The hydration of nitriles catalyzed by the combination of palladium nanoparticles and copper compounds

Article abstract of DOI:10.1246/cl.2009.360

New catalysts based on Pd nanoparticles for the hydration of nitriles to amides were investigated. Copper compounds containing oxygen acted as effective promoters in the catalytic system. The catalysts could be used to prepare aromatic and aliphatic amides from the corresponding nitriles. Chloride ions significantly inhibited the catalytic performance. Copyright

Full text of DOI:10.1246/cl.2009.360

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60
Chemistry Letters Vol.38, No.4 (2009)
The Hydration of Nitriles Catalyzed by the Combination
of Palladium Nanoparticles and Copper Compounds
ꢀ
1
2
1;3
Akinori Ishizuka, Yoshiaki Nakazaki, and Toshiyuki Oshiki
Research Center for Advanced Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530
1
2
Nano Cube Japan Co., Ltd., Incubation Center, Okayama Research Park, Haga, Okayama 701-1221
Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530
3
(Received December 26, 2008; CL-081218; E-mail: arsenicfree75@ybb.ne.jp)
New catalysts based on Pd nanoparticles for the hydration of
373 K in the presence of copper acetylacetonate [Cu(acac)2] as a
promoter to give benzamide in 87% yield (Entry 3). Catalytic
activity was not observed for all NPs and Cu compounds (Entries
1 and 2). At 453 K, benzamide was obtained quantitatively
(Entry 4). Some other copper compounds were also effective
nitriles to amides were investigated. Copper compounds contain-
ing oxygen acted as effective promoters in the catalytic system.
The catalysts could be used to prepare aromatic and aliphatic
amides from the corresponding nitriles. Chloride ions signifi-
cantly inhibited the catalytic performance.
.
(Entries 5–7). When Cu(NO3)2 3H2O was used as a promoter,
the product yield decreased (27%) (Entry 8). CuCl and CuCl2
greatly inhibited the catalytic performance (Entries 9 and 10).
On the basis of these results, it was suggested that a suitable pro-
moter for the hydration would be a copper compound containing
an oxygen atom. Iron and nickel compounds were ineffective
as promoters in the reaction (Entries 11, 12, and 13). Cobalt(II)
nitrate trihydrate, cobalt(II) diacetate 3-hydrate, and tin(II) chlo-
ride 2-hydrate were also ineffective (results not shown). In con-
trast to the Pd NP, the Pt NP catalysts showed low activities
(Entries 14, 15, and 16). Pd powder (Entries 17 and 18) showed
lower catalytic activity than the Pd NP. These results suggest
that the active sites of Pd NPs, i.e., the vertex and edge atoms
that are composed of coordinatively unsaturated atoms on the
surface, behave effectively in the course of hydration. This is
because Pd NPs have more atoms in proportion to the specific
1
Soluble nanoparticles (NP) composed of a few tens to a few
hundred atoms have a number of active sites with high-specific
surface areas in the bulk phase. The chemical properties of NPs
2
have recently attracted attention for diverse catalytic usage. NP
catalysts exhibit not only high selectivity like homogeneous cat-
alysts but also recyclability like heterogeneous catalysts. There-
fore, they meet the needs of modern green sustainable chemis-
3
try. While there have been many reports on NP catalysts for ox-
5
4
idation and hydrogenation, their application to hydration has
