Y. Yan et al. / Tetrahedron: Asymmetry 15 (2004) 2173–2175
2175
Table 2. The Rh(I)-catalyzed asymmetric hydrogenation of a-dehydro-
amino acid derivatives 9b–na
Asymmetric Catalysis in Organic Synthesis; Wiley-Inter-
science: New York, 1994; (e) Sheldon, R. A. Chirotechnol-
ogy; Marcel Dekker: New York, 1993.
Rh(COD)2PF6(1mol%)
COOR'
NHAc
COOR'
NHAc
9b-n
2. (a) Ohe, K.; Morioka, K.; Yonehara, K.; Uemura, S.
Tetrahedron: Asymmetry 2002, 13, 2155; (b) Suarez, A.;
Mendez-Rojas, M. A.; Pizzano, A. Organometallics 2002,
21, 4611; (c) Suarez, A.; Pizzano, A. Tetrahedron: Asym-
metry 2001, 12, 2501; (d) Pamies, O.; Dieguez, M.; Net, G.;
Ruiz, A.; Claver, C. J. Org. Chem. 2001, 66, 8364; (e)
Deerenberg, S.; Pamies, O.; Dieguez, M.; Claver, C.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M. J. Org. Chem.
2001, 66, 7626; (f) Francio, G.; Wittmann, K.; Leitner, W.
J. Organomet. Chem. 2001, 621(1–2), 130; (g) Pamies, O.;
Dieguez, M.; Net, G.; Ruiz, A.; Claver, C. Chem. Commun.
2000;(23), 2383.
3. (a) Nozaki, K.; Matsuo, T.; Shibahara, F.; Hiyama, T. Adv.
Synth. Catal. 2001, 343, 61; (b) Nozaki, K.; Li, W.;
Horiuchi, T.; Takaya, H. Tetrahedron Lett. 1997, 38, 4611;
(c) Horiuchi, T.; Ohta, T.; Shirakawa, E.; Nozaki, K.;
Takaya, H. Tetrahedron 1997, 53, 7795; (d) Horiuchi, T.;
Ohta, T.; Shirakawa, E.; Nozaki, K.; Takaya, H. J. Org.
Chem. 1997, 62, 4285; (e) Nozaki, K.; Sakai, N.; Nanno, T.;
Higashijima, T.; Mano, S.; Horiuchi, T.; Takaya, H. J. Am.
Chem. Soc. 1997, 119, 4413; (f) Horiuchi, T.; Ohta, T.;
Nozaki, K.; Takaya, H. J. Chem. Soc. Chem. Commun.
1996, 2, 155; (g) Nozaki, K.; Kumobayashi, H.; Horiuchi,
T.; Takaya, H.; Saito, T.; Yoshida, A.; Matsumura, K.;
Kato, Y.; Imai, T.; Miura, T. J. Org. Chem. 1996, 61, 7658;
(h) Nozaki, K.; Nanno, T.; Takaya, H. J. Organomet.
Chem. 1997, 527(1–2), 103; (i) Nanno, T.; Sakai, N.;
Nozaki, K.; Takaya, H. Tetrahedron: Asymmetry 1995, 6,
2583; (j) Sakai, N.; Nozaki, K.; Takaya, H. J. Chem. Soc.,
Chem. Commun. 1994, 395; (k) Sakai, N.; Mano, S.; Nozaki,
K.; Takaya, H. J. Am. Chem. Soc. 1993, 115, 7033.
4. (a) Zhou, Y.; Zhang, X. Chem. Commun. 2002, 1124; (b)
Tang, W.; Chi, Y.; Zhang, X. Org. Lett. 2002, 4, 1695; (c)
Zhou, Y.; Tang, W.; Wang, W.; Li, W.; Zhang, X. J. Am.
Chem. Soc. 2002, 124, 4952.
1 or 2 (1.1 mol%)
Ar
Ar
H2 (15psi), rt, THF
Entry
Substrate Ar
R0
Ligand Ee %b
1
9b
9b
9c
9c
9d
9d
9e
9e
9f
Ph
Ph
H
H
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
99
>99
99
2
3
p-FPh
p-FPh
m-BrPh
m-BrPh
o-ClPh
o-ClPh
2-Naphthyl
2-Naphthyl
Ph
H
H
H
H
H
H
H
H
4
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
99
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
9f
9g
9g
9h
9h
9i
H, N-Bz
H, N-Bz
CH3
Ph
Ph
Ph
CH3
CH3
p-FPh
p-FPh
m-BrPh
m-BrPh
o-ClPh
o-ClPh
9i
CH3
CH3
>99
>99
>99
>99
>99
>99
>99
>99
>99
95
9j
9j
CH3
CH3
9k
9k
9l
CH3
2-Naphthyl CH3
2-Naphthyl CH3
9l
9m
9m
9n
9n
Ph
Ph
CH3, N-Bz
CH3, N-Bz
CH3
CH3
2-Thienyl
2-Thienyl
95
a The reactions were carried out at rt under 15 psi of H2 for 12 h with
100% conversion. The catalyst was prepared in situ by stirring a
solution of Rh(COD)2PF6 and chiral ligand in 3 mL of THF [sub-
strate 0.5 mmol/[Rh]/L 1:0.01:0.011].
