D
Q.-D. Wang et al.
Letter
Synlett
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NH2
H
H
Fe(III)
NH
Fe(III)
HCHO
+
NH3
N
H
A
B
N
H
1a
Fe(III)
Fe(II)
O
SET
O2
HN
H
NH2
H2O
N
N
N
H
H
2a
H
D
C
Scheme 3 Proposed reaction mechanism
In conclusion, we have developed a simple and practical
method for the C3-formylation of free (N–H) or N-substitut-
ed indoles by using formaldehyde as a carbon source and
cheap, benign, and nontoxic ferric chloride as the catalyst.13
Air was employed as the economic and safe oxidant, avoid-
ing the use of harmful peroxide oxidants. This procedure
can be applied to gram-scale syntheses and represents an
exceedingly attractive alternative to conventional formyla-
tion methods.
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Funding Information
We thank the National High Technology Research and Development
Program of China (2007AA02Z301), the Natural Science Foundation
of Jiangsu Province (BK20141257), the Natural Science Foundation of
Yancheng Teachers University (09YCKL021, 14YCKL001), and the Fun-
damental Research Funds for the Central University (WY111307) for
their generous financial support
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(6) Wu, W.; Su, W. J. Am. Chem. Soc. 2011, 133, 11924.
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Supporting Information
Supporting information for this article is available online at
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ortioInfgrmoaitn
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© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E