M. Hatano et al. / Tetrahedron Letters 48 (2007) 8590–8594
8593
Chem., Int. Ed. 1997, 36, 186; (c) Sibi, M. P.; Manyem, S.
Tetrahedron 2000, 56, 8033; (d) Krause, N.; Hoffmann-
R o¨ der, A. Synthesis 2001, 171; (e) Alexakis, A.; Benhaim,
C. Eur. J. Org. Chem. 2002, 3221.
Et
Et
O
3
. Pioneering works with P-ligands and P,O-ligands: (a)
Feringa, B. L.; Pineschi, M.; Arnold, L. A.; Imbos, R.; de
Vries, A. H. M. Angew. Chem., Int. Ed. 1997, 36, 2620; (b)
Alexakis, A.; Vastra, J.; Burton, J.; Benhaim, C.; Mange-
ney, P. Tetrahedron Lett. 1998, 39, 7869; (c) Yan, M.;
Yang, L.-W.; Wong, K.-Y.; Chan, A. S. C. Chem.
Commun. 1999, 11; (d) Yan, M.; Zhou, Z.-Y.; Chan, A.
S. C. Chem. Commun. 2000, 115; (e) Alexakis, A.;
Benhaim, C.; Rosset, S.; Humam, M. J. Am. Chem. Soc.
2002, 124, 5262; (f) Taira, S.; Cr e´ py, K. V. L.; Imamoto,
T. Chirality 2002, 14, 386; (g) Huttenloch, O.; Laxman, E.;
Waldmann, H. Chem. Commun. 2002, 673; (h) Choi, Y.
H.; Choi, J. H.; Yang, H. Y.; Kim, Y. H. Tetrahedron:
Asymmetry 2002, 13, 801; (i) Reetz, M. T.; Gosberg, A.;
Moulin, D. Tetrahedron Lett. 2002, 43, 1189; (j) Watan-
abe, T.; Kn o¨ pfel, T. F.; Carreira, E. M. Org. Lett. 2003, 5,
Et
Zn
Et
Zn
H
H
N
Cu
N
Cu
H
H
N
N
H
Zn
Zn H
Et
Et
O
TS-1 (favored
)
TS-2 (disfavored
)
(
S
)-isomer
(R)-isomer
Figure 3. Proposed transition states.
postulated intermediate 17 before carbon–carbon bond-
formation (Fig. 2). In the transition states, si-face attack
TS-1) should be favored to avoid steric repulsion
between substrate (1) and the N-ZnEt moiety (TS-2)
Fig. 3). Eventually, (S)-product can be obtained with
release from the catalyst along with the regeneration
4
557; (k) Liang, L.; Su, L.; Li, X.; Chan, A. S. C.
(
Tetrahedron Lett. 2003, 44, 7217; (l) Monti, C.; Gennari,
C.; Steele, R. M.; Piarulli, U. Eur. J. Org. Chem. 2004,
(
3
557; (m) Ito, K.; Eno, S.; Saito, B.; Katsuki, T.
Tetrahedron Lett. 2005, 46, 3981; (n) Takahashi, Y.;
Yamamoto, Y.; Katagiri, K.; Danjo, H.; Yamaguchi, K.;
Imamoto, T. J. Org. Chem. 2005, 70, 9009; (o) Palais, L.;
Mikhel, I. S.; Bournaund, C.; Micouin, L.; Falciola, C. A.;
Vuagnoux-d’Augustin, M.; Rosset, S.; Bernardinelli, G.;
Alexakis, A. Angew. Chem., Int. Ed. 2007, 46, 7606.
. Pioneering works with N,N-ligands, P,N-ligands, and
P,O,N-ligands (a) Hu, X.; Chen, H.; Zhang, X. Angew.
Chem., Int. Ed. 1999, 38, 3518; (b) Chataigner, I.; Gennari,
C.; Piarulli, U.; Caccarelli, S. Angew. Chem., Int. Ed. 2000,
of 16 by Et Zn.
