Communications
[
2] For reviews, see: a) R. Noyori, Angew. Chem. 2002, 114, 2108 –
123; Angew. Chem. Int. Ed. 2002, 41, 2008 – 2022; b) T.
2
Ohkuma, M. Kitamura, R. Noyori in Catalytic Asymmetric
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[
[
[
[
4] R. Birk, M. Karpf, K. Pünterer, M. Scalone, M. Schwindt, U.
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6] For the asymmetric reduction of several tons of methyl
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[
7] a) M. Kitamura, T. Ohkuma, H. Takaya, R. Noyori, Tetrahedron
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a) L. Chai, H. Chen, Z. Li, Q. Wang, F. Tao, Synlett 2006, 2395 –
[
Figure 5. Progress with time of the AH of a 1:1 (mol/mol) mixture of
b-ketoesters 5c and 5d; ~ 5d, ~ 5d, ^ 6c,
6d. The yields were
determined as detailed in Figure 2. The trifluoroethyl ester 5c was not
&
2
398; b) L. Qiu, F. Y. Kwong, J. Wu, W. H. Lam, S. Chan, W.-Y.
Yu, Y.-M. Li, R. Guo, Z. Zhou, A. S. C. Chan, J. Am. Chem. Soc.
006, 128, 5955 – 5965; c) Y.-Y. Huang, Y.-M. He, H.-F. Zhou, L.
[
24]
quantifiable because of partial ethanolysis to 11 upon injection into
the GC apparatus; the hexafluoroisopropyl ester 5d was quantified as
2
[
24]
Wu, B.-L. Li, Q.-H. Fan, J. Org. Chem. 2006, 71, 2874 – 2877;
d) C.-J. Wang, H. Tao, X. Zhang, Tetrahedron Lett. 2006, 47,
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Chem. 2004, 116, 2555 – 2558; Angew. Chem. Int. Ed. 2004, 43,
its ethanolysis product 12 formed in the GC apparatus
(
(
(
t (12)=24.7 min); t (6c)=11.1 min, t (6d)=21.7 min, t -
R R R R
ꢀ
1
biphenyl)=19.9 min (1 mL, 358C (15 min)/208Cmin !1408C
20 min), p(H )=60 kPa).
2
2
501 – 2504; g) S. Jeulin, S. Duprat de Paule, V. Ratoveloma-
nana-Vidal, J.-P. GenÞt, N. Champion, P. Dellis, Angew. Chem.
004, 116, 324 – 329; Angew. Chem. Int. Ed. 2004, 43, 320 – 325;
ester 5c had reached completion to furnish the corresponding
hydroxyester 6c in 99% yield. In contrast, as much as 95% of
the competing hexafluoroisopropyl ester 5d remained, with
the hydroxyester derivative 6d formed in just 6% yield.
We have detailed herein the sequential asymmetric
hydrogenation of b-ketoesters in mixtures. In particular, we
found that the rate of [{RuCl ((S)-binap)} ]·NEt -catalyzed
2
h) M. Berthod, C. Saluzzo, G. Mignani, M. Lemaire, Tetrahe-
dron: Asymmetry 2004, 15, 639 – 645; i) S. Jeulin, S. Duprat de
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2
2
3
AH of b-ketoesters RC(=O)CH C(=O)OR’ depends on the
2
electronic nature of the substituent OR’. The present data
suggest that the more Lewis basic the C(=O)OR’ moiety is,
the faster the hydrogenation is. This kind of substituent
dependence extends to the AH of b-ketoamides, as reported
elsewhere along with the implications of our findings in terms
of the mechanism of the AH of b-ketocarboxylic acid
[
15]
derivatives.
Received: January 3, 2007
Revised: March 30, 2007
Published online: July 25, 2007
2
001, 73, 299 – 303; t) T. Saito, T. Yokozawa, T. Ishizaki, N. Sayo,
T. Miura, H. Kumobayashi, Adv. Synth. Catal. 2001, 343, 264 –
67.
[9] For catalysts for AH with
2
Keywords: b-ketoesters · asymmetric catalysis · kinetics ·
.
H
at less than 10 bar, see:
2
[17]
reduction · substituent effects
a) “[{RuCl ((S)-binap)} ]·NEt ” , dowex-50 resin: D. F. Taber,
2
2
3
L. Silverberg, Tetrahedron Lett. 1991, 32, 4227 – 4230; b) (R)-
6
binap, [{RuCl (h -C H ) } ]: M. Kitamura, M. Tokunaga, T.
2
6
6 2 2
[
1] a) R. Noyori, T. Ohkuma, M. Kitamura, H. Takaya, N. Sayo, H.
Ohkuma, R. Noyori, Org. Synth. 1992, 71, 1 – 13;
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17]
Kumobayashi, S. Akutagawa, J. Am. Chem. Soc. 1987, 109,
c) “[{RuCl
Thompson, A. O. King, T. R. Verhoeven, J. Org. Chem. 1992,
57, 6689 – 6691; d) (S)-binap, [(cod)Ru(methallyl) ] (cod = 1,5-
2
((S)-binap)}
2
]·NEt
3
”
, HCl: S. A. King, A. S.
5856 – 5858; b) M. Kitamura, T. Ohkuma, S. Inoue, N. Sayo, H.
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Am. Chem. Soc. 1988, 110, 629 – 631; c) R. Noyori, Science 1990,
2
cyclooctadiene), HBr: J.-P. GenÞt, V. Ratovelomanana-Vidal,
M. C. Cano de Andrade, X. Pfister, P. Guerreiro, J. Y. Lenoir,
248, 1194 – 1199.
6
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2007, 46, 6537 –6541