Heck reaction catalyzed by a recyclable palladium supported on shell powder

Article abstract of DOI:10.1002/aoc.1657

Anovel palladium catalyst supported on shell powder has been prepared, and its application to the Heck reaction of aryliodides with olefins has been reported. The results showed that the novel catalyst had extremely high activities for the reactions with the average yield over 90%. Also, this catalyst showed excellent stability in Heck reactions, being reused three times. The catalyst was characterized by X-ray powder diffraction and field-emission scanned electron microscopy images, and the energy dispersive X-ray analyzer. Copyright

Full text of DOI:10.1002/aoc.1657

Full Paper
Received: 18 December 2009
Revised: 4 February 2010
Accepted: 14 March 2010
Published online in Wiley Interscience: 24 May 2010
(www.interscience.com) DOI 10.1002/aoc.1657
Heck reaction catalyzed by a recyclable
palladium supported on shell powder
Yong-Miao Shena, Yi-Jun Dub, Min-Feng Zenga, Duo Zhia, Sheng-Xian Zhaoc,
Lin-Mei Rongc, Shao-Qin Lvc, Lin Dub and Chen-Ze Qia∗
A novel palladium catalyst supported on shell powder has been prepared, and its application to the Heck reaction of aryl iodides
with olefins has been reported. The results showed that the novel catalyst had extremely high activities for the reactions with
the average yield over 90%. Also, this catalyst showed excellent stability in Heck reactions, being reused three times. The
catalyst was characterized by X-ray powder diffraction and field-emission scanned electron microscopy images, and the energy
c
dispersive X-ray analyzer. Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: shell powder; supported palladium; Heck reaction
Introduction
dried at 100 ◦C, and then sieved with 150–200 mesh. The SP was
employed as a support. The supported Pd–SP was prepared by
dipping: the PdCl2 (4.17g, 23.5 mmol) was dissolved in aqueous
NaCl (4g in 60 ml H2O) to give a solution of Na2[PdCl4]. Then
the complex solution was introduced into SP (47.5 g) suspended
in water (150 ml) under stirring. The solution was stirred until
colorless for 20 min. The SP-supported Pd was allowed to settle,
decanted and washed with water repeatedly until it was free of
Cl−. Ethanol (200 ml) was added to the precipitate, which was
reduced with hydrogen. After being filtered and dried, the 5%
Pd–SP catalyst was obtained and stored under sealing.
Pd-catalyzed cross-coupling reactions have become the most
important reactions for forming carbon–carbon bonds in organic
synthesis.[1,2] The Pd-catalyzed Heck reaction between aryl halides
and olefins has proved to be one of the most powerful tool for the
formation of Csp2–Csp2 bonds.[3–6] The traditional Heck reaction
is generally catalyzed by soluble Pd(II) or Pd(0) complexes[7–10]
and the homogeneous process often suffers from the problems of
separationandrecyclingoftheexpensivePdcatalystfromreaction
mixture. To overcome these problems, it is highly desirable to
develop heterogeneous catalysts for the Heck reaction.[11–13]
Pd supported on various materials such as activated charcoal,
metal oxide or zeolites has been applied to the Heck reaction.[14,15]
Kohler et al. investigated Pd supported on a series of activated
carbon catalysts and found that the catalytic activity could be
greatly improved by enhancing the Pd dispersion.[16] Palladium
has also been supported on MgO, Al2O3, TiO2, CaCO3 and ZnO
and used as a catalyst in the Heck reaction.[17–19] In comparison
to homogenous catalytic processes, the heterogeneous catalysis
can facilitate the catalyst separation from the reaction mixture,
simplify catalyst recovery and recycling, and eventually meet
the demands of green chemistry.[20,21] Despite their synthetic
advantages, heterogeneous palladium catalysts for such a cross-
coupling have been much less explored.
Characterization of the Pd–SP Catalyst
The novel catalyst was characterized by X-ray powder diffraction
(Shimadzu XRD-6000) with graphite monochromatized Cu Kα
radiation (k = 0.154060 nm), employing a scanning rate of 0.02
deg s−1 in the 2θ range from 10 to 90◦. The field-emission scanned
electron microscopy (FE-SEM) images and energy dispersive
X-ray analysis (EDXA) were obtained on an S-4800 field-emission
scanning electron microscope with an accelerating voltage of
5 kV. The GC-MS analysis was carried out on a GC 6890/5975 MSD
instrument and rate of increase of the temperature was 10 ◦C/min
◦
1
from 140 to 270 C, maintained for 2 min at every step. The H
NMR spectra were recorded on a Avance 400 MHz spectrometer
using CDCl3 as solvent and TMS as internal standard.
Here we present a novel palladium catalyst supported on shell
powder (SP) and investigate its catalytic activities for the Heck
reaction of aryl iodides with olefins. The results showed that the
novel catalystis very efficient for the reactions, with high yield,
excellent regio- and stereochemical selectivity and easy recovery.
∗
Correspondence to: Chen-Ze Qi, Institute of Chemistry and Chemical Engineer-
ing, Shaoxing University, Shaoxing 312000, China.
E-mail: Qichenze@usx.edu.cn
Experimental
a
InstituteofChemistryandChemicalEngineering,ShaoxingUniversity,Shaoxing
312000, China
Preparation of Pd–SP Catalyst
The shells used in this study were the bivalve shells of Hyriopsis
cumingii, obtained from Zhuji Pearl Farming, Zhejiang Province,
China.[22] The shell was ground after being cleaned with water and
b
c
College of Yuanpei, Shaoxing University, Shaoxing, 312000, China
Esteve Huayi Pharmaceutical Co., LTD., Shaoxing, 312000, China
c
Appl. Organometal. Chem. 2010, 24, 631–635
Copyright ꢀ 2010 John Wiley & Sons, Ltd.

