Organic Letters
Letter
Notes
to a mixture of ethylated and butylated products. This was
probably due to an iodolithium exchange (Bu-Li + Et-I → Bu-I
+ Et-Li) with unreacted butyllithium. This was avoided by
using sBuLi, so that 10c-cis was obtained with 94% yield and,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
1
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judging by H NMR, complete diastereomeric purity. After a
We thank Prof. Dr. Carsten Schmuck from the University of
Duisburg and Essen for his kind support, Prof. Dr. Tim
Gallagher from the University of Bristol for constructive
discussions, and the Deutsche Forschungsgemeinschaft (DFG)
for funding.
brief optimization, lithiation and olefination to the tetrasub-
stituted olefins 11e and 11f were achieved in 41% and 87%
yield, respectively. The anisole derivative 11f can be converted
into E-tamoxifen 11g.24 However, E-tamoxifen 11g can also be
prepared directly by reaction of lithiated 10c-cis with the
appropriate boronic ester, which contains an ether and a
tertiary amine functionality. That way, E-tamoxifen 11g can be
prepared in only two steps from cis-stilbene oxide 9b-cis in 59%
overall yield.
REFERENCES
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In conclusion, lithiated epoxides insert readily into boronic
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ASSOCIATED CONTENT
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S
* Supporting Information
The Supporting Information is available free of charge on the
Preceding experiments, detailed experimental proce-
dures, characterization data and copies of NMR spectra
(14) Review on alkene syntheses with carbenoids: (a) Blakemore, P.
R.; Hoffmann, R. W. Angew. Chem., Int. Ed. 2018, 57, 390−407.
Review on lithiated epoxides: (b) Hodgson, D. M.; Gras, E. Synthesis
2002, 2002, 1625−1642. (c) Capriati, V.; Florio, S.; Luisi, R. Chem.
Rev. 2008, 108, 1918−1942.
(15) The need for 2 equiv for the rearrangement to occur under
these conditions was recognized in ref 13a and is discussed here:
AUTHOR INFORMATION
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Corresponding Author
ORCID
̈
Bojaryn, K.; Hoffmann, C.; Struth, F. R.; Hirschhauser, C. Synlett
2018, 29, 1092−1094.
(16) The use of temperature regime A or B is a matter of
convenience, as shown for 6a. Lithiation can also be performed at
−30 °C (C) as shown for 6g. This can be useful when competing side
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D
Org. Lett. XXXX, XXX, XXX−XXX