Unprecedented effects of achiral oxazolidinones on enantioselective radical-mediated conjugate additions using a chiral zinc triflate

Organic Letters

Volumn 3, Issue 2, 2001, Pages 299-302

  Murakata, Masatoshi ^a   Tsutsui, Hideyuki ^a   Hoshino, Osamu ^a  

^a TOKYO UNIVERSITY OF SCIENCE   (Japan)

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EID: 0000265051     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol006927l     Document Type: Article

References (41)

1. For recent reviews including enantioselective radical reactions, see: (a) Renaud, P.; Gerster, M. Angew. Chem., Int. Ed. 1998, 37, 2562-2579.
2. (b) Sibi, M. P.; Porter, N. A. Acc. Chem. Res. 1999, 32, 163-171.
3. (a) Wu, J. H.; Radinov, R.; Porter, N. A. J. Am. Chem. Soc. 1995, 117, 11029-11030.
4. (b) Sibi, M. P.; Ji, J.; Wu, J. H.; Gürtler, S.; Porter, N. A. J. Am. Chem. Soc. 1996, 118, 9200-9201.
5. (c) Wu, J. H.; Zhang, G.; Porter, N. A. Tetrahedron Lett. 1997, 38, 2067-2070.
6. (d) Sibi, M. P.; Ji, J. J. Org. Chem. 1997, 62, 3800-3801.
7. (e) Iserloh, U.; Curran, D. P.; Kanemasa, S. Tetrahedron: Asymmetry 1999, 10, 2417-2428.
8. (f) Mero, C. L.; Porter, N. A. J. Org. Chem. 2000, 65, 775-781. Other enantioselective radical-mediated conjugate additions, see:
9. (g) Urabe, H.; Yamashita, K.; Suzuki, K.; Kobayashi, K.; Sato, F. J. Org. Chem. 1995, 60, 3576-3577.
10. (h) Nishida, M.; Hayashi, H.; Nishida, A.; Kawahara, N. Chem. Commun. 1996, 579-580.
11. (i) Sibi, M. P.; Shay, J. J.; Ji, J. Tetrahedron Lett. 1997, 38, 5955-5958.
12. For a recent review on nonchiral additives in the enantioselective reactions, see: (a) Vogl, E. M.; Gröger, H.; Shibasaki, M. Angew. Chem., Int. Ed. 1999, 38, 1570-1577 and references therein. For selected recent reports on the use of achiral ligands in the enantioselective reactions catalyzed by chiral Lewis acids, see:
13. (b) Kobayashi, S.; Hachiya, I.; Ishitani, H.; Araki, M. Tetrahedron Lett. 1993, 34, 4535-4538.
14. (c) Kobayashi, S.; Ishitani, H. J. Am. Chem. Soc. 1994, 116, 4083-4084.
15. (d) Desimoni, G.; Faita, G.; Righetti, P. P. Tetrahedron Lett. 1996, 37, 3027-3030.
16. 2O, see:
17. (f) Murakata, M.; Jono, T.; Mizuno, Y.; Hoshino, O. J. Am. Chem. Soc. 1997, 119, 11713-11714.
18. (g) Murakata, M.; Jono, T.; Hoshino, O. Tetrahedron: Asymmetry 1998, 9, 2087-2092.
19. 2OH, 96%] (Chiralcel OJ). The absolute configurations of 4 and 5 were determined by chemical correlation with (S)-4,4-dimethyl-3-phenylpentanoic acid, see: Imajo, S.; Kuritani, H.; Shingu, K.; Nakagawa, M. J. Org. Chem. 1979, 44, 3587-3589. See the Supporting Information for details.
20. 2O-petroleum ether)} was prepared by a similar method to that described in the literature, see: (a) Evans, D. A.; Peterson, G. S.; Johnson, J. S.; Barnes, D. M.; Campos, K. R.; Woerpel, K. A. J. Org. Chem. 1998, 63, 4541-4544.
21. (b) Corey, E. J.; Imai, N.; Zhang, H.-Y. J. Am. Chem. Soc. 1991, 113, 728-729.
22. For substituted N-enoyloxazolidinones as substrates in enantioselective radical reactions, N-enoyldimethyloxazolidinones are known, see ref 2b.
23. 2 signals of 2a would be simpler than those of 1a (Figure 2).
24. A chiral column (Chiralcel OD) was used. The absolute configuration of 6 was determined by chemical correlation with (S)-4-methyl-3-phenyl-pentanoic acid, see: Lardicci, L.; Salvadori, P.; Caporusso, A. M.; Menicagli, R.; Belgodere, E. Gazz. Chim. Ital. 1972, 102, 64-84, and also ref 2b. See the Supporting Information for details.
25. When the measurements were carried out at -78°C, these signals became too broad to allow the spectra to be analyzed.
26. (b) δ 4.57 and 4.61, two sets of a doublet J = 9.2 Hz;
27. 2 signal of 2a:
