Evidence for a kinetic silicon effect in a sigmatropic rearrangement [1]

Journal of the American Chemical Society

Volumn 121, Issue 4, 1999, Pages 856-857

  Lin, Yi Lun ^a   Turos, Edward ^a  

^a UNIVERSITY OF SOUTH FLORIDA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CYCLOPROPANE DERIVATIVE; SILICON;

CHEMICAL MODIFICATION; CHEMICAL REACTION; ISOMERISM; LETTER; STEREOCHEMISTRY; SYNTHESIS;

EID: 0033518591     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja9820339     Document Type: Letter

References (39)

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13. (c) Gajewski, J. J. Hydrocarbon Thermal Isomerizations; Academic Press: New York, 1981.
14. (d) Hudlicky, T.; Koszyk, F. J. Tetrahedron Lett. 1980, 21, 2487.
15. (e) Mazzocchi, P. H.; Tamburin, H. J. J. Am. Chem. Soc. 1975, 97, 555.
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17. (g) Paquette, L. A.; Henzel, R. P.; Eizenber, R. F. J. Org. Chem. 1973, 38, 3257.
18. The 1,5-hydrogen migration of cis-disubstituted vinylcyclopropanes reportedly has an activation barrier of approximately 30-35 kcal/mol (cf. Flowers, M. C.; Frey, H. M. J. Chem. Soc. 1961, 3547), 15-20 kcal lower than that of the 1,3-alkyl migration, and is generally viewed to be a reversible process (Hudlicky, T.; Kutchan, T. M.; Koszyk, F. J.; Sheth, J. P. J. Org. Chem. 1980, 45, 5020).
19. The 1,5-hydrogen migration of cis-disubstituted vinylcyclopropanes reportedly has an activation barrier of approximately 30-35 kcal/mol (cf. Flowers, M. C.; Frey, H. M. J. Chem. Soc. 1961, 3547), 15-20 kcal lower than that of the 1,3-alkyl migration, and is generally viewed to be a reversible process (Hudlicky, T.; Kutchan, T. M.; Koszyk, F. J.; Sheth, J. P. J. Org. Chem. 1980, 45, 5020).
20. Vinylsilanes have become valuable reagents and intermediates in synthesis. For a review, see: Fleming, I.; Barbero, A.; Walter, D. Chem. Rev. 1997, 97, 2063.
21. 1H NMR experiments using 1,4-dinitrodurene as an internal standard.
22. The isomerization of trans-vinylcyclopropanes to cis-vinylcyclopropanes or to cyclopentenes generally takes place at temperatures well-above 200°C (see ref 1).
23. Some very early studies briefly described the effect of olefin substitution and E/Z geometry on 1,5-hydrogen rearrangements of simple vinylcyclopropane systems. See ref 2.
24. The observed ratio of products in this case is not the result of thermodynamic equilibration under the reaction conditions. 1E,4Z- and 1Z,4Z-vinylsilanes 5f are each stable in refluxing toluene for several weeks without any crossover to the other stereoisomer or reversion back to the vinylcyclopropane. Slow equilibration of the vinylsilane in 5f does occur slowly over a period of 10 days in refluxing xylene.
25. The lower selectivity in this example may suggest a deviation in the reaction mechanism due to the presence of the silyl alkoxy ligands, perhaps through stabilization of a β-radical or cation by the electron pair of the ethoxy oxygen (Brook, M. A.; Neuy, A. J. Org. Chem. 1990, 55, 3609).
26. 3Si. (Brook, M. A.; Henry, C.; Jefferson, E.; Juschke, R.; Sebastian, T.; Tomaszewski, M.; Wenzel, S. Bull. Soc. Chem. Fr. 1995, 132, 559.)
27. Woodward, R. B.; Hoffmann, R. J. Am. Chem. Soc. 1965, 87, 2511.
28. Our model is supportive of Berson's earlier theoretical experiments which suggest that hydrogen migration occurs preferentially on the face anti to the cyclopropyl ring (see refs 3a,b).
29. Glass, D. S.; Boikess, R. S.; Winstein, S. Tetrahedron Lett. 1966, 7, 999.
30. For reviews on hyperconjugation effects of silicon, see: (a) Lambert, J. B.; Wang, G.-t.; Finzel, R. B.; Teramura, D. H. J. Am. Chem. Soc. 1987, 109, 7838. (b) Traylor, T. G.; Hanstein, W.; Berwin, H. J.; Clinton, C. A.; Brown, R. S. J. Am. Chem. Soc. 1971, 93, 5715.
