Regioselective ring metalation in [2,4]-bisoxazoles

Tetrahedron Letters

Volumn 39, Issue 44, 1998, Pages 8023-8026

  Williams, David R ^a   Brooks, Dawn A ^a   Meyer, Kevin G ^a   Pagel, Marty ^a  

^a INDIANA UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

2' METHYL 4 METHOXYMETHYL [2,4']BISOXAZOLE; NATURAL PRODUCT; OXAZOLE DERIVATIVE; UNCLASSIFIED DRUG;

ALKYLATION; ARTICLE; CHEMICAL REACTION; CHEMICAL STRUCTURE; PROTON NUCLEAR MAGNETIC RESONANCE; STRUCTURE ACTIVITY RELATION; SYNTHESIS;

EID: 0032578736     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01792-4     Document Type: Article

References (30)

1. 1. For a recent publication in the series see: (a) Faulkner, D.J. Nat. Prod. Rep. 1997, 14, 259.
2. (b) Lewis, J.R. Nat. Prod. Rep. 1996, 13, 435.
3. 2. (a) For oxazoles: Shafer, C.M.; Molinski, T.F. J. Org. Chem. 1998, 63, 551 and references therein. Zhao, Z.; Scarlato, G.R.; Armstrong, R.W. Tetrahedron Lett. 1991, 32, 1609.
4. 2. (a) For oxazoles: Shafer, C.M.; Molinski, T.F. J. Org. Chem. 1998, 63, 551 and references therein. Zhao, Z.; Scarlato, G.R.; Armstrong, R.W. Tetrahedron Lett. 1991, 32, 1609.
5. (b) For thiazoles: Williams, D.R.; Brooks, D.A.; Moore, J.L.; Stewart, A.O. Tetrahedron Lett. 1996, 37, 983.
6. (c) For imidazoles: Phillips, J.G.; Fadnis, L.; Williams, D.R. Tetrahedron Lett. 1997, 38, 7835.
7. 3. (a) Turchi, I.J. In Heterocyclic Compounds; Turchi, I.J., Ed.; J. Wiley: New York, 1986; Vol 45.
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9. 4. These results have been described as a part of our studies for the total synthesis of hennoxazole A. Brooks, D.A.; Williams, D.R. American Chemical Society 214th National Meeting; Las Vegas, NV; Sept. 10, 1997; Abstr. 280.
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13. 6. For recent advances: Vedejs, E.; Monahan, S.D. J. Org. Chem. 1996, 61, 5192. Crowe, E.; Horsner, F.; Hughes, M.J. Tetrahedron 1995, 51, 8889. Harn, N.K.; Gramer, C.J.; Anderson B.A. Tetrahedron Lett. 1995, 36, 9453.
14. 6. For recent advances: Vedejs, E.; Monahan, S.D. J. Org. Chem. 1996, 61, 5192. Crowe, E.; Horsner, F.; Hughes, M.J. Tetrahedron 1995, 51, 8889. Harn, N.K.; Gramer, C.J.; Anderson B.A. Tetrahedron Lett. 1995, 36, 9453.
15. 6. For recent advances: Vedejs, E.; Monahan, S.D. J. Org. Chem. 1996, 61, 5192. Crowe, E.; Horsner, F.; Hughes, M.J. Tetrahedron 1995, 51, 8889. Harn, N.K.; Gramer, C.J.; Anderson B.A. Tetrahedron Lett. 1995, 36, 9453.
16. 7. Williams, D.R.; McClymont, E.L. Tetrahedron Lett. 1993, 34, 7705.
17. 8. (a) Gangloff, A.R.; Akermark, B.; Helquist, P. J. Org. Chem. 1992, 57, 4797 and references therein.
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19. 9. Meyers, A.I.; Lawson, J.P. Tetrahedron Lett. 1981, 22, 3163.
20. 2, 70% EtOAc/hexanes) to afford alcohol 6f (33 mg, 85%) as a viscous oil.
21. 11. Dess, D.B.; Martin, J.C. J. Org. Chem. 1983, 48, 4155.
22. 3, 400 MHz) δ 7.72 (s, 1H), 7.68 (m, 4H), 7.39 (m, 6H), 4.62 (d, J = 1.7 Hz, 1H), 4.31 (d, J = 0.7 Hz, 2H), 4.08 (dd, J = 2.4, 12.2 Hz, 1H), 3.83 (dd, J = 4.4, 12.2 Hz, 1H), 3.47 (ddd, J = 2.2, 2.2, 4.3 Hz, 1H), 3.30 (s, 3H), 2.62 (s, 3H), 1.02 (s, 9H).
23. 13. (a) Meyers, A.I.; Mihelich, E.D. J. Org. Chem. 1975, 40, 3159.
24. (b) Directed metalation of pyridines by oxazolines has also been studied: Meyers, A.I.; Gabel, R.A. Tetrahedron Lett. 1978, 227.
25. 14. Gschwend, H.W.; Hamdan, A. J. Org. Chem. 1975, 40, 2008.
26. 15. Sammakia, T.; Latham, H.A. J. Org. Chem. 1995, 60, 6002. (equation presented)
27. 16. Zoltewicz, J.A.; Dill, C.D. Tetrahedron 1996, 52, 14469.
28. 17. QCPE Program 455, MOPAC Version 93. The authors thank Dr. Marty Pagel for performing these computations.
29. 18. These results correlate well with semiempirical calculations of a model tris-oxazole system of halichondramide: James, D.M.; Wintner, E.; Faulkner, D.J.; Siegel, J.S. Heterocycles 1993, 35, 675.
30. A (at C-5′) can impose undesirable consequences for base-induced reactions. For example, attempted metalation of the vinylic iodide i led to substantial proton transfer providing alkylation (deuterium incorporation) to yield mixtures containing side product ii. (equation presented)