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

Yong Pyun Sang; Rae Cho Bong

doi:10.5012/bkcs.2005.26.7.1017

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

Yong Pyun Sang^*, Rae Cho Bong

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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 language	English
Pages (from-to)	1017-1024
Number of pages	8
Journal	Bulletin of the Korean Chemical Society
Volume	26
Issue number	7
DOIs	https://doi.org/10.5012/bkcs.2005.26.7.1017
Publication status	Published - 2005 Jul 20

Keywords

E2 and E1cb mechanisms
Elimination reactions
Mechanistic borderline

ASJC Scopus subject areas

General Chemistry

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10.5012/bkcs.2005.26.7.1017

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

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.",

keywords = "E2 and E1cb mechanisms, Elimination reactions, Mechanistic borderline",

author = "Sang, \{Yong Pyun\} and Bong, \{Rae Cho\}",

year = "2005",

month = jul,

day = "20",

doi = "10.5012/bkcs.2005.26.7.1017",

language = "English",

volume = "26",

pages = "1017--1024",

journal = "Bulletin of the Korean Chemical Society",

issn = "0253-2964",

publisher = "Wiley-Blackwell",

number = "7",

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TY - JOUR

T1 - Base-promoted, ketene-forming elimination reactions. Mechanistic borderline between E2 and E1cb mechanisms

AU - Sang, Yong Pyun

AU - Bong, Rae Cho

PY - 2005/7/20

Y1 - 2005/7/20

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.

KW - E2 and E1cb mechanisms

KW - Elimination reactions

KW - Mechanistic borderline

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SN - 0253-2964

VL - 26

SP - 1017

EP - 1024

JO - Bulletin of the Korean Chemical Society

JF - Bulletin of the Korean Chemical Society

IS - 7

ER -

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

Abstract

Keywords

ASJC Scopus subject areas

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