ORGANIC
LETTERS
2
004
Vol. 6, No. 20
585-3588
Unsymmetrical Hybrid Ferrocene-Based
Phosphine-Phosphoramidites: A New
Class of Practical Ligands for
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Rh-Catalyzed Asymmetric Hydrogenation
Xiang-Ping Hu and Zhuo Zheng*
Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
457 Zhongshan Road, Dalian 116023, China
Received July 28, 2004
ABSTRACT
The synthesis and application of a new family of air-stable, highly unsymmetrical ferrocene-based phosphine-phosphoramidites is described.
The new ligands exhibit excellent enantioselectivities (over 99% ee) in the Rh-catalyzed asymmetric hydrogenation of enamides, dimethyl
itaconate, and methyl (Z)-acetamidocinnamate even with high catalyst turnovers (S/C
) 10 000). The binaphthyl moiety is crucial for reactivity
and enantioselectivity, and its absolute configuration plays a dominant role in determining the chirality of the hydrogenation products.
Asymmetric catalytic hydrogenations by a metal catalyst
complexed with chiral ligands are some of the most powerful
tools for obtaining a wide range of enantiomerically pure or
been used successfully in this reaction are bidentate P-chelate
3
ligands, and most have a C
2
-symmetrical structure or at least
4
two closely related binding sites. Examples include BINAP,
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5
6
7
8
enriched compounds. In addition to some monodentate
DuPhos, DIPAMP, DIOP, TangPhos, and many ferro-
2
9
phosphorus-containing ligands, most of the ligands that have
cene-based ligands. In contrast, there have been few reports
on unsymmetrical P-chelate ligands. Compared to the widely
(
1) For reviews, see: (a) Brown, J. M. In ComprehensiVe Asymmetric
Catalysis; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer: Berlin,
999; Vol. 1, Chapter 5.1. (b) Ohkuma, T.; Kitamura, M.; Noyori, R. In
2
used C -symmetrical bidentate ligands with two equivalent
1
Catalytic Asymmetric Synthesis, 2nd ed.; Ojima, I., Ed.; Wiley-VCH: New
York, 2000; Chapter 1.
(3) For Reviews, see: (a) Blaser, H.-U.; Malan, C.; Pugin, B.; Spindler,
F.; Steiner, H.; Studer, M. AdV. Synth. Catal. 2003, 345, 103. (b) Tang,
W.; Zhang, X. Chem. ReV. 2003, 103, 3029.
(2) (a) Claver, C.; Fernandez, E.; Gillon, A.; Heslop, K.; Hyett, D. J.;
Martorell, A.; Orpen, a. G.; Pringle, P. G. Chem. Commun. 2000, 961. (b)
Reetz, M. T.; Mehler, G. Angew. Chem., Int. Ed. 2000, 39, 3889. (c) Van
den Berg, M.; Minnaard, A. J.; Schudde, E. P.; van Esch, J.; de Vries, A.
H. M.; de Vries, J. G.; Feringa, B. L. J. Am. Chem. Soc. 2000, 122, 11539.
(4) Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.; Souchi,
T.; Noyori, R. J. Am. Chem. Soc. 1980, 102, 7932.
(5) Burk, M. J. J. Am. Chem. Soc. 1991, 113, 8515.
(6) Vineyard, B. D.; Knowles, W. S.; Sabacky, M. J.; Bachman, G. L.;
Weinkauff, D. J. J. Am. Chem. Soc. 1977, 99, 5946.
(d) Pena, D.; Minnaard, A. J.; de Vries, J. G.; Feringa, B. L. J. Am. Chem.
Soc. 2002, 124, 14552. (e) Hu, A.-G.; Fu, Y.; Xie, J.-H.; Zhou, H.; Wang,
L.-X.; Zhou, Q.-L. Angew. Chem., Int. Ed. 2002, 41, 2348. (f) Reetz, M.
T.; Sell, T.; Meiswinkel, A.; Mehler, G. Angew. Chem., Int. Ed. 2003, 42,
(7) (a) Dang, T.-P.; Kagan, H. B. Chem. Commun. 1971, 481. (b) Kagan,
H. B.; Dang, T.-P. J. Am. Chem. Soc. 1972, 94, 6429.
(8) Tang, W.; Zhang, X. Angew. Chem., Int. Ed. 2002, 41, 1612.
(9) TRAP: Sawamura, M.; Kuwano. R.; Ito, Y. J. Am. Chem. Soc. 1995,
117, 4549. FerroPhos: Kang, J.; Lee, J. H.; Ahn, S. H.; Choi, J. S.
Tetrahedron Lett. 1998, 39, 5523. FerroTANE: (a) Marinetti, A.; Labrue,
F.; Genet, J.-P. Synlett 1999, 1975. (b) Berens, U.; Burk, M. J.; Gerlach,
A.; Hems, W. Angew. Chem., Int. Ed. 2000, 39, 1981.
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90. (g) Pe n˜ a, D.; Minnaard, A. J.; de Vries, A. H. M.; de Vries, J. G.;
Feringa, B. L. Org. Lett. 2003, 5, 475. (h) Reetz, M. T.; Goossen, L. J.;
Meiswinkel, A.; Paetzold, J.; Jensen, J. F. Org. Lett. 2003, 5, 3099. (i)
Hoen, R.; Van den Berg, M.; Bernsmann, H.; Minnaard, A. J.; de Vries, J.
G.; Feringa, B. L. Org. Lett. 2004, 6, 1433.
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0.1021/ol048519d CCC: $27.50
© 2004 American Chemical Society
Published on Web 08/27/2004