Squaric Acid N-Hydroxylamides

Synthesis, Structure, and Properties of Vinylogous Hydroxamic Acid Analogues

Nathaniel C. Lim, Martha D Morton, Hilary A. Jenkins, Christian Brückner

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The synthesis of squaric acid N-hydroxylamide esters 5 and amides 6 from dimethyl squarate 2a is described. These derivatives are analogues of the naturally occurring iron(III) chelator hydroxamic acid. On the basis of a comparative reactivity study, a concerted retro-Cope mechanism for the formation of the N-hydroxylamide esters 5 by reaction of dimethyl squarate with hydroxylamines is proposed. A preliminary iron(III) binding study of these hydroxamic acid analogues is presented, demonstrating binding of iron(III) to amides 6 in aqueous solutions, while the esters 5 did not show any sign of metal ion binding. 13C NMR spectroscopic data (chemical shift and spin-lattice relaxation time determination) of these and related derivatives delineate the resonance structures predominant in these molecules. The resonance structures of the derivatives rationalize their spectroscopic data, chemical reactivity, and iron(III) binding properties. Single-crystal X-ray structure analyses of squaric acid N-hydroxylamide ester 5b and squaric acid N-hydroxylamide amide 6c confirm their connectivity and provide structural evidence supporting the spectroscopically derived conclusions. The squaric acid N-hydroxylamides are potentially useful in the construction of chemosensors for iron(III).

Original languageEnglish (US)
Pages (from-to)9233-9241
Number of pages9
JournalJournal of Organic Chemistry
Volume68
Issue number24
DOIs
StatePublished - Nov 28 2003

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Hydroxamic Acids
Iron
Esters
Amides
Derivatives
Hydroxylamines
Chemical reactivity
Spin-lattice relaxation
Chemical shift
Chelating Agents
Relaxation time
Metal ions
Nuclear magnetic resonance
squaric acid
Single crystals
X rays
Molecules

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Squaric Acid N-Hydroxylamides : Synthesis, Structure, and Properties of Vinylogous Hydroxamic Acid Analogues. / Lim, Nathaniel C.; Morton, Martha D; Jenkins, Hilary A.; Brückner, Christian.

In: Journal of Organic Chemistry, Vol. 68, No. 24, 28.11.2003, p. 9233-9241.

Research output: Contribution to journalArticle

Lim, Nathaniel C. ; Morton, Martha D ; Jenkins, Hilary A. ; Brückner, Christian. / Squaric Acid N-Hydroxylamides : Synthesis, Structure, and Properties of Vinylogous Hydroxamic Acid Analogues. In: Journal of Organic Chemistry. 2003 ; Vol. 68, No. 24. pp. 9233-9241.
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