Competitive endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams

Wing Y. Tsang, Naveed Ahmed, Karl Hemming, Michael I. Page

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The balance between endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams shows that the difference in reactivity between strained β-lactams and their acyclic analogues is minimal. Attack of hydroxide ion occurs preferentially at the exocyclic acyl centre rather than that of the β-lactam during the hydrolysis of N-p-nitrobenzoyl β-lactam. In general, both endo- and exo-cyclic C-N bond fission occurs in the alkaline hydrolysis of N-aroyl β-lactams, the ratio of which varies with the aryl substituent. Hence, the Brønsted β-values differ for the two processes: -0.55 for the ring-opening reaction and -1.54 for the exocyclic C-N bond fission reaction. For the pH-independent and acid-catalysed hydrolysis of N-benzoyl β-lactam, less than 3% of products are derived from exocyclic C-N bond fission.

Original languageEnglish
Pages (from-to)1432-1439
Number of pages8
JournalCanadian Journal of Chemistry
Volume83
Issue number9
DOIs
Publication statusPublished - Sep 2005

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Lactams
Hydrolysis
Fission reactions
Acids
Ions

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Tsang, Wing Y. ; Ahmed, Naveed ; Hemming, Karl ; Page, Michael I. / Competitive endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams. In: Canadian Journal of Chemistry. 2005 ; Vol. 83, No. 9. pp. 1432-1439.
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Competitive endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams. / Tsang, Wing Y.; Ahmed, Naveed; Hemming, Karl; Page, Michael I.

In: Canadian Journal of Chemistry, Vol. 83, No. 9, 09.2005, p. 1432-1439.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Competitive endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams

AU - Tsang, Wing Y.

AU - Ahmed, Naveed

AU - Hemming, Karl

AU - Page, Michael I.

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N2 - The balance between endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams shows that the difference in reactivity between strained β-lactams and their acyclic analogues is minimal. Attack of hydroxide ion occurs preferentially at the exocyclic acyl centre rather than that of the β-lactam during the hydrolysis of N-p-nitrobenzoyl β-lactam. In general, both endo- and exo-cyclic C-N bond fission occurs in the alkaline hydrolysis of N-aroyl β-lactams, the ratio of which varies with the aryl substituent. Hence, the Brønsted β-values differ for the two processes: -0.55 for the ring-opening reaction and -1.54 for the exocyclic C-N bond fission reaction. For the pH-independent and acid-catalysed hydrolysis of N-benzoyl β-lactam, less than 3% of products are derived from exocyclic C-N bond fission.

AB - The balance between endo- and exo-cyclic C-N fission in the hydrolysis of N-aroyl β-lactams shows that the difference in reactivity between strained β-lactams and their acyclic analogues is minimal. Attack of hydroxide ion occurs preferentially at the exocyclic acyl centre rather than that of the β-lactam during the hydrolysis of N-p-nitrobenzoyl β-lactam. In general, both endo- and exo-cyclic C-N bond fission occurs in the alkaline hydrolysis of N-aroyl β-lactams, the ratio of which varies with the aryl substituent. Hence, the Brønsted β-values differ for the two processes: -0.55 for the ring-opening reaction and -1.54 for the exocyclic C-N bond fission reaction. For the pH-independent and acid-catalysed hydrolysis of N-benzoyl β-lactam, less than 3% of products are derived from exocyclic C-N bond fission.

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