B. Malézieux et al. / Tetrahedron: Asymmetry 10 (1999) 3253–3257
3257
References
1
2
. Sawamura, M.; Ito, Y. Chem. Rev. 1992, 92, 857.
. (a) Muchow, G.; Vannoorenberghe, Y.; Buono, G. Tetrahedron Lett. 1987, 28, 6163. (b) Mori, A.; Yu, D.; Inoue, S. Synlett
992, 427.
1
3. Dosa, P. I.; Ruble, J. C.; Fu, G. C. J. Org. Chem. 1997, 62, 444.
4. (a) Uemura, M.; Miyake, R.; Nakayama, K.; Shiro, M.; Hayashi, Y. J. Org. Chem. 1993, 58, 1238. (b) Malfrat, S.; Pelinski,
L.; Brocard, J. Tetrahedron: Asymmetry 1998, 9, 2595.
5
6
7
8
9
. Watanabe, M.; Araki, S.; Butsugan, Y.; Uemura, M. J. Org. Chem. 1991, 56, 2218.
. Bolm, C.; Muniz-Fernandez, K.; Seger, A.; Raabe, G.; Günther, K. J. Org. Chem. 1998, 63, 7860.
. Pastor, S. D.; Togni, A. Helv. Chim. Acta 1991, 74, 905.
. Wally, H.; Wildham, M.; Weissensteiner, W.; Schlögl, K. Tetrahedron: Asymmetry 1993, 4, 285.
. Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. K. J. Am. Chem. Soc. 1970, 92, 5389.
1
0. Watanabe, M.; Hashimoto, N.; Araki, S.; Butsugan, Y. J. Org. Chem. 1992, 57, 742. Also available with alpha substituted
aldehydes: Watanabe, M.; Komota, M.; Nishimura, M.; Araki, S.; Butsugan, Y. J. Chem. Soc., Perkin Trans. 1, 1993, 2193.
Also available with metallocenecarboxaldehydes: Watanabe, M. Synlett 1995, 1050.
1
1
1
1. Nicolosi, G.; Patti, A.; Morrone, R.; Piattelli, M. Tetrahedron: Asymmetry 1994, 5, 1639.
2. Malezieux, B.; Gruselle, M.; Troitskaya, L. L.; Sokolov, V. I. Tetrahedron: Asymmetry 1998, 9, 259.
3. The first method of hydrolysis we employed to perform the catalytic test (first with HCl 0.1N to extract the phenyl propanol,
then neutralization with NaHCO
way the very clean transformation of the (−)-(pS,3S,4R)-1 into another enantiomerically pure amino-alcohol presumably
+)-(pS,3S,4S) as a consequence of a benzylic isomerization. This compound was previously observed and described as a
minor product in the synthesis of 1 and 2 (see Ref. 12). This compound is also a catalyst but less efficient than 1 or 2 (a
% molar ratio gives the (S)-phenyl propanol with 41% yield and in 52% ee).
3
to extract the catalyst) had the consequence of altering the catalyst. We obtained in this
(
3
1
1
1
1
4. Kitamura, M.; Suga, S.; Kawai, K.; Noyori, R. J. Am. Chem. Soc. 1986, 108, 6071.
5. Noyori, R.; Kitamura, M. Angew. Chem., Int. Ed. Engl. 1991, 30, 49.
6. endo-Camphor with furanaldehyde: van Oeveren, A.; Menge, W.; Feringa, B. L. Tetrahedron Lett. 1989, 30, 6427.
7. Gruselle, M.; Malezieux, B.; Troitskaya, L. L.; Sokolov, V. I.; Epstein, L. M.; Shubina, Y. S.; Vaissermann, J.
Organometallics 1994, 13, 200.
1
18. H NMR spectra were recorded in different solvents — chloroform, acetone and methanol. At rt no changes were observed
versus the concentration for each diastereomer in acetone and methanol. In chloroform, when the spectrum of 1 remained
unchanged, that of compound 2 evolved with the concentration. Modifying the concentration from 3 to 180 mmol L−
strongly affected the signals (broadening and shifting) corresponding to the (methylene and dimethyl) bond to the nitrogen
atom, and the ferrocenyl protons. These results are consistent with the major feature of these molecules i.e. 1 exists
as a single conformer with a strong intramolecular H-bond involving the amino and hydroxyl groups while 2 exhibits
1
3 2
two main conformations due to the possible H-bonds for OH which can be either with Fe or with N(CH ) . Then, with
compound 1 the strong intramolecular bond controls the conformation and the molecule is not affected by the concentration
variations. In contrast, for compound 2 the position and the rate of the equilibrium between the two possible conformations
is under dilution control. Lowering the concentration in amino-alcohol 2 results in an increase of the concentration of the
monomeric forms which renders operative the exchange between the two conformations. In 0.1 mol L− methanol solution,
1
addition of ZnBr
2
results in dramatic changes for each diastereomer. Nevertheless these changes are significantly different
from 0.01 to
.00 mol L a general deshielding is observed. The single signal belonging to the methyl groups of the dimethylamino
for each of them. Focusing on the main changes for (pR*,3R*,4S*)-1 in the range of concentration of ZnBr
1
2
−1
function evolves to give two broad signals. This behavior could be the consequence of a strong chelating effect of the
hydroxyl and amino groups on the Zn atom. In contrast with compound (pR*,3S*,4R*)-2, the most significant variations
concern the protons borne by the ferrocene entity and those of the aminated branch. Thus, simultaneous modifications of
the shape and chemical shift affect the methyl groups of the dimethylamino function and the protons of the substituted and
unsubstituted cyclopentadienyl moieties. The splitting of the unsubstituted cyclopentadienyl accompanying the apparition
of, at least, three signals corresponding to the methyl substituents borne by the nitrogen atom could be correlated to the
2
existence of two conformers in slow equilibration process. Further additions of ZnBr lead to the displacement to a unique
conformer. This fact is indicated by the evolution of a single peak related to the cyclopentadienyl moiety.