On the mechanism of oxazoline-directed metalations: Evidence for nitrogen-directed reactions

Journal of Organic Chemistry

Volumn 61, Issue 5, 1996, Pages 1629-1635

  Sammakia, Tarek ^a   Latham, Hallie A ^a  

^a UNIVERSITY OF COLORADO   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000470488     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo951556l     Document Type: Article

References (40)

1. For leading references, see: Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH: New York, 1993.
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3. Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. J. Am. Ckem. Soc. 1970, 92, 5389. Battelle, L. F.; Bau, R.; Gokel, G. W.; Oyakawa, R. T.; Ugi, I. K. J. Am. Chem. Soc. 1973, 95, 482.
4. (a) Riant, O.; Samuel, O.; Kagan, H. B. J. Am. Chem. Soc. 1993, 115, 5835.
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9. (f) Hayashi, T.; Mise, T.; Kumada, M Tetrahedron Lett. 1976, 48, 4351.
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11. (h) Boaz, N. W. Tetrahedron Lett. 1989, 30, 2061.
12. (a) Sammakia, T.; Latham, H. A. J. Org. Chem. 1995, 60, 6002.
13. (b) Sammakia, T.; Latham, H. A.; Schaad, D. R. J. Org. Chem. 1995, 60. 10. For similar studies, see refs 3c and 3d.
14. Meyers, A. I.; Lutomsky, K. J. Org. Chem. 1979, 44, 4464. Meyers, A. I.; Gant, T. G. Tetrahedron 1994, 50, 2297. For related examples, see: Elworth, T. R.; Mevers, A. I. Tetrahedron 1994, 50, 6089. Meyers, A. I.; Slade, J. J. Org. Chem. 1980, 45, 2780.
15. Meyers, A. I.; Lutomsky, K. J. Org. Chem. 1979, 44, 4464. Meyers, A. I.; Gant, T. G. Tetrahedron 1994, 50, 2297. For related examples, see: Elworth, T. R.; Mevers, A. I. Tetrahedron 1994, 50, 6089. Meyers, A. I.; Slade, J. J. Org. Chem. 1980, 45, 2780.
16. Meyers, A. I.; Lutomsky, K. J. Org. Chem. 1979, 44, 4464. Meyers, A. I.; Gant, T. G. Tetrahedron 1994, 50, 2297. For related examples, see: Elworth, T. R.; Mevers, A. I. Tetrahedron 1994, 50, 6089. Meyers, A. I.; Slade, J. J. Org. Chem. 1980, 45, 2780.
17. Meyers, A. I.; Lutomsky, K. J. Org. Chem. 1979, 44, 4464. Meyers, A. I.; Gant, T. G. Tetrahedron 1994, 50, 2297. For related examples, see: Elworth, T. R.; Mevers, A. I. Tetrahedron 1994, 50, 6089. Meyers, A. I.; Slade, J. J. Org. Chem. 1980, 45, 2780.
18. Collum, D. B. Acc. Chem. Res. 1992, 25, 448. Collum, D. B. Acc. Chem. Res. 1993, 26, 227. These articles review the work of the author as well as others in this field.
19. Collum, D. B. Acc. Chem. Res. 1992, 25, 448. Collum, D. B. Acc. Chem. Res. 1993, 26, 227. These articles review the work of the author as well as others in this field.
20. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
21. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
22. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
23. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
24. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
25. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
26. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
27. For examples of directed metalation of ferrocene compounds, see: (a) Slocum, D. W.; Rockett, B. W.; Hauser, C. R. J. Am. Ckem. Soc. 1963, 87, 1241. (b) Botton, E. S.; Pauson, P. L.; Sandhu, M. A.; Watts, W. E. J. Chem. Soc. C 1969,17, 2260. (c) Marr, G. J. Organomet. Chem. 1967, 9, 141. (d) Schmitt, G.; Klein, P.; Ebertz, W. J. Organomet. Chem. 1982, 234, 63. For reviews of directed metalation of aryl compounds, see: (e) Oilman, H.; Morton, J. W., Jr. Org. React. 1954, 8, 258. (f) Reuman, M.; Meyers, A. I. Tetrahedron 1985, 41, 837. (g) Gschwend, H.; Rodriguez, H. R. Org. React. 1979, 26, 1. (h) Snieckus, V. Chem. Rev. 1990, 90, 879.
28. Wright, M. E. Organometallics 1990, 9, 853.
29. Rausch, M. D.; Ciappenelli, D. J. J. Oraganomet. Chem. 1967, 70, 127.
30. (S)-2-Amino-3-methyl-1,3-butanediol (18) was prepared in three steps from L-serine methyl ester by protecting the nitrogen as the CBZ derivative, followed by addition of MeLi to the ester and finally deprotecting the nitrogen by hydrogenation: matrix presented
31. Similar results were-obtained using tert-butyllithium in THF.
32. We do not feel that the oxygen on the tether is playing a significant role in the reaction. If any chelate structure were formed, we would expect to see a difference in the stereochemical outcome of the metalation of unconstrained oxazolines containing heteroatoms at this position as compared to those that do not. However, we have prepared five different oxazolines with an oxygen in the corresponding position and they behave analogously to their nonoxygenated counterparts (i.e., no change in either the sense or magnitude of asymmetric induction). See ref 4b for details.
33. We have chosen to ignore the aggregation state of the butyllithium because it is difficult to know with certainty what the reactive aggregate is, especially in coordinating solvents such as THF. In hexanes in the presence of TMEDA, we speculate that it is a monomer.
34. This type of reaction is well known for d° early transition metal complexes. For a discussion, see: Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987: pp 295-298.
35. For example, metalation of the valine-denried oxazoline with sec-butyllithium in hexanes containing 1 equiv of TMEDA proceeds in excellent yields and stereoselectivities. See ref 4a.
36. For a related transition structure proposal, see ref 3c
37. For a related transition structure hypothesis in an addition reaction, see: Kundig, E, P.; Ripa, A.; Liu, R.; Amurrio, D.; Bernardelli, G. Organometallics 1993, 12, 3737.
38. For further evidence of this, see ref 4a.
39. Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43, 2923.
40. In the stereochemical designation (R, S), the first descriptor (in this example, "R") refers to the stereochemistry of the oxazoline substituent while the second descriptor (in this example, "S") refers to the stereochemistry of the disubstituted ferrocene. See: Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. J. Am. Chem. Soc. 1970, 92, 5389. The author has deposited atomic coordinates for this structure with the Cambridge Cristallographic Data Centre. The coordinates can be obtained, on request, from the Director, Cambridge Cristallographic Data Centre, 12 union Road, Cambridge, CB2 1EZ, UK.