Base-promoted, ketene-forming elimination reactions. Mechanistic borderline between E2 and E1cb mechanisms

Yong Pyun Sang, Bong-Rae Cho

Research output: Contribution to journalArticle

Abstract

Elimination reactions of XC6H4CH2CO 2C6H3-2-Y-4-NO2 have been studied under various conditions. When X was moderately electron-withdrawing, Y = H, and base-solvent was R2NH-MeCN, the reaction proceeded by the E2 mechanism via an E1cb-like transition state. Concave downward curve was noted in the Hammett plots. When X = 4-NO2, Y = Cl, CF3, NO 2, and the base-solvent was R2NH/R2NH 2+ in 70 mol % MeCN(aq), the reaction proceeded by the E2 mechanism. The mechanism changed to a competing E2 and Elcb when X = 4-NO 2 and Y = H, MeO, and to the E1cb when X = 2,4-(NO2) 2, and Y = NO2. From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed.

Original languageEnglish
Pages (from-to)1017-1024
Number of pages8
JournalBulletin of the Korean Chemical Society
Volume26
Issue number7
Publication statusPublished - 2005 Jul 20

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Electrons
ketene

Keywords

  • E2 and E1cb mechanisms
  • Elimination reactions
  • Mechanistic borderline

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Base-promoted, ketene-forming elimination reactions. Mechanistic borderline between E2 and E1cb mechanisms. / Sang, Yong Pyun; Cho, Bong-Rae.

In: Bulletin of the Korean Chemical Society, Vol. 26, No. 7, 20.07.2005, p. 1017-1024.

Research output: Contribution to journalArticle

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N2 - Elimination reactions of XC6H4CH2CO 2C6H3-2-Y-4-NO2 have been studied under various conditions. When X was moderately electron-withdrawing, Y = H, and base-solvent was R2NH-MeCN, the reaction proceeded by the E2 mechanism via an E1cb-like transition state. Concave downward curve was noted in the Hammett plots. When X = 4-NO2, Y = Cl, CF3, NO 2, and the base-solvent was R2NH/R2NH 2+ in 70 mol % MeCN(aq), the reaction proceeded by the E2 mechanism. The mechanism changed to a competing E2 and Elcb when X = 4-NO 2 and Y = H, MeO, and to the E1cb when X = 2,4-(NO2) 2, and Y = NO2. From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed.

AB - Elimination reactions of XC6H4CH2CO 2C6H3-2-Y-4-NO2 have been studied under various conditions. When X was moderately electron-withdrawing, Y = H, and base-solvent was R2NH-MeCN, the reaction proceeded by the E2 mechanism via an E1cb-like transition state. Concave downward curve was noted in the Hammett plots. When X = 4-NO2, Y = Cl, CF3, NO 2, and the base-solvent was R2NH/R2NH 2+ in 70 mol % MeCN(aq), the reaction proceeded by the E2 mechanism. The mechanism changed to a competing E2 and Elcb when X = 4-NO 2 and Y = H, MeO, and to the E1cb when X = 2,4-(NO2) 2, and Y = NO2. From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed.

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