A study of amidocarbonylation reactions catalyzed by Pd/HZSM-5

Article abstract of DOI:10.1246/bcsj.79.806

A HZSM-5-supported palladium catalyst, which was prepared by the conventional impregnation method, was utilized in amidocarbonylation reactions. Several important parameters were optimized to give moderate to excellent yields. The catalyst recycling of Pd/HZSM-5, for the first time, was achieved for at least four run times without depreciation of catalytic activity. The studies of TEM images revealed that agglomeration of the palladium species of Pd/ HZSM-5 catalyst was avoided after reaction, which was quite different from the case of Pd/C catalyst.

Full text of DOI:10.1246/bcsj.79.806

8
06 Bull. Chem. Soc. Jpn. Vol. 79, No. 5, 806–809 (2006)
Ó 2006 The Chemical Society of Japan
A Study of Amidocarbonylation Reactions Catalyzed by Pd/HZSM-5
ꢀ
Ke Wu Yang and Xuan Zhen Jiang
Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, 310027, P. R. China
Received October 14, 2005; E-mail: chejiang@zju.edu.cn
A HZSM-5-supported palladium catalyst, which was prepared by the conventional impregnation method, was uti-
lized in amidocarbonylation reactions. Several important parameters were optimized to give moderate to excellent
yields. The catalyst recycling of Pd/HZSM-5, for the first time, was achieved for at least four run times without depre-
ciation of catalytic activity. The studies of TEM images revealed that agglomeration of the palladium species of Pd/
HZSM-5 catalyst was avoided after reaction, which was quite different from the case of Pd/C catalyst.
The synthesis of various functionalized N-acylamino acids
HZSM-5 powder. After reduction, the black precipitate was fil-
tered and washed with ethanol several times, and then dried in
vacuum before use in the reaction.
The 10 wt % Pd/C catalyst was obtained from Shanghai Chemi-
cal Company.
have been realized via amidocarbonylation. In this one-step
reaction, N-acyl-ꢀ-amino acid was obtained from cheap mate-
rials, i.e., an aldehyde, an amide, and carbon monoxide, with-
out stoichiometric by-products in the presence of transition-
metal catalysis.
Amidocarbonylation. All of the aldehydes and solvents were
dried and distilled before use. Acetamide and LiBr were dried in
Several transition metals can be applied as the catalysts in
amidocarbonylation. The first cobalt-complex was discovered
ꢁ
an oven (120 C) for 4 h.
A 100 mL autoclave with a magnet-driven stirrer was used for
pressurized reaction conditions.
1
by Wakamatsu et al. in 1971, and subsequently palladium-
2
catalyzed amidocarbonylation was reported by Beller et al.
in 1997. The latter group also examined the catalytic activities
of rhodium, iridium, and ruthenium complexes in this type
General Procedure: 30 mmol aldehyde and amide were dis-
solved in 60 mL of solvent, 1.0 mol % 10 wt % Pd/HZSM-5, 6.0
mol % H2SO4, and 35 mol % LiBr were allowed to react under
3
of reaction. Recently, platinum-catalyzed amidocarbonylation
4
6
.0 MPa CO at a designed temperature for 16 h. As the reaction
