Organic Letters
Letter
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Scheme 7. Proposed Reaction Mechanism
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Attack of enamine moiety in 7 to carbonyl group, possible
assisted by gold catalyst due to its σ-acidity, followed by
elimination of water leads to the final product 2.
In summary, we have developed a gold-catalyzed hydro-
amination/cyclization reaction of α-amino ketones with alkynes
to multisubstituted pyrroles with high diversity. Gold catalysts
are effective to catalyze both processes through activation of the
alkyne via π-coordination and carbonyl group via σ-activation.
This method offers several advantages such as high
regioselectivity with the tested cases, wide substrate scope,
and easily accessible starting materials. The synthetic utility of
the obtained pyrroles was demonstrated by their efficient
transformations to 2-vinylated pyrroles via gold-catalyzed
intermolecular hydroarylation. Further studies to extend the
scope of this Au-catalyzed cascade reactions are in progress in
our laboratory.
̆
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(10) Recently, Tokuyama et al. reported that intermolecular reaction
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pyrroles, which proceeded via gold-acetylide addition/intramolecular
hydroamination cascade. See ref 9k.
ASSOCIATED CONTENT
* Supporting Information
Experimental details, spectroscopic characterization of all new
compounds, and X-ray crystallography of compounds 2y, 3a,
and 4a (PDF, CIF). The Supporting Information is available
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S
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2014, 16, 2244. (b) Matsuda, Y.; Naoe, S.; Oishi, S.; Fujii, N.; Ohno,
H. Chem.Eur. J. 2015, 21, 1463.
AUTHOR INFORMATION
Corresponding Authors
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(13) Removing of ester group of 2m in TFA afforded 2a. This result
confirmed the regiochemistry of 2m.
Notes
(14) According to the literature, N-(p-CO2RC6H4) group might be
removed by hydrolysis of the ester functionality under basic conditions
followed by Birch reduction to form N-H pyrrole, see: (a) Birch, A. J.;
Rickards, R. W.; Stapleford, K. J. S. Aust. J. Chem. 1969, 22, 1321.
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(16) The X-ray crystallography of 2y, 3a, and 4a are shown in the
Supporting Information.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We thank the National Natural Science Foundation of China
(grant nos. 21125210, 21421091, 21372244), Chinese
Academy of Science, and the Major State Basic Research
Development Program (grant no. 2011CB808700) for financial
support.
(17) See the Supporting Information.
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