Organic Letters
Letter
1338. (g) Song, W.; Ackermann, L. Chem. Commun. 2013, 49, 6638.
(h) Bernini, R.; Fabrizi, G.; Sferrazza, A.; Cacchi, S. Angew. Chem., Int.
Ed. 2009, 48, 8078.
ate A) under visible-light stimulation and subsequent electron
transfer with molecular oxygen,12 thereby leading to the
formation of radical cation species B/C. Radical cyclization13
would then take place in the shown deprotonation−
aromatization sequence of D−E−F to yield the final indole
product 3 with the elimination of hydrogen peroxide, thus
concluding a formal visible-light-mediated dehydrogenative
coupling cascade.
In summary, motivated by the initial design concept of
exploring possibly synergistic Au-catalysis as well as visible-light
photoredox catalysis, we have described herein some unusually
simple and mild reactivities allowing for direct preparations of a
diverse range of indole substances bearing multiple useful
functionalities. This new protocol accommodates various
anilines and alkyne substrates and mechanistically operates
through a fascinating cascade of Au-catalyzed hydroamination,
visible-light-promoted electron transfer, and dehydrogenative
coupling. The reactivity, not requiring the assistance of any
photosensitizer, adds further to its practicality. Given the widely
appreciated significance of indole-type substances in pharma-
ceutical and chemical contexts, it is well anticipated these
discoveries would find applications and stimulate further studies
in due course.
(5) For recent reviews on Au catalysis, see: (a) Hashmi, A. S. K.
Chem. Rev. 2007, 107, 3180. (b) Gorin, D. J.; Toste, F. D. Nature
2007, 446, 395. (c) Corma, A.; Leyva-Perez, A.; Sabater, M. J. Chem.
Rev. 2011, 111, 1657. (d) Krause, N.; Winter, C. Chem. Rev. 2011, 111,
1994. (e) Liu, L.-P.; Hammond, G. B. Chem. Soc. Rev. 2012, 41, 3129.
(6) For selected reviews on photoredox catalysis, see: (a) Narayanam,
J. M. R.; Stephenson, C. R. J. Chem. Soc. Rev. 2011, 40, 102. (b) Xuan,
J.; Xiao, W.-J. Angew. Chem., Int. Ed. 2012, 51, 6828. (c) Yoon, T. P.;
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D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322.
(7) Our previous studies on transition-metal catalysis and photoredox
catalysis, see: (a) Cai, S. Y.; Liu, Z.; Zhang, W. B.; Zhao, X. Y.; Wang,
D. Z. Angew. Chem., Int. Ed. 2011, 50, 11133. (b) Wang, L.; Cai, S. Y.;
Xing, X. Y.; Gao, Y.; Wang, T.; Wang, D. Z. Org. Lett. 2013, 15, 2362.
(c) Cai, S. Y.; Zhao, X. Y.; Wang, X. B.; Liu, Q. S.; Li, Z. G.; Wang, D.
Z. Angew. Chem., Int. Ed. 2012, 51, 8050. (d) Cai, S. Y.; Zhang, S. L.;
Zhao, Y. H.; Wang, D. Z. Org. Lett. 2013, 15, 2660.
(8) (a) Rueping, M.; Vila, C.; Koenigs, R. M.; Poscharny, K.; Fabry,
D. C. Chem. Commun. 2011, 47, 2360. (b) DiRocco, D. A.; Rovis, T. J.
Am. Chem. Soc. 2012, 134, 8094. (c) Ye, Y.; Sanford, M. S. J. Am.
Chem. Soc. 2012, 134, 9034. (d) Sahoo, B.; Hopkinson, M. N.; Glorius,
F. J. Am. Chem. Soc. 2013, 135, 5505.
(9) Neumann, J. J.; Rakshit, S.; Droge, T.; Wurtz, S.; Glorius, F.
̈
̈
Chem.Eur. J. 2011, 17, 7298.
ASSOCIATED CONTENT
* Supporting Information
■
(10) (a) Wallentin, C. J.; Nguyen, J. D.; Finkbeiner, P.; Stephenson,
C. R. J. J. Am. Chem. Soc. 2012, 134, 8875. (b) Lu, Z.; Yoon, T. P.
Angew. Chem., Int. Ed. 2012, 51, 10329. (c) Zhu, S.-Q.; Das, A.; Bui, L.;
Zhou, H.-J.; Curran, D. P.; Rueping, M. J. Am. Chem. Soc. 2013, 135,
1823. (d) McNally, A.; Prier, C. K.; MacMillan, D. W. C. Science 2011,
S
Experimental procedures and spectral data for all new
compounds. This material is available free of charge via the
334, 1114. (e) Hari, D. P.; Konig, B. Org. Lett. 2011, 13, 3852.
̈
(11) Kramer, S.; Dooleweerdt, K.; Lindhardt, A. T.; Rottlander, M.;
̈
AUTHOR INFORMATION
Corresponding Author
■
Skrydstrup, T. Org. Lett. 2009, 11, 4208.
(12) Maity, S.; Zheng, N. Angew. Chem., Int. Ed. 2012, 51, 9562.
(13) He, Z.; Liu, W.; Li, Z. Chem.Asian J. 2011, 6, 1340.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the NSFC (Grants 20972008 and 21290180 to
D.Z.W.), the national “973 Project” of the State Ministry of
Science and Technology (Grant 2013CB911500 to D.Z.W.),
the Shenzhen Bureau of Science and Technology, and the
Shenzhen “Shuang Bai Project” for financial support.
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