COMMUNICATIONS
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Sorensen, S. J. Danishefsky, Angew. Chem. 1996, 108, 2976; Angew.
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L. He, S. B. Horwitz, Angew. Chem. 1997, 109, 775; Angew. Chem. Int.
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[4] a) Z. Yang, Y. He, D. Vourloumis, H. Vallberg, K. C. Nicolaou, Angew.
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D. Vourloumis, Z. Yang, T. Li, P. Giannakakou, E. Hamel, Nature
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Roschangar, F. Sarabia, S. Ninkovic, Z. Yang, J. I. Trujillo, J. Am.
Chem. Soc. 1997, 119, 7960; e) K. C. Nicolaou, S. Ninkovic, F. Sarabia,
D. Vourloumis, Y. He, H. Vallberg, M. R. V. Finlay, Z. Yang, J. Am.
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[14] a) R. Noyori, T. Ohkuma, M. Kitamura, J. Am. Chem. Soc. 1987, 109,
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3327.
[15] The Noyori reduction of various diketo esters was very dependent on
the amount of acid in the reaction mixture. Without the presence of
stoichiometric acid, the rate of reduction and the selectivity dropped
in the reduction. At higher pressures, the chemoselectivity of the
reduction was poor resulting in reduction of both of the alkene groups.
Furthermore, the carbonyl group at C5 was never reduced under these
conditions, but was absolutely necessary for the reduction of the
carbonyl group at C3. When an alcohol functionality was at C5, no
reduction was seen. A. Balog, unpublished results.
[16] a) I. Mori, K. Ishihara, C. H. Heathcock, J. Org. Chem. 1990, 55, 1114;
b) W. R. Roush, J. Org. Chem. 1991, 56, 4151.
[17] For a statement of the Curtin ± Hammet principle in predicting and
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[5] D. Schinzer, A. Limberg, A. Bauer, O. M. Böhm, M. Cordes, Angew.
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Meng, S. J. Danishefsky, Y.-H. Zheng, T.-C. Chou, L. He, S. B.
Horwitz, Tetrahedron Lett. 1997, 38, 4529; c) D.-S. Su, A. Balog, D.
Meng, P. Bertinato, S. J. Danishefsky, Y.-H. Zheng, T.-C. Chou, L. He,
S. B. Horwitz, Angew. Chem. 1997, 109, 2178; Angew. Chem. Int. Ed.
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He, S. Ninkovic, F. Sarabia, H. Vallberg, F. Roschangar, N. P. King,
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Structures of Solvent-Free, Monomeric LiCCH,
NaCCH, and KCCH**
Douglas B. Grotjahn,* Aldo J. Apponi,
Matthew A. Brewster, Ju Xin, Lucy M. Ziurys*
Organoalkali metal compounds are important reagents for
introducing organic groups into organic and organometallic
compounds in substitution or addition reactions.[1] For exam-
ple, active ingredients in widely used oral contraceptives
contain alkynyl groups that are introduced by the addition of
alkali metal acetylides to steroidal ketones.[2] Organoalkali
metal compounds show a pronounced tendency toward
aggregation,[3] and alkali metal acetylides are no exception.[4, 5]
The organic portion and co-ligand(s) (including solvent)
influence reactivity and structure of the organoalkali metal
compound dramatically, both in solution and in the solid state.
An example of the structural changes induced by subtle
variation of coligands is that whereas the crystallization of
PhCCLi in the presence of tetramethylpropylenediamine
gives dimeric units,[5e] similar treatment with the homologous
tetramethylhexylenediamine gives tetrameric units.[5d] Such
aggregated structures have provided the only experimental
information about alkynyl ± alkali metal bond lengths to date,
but with one recent exception,[4d] the alkali metal acetylides
[9] The aldehyde 5 was readily available by the preparation given in N.-H.
Lin, L. E. Overman, M. H. Rabinowitz, L. A. Robinson, M. J. Sharp, J.
Zablocki J. Am. Chem. Soc. 1996, 118, 9062. The alcohol precursor to
this aldehyde could also be accessed by yeast reduction of the
corresponding allylic alcohol, thereby shortening the synthetic path-
way (24 steps) by three steps.
[10] C. H. Heathcock in Asymmetric Synthesis, Vol. 3 (Ed.: J. D. Morrison),
Academic Press, New York, 1984, p. 111.
[11] The stereochemistry of the minor diastereomer with respect to the
groups on C7 and C8 was presumed to be syn, but was not rigorously
proven. This was based on precedent,[16a] assuming that this isomer
arises from facial selectivity in the aldol reaction and not as a
consequence of the E configuration of the enolate group of 10.
Similarly, the stereochemistry assigned as the syn,syn products 14 was
not proven in each case. Those assignments also rely to varying extents
on the examples given in ref. [16a].
[12] For transition state models for diastereomeric additions on carbonyl
groups, see a) D. J. Cram, F. A. Elhafez, J. Am. Chem. Soc. 1952, 74,
5828; b) D. J. Cram, K. R. Kopecky, J. Am. Chem. Soc. 1959, 81, 2748;
c) J. W. Cornforth, R. H. Cornforth, K. K. Mathew, J. Am. Chem. Soc.
1959, 81, 112; d) G. J. Karabatsos, J. Am. Chem. Soc. 1967, 89, 1367;
e) M. Cherest, H. Felkin, N. Prudent, Tetrahedron Lett. 1968, 2199;
f) N. T. Ahn, O. Eisenstein, Nouv. J. Chem. 1977, 1, 61; g) A. S. Cieplak,
J. Am. Chem. Soc. 1981, 103, 4540, h) E. P. Lodge, C. H. Heathcock, J.
Am. Chem. Soc. 1987, 109, 2819.
[*] Prof. D. B. Grotjahn
Department of Chemistry, San Diego State University
5500 Campanile Drive, San Diego, CA 92182-1030 (USA)
Fax: (1)619-594-4634
Prof. L. M. Ziurys, Dr. A. J. Apponi, M. A. Brewster, Dr. J. Xin
Department of Chemistry, Department of Astronomy
Steward Observatory, University of Arizona
Tucson, AZ 85721 (USA)
Fax: (1)520-621-1532
[**] This research was supported by the U.S. National Science Foundation
grants CHE 9531244 (to D.B.G. and L.M.Z.), AST 95-03274, and
NASA grant NAGW 2989 (to L.M.Z.).
[13] M. T. Reetz, Angew. Chem. 1984, 96, 542; Angew. Chem. Int. Ed. Engl.
1984, 23, 556.
Supporting information for this article is available on the WWW under
2678
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