28. (d) δ 4.89 as a singlet;
29. (e) δ 3.82 and 4.35, two sets of a doublet, J = 8.9 Hz;
30. (f) δ 3.91 and 4.39, two sets of a doublet, J = 8.6 Hz. See the Supporting Information for details.
31. 3 signal of 12: δ 2.58 (free 12), δ 2.38 (a chiral zinc complex containing 12), δ 2.51 (a chiral zinc complex containing 12 and 2).
32. Although the precise structures of the complexes are not interpreted at this time, at least one OTf counteranion might dissociate in the complex combined both with 2a and 2. For reports of OTf as a dissociate anion or an auxiliary ligand in the chiral Lewis acids, see: (a) Evans, D. A.; Kozlowski, M. C.; Tedrow, J. S. Tetrahedron Lett. 1996, 37, 7481-7484.
33. (b) Yao, S.; Johannsen, M.; Jorgensen, K. A. J. Chem. Soc., Perkin Trans. 1 1997, 2345-2349.
34. (c) Crosignani, S.; Desimoni, G.; Faita, G., Righetti, P. P. Tetrahedron 1998, 54, 15721-15730.
35. (d) Evans, D. A.; Tregay, S. W.; Burgey, C. S.; Paras, N. A.; Vojkovsky, T. J. Am. Chem. Soc. 2000, 122, 7936-7943 and references therein. Also see refs 2a-c, 2e,f, and 2i.
36. In some cases 2a enhances chemical yields; however, it is not excluded that operations of the isolation and purification of the products cause a loss to chemical yields, especially workup (MeCN-hexane) to remove organotin compounds.
37. The ee's of 7 and 8 were determined directly by HPLC using a chiral column (Chiralcel OD). The absolute configuration of 7 was determined by converting it to (R)-3-cyclohexyl-3-phenyl-1-propanal. For the antipode, see: Ahlbrecht, H.; Enders, D.; Santowski, L.; Zimmermann, G. Chem. Ber. 1989, 122, 1995-2004. The absolute configuration of 8 was determined by chemical correlation with (R)-3-phenylpentanoic acid, see: Lardicci, L.; Menicagli, R.; Salvadori, P. Gazz. Chim. Ital. 1968, 98, 738-759, and also ref 2i. For the antipode, see: Soai, K.; Machida, H.; Yokota, N. J. Chem. Soc. Perkin Trans. 1 1987, 1909-1914. See the Supporting Information for details.
38. The ee's of 7 and 8 were determined directly by HPLC using a chiral column (Chiralcel OD). The absolute configuration of 7 was determined by converting it to (R)-3-cyclohexyl-3-phenyl-1-propanal. For the antipode, see: Ahlbrecht, H.; Enders, D.; Santowski, L.; Zimmermann, G. Chem. Ber. 1989, 122, 1995-2004. The absolute configuration of 8 was determined by chemical correlation with (R)-3-phenylpentanoic acid, see: Lardicci, L.; Menicagli, R.; Salvadori, P. Gazz. Chim. Ital. 1968, 98, 738-759, and also ref 2i. For the antipode, see: Soai, K.; Machida, H.; Yokota, N. J. Chem. Soc. Perkin Trans. 1 1987, 1909-1914. See the Supporting Information for details.
39. The ee's of 7 and 8 were determined directly by HPLC using a chiral column (Chiralcel OD). The absolute configuration of 7 was determined by converting it to (R)-3-cyclohexyl-3-phenyl-1-propanal. For the antipode, see: Ahlbrecht, H.; Enders, D.; Santowski, L.; Zimmermann, G. Chem. Ber. 1989, 122, 1995-2004. The absolute configuration of 8 was determined by chemical correlation with (R)-3-phenylpentanoic acid, see: Lardicci, L.; Menicagli, R.; Salvadori, P. Gazz. Chim. Ital. 1968, 98, 738-759, and also ref 2i. For the antipode, see: Soai, K.; Machida, H.; Yokota, N. J. Chem. Soc. Perkin Trans. 1 1987, 1909-1914. See the Supporting Information for details.
40. As the pioneering work, one example of the enantioselective radical-mediated conjugate addition of ethyl radical has been known to give 39% ee, see: ref 2i.
41. 4. After filtration, the solvent was removed under reduced pressure. The residue was taken up in MeCN. The mixture was washed with hexane. Concentration followed by purification through column chromatography (hexane-AcOEt) gave 5-8.