Reductive Ullmann coupling of aryl halides by palladium nanoparticles supported on cellulose, a recoverable heterogeneous catalyst

Article abstract of DOI:10.5560/ZNB.2013-3048

Palladium nanoparticles supported on cellulose were prepared without using any reducing agent and used as a highly efficient catalyst for the Ullmann reductive coupling of aryl halides in the presence of zinc, in a water-alcohol mixture as solvent in air. The obtained palladium nanoparticles were characterized by scanning electron microscopy (SEM), FTIR, thermogravimetric analysis (TGA) and ICP-AES analysis. The synthesis of biaryls from chloroarenes was performed by this catalyst with good yield. The catalyst remains stable up to 75 °C and can be recovered and reused several times without loss of activity.

Full text of DOI:10.5560/ZNB.2013-3048

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46
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Reductive Ullmann Coupling of Aryl
Halides by Palladium Nanoparticles
Supported on Cellulose, a Recoverable
Heterogeneous Catalyst
The Ullmann reaction [9], which is often consid-
ered as a simple homocoupling reaction, has been used
for the biaryl synthesis. In the classical method, cop-
per, high temperature and aryl iodides or bromides are
used for the reaction, and dimethylformamide is con-
sidered as a suitable solvent as (i) it can stand up to
high temperatures, (ii) its polarity accelerates the re-
action, and (iii) the products can be easily isolated
and purified using this solvent [10]. Unfortunately, the
yield of the reaction by copper is low, and the reac-
tion is sensitive to air and water. The classical Ull-
mann reaction is restricted to electron-deficient aryl
halides and is not effective for chloroarenes which
are readily accessible in large scales compared to
other haloarenes [11]. The recent trend was to per-
Mohammad Ali Rasouli and Parviz Rashidi Ranjbar
School of Chemistry, University of Tehran, Tehran,
Iran
Reprint requests to Parviz Rashidi Ranjbar.
E-mail: ranjbar@khayam.ut.ac.ir
Z. Naturforsch. 2013, 68b, 946 – 950
DOI: 10.5560/ZNB.2013-3048
Received February 14, 2013
Palladium nanoparticles supported on cellulose were pre- form this reaction under mild conditions with less
pared without using any reducing agent and used as a highly
sensitivity to water or air [12]. This has led to per-
efficient catalyst for the Ullmann reductive coupling of aryl
form the Ullmann coupling variant, catalyzed by nickel
halides in the presence of zinc, in a water-alcohol mix-
or palladium [13]. Palladium-catalyzed carbon-carbon
were characterized by scanning electron microscopy (SEM), bond forming reactions are among the most selec-
ture as solvent in air. The obtained palladium nanoparticles
FTIR, thermogravimetric analysis (TGA) and ICP-AES anal-
ysis. The synthesis of biaryls from chloroarenes was per-
tive and effective reactions in organic synthesis [14,
15]. Homogeneous Ullmann homocoupling of aryl
formed by this catalyst with good yield. The catalyst remains
◦
halides catalyzed by palladium complexes have been
reported by Rawal et al. [16]. Pd/C-catalyzed Ull-
mann coupling reactions in the presence of reduc-
ing agents like zinc [17], hydrogen [18], sodium for-
mate [19], triethylamine [20], alcohols [21], and in-
dium [22] have been developed especially in recent
years. Bamfield et al. synthesized biaryls in moder-
ate yields from haloarenes by using sodium formate
as reducing agent [19]. Various chloro- and bromoben-
stable up to 75 C and can be recovered and reused several
times without loss of activity.
Key words: Ullmann C–C Coupling, Aryl Halides,
Palladium Nanoparticles, Cellulose Support,
Recoverable Catalyst
Introduction
Green chemistry focuses on the design of chemical zenes can form biaryls via Pd/C-catalyzed Ullmann
processes to reduce generation of wastes [1]. Green coupling by using hydrogen as reducing agent in the
methods are based on two main ideas, choice of sol- presence of a small amount of PEG-400 and sodium
vent and using heterogeneous catalytic reactions. Het- hydroxide [18]. Zinc has been used as a reducing
erogeneous catalytic reactions, as selective as possi- agent in the Ullmann coupling of haloarenes, cata-
ble, are superior to the homogenous ones because of lyzed by Pd/C in aqueous acetone under air atmo-
their reusability advantages [2]. The choice of solvent sphere in water in the presence of crown ethers [23].
