaction was continued for further 6 h and it was found
that there is no substantial increment in the catalytic activity,
which confirms the heterogeneous nature of process. The catalytic
activity of various PdO/SBA-15 catalysts toward the oxidation of
cyclohexene to cyclohexenone with t-BuOOH has been investi-
gated and the results are depicted in Fig. 7, which reveals that
the conversion of cyclohexene is 100% and selectivity is 99% with
2 wt% PdO/SBA-15 catalyst. In the case of 1 wt% PdO/SBA-15
the conversion is 76.16% and selectivity is 94.99%.
Scheme 1 The general cyclohexene oxidation products.
PdO catalysts supported on two different forms of SiO2 supports
such as commercial SiO2 (surface area 380 m2 gꢀ1, irregular pores)
and mesoporous SBA-15 SiO2 (689 m2 gꢀ1, uniform mesopores)
are studied. It is found that structural and textural characteristics
of supports play a significant role in catalytic activity of PdO
catalysts. The 2PdO/SBA-15 catalyst exhibited higher activity than
that of 2PdO/SiO2, which may be due to high surface area and
uniform ordered mesopores of SBA-15 support.
Zhu and Diao15 reported that the conversion of cyclohexene
is 100% with 95% selectivity of cyclohexenone over CuO nano-
rods with t-BuOOH in CH3CN solvent, which reveals that
The lower conversion of 1 wt% PdO/SBA-15 catalyst may be due
to an insufficient amount of PdO. In the case of 5 wt% PdO/SBA-15
Table 2 Effect of oxidants on the oxidation of cyclohexene over 2PdO/SBA-15
catalyst
S. no
Catalyst
Oxidant
Conv. (%)
Sel. (%)
TONa
1
2
3
4
5
6
7
Nil
SBA-15
2PdO/SiO2
2PdO/SBA-15
2PdO/SBA-15
2PdO/SBA-15
2PdO/SBA-15
t-BuOOH
t-BuOOH
t-BuOOH
t-BuOOH
O2
H2O2
U H2O2
6
25
71
100
56
64
100
60
81
99
82
60
59
—
—
57.2
98.4
51.2
38.2
46.4
79
Reaction conditions: cyclohexene (1 mmol), oxidant (2 mmol), catalyst
a
(50 mg), CH3CN (3 ml), 85 1C, 12 h. Moles of product formed for a
mole of palladium.
Fig. 6 Effect of molar ratio on cyclohexene oxidation.
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Table 3 Effect of solvent on cyclohexene oxidation
S. no
Solvent
Conv. (%)
Sel. (%)
TONa
1
2
3
4
5
6
7
8
CH3CN
AcOH
CHCl3
PhCl
DCE
DMF
100
90
53
50
27
19
6
99
79
70
65
84
58
67
91
98.4
70.7
36.9
32.3
22.6
11
PhCH3
Neat
4.2
88
97
Reaction conditions: cyclohexene (1 mmol), oxidant (2 mmol), catalyst
a
(50 mg), CH3CN (3 ml), 85 1C, 12 h. Moles of product formed for a
mole of palladium.
Fig. 7 Effect of catalyst loading on cyclohexene oxidation.
the conversion is 90.33% and selectivity is 85.34%. The lower
conversion and selectivity may be due to agglomeration of PdO
particles. Hence, 2PdO/SBA-15 is the best catalyst of the series.
To evaluate the reusability of the catalyst, a series of recycling
experiments were conducted and the results are depicted in
Fig. 8, which reveals that there is no significant loss of catalytic
activity on cyclohexene oxidation.
The effect of various solvents on the oxidation of cyclohexene
with 2PdO/SBA-15 was carried out and the results are shown in
Table 3. In all the cases cyclohexenone is the major product, but the
highest conversion and selectivity were achieved in acetonitrile
solvent. Even in the absence of solvent 97% conversion and
91% selectivity are observed. The results reveal that there is a
strong influence on the nature of solvents used. With the increase
in polarity of a solvent, activity of the catalyst increased sequen-
tially. Accordingly, highly polar CH3CN solvent assisted in getting
superior activity. However, there is a discrepancy in the activity of
the catalyst in the case of DMF.
