Green Chemistry
Communication
Acknowledgements
The research has been funded by the State of Mecklenburg-
Western Pomerania, the BMBF, and Evonik. We thank Dr
W. Baumann, J. Radnik, A. Koch, and T. Peppel for their excel-
lent technical and analytical support.
References
1 P. N. Rylander, Hydrogenation Methods, Academic Press,
New York, 1985, pp. 82–93.
2 O. Mitsunobu, B. M. Trost and I. Fleming, Comprehensive
Organic Synthesis, Oxford, 1991, vol. 6, p. 65.
Fig. 3 Recycling experiments of the reductive amination of benz-
aldehyde with nitrobenzene.
3 (a) S. Nishimura, Handbook of Heterogeneous Catalytic
Hydrogenation for Organic Synthesis, Wiley-VCH, New York,
2001, pp. 170–290; (b) F. Nerozzi, Platinum Met. Rev., 2012,
56, 236–241.
4 (a) K. Shimizu, M. Nishimura and A. Satsuma, Chem-
CatChem, 2009, 1, 497–503; (b) K. Yamaguchi, J. L. He,
T. Oishi and N. Mizuno, Chem. – Eur. J., 2010, 16, 7199–
7207; (c) P. R. Likhar, R. Arundhathi, M. L. Kantam and
P. S. Prathima, Eur. J. Org. Chem., 2009, 5383–5389;
(d) J. W. Kim, K. Yamaguchi and N. Mizuno, J. Catal., 2009,
263, 205–208; (e) J. L. He, K. Shimizu and N. Mizuno,
Chem. Lett., 2010, 39, 1182–1183.
Conclusion
In conclusion, we have described a nano-structured cobalt-
based catalyst for the straightforward reductive amination with
nitroarenes. Employing molecular hydrogen as the reductant,
hydrogenation of the nitro group and the resulting imines
took place to give selectively a variety of secondary amines.
This atom efficient and environmentally friendly methodology
is applicable to both aliphatic and aromatic nitro compounds,
aldehydes and ketones.
5 (a) L. Li, Z. Niu, S. Cai, Y. Zhi, H. Li, H. Rong, L. Liu, L. Liu,
W. He and Y. Li, Chem. Commun., 2013, 49, 6843–6845;
(b) C.-H. Tang, L. He, Y.-M. Liu, Y. Cao, H.-Y. He and
Experimental section
The general procedure for the one-pot reductive amination is
as follows: in a reaction vial (8 mL), nitroarene (0.5 mmol) and
aromatic aldehyde (1.0 mmol) were dissolved in 3 mL THF–
H2O (10 : 1)-solvent mixture. Then, 2 mol% of the cobalt-based
catalyst was added. The reaction vials (up to 7) were placed
into a 300 mL autoclave. The autoclave was flushed with hydro-
gen twice (ca. 40 bar) and pressurized to 50 bar hydrogen. It
was then placed into an aluminium block, heated up to 110 °C
or 125 °C, and stirred for the indicated time (24 h). After the
reaction was complete, the autoclave was cooled to room temp-
erature and the hydrogen was released. To the crude reaction
mixture was added n-hexadecane (52 μL) as an internal stan-
dard. Subsequently, the solution was filtered through silica gel
and analysed to determine the yield by using GC.
K.-N. Fan, Chem.
– Eur. J., 2011, 17, 7172–7177;
(c) B. Sreedhar, P. S. Reddy and D. K. Devi, J. Org. Chem.,
2009, 74, 8806–8809.
6 U. Siegrist, P. Baumeister and H.-U. Blaser, Catalysis of
Organic Reactions, ed. F. Herkes, M. Dekker, Chemical
Industries Series 75, 1998, pp. 207–219.
7 A. Onopchenko, E. T. Sabourin and C. M. Selwitz, J. Org.
Chem., 1979, 44, 1233–1236.
8 P. Baumeister, H. U. Blaser and W. Scherrer, Stud. Surf. Sci.
Catal., 1991, 59, 312.
9 E. Auer, A. Freud, M. Gross, R. Hartung and P. Panster,
Catalysis of Organic Reactions, ed. F. Herkes, M. Dekker,
Chemical Industries Series 75, 1998, pp. 225–231.
10 F. Cardenas-Lizana, S. Gomez-Quero and M. A. Keane,
ChemSusChem, 2008, 1, 215–221.
Synthesis of 3 wt% carbon-supported cobalt-based catalyst
11 F. Cardenas-Lizana, S. Gomez-Quero, A. Hugon, L. Delannoy,
C. Louis and M. A. Keane, J. Catal., 2009, 262, 235–243.
In a 100 mL round bottom flask, Co(OAc)2 (124.5 mg,
0.5 mmol) and 1,10-phenanthroline (180.2 mg, 1.0 mmol) 12 (a) M. Takasaki, Y. Motoyama, K. Higashi, S.-H. Yoon,
were dissolved in 20 mL EtOH and stirred for 1 h at 60 °C,
leading to the formation of a dark yellow solution. Next,
Vulcan XC72R carbon powder (700 mg) was added and the
I. Mochida and H. Nagashima, Org. Lett., 2008, 10, 1601–
1604; (b) C.-H. Li and Z.-X. Yu, J. Mol. Catal. A: Chem., 2005,
226, 101–105.
mixture was stirred overnight at room temperature. Afterwards, 13 G. G. Ferrier and F. King, Platinum Met. Rev., 1983, 27,
the solvent of the suspension was evaporated and the 72–77.
remained carbon powder was dried for 4 h. Finally, the catalyst 14 R. Raja, V. B. Golovko, J. M. Thomas, A. Berenger-Murcia,
was pyrolysed at 800 °C for 2 h under an argon atmosphere
(elemental analysis of Co3O4/NGr@C (wt%): C = 92.28, H =
0.20, N = 2.70, Co = 3.50, O = 1.32).
W. Z. Zhou, S. H. Xie and B. F. G. Johnson, Chem.
Commun., 2005, 2026–2028.
15 L. P. Kuhn, J. Am. Chem. Soc., 1951, 73, 1510–1512.
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