31. For reviews on hyperconjugation effects of silicon, see: (a) Lambert, J. B.; Wang, G.-t.; Finzel, R. B.; Teramura, D. H. J. Am. Chem. Soc. 1987, 109, 7838. (b) Traylor, T. G.; Hanstein, W.; Berwin, H. J.; Clinton, C. A.; Brown, R. S. J. Am. Chem. Soc. 1971, 93, 5715.
32. Silylmethylcyclopropanes have pronounced reactivity towards electrophilic ring-opening, to give adducts which lack the silyl group. (a) Ryu, I.; Harai, A.; Suzuki, H.; Sonoda, N.; Murai, S. J. Org. Chem. 1990, 55, 1409. (b) Ochiai, M.; Sumi, K.; Fujita, E. Chem. Pharm. Bull. 1983, 31, 3931. (c) Grignon-Dubois, M.; Dunogues, J.; Calas, R. Can. J. Chem. 1981, 59, 802. (d) Grignon-Dubois, M.; Dunogues, J.; Calas, R. J. Chem. Research (S) 1979, 6. (e) Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
33. Silylmethylcyclopropanes have pronounced reactivity towards electrophilic ring-opening, to give adducts which lack the silyl group. (a) Ryu, I.; Harai, A.; Suzuki, H.; Sonoda, N.; Murai, S. J. Org. Chem. 1990, 55, 1409. (b) Ochiai, M.; Sumi, K.; Fujita, E. Chem. Pharm. Bull. 1983, 31, 3931. (c) Grignon-Dubois, M.; Dunogues, J.; Calas, R. Can. J. Chem. 1981, 59, 802. (d) Grignon-Dubois, M.; Dunogues, J.; Calas, R. J. Chem. Research (S) 1979, 6. (e) Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
34. Silylmethylcyclopropanes have pronounced reactivity towards electrophilic ring-opening, to give adducts which lack the silyl group. (a) Ryu, I.; Harai, A.; Suzuki, H.; Sonoda, N.; Murai, S. J. Org. Chem. 1990, 55, 1409. (b) Ochiai, M.; Sumi, K.; Fujita, E. Chem. Pharm. Bull. 1983, 31, 3931. (c) Grignon-Dubois, M.; Dunogues, J.; Calas, R. Can. J. Chem. 1981, 59, 802. (d) Grignon-Dubois, M.; Dunogues, J.; Calas, R. J. Chem. Research (S) 1979, 6. (e) Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
35. Silylmethylcyclopropanes have pronounced reactivity towards electrophilic ring-opening, to give adducts which lack the silyl group. (a) Ryu, I.; Harai, A.; Suzuki, H.; Sonoda, N.; Murai, S. J. Org. Chem. 1990, 55, 1409. (b) Ochiai, M.; Sumi, K.; Fujita, E. Chem. Pharm. Bull. 1983, 31, 3931. (c) Grignon-Dubois, M.; Dunogues, J.; Calas, R. Can. J. Chem. 1981, 59, 802. (d) Grignon-Dubois, M.; Dunogues, J.; Calas, R. J. Chem. Research (S) 1979, 6. (e) Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
36. Silylmethylcyclopropanes have pronounced reactivity towards electrophilic ring-opening, to give adducts which lack the silyl group. (a) Ryu, I.; Harai, A.; Suzuki, H.; Sonoda, N.; Murai, S. J. Org. Chem. 1990, 55, 1409. (b) Ochiai, M.; Sumi, K.; Fujita, E. Chem. Pharm. Bull. 1983, 31, 3931. (c) Grignon-Dubois, M.; Dunogues, J.; Calas, R. Can. J. Chem. 1981, 59, 802. (d) Grignon-Dubois, M.; Dunogues, J.; Calas, R. J. Chem. Research (S) 1979, 6. (e) Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
37. Vinylcyclopropanes having a silyl group directly attached to the ring undergo ring expansion to vinylsilanes at high temperature (flash vacuum conditions). However, the authors do not mention whether the silicon moiety influences the rate of rearrangement. (a) Paquette, L. A.; Wells, G. J.; Horn, K. A.; Yan, T. H. Tetrahedron Lett. 1982, 23, 263. (b) Yan, T. H.; Paquette, L. A. Tetrahedron Lett. 1982, 23, 3227.
38. Vinylcyclopropanes having a silyl group directly attached to the ring undergo ring expansion to vinylsilanes at high temperature (flash vacuum conditions). However, the authors do not mention whether the silicon moiety influences the rate of rearrangement. (a) Paquette, L. A.; Wells, G. J.; Horn, K. A.; Yan, T. H. Tetrahedron Lett. 1982, 23, 263. (b) Yan, T. H.; Paquette, L. A. Tetrahedron Lett. 1982, 23, 3227.
39. Heteroatomic and anionic substituents are known to accelerate the vinylcyclopropane-cyclopentene ring expansions (for examples, see: Richey, H. G., Jr.; Shull, D. W. Tetrahedron Lett. 1976, 20, 575 and ref 1), but the effects of these substituents on the 1,5-hydrogen migration in vinylcyclopropanes have not been investigated.