was reported by Sagae et al. Among them, palladium demon-
finished, Pd/HZSM-5 was filtered and the volatile components
were removed in vacuum; the residue was taken up into a 50 mL
saturated aqueous solution of NaHCO3. Washing with 50 mL of
chloroform and 50 mL of ethyl acetate, the aqueous solution was
adjusted to pH 2 with 50% phosphoric acid. The precipitate was
filtered off and washed with water. The aqueous phase was
extracted with ethyl acetate (80 mL, 3 times) and the combined
4
organic phase was dried over MgSO . Then, the organic solvent
was removed under vacuum, the residue and the precipitate were
combined and dried in the oven. The purity of the products, as
measured by HPLC, was greater than 97%.
The procedure of catalyst recycling is as follows: after reaction,
strated the highest activity. For practical application, however,
the homogeneous palladium catalysts are expensive and unre-
coverable. To solve these problems the heterogeneous catalyst
Pd/C in amidocarbonylation was improved by Beller et al.5
and another heterogeneous catalyst (polymer incarcerated pal-
6
ladium) was reported by Kobayashi et al. The heterogeneous
catalyst could be recoverable by filtering, but no experimental
evidence on the reuse of catalysts have been provided in the
5
,6
literature. From an economic point, the reuse of expensive
palladium catalysts is very important. In the present study, Pd/
HZSM-5 catalyst was prepared by the conventional impregna-
tion method and applied in the amidocarbonylation. The cata-
lyst recycling of Pd/HZSM-5 catalyst, for the first time, was
achieved without loss of catalytic activity in four run times.
This finding makes amidocarbonylation greatly attractive in
practical application.
1
0 wt % Pd/HZSM-5 catalyst was filtered off and washed by fresh
ꢁ
NMP, and then the catalyst was dried at 55 C for 8 h before the
next run.
The purity of the product was measured by HPLC (Aglient
1
100 series) equipped with a C18 column: The mobile phase was
ꢂ1
methanol and the flow rate was 1.0 mL min . The TEM images
of the 10 wt % Pd/HZSM-5 and 10 wt % Pd/C were taken by a
JEM-200CX. The leaching of Pd/HZSM-5 and Pd/C to the organ-
ic solvent were measured by a Thermo Jarrell Ash Corporation’s
IRIS Intrepid II (detecting limit was 5 ppm).
Experimental
Catalyst Preparation. HZSM-5 support with the SiO2/Al2O3
ratio = 30 was purchased from PQ Corporation (Netherlands).
The preparation of 10 wt % Pd/HZSM-5 catalyst as follow: 0.185
g of PdCl2 was solved in 20 mL of water (5 mL of hydrochloric
acid was necessary to make the solution of PdCl2) and 1.0 g of
HZSM-5 powder was dipped into the solution for 3 days. The
solution was baked, the PdCl2/HZSM-5 powder was added into
Results and Discussion
In the present work, amidocarbonylation of isovaleralde-
hyde catalyzed by Pd/HZSM-5 was performed under similar
reaction conditions to those described in the references
(Scheme 1).5
25 mL of ethanol, and then 2.0 mL of 85% hydrazine hydrate
was added under stirring into the mixture of ethanol and PdCl2/
Published on the web May 12, 2006; DOI: 10.1246/bcsj.79.806