as the main component of a reaction system is very im- The yields were high, but only iodo- and bromoarenes
portant. The appropriate solvent in green chemistry is could be used in the latter method, also the separa-
water which is safe, nontoxic, cheap, odorless and ac- tion of crown ethers made the process uneconomi-
cessible everywhere, but with limited chemical com- cal [24]. Zinc-mediated Ullman-type coupling could
patibility [3]. There is much attention to develop new be implemented with chloroarenes when the reac-
methods and technologies to perform reactions in wa- tion was performed in liquid carbon dioxide [25]. In
ter by the use of co-solvents [4], phase transfer cata- a two-phase system (like oil-water microemulsion) un-
lysts [5], surfactants [6], cyclodextrines [7], and ionic der phase-transfer catalyst conditions, biaryls were ob-
derivatization [8].
tained in excellent yields. However, the difficulty of
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the product purification still remains as a challenging in concentrated HNO , diluted with distilled water and
3
problem [26].
subjected to the ICP-AES analysis. The concentra-
Nowadays, due to its cheapness, availability, chemi- tion of palladium particles in the catalyst is 0.00416 g
cal inertness, thermal stability and insolubility in most (0.039 mmol) per 1 g of catalyst.
organic solvents as well as water, the application of
It is well demonstrated that sodium dodecyl sulfate
cellulose as the catalyst support is increasing [27]. Re- (SDS) gives stability to the aqueous dispersion of cel-
cently, the preparation of palladium nanoparticles sup- lulose molecules in water when the catalyst is synthe-
ported on cellulose or cellulose nanocrystallites have sized. The adsorption of surfactant on the cellulose sur-
been reported [28, 29]. The Pd(0)-supported catalyst face increases the wetting behavior and interfacial ad-
was prepared by reducing Pd(II) with hydrazine hy- hesion of cellulose, leading to better dispersion in wa-
drate and used for Suzuki coupling of aryl halides ter [30].
and aryl boronic acids [28]. The Pd(0) catalyst on
nanocrystalline cellulose was also prepared by reduc- Catalyst testing for Ullmann homocoupling
tion of Pd(II) by hydrogen and used in Heck cou-
pling [29].
To test the catalytic activity of palladium nanopar-
In this study palladium nanoparticles supported on ticles supported on cellulose, the coupling reaction
cellulose were prepared, and the catalytic performance of iodo- , bromo- and chlorobenzene were studied as
and the reusability of the catalyst were studied by per- model systems in the presence of zinc. To do this,
forming the homocoupling of haloarenes.
a mixture of water-alcohol was used as solvent sys-
tem. The palladium particles supported on cellulose
represent an efficient and economical catalyst for the
Ullmann reaction in water with zinc with no sensitiv-
ity to air. Under the reaction conditions, biaryls were
synthesized from chloroarenes with good yields with
Results and Discussion
Catalyst characterization
Scanning electron micrographs were recorded with no need to add any additive or using harsh conditions
a Hitachi S4160 instrument. SEM images indicated the (Scheme 1).
formation of palladium nanoparticles on the surface of
The reaction was performed with substituted aryl
cellulose (Fig. S-1; Supporting Information; see note at halides as well. It seems that substituents in the ortho
the end of the paper for availability). The Pd nanopar- position lower the reaction rate and yield due to steric
ticles seem to be deposited homogeneously on the sur- hindrance. The results are summarized in Table 1.
face of cellulose.
The coupling reaction by the prepared catalyst is
To determine the thermal stability of the catalyst, applicable for chloroarenes but it needs more catalyst
thermogravimetric analysis (Fig. S-2) was run from (7 – 10 mol-%) and high temperature. In the coupling
◦
ambient temperature up to 600 C. The sample was reduction of aryl halides bearing carbonyl groups (en-
◦
−1
heated at the rate of 20 C min under the flow of ni- try 9 and 11 in Table 1), the use of zinc will end up in
trogen. Up to 200 C the thermal weight loss of the cel- the reduction of the carbonyl group. In this case, hy-
◦
lulose support was negligible, and the catalyst showed drazine in basic media was used as a reducing agent to
good thermal stability. A decline in the weight of cata- hinder the reduction of ester groups.
◦
◦
lyst was observed from 220 C to 300 C. This result
was confirmed by the thermogravimetric dW/dT curve ture but the stability of the particles on the cellulose
Fig. S-3). support was decreased. The stability of the catalyst
The FT-IR spectra indicate the chemical and thermal was studied as a function of reaction temperature. Up
The reaction rate went up with increasing tempera-
(
stability of palladium supported on cellulose under the
reaction conditions. The negligible differences in the
FT-IR spectra show that the catalyst is stable under the
coupling reaction conditions.
