LETTER
New Bidentate Phosphorus Ligands
3009
(8) Bernsmann, H.; van den Berg, M.; Hoen, R.; Minnaard, A.
J.; Mehler, G.; Reetz, M. T.; De Vries, J. G.; Feringa, B. L.
J. Org. Chem. 2005, 70, 943.
The catalyst system Rh/4c also performed very well in the
asymmetric hydrogenation of dimethyl itaconate
(Table 3). It was shown that even when the substrate-to-
catalyst ratio was at 1000, the substrate can be completely
converted into the optically active product within 1 hour
under 10 atm pressure of H2 (Table 3, entry 4). When the
Rh/4b system was applied to the hydrogenation of di-
methyl itaconate, high product ee value (98%) was also
achieved (Table 3, entry 1).
(9) Zhang, X. M. Enantiomer 1999, 4, 451.
(10) Reetz, M. T.; Li, X. G. J. Am. Chem. Soc. 2006, 128, 1044.
(11) Hayashi, T.; Ueyama, K.; Tokunaga, N.; Yoshida, K. J. Am.
Chem. Soc. 2003, 125, 11508.
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Vogl, N.; Lex, J.; Neudörfl, J. M. J. Org. Chem. 2004, 69,
3050.
(13) Berkessel, A.; Menche, D.; Sklorz, C. A.; Schröder, M.;
Paterson, I. Angew. Chem. Int. Ed. 2003, 42, 1032.
(14) Vandyck, K.; Matthys, B.; Willen, M.; Robeyns, K.; Van
Meervelt, L.; Van der Eycken, J. V. Org. Lett. 2006, 8, 363.
(15) (a) Uozumi, Y.; Lee, S. Y.; Hayashi, T. Tetrahedron Lett.
1992, 33, 7185. (b) Weissfloch, A.; Azerad, R. Bioorg. Med.
Chem. 1994, 2, 493.
In conclusion, a new class of bidentate phosphorus
ligands based on norbornane has been developed and ap-
plied to the Rh(I)-catalyzed asymmetric hydrogenation of
a variety of olefin derivatives, affording the correspond-
ing optically active compounds in excellent yields and
high enantioselectivities even under low H2 pressure. Fur-
ther investigations are now under way.
(16) Cai, C. L.; Xia, C. G. Synthesis 2006, 2297.
(17) Ligands Preparation (Scheme 1)
The Preparation of Ligand 3
A 10 mL Schlenk flask was charged with diol 2 (100 mg,
0.78 mmol), DMAP (20 mg), Et3N (160 mg, 1.6 mmol) and
THF (5 mL) under nitrogen. The mixture was stirred at 0 °C.
A solution of chlorodiphenylphosphine (0.3 mL, 1.56 mmol)
in THF (2 mL) was added dropwise with stirring, then stirred
at r.t. for 24 h. After filtration, the solvent was removed
under vacuum. The crude product was purified through flash
chromatography to give pure product as a thick liquid; yield
233 mg (47%). MS (EI): m/z = 496 [M+]. 1H NMR (400
MHz, CDCl3): d =7.44–7.13 (m, 20 H, Ph), 4.70–4.69 (b, 2
H, C2 and C5), 2.25 (s, 2 H, bridgehead), 1.92 (d, 2 H, endo
of C3 and C5), 1.69 (m, 2 H, exo of C3 and C5), 1.23 (s, 2 H,
bridge). 13C NMR (100 MHz, CDCl3): d = 149.678–122.009
(Ph), 75.628 (O–C), 42.500(bridgehead), 34.849 (bridge),
28.965 (C3 and C5). 31P NMR (162 MHz, CDCl3): d =
109.130.
Acknowledgment
The authors are grateful to the National Natural Science Foundation
of China (20625308) and Chinese Academy of Sciences for finan-
cial support of this work.
References and Notes
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C. C.; Lau, C. P. J. Am. Chem. Soc. 1997, 119, 9570.
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67, 3796.
(2) (a) Diéguez, M.; Pàmies, O.; Ruiz, A.; Castillón, S.; Claver,
C. Chem. Eur. J. 2001, 7, 3086. (b) Diéguez, M.; Pàmies,
O.; Claver, C. Tetrahedron: Asymmetry 2004, 15, 2113.
(3) (a) Landis, C. R.; Hilfenhaus, P.; Feldgus, S. J. Am. Chem.
