Table 3 Pt NW catalysed reductive amination of different aldehydes
with aqueous ammonia under H (1 bar) atmosphere
We envision that the Pt catalyst will be an important type of
catalyst for the industrial synthesis of amines.
a
2
b
Conv. Selectivity
b
H. W. G. acknowledges financial support from the National
Natural Science Foundation of China (No. 21003092), the
Key Project of Chinese Ministry of Education (No. 211064),
the Priority Academic Program Development of Jiangsu Higher
Education Institutions; X. Q. C. is grateful for financial support
from the National Engineering Laboratory for Modern Silk,
Soochow University, China.
Entry R-CHO
Product
(%)
100
100
(%)
1
2
93.2(92)
77.8(73)
3
4
100
100
93.1(90)
87.8(85)
Notes and references
1
W. T. Horst, US Patent 2,243,544, 1941; T. Shimizu, US Patent
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5
6
100
100
96.9(96)
71.3(65)
2
c
7
90.9 76.8(71)
3
4
O. Saidi, A. J. Blacker, M. M. Farah, S. P. Marsden and
J. M. Williams, Angew. Chem., Int. Ed., 2009, 48, 7375.
R. Kawahara, K. I. Fujita and R. Yamaguci, Adv. Synth. Catal.,
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d
8
100
80
90.2(90)
70.0(67)
d
9
5
X. J. Cui, Y. Zhang, F. Shi and Y. Q. Deng, Chem.–Eur. J., 2011,
1
a
Reaction conditions: aldehyde (1.0 mmol), 25% aqueous ammonia
7, 2587.
(
2 equiv.) and ethanol (2 mL) at 80 1C ,1 bar H with the 0.005 mmol
2
6 H. Greenfield, Ind. Eng. Chem. Prod. Res. Dev., 1976, 15, 156;
S. Galvagno, J. Mol. Catal., 1990, 58, 215; M. Chatterjee,
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b
c
d
Pt NW catalyst for 24 h. GC yield. 40 1C. CH
1 mmol) was used instead of ammonia. The values in the parentheses
are the yield of isolated products.
3 4
COONH
(
7
T. Gross, A. M. Seayad, M. Ahmad and M. Beller, Org. Lett.,
002, 4, 2055.
2
In this reaction, the Pt NW catalyst can be separated by
simple centrifugation or precipitation easily. The catalytic
activity is maintained and the catalyst can be reused up to
8
C. F. Winans, J. Am. Chem. Soc., 1939, 61, 3566; A. R. Surrey and
G. Y. Lesher, J. Am. Chem. Soc., 1956, 78, 2573; G. Grethe,
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A. W. Heinen, J. A. Peters and H. V. Bekkum, Eur. J. Org. Chem.,
9
6
times (Fig. S5, ESIw). The Pt NWs are relatively stable
2
000, 2501.
(
Fig. S6, ESIw) and no Pt leaching was detected by ICP.
With the optimized reaction conditions for the preparation
1
0 S. Gomez, J. A. Peters and T. Maschmeyer, Adv. Synth. Catal.,
2002, 344, 1037.
of DBA, the Pt NW catalyst was tested with a series of
aldehydes (aromatic and aliphatic aldehydes) in the presence
of ammonia (Table 3). Irrespective of the electronic nature of
the substituent, we obtained good to excellent yields of DBAs
from the aromatic aldehydes (entries 1–4). Aliphatic aldehydes
11 B. J. Hu, K. L. Ding, T. B. Wu, X. S. Zhou, H. L. Fan, T. Jiang,
Q. wang and B. X. Han, Chem. Commun., 2010, 46, 8552;
G. W. Qin, W. L. Pei, X. M. Ma, X. N. Xu, Y. P. Ren, W. Sun
and L. Zuo, J. Phys. Chem. C, 2010, 114, 6909; H. Y. Hong, L. Hu,
M. Li, J. W. Zheng, X. H. Sun, X. H. Lu, X. Q. Cao, J. M. Lu and
H. W. Gu, Chem.–Eur. J., 2011, 17, 8726.
1
2 T. S. Hamilton and R. Adams, J. Am. Chem. Soc., 1928, 50, 2260;
H. Greenfield, J. Org. Chem., 1964, 29, 3082.
(
linear or a-branched) can also react with ammonia and
the corresponding DBAs will be obtained with good yields
entries 5–6). When furan-2-carbaldehyde was used, 76.8% of
13 L. Hu, X. Q. Cao, D. H. Ge, H. Y. Hong, Z. Q. Guo, L. Chen,
Z. Q. Guo, X. H. Sun, J. X. Tang, J. W. Zheng, J. M. Lu and
H. W. Gu, Chem.–Eur. J., 2011, 17, 14283.
(
the corresponding DBA was obtained (entry 7). Using ammonium
acetate instead of ammonia in the presence of BzH, a yield of
1
4 L. Y. Shi, L. Hu, J. Q. Wang, X. Q. Xue and H. W. Gu, Org. Lett.,
012, 14, 1876.
2
9
0.2% DBA can be obtained (entry 8). Acetophenone, which
15 M. Li, L. Hu, X. Q. Cao, H. Y. Hong, J. M. Lu and H. W. Gu,
Chem.–Eur. J., 2011, 17, 2763; L. Hu, X. Q. Cao, L. Chen,
J. W. Zheng, J. M. Lu, X. H. Sun and H. W. Gu, Chem. Commun.,
shows no activity in aqueous ammonia, was successfully
converted to the corresponding DBA with a yield of 56%
when ammonium acetate was used as the ammonia source
2012, 48, 3445; Z. Q. Guo, L. Hu, H. H. Yu, X. Q. Cao and
H. W. Gu, RSC Adv., 2012, 2, 3477.
(
entry 9). Unsymmetrical DBAs can also be obtained with this
16 S. Gomez, J. A. Peters, J. C. Vanderwaal, W. Z. Zhou and
T. Maschmeyer, Catal. Lett., 2002, 84, 1; S. Gomez, J. A. Peters,
J. C. Vanderwaal and T. Maschmeyer, Appl. Catal., A, 2003, 254, 77;
S. Gomez, J. A. Peters, J. C. Vanderwaal, P. J. Vanderbrink and
T. Maschmeyer, Appl. Catal., A, 2004, 261, 119.
catalytic system in good yield (33–63%) (Table S1, ESIw).
In conclusion, a facile and efficient process for the synthesis
of DBAs through direct reductive amination of aldehydes has
been developed using the unsupported Pt NW catalyst under
mild reaction conditions. The Pt NW catalyst exhibited excellent
activity and selectivity in reductive amination using ammonia or
ammonium acetate as the substrate and can be recycled easily.
17 C. Wang, Y. L. Hou, J. Kim and S. H. Sun, Angew. Chem., Int. Ed.,
2
007, 46, 6333.
1
8 J. A. Moulijn and F. Kapteijn, Appl. Catal., A, 2001, 212, 3;
K. Arnby, A. Torncrona and M. Skoglundh, Appl. Catal., B, 2004,
49, 51.
This journal is c The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 9631–9633 9633