Pd(0) supported on cellulose
Zn, H O-alcohol
Ar−X
Ar−Ar
2
An ICP-AES analysis of the catalyst was performed
to determine the amount of active palladium particles
X= I, Br, Cl
supported on the cellulose. The catalyst was dissolved Scheme 1. Ullmann homocoupling of aryl halides.
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Table 1. Ullmann homocoupling of different haloarenes using Pd nanoparticles supported on cellulose (4 – 10 mol-%).
◦
a
◦
Entry
1
Substrate
Product
Temp. ( C)
Yield (%)
Melting point ( C)
found reported
66 – 68
I
Ph
25
94
68.2 [31]
2
3
4
Br
Ph
Ph
25
70
40
96
83
93
66 – 68
65 – 68
69 – 71
Cl
70 – 71 [32]
N
N
Br
N
5
6
7
OMe
50
50
70
88
92
79
174 – 176
117 – 120
117 – 120
175 – 176 [33]
Br
OMe
OMe
Me
118 – 120 [34]
Br
Me
Me
Me
Cl
Me
Me
8
9
90
70
40
70
56
78
86
79
59 – 62
70 – 72
61 – 63 [35]
72 – 73 [36]
158 [37]
Br
Cl
Cl
Cl
Br
MeOOC
COOMe
COOMe
1
0
1
154 – 157
151 – 154
Br
1
154 [38]
Br
MeOOC
COOMe
COOMe
a
Isolated yields.
◦
to 75 C good stability was observed, and the catalyst Conclusion
could be recovered and reused several times without
◦
loss of activity. At temperatures above 80 C, stability
and reusability of the catalyst decreased.
Palladium nanoparticles supported on cellulose
could be used as effective and economical catalyst for
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the Ullmann reductive coupling of haloarenes in the added the catalyst (2 g of cellulose, 0.00832 g, 0.078 mmol
presence of zinc as reducing agent and water-alcohol of palladium). The mixture was stirred at the temperature
given in Table 1, and the reaction progress was monitored by
TLC. After the completion of the reaction, the mixture was
filtered, and the catalyst was washed with diethyl ether sev-
eral times. Recovered catalyst was grinded by mortar imme-
diately after initial drying to be used in the next run. The fil-
trates were extracted using diethyl ether; the organic solvent
was dried over sodium sulfate and evaporated under reduced
pressure. All products were recrystallized from suitable sol-
mixtures as solvent in the presence of air. The pre-
pared catalyst was used for the Ullmann coupling of
chloroarenes. Good stability and recovery of the cata-
◦
lyst was observed at temperatures below 75 C.
Experimental
Catalyst preparation
1
vents and characterized by melting points, H NMR and IR
spectroscopy.
Microcrystalline cellulose (1 g) and sodium dodecyl sul-
fate (SDS) (0.23 g) were added to a solution of PdCl2
Supporting information
(0.017 g) in water (50 mL), and the mixture was refluxed for
4
h. The reaction mixture was cooled to room temperature,
SEM photographs, TGA and thermogravimetry curves
and the precipitated particles were filtered and washed sev- of the palladium nanoparticles supported on cellulose are
eral times with distilled water. The particles were dried in air given as Supporting Information available online (DOI:
and grinded in a mortar to be used for the Ullmann reaction.
10.5560/ZNB.2013-3048).
Ullmann homocoupling
Acknowledgement
To a mixture of haloarene (2 mmol) and zinc (0.39 g,
Financial support of this work by the research council of
6
mmol) in distilled water (20 mL) and ethanol (2 mL) was the University of Tehran is highly acknowledged.
[1] I. T. Horvath, P. T. Anastas, Chem. Rev. 2007, 127, [14] Y. Q. Zhang, X. W. Wei, R. Yu, Catal. Lett. 2010, 135,
2
167 – 2168.
256 – 262.
[
[
2] C. Li, Chem. Rev. 2005, 105, 3095 – 3166.
3] C. C. Tzschucke, C. Market, W. Bannwarth, S. Roller,
[15] A. Kamal, V. Srinivasulu, B. N. Seshadri, N. Markan-
deya, A. Alarifi, N. Shankaraiah, Green Chem. 2012,
14, 2513 – 2522.
A. Hebel, R. Haag, Angew. Chem. Int. Ed. 2002, 41,
3
964 – 4000.
[16] D. D. Hennings, T. V. Iwama, H. Rawal, Org. Lett.
1999, 1, 1205 – 1208.
