Organic Letters
Letter
nucleophilic attack of the indole nitrogen on the carbonyl
moiety gives 5aa with the release of MeOH. In the presence of
excess NCS, 5aa is converted to the undesired product 14.
In conclusion, we have developed a novel acid-catalyzed
amination/cyclization cascade under mild conditions. Phaitan-
thrin E derivatives were obtained in good yields from simple
starting materials, and the reaction exhibits good functional
group tolerance and scalability. The cascade proceeds through
chlorine-mediated dearomatization/acid-catalyzed protonation
of indolenine/C-2 amination/base-promoted aromatization and
cyclization in a one-pot manner.
5018. (c) Abe, T.; Nakamura, S.; Yanada, R.; Choshi, T.; Hibino, S.;
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(14) Chen, T.; Foo, T. J. Y.; Yeung, Y.-Y. ACS Catal. 2015, 5, 4751.
(15) For selected examples of reactions initiated by chlorine-
mediated dearomatization of indoles, see: (a) Awang, D. V. C.;
Vincent, A.; Kindack, D. Can. J. Chem. 1984, 62, 2667. (b) Booker-
Milburn, K. I.; Fedouloff, M.; Paknoham, S. J.; Strachan, J. B.; Melville,
J. L.; Voyle, M. Tetrahedron Lett. 2000, 41, 4657. (c) Bergman, J.;
Engqvist, R.; Stalhandske, C.; Wallberg, H. Tetrahedron 2003, 59,
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(
e) He, L.; Yang, L.; Castle, S. L. Org. Lett. 2006, 8, 1165. (f) Hu, W.;
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g) Ma, B.; Banerjee, B.; Litvinov, D. N.; He, L.; Castle, S. L. J. Am.
ASSOCIATED CONTENT
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S
Supporting Information
Chem. Soc. 2010, 132, 1159. (h) Feng, Y.; Chen, G. Angew. Chem., Int.
Ed. 2010, 49, 958.
(16) For selected examples of reactions via the reactive indolenium
ion, see: (a) Li, Y.-X.; Ji, K.-G.; Wang, H.-X.; Ali, S.; Liang, Y.-M. J.
Org. Chem. 2011, 76, 744. (b) Wu, W.-B.; Huang, J.-M. Org. Lett.
2
012, 14, 5832. (c) Liu, K. G.; Robichaud, A. J.; Lo, J. R.; Mattes, J. F.;
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data, including H and C NMR spectra (PDF)
Cai, Y. Org. Lett. 2006, 8, 5769. (d) Austin, J. F.; Kim, S.-G.; Sinz, C. J.;
Xiao, W.-J.; MacMillan, D. W. C. Proc. Natl. Acad. Sci. U. S. A. 2004,
101, 5482. (e) Jones, S. B.; Simmons, B.; MacMillan, D. W. C. J. Am.
Chem. Soc. 2009, 131, 13606. (f) Tan, B.; Hernandez-Torres, G.;
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Barbas, C. F., III J. Am. Chem. Soc. 2011, 133, 12354. (g) Xiao, Y. C.;
Wang, C.; Yao, Y.; Sun, J.; Chen, Y.-C. Angew. Chem., Int. Ed. 2011, 50,
AUTHOR INFORMATION
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0661.
17) Protonation of the indole nitrogen generates a reactive iminium
ORCID
Notes
ion that can be trapped by a nucleophile. See: Poirier, M.; Goudreau,
S.; Poulin, J.; Savoie, J.; Beaulieu, P. L. Org. Lett. 2010, 12, 2334.
(18) Leong, S. Y.; Smith, P. W.; Zou, B. Chin. J. Chem. 2014, 32,
The authors declare no competing financial interest.
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217.
ACKNOWLEDGMENTS
This work was financially supported by JSPS KAKENHI Grant
6K18849 (T.A.) as a Grant-in-Aid for Young Scientists (B).
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