2
In summary, the enantioselective conjugate addition of
dialkylzinc to cyclic enones was achieved by using chiral
binaphthyldiamine–copper(I) catalysts. Sterically less-
hindered C -symmetric chiral binaphthyldiamine was
easily modified in two primary amino groups, and the
expected sterically demanding [RZn(II)] -binaphthyldi-
amine–Cu(I) complexes were formed via deprotonation
by R Zn in situ. The reaction of 2-cyclohexenone with
Et Zn proceeded smoothly in the presence of chiral
Cu(I) catalyst (5 mol %) and achiral 2,6-diphenylaniline
10 mol %) at 0 ꢁC for 1.5 h, and the corresponding
Et-adduct was obtained with up to 76% ee in 95% yield.
Further studies are in progress toward other catalytic
enantioselective reactions with the modified catalysts
by organometallic reagents in situ.
4
2
2
3
9, 916; (c) Escher, I. H.; Pfaltz, A. Tetrahedron 2000, 56,
2
2879; (d) Morimoto, T.; Yamaguchi, Y.; Suzuki, M.;
Saitoh, A. Tetrahedron Lett. 2000, 41, 10025; (e) Degrado,
S. J.; Mizutani, H.; Hoveyda, A. H. J. Am. Chem. Soc.
2001, 123, 755; (f) Schinnerl, M.; Seitz, M.; Kaiser, A.;
Reiser, O. Org. Lett. 2001, 3, 4259; (g) Mizutani, H.;
Degrado, S. J.; Hoveyda, A. H. J. Am. Chem. Soc. 2002,
2
(
124, 779; (h) Shintani, R.; Fu, G. C. Org. Lett. 2002, 4,
3699; (i) Krauss, I. J.; Leighton, J. L. Org. Lett. 2003, 5,
3201; (j) Hu, Y.; Liang, X.; Wang, J.; Zheng, Z.; Hu, X. J.
Org. Chem. 2003, 68, 4542; (k) Wan, H.; Hu, Y.; Liang,
Y.; Gao, S.; Wang, J.; Zheng, Z.; Hu, X. J. Org. Chem.
2
003, 68, 8277; (l) Liang, Y.; Gao, S.; Wan, H.; Hu, Y.;
Chen, H.; Zheng, Z.; Hu, X. Tetrahedron: Asymmetry
003, 14, 3211; (m) Hu, Y.; Liang, X.; Wang, J.; Zheng,
Z.; Hu, X. Tetrahedron: Asymmetry 2003, 14, 3907; (n)
Hird, A. W.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003,
Acknowledgments
2
Financial support for this project was provided by
Grant-in-Aid for Young Scientists B (19750072) of
MEXT, Toray Science Foundation, and Toyoaki Schol-
arship Foundation.
4
2, 1276; (o) Morimoto, T.; Mochizuki, N.; Suzuki, M.
Tetrahedron Lett. 2004, 45, 5717; (p) Shi, M.; Wang, C.-J.;
Zhang, W. Chem. Eur. J. 2004, 10, 5507; (q) Shi, M.;
Zhang, W. Adv. Synth. Catal. 2005, 347, 535; (r) Morim-
oto, T.; Obara, N.; Yoshida, I.; Tanaka, K.; Kan, T.
Tetrahedron Lett. 2007, 48, 3093; Pioneering works with
N-heterocyclic carbene ligands (s) Lee, K.-S.; Brown, M.
K.; Hird, A. W.; Hoveyda, A. H. J. Am. Chem. Soc. 2006,
Supplementary data
1
28, 7182.
5
6
. (a) Bordwell, F. G.; Algrim, D.; Vanier, N. R. J. Org.
Chem. 1977, 42, 1817; (b) Bordwell, F. G.; Algrim, D. J. J.
Am. Chem. Soc. 1988, 110, 2946.
. Multi-functionalized polymetallic catalyses (a) Oshima, K.
J. Organomet. Chem. 1999, 575, 1; (b) Boudier, A.;
Bromm, L. O.; Lotz, M.; Knochel, P. Angew. Chem.,
Int. Ed. 2000, 39, 4414; (c) Trost, B. M.; Ito, H. J. Am.
Chem. Soc. 2000, 122, 12003; (d) Trost, B. M.; Ito, H.;
Silcoff, E. R. J. Am. Chem. Soc. 2001, 125, 3367; (e)
References and notes
. Jacobsen, E. N.; Pfaltz, A.; Yamamoto, H. Comprehensive
1
Asymmetric Catalysis; Springer: New York, 1999.
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2