Synthesis of phenylalanine-derived β-hydroxy and β-keto phosphine oxides -investigation of the configurational stability of lithiated phosphine oxides using the Hoffmann test

Tetrahedron Letters

Volumn 37, Issue 24, 1996, Pages 4271-4274

  O'Brien, Peter ^a   Warren, Stuart ^a  

^a UNIVERSITY OF CAMBRIDGE   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ALDEHYDE; ORGANOLITHIUM COMPOUND; PHENYLALANINE; PHOSPHINE OXIDE DERIVATIVE;

ACYLATION; ARTICLE; CHEMICAL STRUCTURE; NUCLEAR MAGNETIC RESONANCE; RACEMIC MIXTURE; STEREOCHEMISTRY; X RAY CRYSTALLOGRAPHY;

EID: 0029950746     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)00814-3     Document Type: Article

References (17)

1. O'Brien, P.; Warren, S. Tetrahedron Lett., 1995, 36, 8473-8476.
2. The timescale of investigation could be shortened using faster reacting electrophiles under in situ quench conditions. For example, Seebach has successfully used benzaldehyde as an internal electrophile to trap a lithium enolate derived from an amino acid: Seebach, D.; Weber, T. Tetrahedron Lett., 1983, 24, 3315-3318. In contrast, we did not see any addition product when we reacted a simple phosphine oxide (3; R = n-Pr) using a similar procedure (LDA added to a solution of the phosphine oxide and benzaldehyde).
3. Hoffmann, R. W.; Julius, M.; Chemla, F.; Ruhland, T.; Frenzen, G. Tetrahedron, 1994, 50, 6049-6060.
4. Hirsch, R.; Hoffmann, R. W. Chem. Ber., 1992, 125, 975-982.
5. Hoffmann, R. W.; Lanz, J.; Metternich, R.; Tarara, G.; Hoppe, D. Angew. Chem., Int. Ed. Engl., 1987, 26, 1145-1146.
6. Hoffmann, R. W.; Rühl, T.; Harbach, J. Liebigs Ann. Chem., 1992, 725-730.
7. Hoffmann, R. W.; Rühl, T.; Chemla, F.; Zahneisen, T. Liebigs Ann. Chem., 1992, 719-724.
8. Thayumanavan, S.; Lee, S.; Liu, C.; Beak, P. J. Am. Chem. Soc., 1994, 116, 9755-9756.
9. Reetz, M. T.; Drewes, M. W.; Schmitz, A. Angew. Chem., Int. Ed. Engl., 1987, 26, 1141-1143.
10. 3N → 0°C, 93% Aldehyde 4 cannot be purified by chromatography on silica without decomposition. However, we found that washing the crude product quickly with 3 M HCl during the Swern work up generated essentially pure material. Aldehyde 4 prepared using Dess-Martin periodinane oxidation was of lower purity.
11. Chérest, M.; Felkin, H.; Prudent, N. Tetrahedron Lett., 1968, 2199-2204.
12. Reetz, M. T.; Drewes, M. W.; Lennick, K.; Schmitz, A.; Holdgrün, X. Tetrahedron: Asymmetry, 1990, 1, 375-378.
13. Hoffmann encountered the same problem when he described the first use of the test (see ref 5).
14. We are grateful to H. R. Powell and P. R. Raithby for carrying out the X-ray crystal structure analyses depicted in this paper. Full details of the crystal sructure investigation of alcohol anti,anti-10 and ketone anti-11 have been deposited at the Cambridge Crystallographic Data Centre, Lensfield Road, UK.
15. 1,3syn- and anti-10 generated a 90:10 ratio of β-keto phosphine oxides anti- and syn-11. This clearly demostrates that epimerisation had occurred even under these mild oxidising conditions.
16. We have not been able to identify the major alcohol 10 obtained from this reduction reaction.
17. A related example: Clayden, J.; Collington, E. W.; Warren, S. Tetrahedron Lett., 1993, 34, 1327-1330.