Organic Letters
Letter
(8) For diastereoselective additions to chiral N-sulfinyl ketimines,
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(10) (a) Kolb, A.; Zuo, W.; Siewert, J.; Harms, K.; von Zezschwitz, P.
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7122.
1d provide insight into the mechanisms of both addition
modes. We are now working on gaining a better understanding
of the catalytic cycles and on optimizing the asymmetric
conjugate addition of alkyl and aryl groups.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures and analytical data for all compounds;
crystallographic data for compounds (S)-2a, (1S,5S)-2d, (S)-4a,
and (1R,4S)-5e. This material is available free of charge via the
AUTHOR INFORMATION
Corresponding Author
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(11) For reviews, see: (a) Kolb, A.; von Zezschwitz, P. Top.
Organomet. Chem. 2013, 41, 245. (b) von Zezschwitz, P. Synthesis
2008, 1809. (c) Oishi, M. Sci. Synth. 2004, 7, 261.
Notes
(12) Hirner, S.; Westmeier, J.; Gebhardt, S.; Muller, C. H.; von
̈
Zezschwitz, P. Synlett 2014, DOI: 10.1055/s-0034-1378203.
(13) For a preparation of compound 2a via enantioselective
aziridination and subsequent Wharton reaction, see: Jiang, H.;
Holub, N.; Jorgensen, K. A. Proc. Natl. Acad. Sci. U.S.A. 2010, 107,
20630.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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This manuscript is dedicated to Professor Armin de Meijere on
the occasion of his 75th birthday. The authors thank the Bengt
Lundqvist Foundation, the Fonds der Chemischen Industrie,
and the Konrad-Adenauer-Stiftung for providing scholarships
for S.H., A.K., and J.W., respectively, and Sophie Schlondorff
for careful proofreading.
(14) For diastereoselective conjugate additions of cuprates to chiral
cyclic and acyclic ketimines or hydrazones, see: (a) Sammet, K.; Gastl,
C.; Baro, A.; Laschat, S.; Fischer, P.; Fettig, I. Adv. Synth. Catal. 2010,
352, 2281. (b) McMahon, J. P.; Ellman, J. A. Org. Lett. 2005, 7, 5393.
For asymmetric Cu-catalyzed conjugate additions of organozinc
reagents to acyclic imines, see: (c) Palacios, F.; Vicario, J. Org. Lett.
2006, 8, 5405. (d) Esquivias, J.; Arrayas, R. G.; Carretero, J. C. J. Org.
́
Chem. 2005, 70, 7451. (e) Soeta, T.; Kuriyama, M.; Tomioka, K. J.
Org. Chem. 2005, 70, 297.
(15) Caution: neat AlMe3 is highly pyrophoric; thus, we recommend
use of commercially available solutions of AlMe3 in hexanes if not
familiar with the handling of pyrophoric compounds.
(16) The N-tert-butylsulfonyl imine of cyclohex-2-enone underwent
1,2-addition of AlMe3 in a 32% yield with >99% ee while the respective
N-diphenylphosphinoyl imine was deprotonated by AlMe3. Use of
AlEt3 led to reduction of N-tosyl ketimine 1a, presumably due to β-
hydride elimination.
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