Reactions of aryl phenylacetates with secondary amines in MeCN. Structure-reactivity relationship in the ketene-forming eliminations and concurrent E2 and E1cb mechanisms

Bong-Rae Cho, Yong Kwan Kim, C. O M Yoon

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol% MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol% MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.

Original languageEnglish
Pages (from-to)691-697
Number of pages7
JournalJournal of the American Chemical Society
Volume119
Issue number4
DOIs
Publication statusPublished - 1997 Jan 29

Fingerprint

Phenylacetates
Proton transfer
Amines
Protons
Esters
Buffers
Electrons
Acids
ketene

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{be1b3d0a6635494e819d32742e1470dc,
title = "Reactions of aryl phenylacetates with secondary amines in MeCN. Structure-reactivity relationship in the ketene-forming eliminations and concurrent E2 and E1cb mechanisms",
abstract = "Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol{\%} MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol{\%} MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.",
author = "Bong-Rae Cho and Kim, {Yong Kwan} and Yoon, {C. O M}",
year = "1997",
month = "1",
day = "29",
doi = "10.1021/ja961294k",
language = "English",
volume = "119",
pages = "691--697",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "4",

}

TY - JOUR

T1 - Reactions of aryl phenylacetates with secondary amines in MeCN. Structure-reactivity relationship in the ketene-forming eliminations and concurrent E2 and E1cb mechanisms

AU - Cho, Bong-Rae

AU - Kim, Yong Kwan

AU - Yoon, C. O M

PY - 1997/1/29

Y1 - 1997/1/29

N2 - Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol% MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol% MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.

AB - Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol% MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol% MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.

UR - http://www.scopus.com/inward/record.url?scp=0031048516&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031048516&partnerID=8YFLogxK

U2 - 10.1021/ja961294k

DO - 10.1021/ja961294k

M3 - Article

VL - 119

SP - 691

EP - 697

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 4

ER -