The Hydrolysis of Azetidinyl Amidinium Salts. Part 2. Substituent Effects, Buffer Catalysis, and the Reaction Mechanism

Michael I. Page, Philip S. Webster, Leon Ghosez

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The hydrolysis of azetidin-2-ylideneammonium salts gives a mixture of β-lactams, by exocyclic C-N bond fission, and β-amino amides, by endocyclic C-N bond breakage and opening of the four-membered ring. The reaction is general-base catalysed and more β-lactam is formed using a less basic buffer. The mechanism of the buffer-catalysed reaction is the general-acid-catalysed breakdown of a reversibly formed neutral tetrahedral intermediate. The Brønsted α-values vary with substituents in the amidinium salt so that they decrease with increasing electron withdrawal in the nitrogen amine which is expelled. Electron-withdrawing substituents attached to either nitrogen of the amidinium salt favour expulsion of that leaving-group amine. The Brønsted β1g for endocyclic C-N bond fission and β-amino amide formation is -0.52 whereas that for exocyclic C-N bond fission and β-lactam formation is -0.83. Substituent effects on the nitrogen amine which is not expelled but forms the product amide or β-lactam generate βp values of -0.71 and -0.07, respectively. Changes in structure-reactivity relationships with substituents are examined by an analysis of the reaction mechanism.

LanguageEnglish
Pages813-823
Number of pages11
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number5
DOIs
Publication statusPublished - May 1990

Fingerprint

beta-Lactams
Catalysis
Hydrolysis
Buffers
Salts
Amides
Amines
Nitrogen
Electrons
Acids

Cite this

@article{f6f675ca29414f3da9474e33344474a0,
title = "The Hydrolysis of Azetidinyl Amidinium Salts. Part 2. Substituent Effects, Buffer Catalysis, and the Reaction Mechanism",
abstract = "The hydrolysis of azetidin-2-ylideneammonium salts gives a mixture of β-lactams, by exocyclic C-N bond fission, and β-amino amides, by endocyclic C-N bond breakage and opening of the four-membered ring. The reaction is general-base catalysed and more β-lactam is formed using a less basic buffer. The mechanism of the buffer-catalysed reaction is the general-acid-catalysed breakdown of a reversibly formed neutral tetrahedral intermediate. The Br{\o}nsted α-values vary with substituents in the amidinium salt so that they decrease with increasing electron withdrawal in the nitrogen amine which is expelled. Electron-withdrawing substituents attached to either nitrogen of the amidinium salt favour expulsion of that leaving-group amine. The Br{\o}nsted β1g for endocyclic C-N bond fission and β-amino amide formation is -0.52 whereas that for exocyclic C-N bond fission and β-lactam formation is -0.83. Substituent effects on the nitrogen amine which is not expelled but forms the product amide or β-lactam generate βp values of -0.71 and -0.07, respectively. Changes in structure-reactivity relationships with substituents are examined by an analysis of the reaction mechanism.",
author = "Page, {Michael I.} and Webster, {Philip S.} and Leon Ghosez",
year = "1990",
month = "5",
doi = "10.1039/P29900000813",
language = "English",
pages = "813--823",
journal = "Journal of the Chemical Society, Perkin Transactions 2",
issn = "0300-922X",
publisher = "Chemical Society",
number = "5",

}

The Hydrolysis of Azetidinyl Amidinium Salts. Part 2. Substituent Effects, Buffer Catalysis, and the Reaction Mechanism. / Page, Michael I.; Webster, Philip S.; Ghosez, Leon.

In: Journal of the Chemical Society, Perkin Transactions 2, No. 5, 05.1990, p. 813-823.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Hydrolysis of Azetidinyl Amidinium Salts. Part 2. Substituent Effects, Buffer Catalysis, and the Reaction Mechanism

AU - Page, Michael I.

AU - Webster, Philip S.

AU - Ghosez, Leon

PY - 1990/5

Y1 - 1990/5

N2 - The hydrolysis of azetidin-2-ylideneammonium salts gives a mixture of β-lactams, by exocyclic C-N bond fission, and β-amino amides, by endocyclic C-N bond breakage and opening of the four-membered ring. The reaction is general-base catalysed and more β-lactam is formed using a less basic buffer. The mechanism of the buffer-catalysed reaction is the general-acid-catalysed breakdown of a reversibly formed neutral tetrahedral intermediate. The Brønsted α-values vary with substituents in the amidinium salt so that they decrease with increasing electron withdrawal in the nitrogen amine which is expelled. Electron-withdrawing substituents attached to either nitrogen of the amidinium salt favour expulsion of that leaving-group amine. The Brønsted β1g for endocyclic C-N bond fission and β-amino amide formation is -0.52 whereas that for exocyclic C-N bond fission and β-lactam formation is -0.83. Substituent effects on the nitrogen amine which is not expelled but forms the product amide or β-lactam generate βp values of -0.71 and -0.07, respectively. Changes in structure-reactivity relationships with substituents are examined by an analysis of the reaction mechanism.

AB - The hydrolysis of azetidin-2-ylideneammonium salts gives a mixture of β-lactams, by exocyclic C-N bond fission, and β-amino amides, by endocyclic C-N bond breakage and opening of the four-membered ring. The reaction is general-base catalysed and more β-lactam is formed using a less basic buffer. The mechanism of the buffer-catalysed reaction is the general-acid-catalysed breakdown of a reversibly formed neutral tetrahedral intermediate. The Brønsted α-values vary with substituents in the amidinium salt so that they decrease with increasing electron withdrawal in the nitrogen amine which is expelled. Electron-withdrawing substituents attached to either nitrogen of the amidinium salt favour expulsion of that leaving-group amine. The Brønsted β1g for endocyclic C-N bond fission and β-amino amide formation is -0.52 whereas that for exocyclic C-N bond fission and β-lactam formation is -0.83. Substituent effects on the nitrogen amine which is not expelled but forms the product amide or β-lactam generate βp values of -0.71 and -0.07, respectively. Changes in structure-reactivity relationships with substituents are examined by an analysis of the reaction mechanism.

UR - http://www.scopus.com/inward/record.url?scp=37049073387&partnerID=8YFLogxK

U2 - 10.1039/P29900000813

DO - 10.1039/P29900000813

M3 - Article

SP - 813

EP - 823

JO - Journal of the Chemical Society, Perkin Transactions 2

T2 - Journal of the Chemical Society, Perkin Transactions 2

JF - Journal of the Chemical Society, Perkin Transactions 2

SN - 0300-922X

IS - 5

ER -