To understand the nature of the 2PdO/SBA-15 catalyst
towards the oxidation of cyclohexene, a time-on-stream experi-
ment was conducted and the results are displayed in Fig. 9,
which reveals that the induction period is about 1 to 1.5 h. At
the end of 2 and 4 h the conversions are lower, but the sole
product is cyclohexenone. At the end of 6 h, cyclohexenol also
formed as a minor product, which also appeared in 8 and 10 h
products. But at the end of 12 h the yield of cyclohexenone is
99%. As shown in the Fig. 9 inset (a), cyclohexenol that formed
was oxidized into cyclohexenone. Similar kind of observation
was made by other authors on different catalytic systems.45
Fig. 9 Effect of reaction time on cyclohexene oxidation.
PdO nanoparticles were finely deposited on the pore
surfaces of hexagonally ordered arrays of SBA-15, which can
also be considered as nanoreactors. While the reactants pass
through the nanopores of catalysts, there will be an intimate
contact with the reactive PdO nanoparticles, which may be the
reason for high activity and selectivity.
It can be concluded that the mesoporous PdO/SBA-15 catalysts
are capable of oxidizing cyclohexene with nearly 100% conversion
and 99% selectivity using t-BuOOH as an oxidant in CH3CN
solvent. The structural and textural characteristics of PdO/SBA-
15 are responsible for their higher activity.
Acknowledgements
Saidulu and Venkateswarlu are thankful to Council of Scientific
and Industrial Research (CSIR) New Delhi, for awarding
research fellowships.
Notes and references
1 T. Punniyamurthy and L. Rout, Coord. Chem. Rev., 2008, 252, 134.
2 S. E. Dapurkar, H. Kawanami, K. Komura, T. Yokoyama and
Y. Ikushima, Appl. Catal., A, 2008, 346, 112.
3 M. Salavati-Niasari, M. R. Elzami, M. R. Mansournia and
S. Hydarzadeh, J. Mol. Catal. A: Chem., 2004, 221, 169.
4 S. Mukherjee, S. Samanta, B. C. Roy and A. Bhaumik, Appl. Catal., A,
2006, 301, 79.
Fig. 8 Reusability of 2PdO/SBA-15 on cyclohexene oxidation.
c
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5 D. Jiang, T. Mallat, D. M. Meier, A. Urakawa and A. Baiker, J. Catal., 25 K. P. Peterson and R. C. Larock, J. Org. Chem., 1998, 63, 3185.
2010, 270, 26.
26 T. Nishimura, T. Onoue, K. Ohe and S. Uemura, J. Org. Chem., 1999,
64, 6750.
27 G. J. Ten Brink, I. W. C. E. Arends and R. A. Sheldon, Science, 2000,
287, 1636.
28 D. Zhao, J. Feng, Q. Huo, N. Melosh, G. H. Fredrickson,
B. F. Chmelka and G. D. Stucky, Science, 1998, 279, 548.
29 K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R. A. Pierotti,
J. Rouque0rol and T. Siemieniewska, Pure Appl. Chem., 1985, 57, 603.
30 Y. Liu, J. Zhang, W. Hou and J. J Zhu, Nanotechnology, 2008,
19, 135707.
6 R. M. Wang, Z. F. Duan, Y. F. He and Z. Q. Lei, J. Mol. Catal. A:
Chem., 2006, 260, 280.
7 A. Sakthivel, S. E. Dapurkar and P. Selvam, Appl. Catal., A, 2003,
246, 283.
8 Q. Zhang, Q.-H. Xia, X.-H. Lu, H.-J. Zhan and G. Xu, Indian J. Chem.,
2007, 46, 909.
9 G. A. Eimer, S. G. Casuscelli, G. E. Ghione, M. E. Crivello and
E. R. Herrero, Appl. Catal., A, 2006, 298, 232.
10 Y. Mi, Z. Yang, Z. Liu, F. Yang, Q. Sun, H. Tao, W. Wang and J. Wang,
Catal. Lett., 2009, 129, 499.
