2
(a) R. Noyori, Asymmetric Catalysis in Organic Synthesis, Wiley, New
York, 1994; (b) I. Ojima, Catalytic Asymmetric Synthesis, Wiley, New
York, 2nd edn, 2000; (c) Comprehensive Asymmetric Catalysis, ed. E. N.
Jacobsen, A. Pfaltz and H. Yamamoto, Springer, Berlin, 1999, vol. 2; (d)
G. Lin, Y. Li and A. S. C. Chan, Principles and Applications of
Asymmetric Synthesis, Wiley-Interscience, New York, 2001.
Table 3 Recycling of the Ir–L
quinaldine
1
catalyst in the hydrogenation of
a
3
4
For a recent review, see: F. Glorius, Org. Biomol. Chem., 2005, 3, 4171.
For some recent publications, see: (a) R. Kuwano, K. Kaneda, T. Ito,
K. Sato, T. Kurokawa, D. Karube and Y. Ito, Org. Lett., 2004, 6, 2213;
(b) J. Henschke, M. Burk, C. Malan, D. Herzberg, J. Peterson,
A. Wildsmith, C. Cobley and G. Casy, Adv. Synth. Catal., 2003, 345,
300; (c) F. Glorious, N. Spielkamp, S. Holle, R. Goddard and
C. Lehmann, Angew. Chem., Int. Ed., 2004, 43, 2850; (d) C. Legault and
A. Charette, J. Am. Chem. Soc., 2005, 127, 8966; (e) R. Kuwano and
M. Kashiwabara, Org. Lett., 2006, 8, 2653; (f) M. Ruping,
A. Antonchick and T. Theissmann, Angew. Chem., Int. Ed., 2006, 45,
3683; (g) T. Yamagata, H. Tadaoka, M. Nagata, T. Hirao, Y. Kataoka,
V. Ratovelomanana-Vidal, J. Gen eˆ t and K. Mashima, Organometallics,
Run
1
2
3
4
5
b
Conv. (%)
.99
92
75
91
62
90
43
89
40
86
b
Ee (%)
a
The reaction was carried out at room temperature with 3 mmol
for 20 h in
DMPEG–hexane (5 ml, 1 : 1, v/v). The convention was determined
quinaldine using Ir catalyst (0.1%) under 700 psi H
2
b
1
by H NMR and the ee value was determined by chiral OJ–H
column.
2
006, 25, 2505.
(a) W. Wang, S. Lu, P. Yang, X. Han and Y. Zhou, J. Am. Chem. Soc.,
003, 125, 10536; (b) P. Yang and Y. Zhou, Tetrahedron: Asymmetry,
004, 15, 1145; (c) S. Lu, X. Han and Y. Zhou, Adv. Synth. Catal., 2004,
46, 909; (d) S. Lu, Y. Wang, X. Han and Y. Zhou, Angew. Chem., Int.
5
2
2
3
was not observed in comparison with those obtained in THF
solvent. The only exception was 2-phenylquinoline (1i) (Table 2,
entry 9), which gave 65% ee in DMPEG–hexane in comparison to
the lower ee of 43% in THF.
Ed., 2006, 45, 2260.
6
7
(a) L. Xu, K. Lam, J. Ji, J. Wu, Q. Fan, W. Lo and A. S. C. Chan,
Chem. Commun., 2005, 1390; (b) K. Lam, L. Xu, L. Feng, Q. Fan,
F. Lam, W. Lo and A. S. C. Chan, Adv. Synth. Catal., 2005, 347, 1755.
M. Reetz and X. Li, Chem. Commun., 2006, 2159.
8 For recent publications about spiro chiral ligands, see: (a) Y. Fu, J. Xie,
A. Hu, H. Zhou, L. Wang and Q. Zhou, Chem. Commun., 2002, 480; (b)
A. Hu, Y. Fu, J. Xie, H. Zhou, L. Wang and Q. Zhou, Angew. Chem.,
Int. Ed., 2002, 41, 2348; (c) J. Xie, L. Wang, Y. Fu, S. Zhu, B. Fan,
H. Duan and Q. Zhou, J. Am. Chem. Soc., 2003, 125, 4404; (d) Y. Fu,
X. Guo, S. Zhu, A. Hu, J. Xie and Q. Zhou, J. Org. Chem., 2004, 69,
4648; (e) W. Shi, J. Xie and Q. Zhou, Tetrahedron: Asymmetry, 2005,
The immobilization of chiral homogeneous catalysts have
attracted much attention recently since it affords an attractive
approach for the separation of product from the catalytic system
1
1
and the recycling of the catalyst. Following our effort in this
11a,12
area,
we have recently found that the asymmetric hydrogena-
tion of quinolines could be carried out smoothly in a DMPEG–
hexane biphasic system, resulting in efficient separation and
6
a
1
recycling of the catalyst. The recyclability of the complex Ir–L in
16, 705.
