Preparation of enantioenriched α-silyl-benzylcarbamates

Tetrahedron Letters

Volumn 39, Issue 38, 1998, Pages 6807-6810

  Barberis, Claude ^a   Voyer, Normand ^a  

^a UNIVERSITÉ LAVAL   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

BENZYLAMINE DERIVATIVE; CARBAMIC ACID DERIVATIVE; LITHIUM; SILICON; SPARTEINE;

ARTICLE; DRUG SYNTHESIS; ENANTIOMER; REACTION ANALYSIS;

EID: 0032541691     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01463-4     Document Type: Article

References (14)

1. 1. (a) Voyer, N.; Roby, J. Tetrahedron Lett. 1995, 36, 6627.
2. (b) Voyer, N.; Roby, J.; Chenard, S.; Barberis, C. Tetrahedron Lett. 1997, 38, 6505.
3. 2. Roby, J.; Voyer, N. Tetrahedron Lett. 1997, 38, 191.
4. 3. (a) For a leading reference on the use of (-)sparteine.s-BuLi in enantioselective deprotonation see: Beak, P.; Basu, A.; Gallagher, D. J.; Park, Y. S.; Thayumanavan, S. Acc. Chem. Res. 1996, 29, 552.
5. (b) For its use in enantioselective ring opening rearrangements see: Lautens, M.; Gajda, C.; Chui, P. J. Chem. Soc., Chem.Comm., 1993, 1193-94.
6. 4. The present rearrangement is analogous to the [1,2] Aza-Wittig rearrangement which creates a C-C bond.For a recent review on this transformation see: Vogel, C. Synthesis, 1997, 497.
7. 5. For a recent example of achiral [1,2] silicon rearrangement see: Sieburth, S. McN.; Somers, J. J.; O'Hare, H. K.; Hewitt, G. W. Appl. Organometal. Chem. 1997, 11, 337.
8. 6. Thayumanavan, S.; Yong Sun Park; Farid, P.; and Beak, P. Tetrahedron Lett. 1997, 31, 5429-32 and references therein.
9. 7. Typical procedure: At -78°C, 1.1 eq of s-BuLi (1.24mmol) was added to freshly distilled (-) sparteine in 3 mL of solvent. The mixture was stirred for 15 min then cannulated to a solution of 1a or 1b (1.13mmol) in 1.5 mL of solvent. The resulting mixture was stirred at -78°C for 3h before being warmed to 0°C for 2h. After quenching with 1N HCl, the solution was extracted twice with ether. The organic layers were combined, dried over MgSO4 and evaporated to give the crude product 2a or 2b. The latter was purified by flash chromatography with a hexane-AcOEt mixture (9:1) as eluent to give a white solid.
10. 8. Hoppe, D.; Carsten, A.; Kramer, T. Angew. Chem. Int. Ed. Engl. 1990, 29, 1424.
11. (b) Haller, J.; Hense, T.; Hoppe, D. Synlett 1993, 726.
12. 9. Faibish, N. C.; Park, Y. S.; Lee S.; Beak, P. J. Am. Chem. Soc., 1997, 119, 11561-70.
13. 10. Schlosser, M. and Limat, D. J. Am. Chem. Soc., 1995, 117, 11561-70.
14. 1H NMR measurement of the diastereomeric complexes, formed in situ by the addition of 1 eq of (S) (+)-mandelic acid, were performed. The signals of the α-CH groups of the two diastereomeric complexes are easily measured at 3.03 (major) and 2.81 (minor) ppm.