[17] N. Ple, A. Turck, K. Couture, G. Queguiner, Tetrahe-
dron 1994, 50, 10299 – 10308.
[18] M. B. Goldfinger, K. B. Crawford, T. M. Swager, J. Am.
Chem. Soc. 1997, 119, 4578 – 4593.
[
4] F. Amoroso, S. Colussi, A. Dell Zotto, J. Llorca,
A. Trovarelli, Catal. Commun. 2011, 12, 563 – 567.
5] B. K. Allan, K. N. Singh, Synthesis 2011, 1125 – 1131.
6] P. Ghosh, A. Mandal, Catal. Commun. 2011, 12, 744 –
[
[
7
47.
[
[
[
7] J. A. Imaonigie, D. H. Macartney, Inorg. Chem. 1993, [19] A. Arcadi, A. Burini, S. Cacchi, M. Delmastro, F. Mari-
2, 1007 – 1012. nelli, B. Pietroni, Synlett 1990, 47.
8] J. F. W. Keana, A. P. C. Morat, J. J. Volwerk, J. Org. [20] Y. Han, A. Roy, A. Giroux, Tetrahedron Lett. 2000, 41,
3
Chem. 1983, 48, 2661 – 2666.
5447 – 5451.
9] F. Ullmann, J. Bielecki, Chem. Ber. 1901, 34, 2174 –
[21] D. Gittis, S. Mukhopadhyay, G. Rothenberg, Y. Sasson,
Org. Proc. Res. Dev. 2003, 7, 109 – 114.
2
185.
[
[
[
10] A. P. Degnan, A. I. Meyers, J. Am. Chem. Soc. 1999, [22] M. Rottl a¨ nder, P. Knochel, Synlett 1997, 1084 – 1086.
1
21, 2762 – 2769.
[23] S. Ventrakaman, C. J. Li, Org. Lett. 1999, 1, 1133 –
11] J. Hessan, M. Sevignon, C. Gozzi, E. Schulz, M. Le-
1135.
maire, Chem. Rev. 2002, 102, 1359 – 1470.
[24] S. Ventrakaman, C. J. Li, Tetrahedron Lett. 2000, 41,
12] F. E. Ziegler, I. Chliwner, K. W. Fowler, S. J. Kanfer,
4831 – 4834.
S. J. Kuo, N. D. Sinha, J. Am. Chem. Soc. 1980, 102, [25] J. Li, Y. Xie, H. Jiang, M. J. Chen, Green Chem. 2002,
90 – 798. 4, 424 – 425.
13] T. D. Nelson, R. D. Crouch, Org. React. 2004, 63, [26] C. J. Z. Jiang, J. Cai, Colloids. Surf. A 2007, 305,
7
[
2
65 – 555.
145 – 148.
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Download Date | 7/29/15 4:21 PM

9
50
Note
[
[
[
[
27] L. Zhou, J. He, J. Zhang, Z. He, Y. Hu, C. Zhang, H. He, [33] J. Bergman, R. Carlsson, B. Sjoberg, Org. Synth. 1977,
J. Phys. Chem. C 2011, 115, 16873 – 16878. 57, 18.
28] N. Jamwal, R. K. Sodhi, P. Gupta, S. Paul, Int. J. Biol. [34] L. F. Elsom, A. Mckillop, E. C. Taylor, Org. Synth.
Macromol. 2011, 49, 930 – 935. 1976, 55, 48.
29] C. M. Cirtiu, A. F. D. Briere, A. Moores, Green Chem. [35] J. J. Dobbie, J. J. Fox, A. J. H. Gauge, J. Chem. Soc.
011, 13, 288 – 291. Trans. 1911, 99, 1615 – 1620.
30] N. Karousis, G. E. Tsotsou, F. Evangelista, P. Rudolf, [36] R. B. Hill, R. L. Sublett, H. G. Ashburn, J. Chem. Eng.
2
N. Ragoussis, N. Tagmatarchis, J. Phys. Chem. C 2008,
12, 13463 – 13469.
31] W. F. Newhall, E. J. Elvin, L. R. Knodel, Anal. Chem.
954, 26, 1234 – 1236.
32] W. H. F. Sasse, Org. Synth. 1966, 46, 5.
Data 1963, 8, 233 – 234.
[37] K. R. Wilson, R. E. Pincock, J. Am. Chem. Soc. 1975,
97, 1474 – 1478.
[38] J. I. Kim, G. B. Shuster, J. Am. Chem. Soc. 1992, 114,
9309 – 9317.
1
[
[
1
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