DMPEG–hexane was studied with the hydrogenation of 1a as a
model reaction. At the end of each experiment the product was
separated via simple decantation of the upper hexane layer
followed by three additional extractions with degassed hexane. The
results were summarized in Table 3. The conversion and
enantioselectivity were consistent with the results obtained in
THF in the first run. Although the conversion dropped to 40%
after four runs, the enantioselectivities remained high. The decrease
of conversion might be due to the decomposition or a certain
degree of leaching of the catalyst in the course of recycling.
In conclusion, we have developed a highly effective catalyst for
the asymmetric hydrogenation of quinolines with high substrate/
catalyst ratio (up to 5000) and high enantioselectivity (up to 94%).
In view of the high activity of the catalyst and the ready
accessibility of the ligand, the method described here provides a
practical route to optically active tetrahydroquinoline derivatives.
We are grateful for the financial support from the Hong Kong
Research Grants Council (N-Polyu 506/04), CAS and the National
Natural Science Foundation of China.
9
For recent publications about phosphinite ligands in asymmetric
hydrogenation, see: (a) Y. Zhou, W. Tang, W. Wang, W. Li and
X. Zhang, J. Am. Chem. Soc., 2002, 124, 4952; (b) T. RajanBabu,
T. Ayers and A. Casalnuovo, J. Am. Chem. Soc., 1996, 116, 4101; (c)
T. RajanBabu, T. Ayers, G. Halliday, K. You and J. Calabrese, J. Org.
Chem., 1997, 62, 6012; (d) K. Yonehara, T. Hashizume, K. Mori,
K. Ohe and S. Uemura, J. Org. Chem., 1999, 64, 5593.
1
0 (a) A. S. C. Chan, W. Hu, C. Pai, C. Lau, Y. Jiang, A. Mi, M. Yan,
J. Sun, R. Lou and J. Deng, J. Am. Chem. Soc., 1997, 117, 9570; (b)
Y. Chen, X. Li, S. Tong, M. Choi and A. S. C. Chan, Tetrahedron Lett.,
1999, 40, 957; (c) F. Zhang, W. Kwok and A. S. C. Chan, Tetrahedron:
Asymmetry, 2001, 12, 2337; (d) R. Guo, T. Au-Yeung, J. Wu, M. Choi
and A. S. C. Chan, Tetrahedron: Asymmetry, 2002, 13, 2519; (e) T. Au-
Yeung, S. Chan and A. S. C. Chan, Adv. Synth. Catal., 2003, 345, 537.
1
1 For recent reviews, see: (a) Q. Fan, Y. Li and A. S. C. Chan, Chem.
Rev., 2002, 102, 3385; (b) C. Song and S. Lee, Chem. Rev., 2002, 102,
3495; (c) I. Vankelekom, Chem. Rev., 2002, 102, 3779; (d) S. Kobayashi
and R. Akiyama, Chem. Commun., 2003, 449; (e) C. Saluzzo and
M. Lemaire, Adv. Synth. Catal., 2002, 344, 915; (f) H. Ngo and W. Lin,
Top. Catal., 2005, 34, 85; (g) D. Sinou, Adv. Synth. Catal., 2002, 344,
221; (h) C. Song, Chem. Commun., 2004, 1033; (i) G. Pozzi and
I. Shepperson, Coord. Chem. Rev., 2003, 242, 115.
1
2 (a) Q. Fan, C. Ren, C. Yeung, W. Hu and A. S. C. Chan, J. Am. Chem.
Soc., 1999, 121, 7407; (b) Q. Fan, Y. Chen, X. Chen, D. Zhang, F. Xi
and A. S. C. Chan, Chem. Commun., 2000, 789; (c) G. Deng, Q. Fan,
X. Chen, D. Liu and A. S. C. Chan, Chem. Commun., 2002, 1570; (d)
B. Yi, Q. Fan, G. Deng, Y. Li and A. S. C. Chan, Org. Lett., 2004, 6,
1361; (e) W. Tang, N. Yang, B. Yi, G. Deng, Y. Huang and Q. Fan,
Chem. Commun., 2004, 1378; (f) Y. Huang, Y. He, H. Zhou, L. Wu,
B. Li and Q. Fan, J. Org. Chem., 2006, 71, 2874.
Notes and references
1
(a) H. Blaser, C. Malan, B. Pugin, F. Splindler, H. Steiner and
M. Studer, Adv. Synth. Catal., 2003, 345, 103; (b) W. Tang and
X. Zhang, Chem. Rev., 2003, 103, 3029.
This journal is ß The Royal Society of Chemistry 2007
Chem. Commun., 2007, 613–615 | 615