Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes

D I Rawson, B. K. Carpenter, H. M R Hoffmann

Research output: Contribution to journalArticle

Abstract

The cycloaddition of W-configurated 1,3-dimethyl-2-oxyallyl cations to electron-rich cyclic conjugated dienes is accompanied by configurational losses and leads to cycloadducts with a,ß-configurated (equatorial, axial) methyl groups. For aromatic "dienes" such as benzene and N-alkylpyrroles, clectrophilic substitution competes strongly with [4 + 3 ? 7] cycloaddition which, nonetheless, can be accomplished by choice of an oxyallyl moiety with the proper blend of electrophilicity and nucleophilicity. It is suggested that formation of the seven-membered ring proceeds in two distinct stages, i.e., the stepwise pull-push mechanism involving formation of the first s bond in an electrophilic step and the second s bond in a nucleophilic step. © 1979 American Chemical Society.

Original languageEnglish
Pages (from-to)1786-1793
Number of pages8
JournalJournal of the American Chemical Society
Volume101
Issue number7
Publication statusPublished - 1979

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Cycloaddition
Cations
Electrons
Benzene
Substitution reactions

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Rawson, D. I., Carpenter, B. K., & Hoffmann, H. M. R. (1979). Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes. Journal of the American Chemical Society, 101(7), 1786-1793.
Rawson, D I ; Carpenter, B. K. ; Hoffmann, H. M R. / Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes. In: Journal of the American Chemical Society. 1979 ; Vol. 101, No. 7. pp. 1786-1793.
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Rawson, DI, Carpenter, BK & Hoffmann, HMR 1979, 'Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes', Journal of the American Chemical Society, vol. 101, no. 7, pp. 1786-1793.

Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes. / Rawson, D I; Carpenter, B. K.; Hoffmann, H. M R.

In: Journal of the American Chemical Society, Vol. 101, No. 7, 1979, p. 1786-1793.

Research output: Contribution to journalArticle

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T1 - Loss of allyl cation configuration in cycloadditions to electron-rich conjugated dienes

AU - Rawson, D I

AU - Carpenter, B. K.

AU - Hoffmann, H. M R

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AB - The cycloaddition of W-configurated 1,3-dimethyl-2-oxyallyl cations to electron-rich cyclic conjugated dienes is accompanied by configurational losses and leads to cycloadducts with a,ß-configurated (equatorial, axial) methyl groups. For aromatic "dienes" such as benzene and N-alkylpyrroles, clectrophilic substitution competes strongly with [4 + 3 ? 7] cycloaddition which, nonetheless, can be accomplished by choice of an oxyallyl moiety with the proper blend of electrophilicity and nucleophilicity. It is suggested that formation of the seven-membered ring proceeds in two distinct stages, i.e., the stepwise pull-push mechanism involving formation of the first s bond in an electrophilic step and the second s bond in a nucleophilic step. © 1979 American Chemical Society.

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