Organic Letters
Letter
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product 5 could be explained by a reversible enamine formation
from intermediate II.
In summary, a diastereoselective, Ag- (or Cu)-catalyzed
cyclization reaction of 2-(2-enynyl)pyridines and enamines was
developed. With preformed enamines, high yields of polycyclic
indolizines were obtained with high to excellent diastereose-
lectivities. When the enamine was formed in situ, indolizines 5
were formed in excellent yields. In this reaction, low
diastereomeric ratios were generally observed, with the
exception of alkyl-substituted 2-(2-enynyl)pyridine starting
materials. An asymmetric organocatalyzed reaction of 2-(2-
enynyl)pyridines, cyclopentanone, and enantioenriched amines
was performed (ee up to 79%). The indolizine products are
proposed to be formed from a common intermediate with the
Ag (or Cu) catalyst functioning as a π-Lewis acid activating the
alkyne moiety.
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ASSOCIATED CONTENT
* Supporting Information
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S
(e) Zhu, H.; Stockigt, J.; Yu, Y.; Zou, H. Org. Lett. 2011, 13, 2792.
̈
The Supporting Information is available free of charge on the
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́ ́
G.; Riesgo, L.; Lopez, L. A.; Tomas, M. J. Am. Chem. Soc. 2010, 132,
Detailed experimental data and characterization data
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(10) Pathipati, S. R.; van der Werf, A.; Eriksson, L.; Selander, N.
Angew. Chem., Int. Ed. 2016, 55, 11863.
AUTHOR INFORMATION
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Corresponding Author
ORCID
(11) Bicyclo[3.n.1]alkenones were obtained; see: Pathipati, S. R.;
Eriksson, L.; Selander, N. Chem. Commun. 2017, 53, 11353.
(12) (a) Liu, R.-R.; Cai, Z.-Y.; Lu, C.-J.; Ye, S.-C.; Xiang, B.; Gao, J.;
Jia, Y.-X. Org. Chem. Front. 2015, 2, 226. (b) Liu, R.-R.; Lu, C.-J.;
Zhang, M.-D.; Gao, J.-R.; Jia, Y.-X. Chem. - Eur. J. 2015, 21, 7057.
(13) (a) Bagle, P. N.; Mane, M. V.; Vanka, K.; Shinde, D. R.; Shaikh,
S. R.; Gonnade, R. G.; Patil, N. T. Chem. Commun. 2016, 52, 14462.
(b) Mahesh, S.; Anand, R. V. Eur. J. Org. Chem. 2017, 2698.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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Financial support from the Swedish Research Council is
gratefully acknowledged.
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