been limited.6
The catalytic hydration of nitriles is essentially an atom-eco-
nomical reaction and an ideal sustainable method for the prepa-
ration of amides (Scheme 1). Toshima and co-workers reported
7
9
that NP comprising a palladium–copper alloy acts as a catalyst
for the hydration of acrylonitrile.6b–6d We found that palladium
and platinum single NPs acted as catalysts for the hydration of
various nitriles without requiring the preparation of an NP alloy.
In this paper, we report new catalysts composed of a single NP
and a copper compound for selective production of amides.
The Pd and Pt NPs were prepared in the presence of a water-
soluble polymer for the stabilization of NPs, poly(N-vinyl-2-pyr-
rolidone) (PVP), by reduction of the corresponding precursors,
surface area than Pd powder. Regarding Entries 9 and 10, there
is a possibility that the dissociated chloride ion in the reaction
media acted as an inhibitor in the reaction catalyzed by the NP
system. Figure 1 shows the effects of NaCl as a chloride ion
source on nitrile hydration using the NP catalyst. NaCl added
at 0.01 and 0.02 mmol levels to Entry 3 significantly decreased
the yield from 87% to 2.7% and 0.6%, respectively. These
results provide further evidence that chloride ion has a negative
effect on the hydration of benzonitrile. The same reasoning
applies to the cases of Pt NPs, because the precursor material of
II
IV
8
Pd acetate and H2Pt Cl6, respectively. The particle size of
all NP samples were characterized by transmission electron
microscopy. The average size of Pd and Pt NPs were 1.8 nm with
ꢂ
Pt NPs includes chlorine. We think that Cl causes a decreased
yield by inhibiting the coordination between Cu compounds with
the NP surface, and/or the adsorption of substrate to the active
site on the NP.
ꢂ3
the standard deviation (ꢀ): 1:6 ꢁ 10 and 1.5 nm with ꢀ ¼
ꢂ4
3
:3 ꢁ 10 . Pd powder with 1000–1500 nm (Sigma-Aldrich
Co.) was used as the comparative material for Pd NPs. All cata-
lytic reactions were carried out using standard Schlenk tech-
niques under argon. The products were detected by gas chroma-
tography (Shimadzu Co., GC-2014) using nonpolar packed col-
umns (Restek Co., Rtx-1 and Rtx-Wax).
Table 2 shows the results of catalytic hydration of various
nitriles. Our new catalysts were effective for various nitriles,
e.g., aliphatic, aromatic, and heteroatom-containing aromatic
nitriles. The hydration of less reactive aliphatic nitriles,7c e.g.,
butyronitrile and 3-phenylpropanenitrile, also proceeded.
Nicotinamide, which is part of the vitamin B group, was pre-
pared in 69% yield using Cu(acac)2 as a promoter. An aromatic
nitrile bearing an electron-donating group, p-methoxybenzoni-
trile, was also hydrated and the corresponding amide was ob-
tained in 84% yield. The yield was comparable to that observed
in the case of benzonitrile. In contrast to our results described
above, Toshima’s Pd–Cu alloy only gave acrylamide.
We examined the hydration of benzonitrile using the NP-
based catalysts, and the results are summarized in Table 1 with
experimental conditions. The Pd-catalyzed reaction proceeded at
O
Catalyst
R
C
N + H2O
R C
NH2
In summary, a new catalytic system (Pd NP–Cu compound)
showed high catalytic activities for the hydration of various ni-
Scheme 1.
Copyright Ó 2009 The Chemical Society of Japan

