Structural effects on thermal rearrangement of fulleroids to methanofullerenes. The prominent role of cyclopropyl vs aryl substituent

Organic Letters

Volumn 10, Issue 2, 2008, Pages 293-296

  Kitamura, Hiroshi ^a   Oshima, Takumi ^a  

^a OSAKA UNIVERSITY   (Japan)

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EID: 38749091359     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol702691y     Document Type: Article

References (25)

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12. Only the thermolysis of p-anisyl- and cyclopropyl-substituted fulleroid is reported; see ref 2d.
13. (a) Suzuki, T.; Li, Q.; Khemani, K. C.; Wudl, F.; Almarsson, O. Science 1991, 254, 1186.
14. (b) Shi, S.; Khemani, K. C.; Li, Q.; Wudl, F. J. Am. Chem. Soc. 1992, 114, 10656.
15. Unfortunately, a detailed structure of the rearranged product for 1b was not confirmed due to the poor solubility.
16. Minimum energy of the possible monocyclopropyl-substituted [5,6] closed isomer was not obtained as in the case of the unsubstituted [5,6] closed isomer; see ref 2a. This may be one of the reasons for the very slow or negligible rearrangement of these [5,6] open fulleroids.
17. Such a steric bulk effect is well recognized in the valence equilibration between 7-substituted cycloheptatriene and norcaradiene: Takahashi, K.; Takase, K.; Toda, H. Chem. Lett. 1981, 979.
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22. 1H NMR mesurements, the lifetimes of biradical intermediate from 1c and 1d were estimated to be shorter than 6.4 ps.
23. The cyclopropyl group is less effective in radical stabilization than the phenyl group: Engel, P. S.; Nalepa, C. J.; Horsey, D. W.; Keys, D. E.; Grow, R. T. J. Am. Chem. Soc. 1983, 105, 7102.
24. Cyclopropyl group is more effective in cation stabilization than phenyl group: Brown, H. C.; Peters, E. N. J. Am. Chem. Soc. 1977, 99, 1712.
25. Gûnther, H. Tetrahedron Lett. 1970, 11, 5173.