b The S absolute configuration was assigned by comparison of the
specific rotation with reported data. Enantiomeric excesses were
determined by chiral GC (Chiralsil-VAL III FSOT). The enantio-
meric excesses of the acids were determined with the corresponding
methyl ester.
5. Ishihara, K.; Kurihara, H.; Matsumoto, M.; Yamamoto,
H. J. Am. Chem. Soc. 1998, 120, 6920.
20
D
1
6. Spectra data for 1: ½a ¼ )193.6 (c 0.5, CHCl3); H NMR
(CD2Cl2, 300 MHz) d 8.18–8.02 (m, 3H), 7.90–7.82 (m, 3H),
7.78–7.60 (m, 7H), 7.55–7.02 (m, 18H), 6.99–6.93 (m, 1H),
6.90–6.85 (m, 1H), 6.76 (d, J ¼ 8.8 Hz, 1H), 6.64–6.58 (m,
2H), 6.24 (d, J ¼ 8.8 Hz, 1H), 5.84 (d, J ¼ 8.8 Hz, 1H) ppm;
13C NMR (CD2Cl2, 75 MHz) d 148.07, 148.01, 147.02,
146.25, 146.17, 141.64, 141.19, 138.92, 137.88, 137.71,
137.06, 136.89, 135.79, 135.75, 134.53, 134.26, 133.41,
133.17, 132.75, 131.31, 131.27, 131.07, 130.26, 129.48,
128.93, 128.78, 128.71, 128.61, 128.51, 128.41, 128.21,
128.13, 128.05, 128.92, 127.47, 127.05, 126.99, 126.57,
126.53, 126.41, 126.24, 125.69, 125.31, 125.13, 122.25 ppm;
31P NMR (CD2Cl2, 146 MHz) d 145.2 (d, Jpp ¼ 21.1 Hz),
)12.9 (d, Jpp ¼ 21.1 Hz) ppm; HRMS calculated for
C58H39O3P2 (MHþ): 845.2369, found 845.2369.
show excellent enantioselectivity in asymmetric hydro-
genation of a-dehydroamino acid derivatives. Further
investigations of other asymmetric applications using
these two ligands are now underway and will be
reported in due course.
Acknowledgements
20
D
1
7. Spectra data for 2: ½a ¼ +73.0 (c 0.5, CH3Cl); H NMR
This work was supported by the National Institutes of
Health.
(CD2Cl2, 300 MHz) d 7.94 (s, 1H), 7.88 (d, J ¼ 8.1 Hz, 1H),
7.69 (d, J ¼ 8.5 Hz, 1H), 7.62–7.56 (m, 3H), 7.49–7.44 (m,
6H), 7.36–6.85 (m, 17H), 6.79–6.67 (m, 5H), 6.55–6.48 (m,
2H) ppm; 13C NMR (CD2Cl2, 75 MHz) d 152.66, 152.55,
142.60, 142.43, 142.39, 142.15, 141.97, 141.89, 138.71,
138.67, 138.54, 138.13, 135.91, 134.80, 134.53, 133.98,
133.71, 133.44, 131.18, 130.65, 129.63, 129.37, 129.30,
129.04, 128.96, 128.86, 128.77, 128.68, 128.45, 128.36,
128.27, 127.95, 127.84, 127.73, 127.60, 127.50, 127.49,
126.77, 126.33, 125.16 ppm; 31P NMR (CD2Cl2, 146 MHz)
References and notes
1. For recent reviews, see: (a) Tang, W.; Zhang, X. Chem. Rev.
(Washington DC, United States) 2003, 103, 3029; (b)
Ohkuma, T.; Kitamura, M.; Noyori, R. In Catalytic
Asymmetric Synthesis; Ojima, I., Ed.; 2nd ed.; Wiley: New
York, 2000; (c) Comprehensive Asymmetric Catalysis; Jac-
obsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer:
Berlin, New York, 1999; Vols. I–III; (d) Noyori, R.
d 114.2 (d, Jpp ¼ 5.2 Hz), )12.4 (d, Jpp
¼
4.7 Hz) ppm;
HRMS calculated for C50H37OP2 (MHþ): 715.2289, found
715.2314.