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Table 3 Formation of aromatic benzyl imines from the corresponding
benzyl aminea
Entry
1
Substrate
Product
Yieldb (%)
85.8
2
3
4
499
499
499
5
6
499
499
a
All reactions were carried out with 10 mg red copper, 1 mmol
benzylamine, 1 mmol NH4Br, 1.5 mmol 1, 10-phenanthroline, and
b
2 mL toluene at 100 1C under 1 atm of oxygen. GC yields.
nitriles or imines effectively using the same benzylic oxidation
methodology. Further studies on this catalytic system are
ongoing in our laboratory to investigate wider applications.
H.W.G. acknowledges the financial support from the NSFC
(No. 21373006), the Key Project of Chinese Ministry of Educa-
tion (No. 211064), and the Priority Academic Program Develop-
ment of Jiangsu Higher Education Institutions.
Fig. 3 Proposed mechanism of this catalytic reaction using red copper.
Table 2 Formation of aromatic nitriles from the corresponding benzyl
aminesa
Notes and references
1 (a) R. A. Sheldon and J. K. Kochi, Metal-Catalyzed Oxidations of
Organic Compounds, Academic Press, New York, 1981; (b) B. M. Trost
and I. Fleming, Comprehensive Organic Synthesis (Oxidation), Perga-
mon, New York, 1991, vol. 7; (c) J. D. Nguyen, B. S. Matsuura and
C. R. J. Stephenson, J. Am. Chem. Soc., 2014, 136, 1218;
(d) M. Nakanishi and C. Bolm, Adv. Synth. Catal., 2007, 349, 861.
2 (a) A. J. Fatiadi, in Preparation and Synthetic Applications of Cyano
Compounds, ed. S. Patai and Z. Rappaport, Wiley, New York, 1983;
(b) J. S. Miller and J. L. Manson, Acc. Chem. Res., 2001, 34, 563;
(c) P. Magnus, D. A. Scott and M. R. Fielding, Tetrahedron Lett., 2001,
42, 4127.
Entry
Substrate
Product
Yieldb (%)
64.9
1
2
3
4
96.4
97.5
3 (a) S. Patai, The Chemistry of the Carbon-Nitrogen Double Bond
(Chemistry of Functional Groups), Wiley-Interscience, New York,
84.0
¨
1970; (b) J.-A. Ma, Chem. Soc. Rev., 2006, 35, 630; (c) A. Domling,
5
499
¨
Chem. Rev., 2006, 106, 17; (d) A. Erkkila, I. Majander and P. M.
Pihko, Chem. Rev., 2007, 107, 5416; (e) J. Gawronski, N. Wascinska
6c
67.2
´˜
and J. Gajewy, Chem. Rev., 2008, 108, 5227; ( f ) M. Ordonez, H. Rojas-
Cabrera and C. Cativiela, Tetrahedron, 2009, 65, 17; (g) S. F. Martin,
Pure Appl. Chem., 2009, 81, 195; (h) S. Kobayashi, Y. Mori, J. S. Fossey
and M. M. Salter, Chem. Rev., 2011, 111, 2626; (i) J.-H. Xie, S.-F. Zhu
and Q.-L. Zhou, Chem. Rev., 2011, 111, 1713; ( j) J. Adrio and
J. C. Carretero, Chem. Commun., 2011, 47, 6784; (k) C. S. Marques
and A. J. Burke, ChemCatChem, 2011, 3, 635; (l) T. R. Ramadhar and
R. A. Batey, Synthesis, 2011, 1321; (m) M. Nielsen, D. Worgull,
T. Zweifel, B. Gschwend, S. Bertelsen and K. A. Jøgensen, Chem.
Commun., 2011, 47, 632.
4 (a) K. T. Venkateswara, B. Haribabu, P. S. Sai Prasad and
N. Lingaiah, Green Chem., 2013, 15, 837; (b) G. Dasgupta and
M. K. Mahanti, Oxid. Commun., 2011, 34, 579; (c) S. MacMillar,
D. E. Edmondson and O. Matsson, J. Am. Chem. Soc., 2011,
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a
All reactions were carried out with 10 mg red copper, 1 mmol
benzylamine, 1 mmol NH4Br, 1.2 mmol isoquinoline, and 2 mL toluene
b
c
at 100 1C under 1 atm of oxygen. GC yields. Isolated yields.
the corresponding imines. Surprisingly, it also afforded a high yield
close to 100% (Table 3, entry 6).
In summary, we have successfully developed an efficient,
convenient and environmentally friendly method for red
copper-catalysed oxidation of benzylamines under mild reac-
tion conditions. By using the appropriate additive, we can select
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