Organic Letters
Letter
543−562. (b) Inuki, S. Platinum Metals Rev. 2012, 56, 194−199.
(c) Yoshida, M. Chem. Pharm. Bull. 2012, 60, 285−299.
(6) For reports of Pd-catalyzed propargylation see, inter alia:
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(g) Duan, X.-h.; Liu, X.-y.; Guo, L.-n.; Liao, M.-c.; Liu, W.-M.;
Liang, Y.-m. J. Org. Chem. 2005, 70, 6980−6983. (h) Yoshida, M.;
Ueda, H.; Ihara, M. Tetrahedron Lett. 2005, 46, 6705−6708.
(i) Behenna, D. C.; Mohr, J. T.; Sherden, N. H.; Marinescu, S. C.;
́
Harned, A. M.; Tani, K.; Seto, M.; Ma, S.; Novak, Z.; Krout, M. R.;
McFadden, R. M.; Roizen, J. L.; Enquist, J. A., Jr.; White, D. E.; Levine,
S. R.; Petrova, K. V.; Iwashita, A.; Virgil, S. C.; Stoltz, B. M. Chem.
́
Eur. J. 2011, 17, 14199−14223. (j) Millan
́
, A.; Alvarez de Cienfuegos,
Figure 1. Proposed catalytic cycle.
L.; Martín-Lasanta, A.; Campana, A. G.; Cuerva, J. M. Adv. Synth.
̃
Catal. 2011, 73−78. (k) Yoshida, M.; Sugimura, C. Tetrahedron Lett.
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̈
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Franckevicius, V. Org. Lett. 2013, 15, 3778−3781.
of oxindole-based bis-nucleophiles and the use of chiral
phosphines in such reactions are currently under investigation.
(7) The initial propargylation results with indole substrates were
reported in the 2012 doctoral dissertation cited in ref 3b.
(8) During the course of these studies, two reports appeared on the
propargylation of indole substrates, both utilizing a tethered alkyne for
an intramolecular reaction: (a) Nemoto, T.; Zhao, Z.; Yokosaka, T.;
Suzuki, Y.; Wu, R.; Hamada, Y. Angew. Chem., Int. Ed. 2013, 52, 2217−
2220. (b) Iwata, A.; Inuki, S.; Oishi, S.; Fuji, N.; Ohno, H. Chem.
Commun. 2014, 50, 298−300.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures and spectroscopic data for all
reported compounds. This material is available free of charge
(9) We have found no other reports of a Pd-catalyzed intermolecular
reaction between indole and propargyl carbonate.
(10) Small amounts of oligomeric byproducts form at higher
concentration, and these appear to slow down the reaction. Addition
of a small quantity of the oligomeric compounds significantly slowed
the reaction versus the control reaction.
(11) The use of other chiral phosphines is currently under
investigation, and the results will be reported in due course.
(12) The structure of “dimer” 5 was determined to be:
AUTHOR INFORMATION
Corresponding Author
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Financial support from the National Institutes of Health
(GM069990 and P50 GM086145) is gratefully acknowledged.
■
REFERENCES
■
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