K. W. Yang et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 5 (2006)
807
O
Table 1. Screening Different Solvent in the Amidocarbon-
ylation Catalyzed by Pd/HZSM-5a)
O
COOH
CO, Pd/HZSM-5
+
AcNH2
Solventb) (V/V)
c)
Entry
Yield /%
H
N
H
H2SO4, LiBr/NMP
1
2
3
4
5
6
NMP
47.0
46.9
56.0
40.4
43.7
43.1
NMP/Tol = 2
NMP/Tol = 3
NMP/Tol = 4
DMI/THN = 3
NMP/THN = 3
Scheme 1.
50
40
30
20
10
0
a) Reaction conditions: 30 mmol isovaleraldehyde and amide,
6
3
1
0 mL solvent, 1.0 mol % Pd/HZSM-5, 6 mol % H2SO4, and
5 mol % LiBr were treated with 6.0 MPa CO at 90 C for
6 h without addition of PPh3. b) Tol: toluene; DMI: 1,3-di-
ꢁ
methyl-2-imidazolidinone; THN: 1,2,3,4-tetrahydronaphtha-
lene. c) Product yield: based on the purity determined by
HPLC and isolated yield.
Table 2. Amidocarbonylation Catalyzed by 10 wt % Pd/
a)
0
2
4
6
8
10 12
HZSM-5 Catalyst
b)
c)
Addition of sulfuric acid(mol%)
Entry Staring compound N-acylamino acid
Yield/%
62.3
O
COOH
O
Fig. 1. Influence of H2SO4 concentration in the amido-
carbonylation catalyzed by Pd/HZSM-5. Reaction condi-
tions: 30 mmol isovaleraldehyde and amide, 60 mL NMP,
1
2
H
N
H
1.0 mol % Pd/HZSM-5, and 35 mol % LiBr were treated
with 6.0 MPa CO at 90 C for 16 h, without addition of
O
COOH
O
ꢁ
H
39.2
N
H
PPh3.
O
COOH
O
According to the reaction mechanism proposed by Beller et
7
d)
3
4
H
H
N
H
88.4
al., the co-catalyst H2SO4 was necessary for the formation of
an ꢀ-haloamide intermediate, which leads to the formation of
N-acyl-ꢀ-amino acid. The influence of the concentration of
H2SO4 on catalytic performance was studied and the results
revealed that more than 4.0 mol % of acid is necessary, as
shown in Fig. 1.
O
COOH
O
40.0e)
N
H
Almost no N-acylleucine was obtained without adding
H2SO4 into the catalyst system. With increasing the H2SO4
concentration, the yield of N-acylleucine gradually increased
till the addition of H2SO4 reached 6.0 mol %. However, the
yields of N-acylleucine were slightly decreased when the con-
centration of H2SO4 exceeded 6.0 mol %. These results were
a) Reaction conditions: 30 mmol aldehyde and amide, 45 mL
NMP, 15 mL toluene, 1.0 mol % Pd/HZSM-5, 1.0 mol %
PPh3, 6 mol % H2SO4, and 35 mol % LiBr were treated with
ꢁ
6
and 2 were confirmed by HPLC analysis. The products in
.0 MPa CO at 90 C for 16 h. b) The products in Entries 1
Entries 3 and 4 were confirmed by direct insertion ESI-MS
þ
7
analogous to those reported by Beller et al. in the amidocar-
bonylation of propionaldehyde.
(
esquire 3000 plus), M þ Na ¼ 222 in Entry 3 and M þ
þ
Na ¼ 216 in Entry 4. c) Product yield: based on the purity
determined by HPLC and isolated product. d) The byproduct I
was isolated and confirmed by direct insertion ESI-MS
The solvent was an important parameter in this reaction.6,7
6
Kobayashi et al. found that the mixture solvents accelerated
the amidocarbonylation. Therefore, in the present study several
types of solvent mixture were examined (see Table 1). The
results showed that the mixture solvent NMP/toluene = 3
M þ Naþ ¼ 235). e) The byproduct II was isolated and con-
(
þ
firmed by direct insertion ESI-MS (M þ Na ¼ 229).
NHAc
NHAc
(Entry 3) exhibited the best performance (56.0% yield without
adding PPh3), which is applicable for further study.
According to the reference, the phosphine ligand was not
necessary in the amidocarbonylation, but we found that in
the presence of triphenylphosphine could increase the yield
of N-acylamino acid (Entry 1 in Table 2 compared with Entry
NHAc
NHAc
5
I
II
In these reactions, Pd/HZSM-5 catalyst gave moderate
(Entries 1, 2, and 4) to excellent yields (Entry 3). It indicated
that the HZSM-5-supported palladium catalyst demonstrated
efficient catalytic activities in the amidocarbonylation reac-
tions.
3
in Table 1). The reason is under investigation. Therefore, tri-
phenylphosphine was added into the system for 10 wt % Pd/
HZSM-5 catalyzed amidocarbonylation of other aldehydes.
The results are given in Table 2.