31 S. C. Chang and M. H. Huang, J. Phys. Chem. C, 2008, 112, 2304.
11 C. Yin, Z. Yang, B. Li, F. Zhang, J. Wang and E. Ou, Catal. Lett., 2009, 32 Y. Takasu, R. Unwin, B. Tesche and A. M. Bradshaw, Surf. Sci., 1978,
131, 440. 77, 219.
12 S. Mukherjee, S. Samanta, B. C. Roy and A. Bhaumik, Appl. Catal., A, 33 E. H. Voogt, A. J. M. Mens, O. L. J. Gijzeman and J. W. Geus, Surf.
2006, 301, 79. Sci., 1996, 350, 21.
13 L. Wang, H. Wang, P. Hapala, L. Zhu, L. Ren, X. Meng, J. P. Lewis 34 Y. J. Han, J. M. Kim and G. D. Stucky, Chem. Mater., 2000, 12, 2068.
and F. S. Xiao, J. Catal., 2011, 281, 30.
14 M. Ghiaci, B. Aghabarari, A. M. Botelho do Rego, A. M. Ferraria and
S. Habibollahi, Appl. Catal., A, 2011, 393, 225.
15 M. Zhu and G. Diao, Catal. Sci. Technol., 2012, 2, 82.
16 Handbook of Organopalladium Chemistry for Organic Synthesis, ed.
E. Negishi, John Wiley & Sons, New York, 2002.
35 J. Tong, Y. Zhang, Z. Li and C. Xia, J. Mol. Catal. A: Chem., 2006,
249, 47.
36 K. Sato, M. Aoki and R. Noyori, Science, 1998, 281, 1646.
37 Y. Chang, Y. Lv, F. Lu, F. Zha and Z. Lei, J. Mol. Catal. A: Chem., 2010,
320, 56.
38 M. S. Hamdy and G. Mul, Catal. Sci. Technol., 2012, 2, 1894.
17 J. Tsuji, Palladium Reagents and Catalysts: New Perspectives for the 39 Y. Fu, D. Sun, M. Qin, R. Huang and Z. Li, RSC Adv., 2012, 2, 3309.
21st century, John Wiley & Sons, Chichester, 2004.
18 T. W. Lyons and M. S. Sanford, Chem. Rev., 2010, 110, 1147.
40 B. P. C. Hereijgers, R. F. Parton and B. M. Weckhuysen, Catal. Sci.
Technol., 2012, 2, 951.
19 L.-M. Xu, B.-J. Li, Z. Yang and Z.-J. Shi, Chem. Soc. Rev., 2010, 39, 712. 41 K. Leus, I. Muylaert, M. Vandichel, G. B. Marin, M. Waroquier,
20 H. Wang, S.-X. Deng, Z.-R. Shen, J.-G. Wang, D.-T. Ding and
V. Van Speybroeck and P. Van Der Voort, Chem. Commun., 2010,
46, 5085.
T.-H. Chen, Green Chem., 2009, 11, 1499.
21 T. F. Blackburn and J. Schwartz, J. Chem. Soc., Chem. Commun., 1977, 42 H. Weiner, A. Trovarelli and R. G. Finke, J. Mol. Catal. A: Chem.,
157. 2003, 191, 217.
22 Y. Tamaru, Y. Yamamoto, Y. Yamada and Z. Yoshida, Tetrahedron 43 L. M. Gonzalez, A. L. Villa de P, C. Montes de Correa and A. Sorokin,
Lett., 1979, 20, 1401.
23 H. Nagashima and J. Tsuji, Chem. Lett., 1981, 1171.
Tetrahedron Lett., 2006, 47, 6465.
44 J. Liu, F. Wang and X. Xu, Catal. Lett., 2008, 120, 106.
24 S. Ait-Mohand, F. Henin and J. Muzart, Tetrahedron Lett., 1995, 45 A. A. Costa, G. F. Ghesti, J. L. de Macedo and V. S. Braga, J. Mol.
36, 2473.
Catal., 2008, 282, 149.
c
This journal is The Royal Society of Chemistry 2013
414 Catal. Sci. Technol., 2013, 3, 409--414