Chemistry Letters Vol.38, No.4 (2009)
Table 1. The catalytic hydration of benzonitrile using the nanoparticle systema
361
b
b
Entry
Catalyst
Dia./nm
1.8
Promoter
Temp/K
Conversion/%
Yield/%
1
2
3
4
5
6
7
8
9
Pd NP
None
Pd NP
None
373
373
373
453
373
373
373
373
373
373
373
373
373
373
373
453
373
453
1
<1
91
>99
98
73
96
27
<1
<1
<1
<1
<1
<1
5
37
<1
62
<1
<1
87
>99
98
73
96
27
<1
<1
<1
<1
<1
<1
<1
7
Cu(acac)2
Cu(acac)2
Cu(acac)2
CuSO4
1.8
CuO
.
CuCO3 Cu(OH)2
.
Cu(NO3)2 3H2O
CuCl
10
11
12
13
14
15
16
17
18
CuCl2
NiSO4
.
FeSO4 7H2O
.
FePO4 4H2O
None
Pt NP
1.5
Cu(acac)2
Cu(acac)2
Cu(acac)2
Cu(acac)2
Pd powder
1000–1500
<1
59
a
Reaction conditions: catalyst 0.01 mmol, promoter 0.02 mmol, benzamide 0.2 mmol, water 11 mmol, EtOH (solvent) 0.25 mL,
6 h. GC analysis using internal standard technique.
b
1
1
00
This work was supported by the JST-project to develop ‘‘in-
novative seeds’’ and an Industrial Technology Research Grant
Program in 2006 from NEDO of Japan.
8
6
4
2
0
0
0
0
0
References and Notes
1
a) T. Teranishi, M. Miyake, Chem. Mater. 1998, 10, 594. b) M.-C.
Daniel, D. Astruc, Chem. Rev. 2004, 104, 293. c) B. He, Y. Ha,
H. Liu, K. Wang, K. Liew, J. Colloid Interface Sci. 2007, 308, 105.
a) M. Haruta, T. Kobayashi, H. Sano, N. Yamada, Chem. Lett. 1987,
405. b) Y. Shiraishi, N. Toshima, Colloids Surf., A 2000, 169, 59.
c) K. Ebitani, K.-M. Choi, T. Mizugaki, K. Kaneda, Langmuir 2002,
18, 1849. d) M. Haruta, Nature 2005, 437, 1098. e) J. C. Serrano-Ruiz,
A. L o´ pez-Cudero, J. Solla-Gull o´ n, A. Sep u´ lveda-Escribano, A. Aldaz,
F. Reinoso, J. Catal. 2008, 253, 159.
2
Pd-Cu(acac)
entry 3)
2
NaCl dose
0.01 mmol
NaCl dose
0.02 mmol
(
Figure 1. Effect of NaCl as Cl ion on the yield of benzamide
373 K).
(
3
4
5
a) D. Astruc, Inorg. Chem. 2007, 46, 1884. b) D. Astruc, in Nano-
particles and Catalysis, ed. by D. Astruc, Wiley-VCH, Weinheim,
Table 2. The catalytic hydration of various nitriles by the NP
a
2
008, Chap. 1, pp. 1–2.
a) K. Bergamaski, E. R. Gonzalez, F. C. Nart, Electrochim. Acta 2008,
3, 4396. b) L. M. Neal, H. E. Hagelin-Weaver, J. Mol. Catal. A:
catalysts
5
Yield/%
Chem. 2008, 284, 141.
Nitrile
Promoter
Cu(acac)
a) X.-D. Mu, D. G. Evans, Y. Kou, Catal. Lett. 2004, 97, 151. b) G.
Berhault, L. Bisson, C. Thomazeau, C. Verdon, D. Uzio, Appl. Catal.,
A 2007, 327, 32. c) J. M. Nadgeri, M. M. Telkar, C. V. Rode, Catal.
Commun. 2008, 9, 441.
None
2
CuO
CN
CN
CN
<1
88
36
90
69
84
73
<
<
<
1
1
1
30
75
62
25
6
7
a) H. Hayashi, H. Nishi, Y. Watanabe, T. Okazaki, J. Catal. 1981, 69,
4
4. b) N. Toshima, Y. Wang, Chem. Lett. 1993, 1611. c) N. Toshima,
Y. Wang, Langmuir 1994, 10, 4574. d) Y. Wang, H. Liu, N. Toshima,
J. Phys. Chem. 1996, 100, 19533.
CN
N
MeO
CN
<1
Representative examples of catalytic nitrile hydration: a) S.-I.
Murahashi, T. Naota, Bull. Chem. Soc. Jpn. 1996, 69, 1805. b) T.
Ghaffar, A. W. Parkins, J. Mol. Catal. A: Chem. 2000, 160, 249. c) K.
Yamaguchi, M. Matsushita, N. Mizuno, Angew. Chem., Int. Ed. 2004,
aPd NP 0.01 mmol, promoter 0.02 mmol, nitrile 0.2 mmol, water
1 mmol, 373 K, 16 h.
1
4
3, 1576. d) T. Oshiki, H. Yamashita, K. Sawada, M. Utsunomiya, K.
triles. More than 99% yield on benzonitrile hydration was re-
corded at 453 K by Pd NP–Cu(acac)2. Chloride ion acted as an
inhibitor in the catalytic hydration by the NP system. Further
studies on the reactions and mechanism of NP catalysis are cur-
rently in progress.
Takahashi, K. Takai, Organometallics 2005, 24, 6287. e) A. Goto, K.
Endo, S. Saito, Angew. Chem., Int. Ed. 2008, 47, 3607.
Y. Nakazaki, Jpn. Pat. Appl. 2005-264199.
8
9
J. R. Anderson, Structure of Metallic Catalysts, Academic Press,
London, 1975, p. 245.
Published on the web (Advance View) March 21, 2009; doi:10.1246/cl.2009.360