Y.-M. Shen et al.
catalystwasaddedtothereactorwithEtOH(5 ml), andactivatedat
hydrogenatmospherewithstirringatroomtemperature.TheEtOH
was removed under reduced pressure and blown with hydrogen.
Then reaction materials were added under argon atmosphere and
the reaction proceeded as described in the general procedure for
the coupling reaction.
Results and Discussion
Characterizations of the Pd–CP
The support SP contained mainly CaCO3 in the form of aragonite,
together with small amount of organic phase.[22] The XRD patterns
of SP and Pd–SP are shown in Fig. 1. It can be seen that the
diffraction peaks of Pd–SP and SP are almost the same. All sharp
peaks could contribute to the diffraction of the supporting SP. No
peak of palladium was detected for Pd–SP, which confirmed that
the Pd was dispersed uniformly on the SP with the Pd crystallites
(below the XRD detection limit) or an amorphous Pd phase.[25]
Figure 2 shows the Pd–SP composition measured by EDXA. The
distribution of Pd atoms supported on SP was uniform, with no
evidence of clustering at the micronscale.
Figure 1. XRD patterns of samples: (A) SP, (B) Pd–SP.
General Procedure for Coupling Reaction
In 20 ml of tabular reactor, the aryl iodides (1 mmol), n-butyl
acrylate (2 ml), DMSO (5 ml), Pd catalyst (5 mol% based on
substrate, 0.05 mmol), cesium fluoride (3 mmol) and solvent (5 ml)
were added under argon atmosphere, and stirred at 135 ◦C. The
reaction was monitored by TLC. On completion, the reaction
mixture was cooled to room temperature, and quenched with
10 ml of water. The mixture was extracted three times with ethyl
acetate (3 × 20 ml), combined the organic layers and washed with
water (3 × 20 ml), then with saturated brine, dried on anhydrous
Na2SO4 and filtered.[23,24] The solution obtained was determined
by GC-MS. The solvents were evaporated under reduced pressure.
The residue was purified by chromatography on silica gel
(n-hexane and n-hexane : ethyl acetate, 8 : 1, as eluants) to afford
the corresponding product.
Catalytic Activity of Pd–SP
The catalytic activity of Pd–SP for the Heck coupling reaction
was examined. To figure out the optimal catalytic system, various
reaction conditions including temperature, solvent and base were
examined for the reaction of iodobenzene and n-butyl acrylate.
The results are summarized in Table 1. The yield increased with
the reaction temperature and complete conversion was achieved
when the temperature was increased to 135 ◦C (entries 1–5).
Solvents also had a major effect on the reaction (entries 6–13) and
DMSO gave the best yields and clean selectivity of the coupling
product. Among the various bases tested in DMSO (entries 14–20),
cesium fluoride gave the best result. Consequently, 5 mol% of
Pd–SP in DMSO in the presence of cesium fluoride at 135 ◦C was
found to be the most effective condition.
ToexaminethesuitablescopeofthePd–SPcatalyticsystem, the
catalytic activities for a variety of aryl iodides and olefins under the
optimized reaction conditions were tested (Table 2). It was found
that aryl iodides which contain electron-donating groups give
favorite yields and the yields of electron-poor aryls were relatively
low,especiallytheiodbenzenecontaininganitrogroupwithayield
of 72.2%. Likewise the stereoselectivities were dropped while the
Recovery and Activating Procedure of the Pd–SP Catalyst
After completing reaction, the catalyst was filtered. Then it was
suspended in ethyl acetate (5–10 ml), stirred for 2–3 min and
decanted. This treatment was repeated once again with ethyl
acetate, then with H2O three times and with EtOH twice. Finally
it was dried under vacuum at 50–70 ◦C. In the next reaction, the
(a)
(b)
Figure 2. (a) TEM images of 5% Pd–SP; (b) EDXA of the 5% Pd–SP.
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2010, 24, 631–635