8
08 Bull. Chem. Soc. Jpn. Vol. 79, No. 5 (2006)
A Study of Amidocarbonylation
By-products I and II were isolated and identified by direct
ity (Entries 2 and 4), while Pd/C catalyst gave unsatisfactory
results. The fresh Pd/C catalyst gave the target product yields
of 64.4% (Entry 1) and 94.3% (Entry 3). However, in the
catalyst recycling, the yields dramatically declined, and then
almost remained at the same level for the remaining runs
(ꢃ30% yields in Entry 1 and ꢃ60% yields in Entry 3). Never-
theless, after reaction no palladium leaching of Pd/HZSM-5 or
Pd/C catalysts to the organic solvent was detected in all runs.
To explain these results, the images of transmission electron
micrographs of Pd/HZSM-5 and Pd/C catalysts were taken
and are presented in Figs. 2 and 3, respectively. It can be seen
from Figs. 2a and 3a that before reaction the dispersion status
of palladium particles was quite uniform over both Pd/HZSM-
insertion ESI-MS (Esquire 3000 plus). The bisamides were
formed in a side reaction (Scheme 2) by condensation of alde-
hyde with two equivalents of acetamide catalyzed by H2SO4.8,9
In order to examine the catalyst recycling of the heterogene-
ous palladium catalysts, amidocarbonylation of isovaleralde-
hyde and cyclohexanecarboxaldehyde catalyzed by recovered
Pd/HZSM-5 and Pd/C was performed. The results are present-
ed in Table 3.
It can be seen from Table 3 that the Pd/HZSM-5 catalyst
can be reused at least four times without loss of catalytic activ-
O
NHAc
5
and Pd/C catalysts. After reaction, however, the palladium
particles over Pd/C catalyst agglomerated and formed a
network (Fig. 2b), which led to loss of the active sites of the
palladium species and a decrease in its catalytic activity. How-
ever, the dispersion of the palladium particles of Pd/HZSM-5
H+
+
2 AcNH2
R
H
R
NHAc
Scheme 2.
Table 3. A Comparison of the Catalyst Recycling of Pd/HZSM-5 and Pd/C Catalysts in
Amidocarbonylationa)
Yield/%c)
Entry
Catalyst
Productb)
1
st run
2nd run
3rd run
4th run
5th run
1
2
3
4
Pd/C
A
A
B
B
64.4
62.3
94.3
88.4
30.8
61.6
61.0
88.4
30.5
61.2
60.2
88.2
30.6
60.2
59.8
88.0
—
59.9
—
Pd/HZSM-5
Pd/C
Pd/HZSM-5
87.5
a) Reaction conditions: 30 mmol aldehyde and amide, 45 mL NMP, 15 mL toluene, 1.0 mol %
Pd/HZSM-5, 1.0 mol % PPh3, 6 mol % H2SO4, and 35 mol % LiBr were treated with 6.0 MPa
ꢁ
CO at 90 C for 16 h. b) A: N-acylleucine, B: N-acylcyclohexylglycine. c) Product yield: based
on the purity determined by HPLC and isolated yield.
(a)
(b)
Fig. 2. (a) TEM image of Pd/C before reaction. (b) TEM image of Pd/C after reaction.
(
a)
(b)
Fig. 3. (a) TEM image of Pd/HZSM-5 before reaction. (b) TEM image of Pd/HZSM-5 after reaction.

K. W. Yang et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 5 (2006)
809
catalyst almost remains the same uniform dispersion status
(Fig. 3b). Agglomeration of the palladium species of Pd/
HZSM-5 catalyst is avoided during reaction by using HZSM-
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Conclusion
6
The heterogeneous palladium catalyst, Pd/HZSM-5, was
successfully utilized in amidocarbonylation reactions. Particu-
larly, the reuse of this catalyst for at least four run times with-
out loss of catalytic activity was achieved; while Pd/C catalyst
demonstrated unsatisfactory recycling owing to agglomeration
of palladium particles after reaction. The TEM images re-
vealed that no agglomeration took place over Pd/HZSM-5 cat-
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corporation into the cages of HZSM-5 support.
7
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1
We are grateful for the financial support of the National
Natural Science Foundation of China under grant No.
5990.
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