6318
J. M. Kim et al. / Tetrahedron Letters 44 (2003) 6317–6318
Table 1. Synthesis of a-iodo enaminones 2
separated by silica gel column chromatography (CH2Cl2
followed by hexane/ethyl acetate, 1:1) to give the desired
a-iodo enaminone 2a as a light tan solid, 595 mg (95%).
The postulated reaction mechanism is shown in Scheme
2.11 a-Iodo iminium salt (I) could be formed via direct
attack of iodine at the a-position of 1a. Or, (I) could be
generated via an SN2% type reaction of the initially formed
N-iodonium salt (II).5,12 Following abstraction of a-pro-
ton from (I) by triethylamine gave the product 2a.
In summary, we report herein the facile synthesis of
a-iodo enaminones by the use of iodine and triethylamine
in short time in excellent yields.
Acknowledgements
This work was supported by Korea Research Founda-
tion Grant (KRF-2002-015-CP0215).
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Scheme 2.
11. The reaction mechanism in Figure 1 was suggested by one
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Figure 1.