Soc. 1999, 121, 8741. (b) Feldgus, S.; Landis, C. R. J. Am.
Chem. Soc. 2000, 122, 2714. (c) Landis, C. R.; Feldgus, S.
Angew. Chem. Int. Ed. 2000, 39, 2863. (d) Feldgus, S.;
Landis, C. R. Organometallics 2001, 20, 2374.
(4) (a) Jia, X.; Li, X.; Xu, L.; Shi, Q.; Yao, X.; Chan, A. S. C.
J. Org. Chem. 2003, 68, 4539. (b) Zeng, Q. L.; Liu, H.; Cui,
X.; Mi, A. Q.; Jiang, Y. Z.; Li, X. S.; Chio, M. C. K.; Chan,
A. S. C. Tetrahedron: Asymmetry 2002, 13, 115. (c) Jia, X.;
Guo, R.; Li, X.; Yao, X.; Chan, A. S. C. Tetrahedron Lett.
2002, 43, 5541.
(5) Reetz, M. T.; Meiswinkel, A.; Mehler, G.; Angermund, K.;
Graf, M.; Thiel, W.; Mynott, R.; Blackmond, D. G. J. Am.
Chem. Soc. 2005, 127, 10305.
(6) (a) Hu, A. G.; Fu, Y.; Xie, J. H.; Zhou, H.; Wang, L. X.;
Zhou, Q. L. Angew. Chem. Int. Ed. 2002, 41, 2348. (b) Fu,
Y.; Guo, X. X.; Zhu, S. F.; Hu, A. G.; Xie, J. H.; Zhou, Q. L.
J. Org. Chem. 2004, 69, 4648. (c) Liu, Y.; Ding, K. L. J.
Am. Chem. Soc. 2005, 127, 10488. (d) Zhao, B. G.; Wang,
Z.; Ding, K. L. Adv. Synth. Catal. 2006, 348, 1049. (e) Liu,
Y.; Sandoval, C. A.; Yamaguchi, Y.; Zhang, X.; Wang, Z.;
Kato, K.; Ding, K. L. J. Am. Chem. Soc. 2006, 128, 14212.
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Jensen, J. F. Org. Lett. 2003, 5, 3099.
Preparation of Ligand 4a
Under nitrogen, the freshly prepared chlorophosphoric acid
ester (1.56 mmol) from 2,2-dihydroxy-1,1-biphenyl was
dissolved in THF (6 mL) and cooled to –30 °C. Then, Et3N
(3.12 mmol) and DMAP (10 mg) in THF (1 mL) was added
dropwise and the reaction was stirred for 30 min.
Afterwards, diol 2 (100 mg, 0.78 mmol) in THF (3mL) was
added dropwise at –30 °C and the mixture was allowed to
warm to r.t. and stirred for 24 h. The mixture was filtrated
and the filtrate was then passed through a short alumina
column (d = 0.5 cm, L = 3 cm) to give the corresponding
product as a white solid; 390 mg (90%). 1H NMR (400 MHz,
CDCl3): d = 7.52–7.23 (m,16 H, Ph), 4.42–4.37 (b, 2 H, C2
and C5), 2.31 (s, 2 H, bridgehead), 2.01–1.98 (d, 2 H, endo
of C3 and C5), 1.77–1.70 (m, 2 H, exo of C3 and C5), 1.36
(s, 2 H, bridge). 13C NMR (100 MHz, CDCl3): d = 142.603–
128.159 (Ph), 80.685 (C2 and C5), 42.303 (bridgehead),
35.365 (bridge), 29.268 (C3 and C5). 31P NMR (162 MHz,
CDCl3): d = 145.473. ESI-HRMS: m/z calcd for C31H26O6P2
[M + K]: 595.0836; found: 595.0846.
Preparation of Ligand 4b
Same procedure as for preparation of 4a; yield 78%. 1H
NMR (400 MHz, CDCl3): d = 7.96–7.22 (m, 24 H, BINOL),
4.59 (b, 2 H, C2 and C5), 2.25 (s, 2 H, bridgehead), 1.93–
1.897 (d, 2 H, endo of C3 and C5), 1.77–1.72 (m, 2H, exo of
C3 and C5), 1.24 (s, 2 H, bridge). 13C NMR (100 MHz,
CDCl3): d = 148.556–121.919 (BINOL), 76.02 (C2 and C5),
Synlett 2007, No. 19, 3007–3010 © Thieme Stuttgart · New York