Heck reaction catalyzed by a recyclable palladium
Table 1. Effects of temperature on the coupling reactiona
O
O
Pd/SP 5mol%
Base, Solvent
O
O
+
I
3
2
1
Entry
Temperature (◦C)
Solvent
Base
Yield (%)b
1
70
90
DMSO
DMSO
CsF
CsF
CsF
56.9
60.3
87.5
98.7
98.9
100
22.9
35.5
69.2
6.4
2
3
120
135
145
135
135
135
135
135
135
135
135
135
135
135
135
135
135
135
DMSO
4
DMSO
CsF
5
DMSO
CsF
6
DMSO
CsF
7
Ethanol
Isopropanol
DMF
CsF
8
CsF
CsF
9
10
11
12
13
14
15
16
17
18
19
20
Toluene
Acetonitrile
1,4-Dioxane
DMAC
CsF
CsF
0
CsF
42.5
90.5
14.0
97.5
98.7
86.9
91.3
98.0
78.2
CsF
DMSO
–
DMSO
K2CO3
CSF
EtONa
KF
DMSO
DMSO
DMSO
DMSO
KOAC
KOH
DMSO
a Reagents and conditions: iodobenzene, 1 mmol; n-butyl acrylate, 2 mmol; base, 3 mmol; solvent, 3 ml; Pd–SP, 5 mol%; 5 h. b GC-MS yield.
Table 2. Heck reaction of aryl iodides with olefinsa
Temperature
(◦C)
Yield
Entry
Aryl iodides
Olefins
3
Time (h)
(cis:trans, %)b
1
p-MeC6H4I
p-MeCOC6H4I
p-ClC6H4I
p-FClC6H4I
p-BrC6H4I
p-MeOC6H4I
p-NH2C6H4I
p-O2NC6H4I
p-EtO2CC6H4I
C6H5I
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
n-Butyl acrylate
Acrylonitrile
a[26]
b[27]
c[28]
d[29]
e[26]
f[27]
5
5
135
135
135
135
135
135
135
135
135
135
90
99.1 (0.5 : 99.5)
97.7 (0.4 : 99.6)
99.1 (0.8 : 99.2)
99.8 (1.2 : 98.3)
99.6 (0.5 : 99.1)
96.9 (12.3 : 87.7)
98.8 (1.2 : 98.8)
72.2 (11.4 : 88.6)
94.5 (12.6 : 87.4)
99.7 (1.8 : 98.2)
92.0 (28.8 : 71.2)
97.7(1.1 : 98.9)
74.8 (47.1 : 52.9)
2
3
8
4
8
5
5
6
8
7
g[26]
h[26]
i[30]
20
20
8
8
9
10
11
12
13
j[27]
5
C6H5I
k[31]
28
25
12
C6H5I
Methyl acrylate
Methyl methacrylate
l[32]
90
C6H5I
m[26]
90
a Reagents and conditions: iodobenzene, 1 mmol; olefins, 2 mmol; cesium fluoride, 3 mmol; DMSO, 3 ml; temperature, 135 ◦C; Pd–SP, 5 mol%. b GC-MS
yield.
substrates with electron-withdrawing groups were applied to the
reaction (entries 6, 8 and 9). Besides the aryl iodides, various olefin
derivative were also investigated in the reactions (entries 11–13).
The supported palladium catalyst also showed high activities for
various olefins with excellent yields. The methyl group attached
to the C C bond had a significant influence on the reaction of
methyl methacrylate. The steric hindrance of the methyl group not
only decreased the yield, but also dropped the stereoselectivity of
methyl methacrylate to cis : trans = 47.1 : 52.9.
Recycling of the Catalyst
The performance of the recycled catalyst for the reaction up
to three successive runs is summarized in Table 3. The catalytic
