Organic & Biomolecular Chemistry
Communication
green methodology makes use of molecular oxygen and
aqueous ammonia and does not need any toxic cyanides. Key
to success for this reaction is the use of a nanostructured
cobalt oxide material, which is activated by nitrogen-doped
graphene layers. The general applicability of this methodology
is demonstrated by the synthesis of >40 structurally diverse
and interesting nitriles in good to excellent yields. Notably, the
heterogeneous catalyst is stable, easily recycled and can be
conveniently re-used.
Acknowledgements
The Federal Ministry of Education and Research (BMBF) and
the State of Mecklenburg-Vorpommern are gratefully acknowl-
edged for their general support. We are grateful to
Prof. A. Brückner, Dr J. Radnik and Dr M.-M. Pohl for catalyst
characterization.
Scheme 3 Co3O4/NGr@C-catalyzed synthesis of heterocyclic nitriles.
Reaction conditions: 0.5 mmol amine, 40 mg catalyst (4 mol% Co),
200 µL aq. NH3 (28–30% NH3 basis), 2 bar O2, 4 mL t-amyl alcohol,
110 °C, 15 h, yields were determined by GC using n-hexadecane stan-
dard. a Isolated yields.
Notes and references
(b) S. M. Holzwarth and B. Plietker, ChemCatChem, 2013, 5,
1650; (c) M. R. Bullock, Science, 2013, 342, 1054; (d) L. Que
Jr. and B. W. Tolman, Nature, 2008, 455, 333.
2 L. Kesavan, R. Tiruvalam, M. H. Ab Rahim, M. I. bin
Saiman, D. I. Enache, R. L. Jenkins, N. Dimitratos,
J. A. Lopez-Sanchez, S. H. Taylor, D. W. Knight, C. J. Kiely
and G. J. Hutchings, Science, 2011, 331, 195.
3 (a) R. V. Jagadeesh, A.-E. Surkus, H. Junge, M.-M. Pohl,
J. Radnik, J. Rabeah, H. Huan, V. Schünemann,
A. Brückner and M. Beller, Science, 2013, 342, 1073;
(b) F. A. Westerhaus, R. V. Jagadeesh, G. Wienhöfer,
M.-M. Pohl, J. Radnik, A.-E. Surkus, J. Rabeah, K. Junge,
H. Junge, M. Nielsen, A. Brückner and M. Beller, Nat.
Chem., 2013, 5, 537; (c) R. V. Jagadeesh, H. Junge,
M.-M. Pohl, J. Radnik, A. Brückner and M. Beller, J. Am.
Chem. Soc., 2013, 135, 10776; (d) R. V. Jagadeesh, H. Junge
and M. Beller, Nat. Commun., 2014, 5, 4123;
(e) R. V. Jagadeesh, K. Natte, H. Junge and M. Beller, ACS
Catal., 2015, 5, 1526.
4 (a) S. A. Lawrence, in Amines: Synthesis, Properties, and
Application, Cambridge University Press, Cambridge, 2004;
(b) M. Johannsen and K. A. Jørgensen, Chem. Rev., 1998,
98, 1689.
5 For transformation of amine, see: (a) D. Koszelewski,
B. Grischek, S. M. Glueck, W. Kroutil and K. Faber, Chem. –
Eur. J., 2011, 17, 378; (b) S. Bahn, S. Imm, L. Neubert,
M. Zhang, H. Neumann and M. Beller, ChemCatChem,
2011, 3, 1853; (c) C. Gunanathan and D. Milstein, Science,
2013, 341, 249.
Fig. 2 Synthesis of benzonitrile: recycling of Co3O4/NGr@C-catalysts.
Reaction conditions: 1 mmol benzylamine, 80 mg catalyst (4 mol% Co),
400 µL aq. NH3 (28–30% NH3 basis), 2 bar O2, 4 mL t-amyl alcohol, 110 °C,
15–20 h, yields were determined by GC using n-hexadecane standard.
Finally, we showed the broad applicability of this method-
ology by synthesizing a number of heterocyclic nitriles. Hetero-
cycles including pyridines, oxazoles, thiazoles, indoles,
pyrazines and others were well tolerated and the corres-
ponding products are obtained in good to excellent yield
(Scheme 3). Several of these heterocyclic nitriles are valuable
precursors and intermediates for active life science products.
From a practical point of view the stability and recyclability
of our Co-based catalyst is noteworthy. Such recycling is an
important aspect for industry. Indeed, the catalyst is highly
stable in the bench mark reaction and can be conveniently re-
used up to 4 times (Fig. 2).
6 For oxidation of amines, see: (a) A. E. Wendlandt and
S. S. Stahl, J. Am. Chem. Soc., 2014, 136, 506;
(b) K. Yamaguchi and N. Mizuno, Angew. Chem., Int. Ed.,
2003, 42, 1480; (c) M. L. Deb, S. S. Dey, I. Bento,
Conclusions
In summary, we developed a highly selective and general oxi-
dation process for the synthesis of nitriles from amines. This
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