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Scheme 3 Evidence that 4 is not an intermediate of this nBu4NI-
catalyzed radical oxidative transformation.
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Scheme 4 Proposed preliminary mechanisms.
6 D. Shanmugapriya, R. Shankar, G. Satyanarayana, V. H.
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standard conditions was investigated. However, the product 3ba
was not obtained. This result indicates that 4 is not intermediate
of this nBu4NI-catalyzed radical oxidative transformation
(Scheme 3). On the basis of the above results and Wan’s studies
on the ‘‘nBu4NI-TBHP’’ system,12b–d a plausible mechanism for
the radical oxidative coupling is illustrated in Scheme 4. At the
beginning, the tert-butoxyl radical forms catalytically with the
assistance of the iodide anion. This radical traps H from the aryl
methyl ketone and DMF respectively to form radicals A and B.
Then, aminyl radical C12b produced from A coupled with radical
B to generate intermediate D. Finally, D is oxidized by TBHP to
form the desired product E (Scheme 4).
Chem. Commun., 2000, 985; (c) L. El. Kaım, R. Gamez-Montano,
¨
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In conclusion, we have developed a novel protocol for direct
synthesis of a-ketoamides which are important structural units
in lots of biological compounds or drugs. This transformation
catalyzed by nBu4NI in water is free of metal, environmentally
friendly and both substrates were cheap and easily available.
Further investigation on the reaction are ongoing in our
laboratory.
We gratefully acknowledge NSFC (No. 21172055).
12 (a) M. Uyanik, H. Okamoto, T. Yasui and K. Ishihara, Science,
2010, 328, 1376; (b) Z. J. Liu, J. Zhang, S. L. Chen, E. Shi, Y. Xu
and X. B. Wan, Angew. Chem., Int. Ed., 2012, 51, 3231;
(c) L. Chen, E. Shi, Z. J. Liu, S. L. Chen, W. Wei, H. Li, K. Xu
and X. B. Wan, Chem.–Eur. J., 2011, 17, 4085; (d) W. Wei,
C. Zhang, Y. Xu and X. B. Wan, Chem. Commun., 2011, 47, 10827.
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c
This journal is The Royal Society of Chemistry 2012
Chem. Commun.