activities of recovered shell powder-supported palladium catalyst
c
Appl. Organometal. Chem. 2010, 24, 631–635
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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Y.-M. Shen et al.
crystalline palladium is a little clustered at the catalyst surface after
the catalyst has been used four times.
Table 3. Catalytic activities of the recovered catalysta
Cycles
Time (h)
Temperature (◦C)
Yieldb (cis:trans, %)
5
5
5
5
135
135
135
135
99.7 (1.9 : 98.1)
97.2 (2.7 : 97.3)
96.7 (1.2 : 98.8)
96.9 (1.2 : 98.8)
Conclusion
First
Second
Third
In conclusion, a novel, efficient procedure for Heck coupling
using palladium supported on a shell powder catalyst has been
developed successfully. The novel catalyst exhibited high activity
and stability for the Heck arylation reactions of aryl iodides with
olefins. The average yields of most reactions were up to 95%
with high regio- and stereoselectivities. The catalyst can be easily
recovered and reused at least three times without loss of activity.
a
Reagents and conditions: iodobenzene, 1 mmol; n-butyl acrylate,
2 mmol; cesium fluoride, 3 mmol; DMSO, 3 ml; Pd–SP, 5 mol%.
Determined by GC-MS.
b
remained almost the same for the Heck coupling reaction of n-
butyl acrylate and iodobenzene. These results indicated that the
Pd–SP catalyst was very stable in this reaction, and could be
reused conveniently. Furthermore, the SEM images of the recycled
catalyst showed no changes of the morphologies even after the
catalyst had been cycled three times (Fig. 3). The XRD patterns
of Pd–SP after one reaction cycle and Pd–SP after four reaction
cycles are shown in Fig. 4. One weak peak 38.8 could be assigned
to the diffraction of the palladium [Pd(222)], which shows that
Acknowledgments
We thank the Natural Science Foundation of Zhejiang Province
(nos Y4080450 and Y4080395) for financial support.
Supporting information
Supporting information may be found in the online version of this
article.
(a)
(b)
Figure 3. (a) TEM images of the recovered 5% Pd–SP after four reaction cycles; (b) EDXA of the 5% Pd–SP after four reaction cycles.
Pd 222
(B)
Pd 222
(A)
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Two-Theta/degree
Figure 4. XRD patterns of samples: (A) Pd–SP after one reaction cycle; (B) Pd–SP after four reaction cycles.
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2010, 24, 631–635

Heck reaction catalyzed by a recyclable palladium
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