The Chemistry of Hydroxamic Acids and <i>N</i>‐Hydroxyimides

Bauer, Ludwig; Exner, Otto

doi:10.1002/anie.197403761

Cited by 306 publications

(170 citation statements)

References 122 publications

(6 reference statements)

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“…Most of the previously reported Lossen rearrangement reactions take place only under alkaline conditions and/or through heating to a requisite temperature (20)(21)(22)(23). In the present study, we found that the reaction between BHA and TCBQ could occur at room temperature and under neutral or even weakly acidic pH.…”

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbsupporting

confidence: 59%

“…It has been shown (20,21) that I could be formed through nucleophilic addition of phenyl isocyanate with a molecule of BHA: and II could be formed through the hydrolysis of phenyl isocyanate to aniline, followed by reaction of aniline with another molecule of phenyl isocyanate: The above analysis strongly suggests that phenyl isocyanate (Ar─N═C═O) should be formed as an initial unstable product during the reaction of BHA and TCBQ.…”

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 92%

“…It has been shown that one typical way could be through the classic Lossen rearrangement, a wellknown reaction that describes the transformation of an O-activated hydroxamic acid (R-C(O)-NH-OX) into the corresponding isocyanate (21,22). The rate-limiting step of this reaction is the activation of the hydroxamic acid by various agents (i.e., sulfonyl and benzoyl chloride, etc.…”

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

“…It has been well established that the activation of the oxygen atom of hydroxamic acids is essential for the Lossen rearrangement to take place. Therefore, the Lossen rearrangement is customarily carried out by using prepared O-activated hydroxamic acid derivatives or by in situ activation of free hydroxamic acids with various activating agents such as polyphosphoric acid and carbodiimides (20)(21)(22)(23). To our knowledge, this is the only report demonstrating that TCBQ and other tetrahalogenated quinones could serve as a unique class of agents for the activation of free hydroxamic acids, forming unstable O-trihaloquinonated hydroxamic acids, leading spontaneously to two consecutive Lossen-type rearrangements.…”

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

“…This is possibly due to the unusually rapid and facile rearrangement of the postulated reaction intermediate, the O-trichloroquinonated BHA. It has been shown that the rate-limiting step in the Lossen rearrangement is the activation of the hydroxamic acid, and the rate of the rearrangement is directly proportional to the relative acidity of the conjugate acid of the anionic leaving group (21,22). Due to the strong acidity of TrCBQ-OH (pK a : 1.10) and DDBQ (pK a 1: 0.58; pK a 2: 2.72) (7,18), which are the conjugate acids of the anionic leaving groups in the present study, it is expected that the rate of the rearrangement of the postulated reaction intermediates should be very fast.…”

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

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Detoxifying carcinogenic polyhalogenated quinones by hydroxamic acids via an unusual double Lossen rearrangement mechanism

Zhu

Mao

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Hydroxamic acids, which are best-known for their metal-chelating properties in biomedical research, have been found to effectively detoxify the carcinogenic polyhalogenated quinoid metabolites of pentachlorophenol and other persistent organic pollutants. However, the chemical mechanism underlying such detoxication is unclear. Here we show that benzohydroxamic acid (BHA) could dramatically accelerate the conversion of the highly toxic tetrachloro-1, 4-benzoquinone (p-chloranil) to the much less toxic 2, 5-dichloro-3, 6-dihydroxy-1, 4-benzoquonine (chloranilic acid), with rate accelerations of up to 150,000-fold. In contrast, no enhancing effect was observed with O-methyl BHA. The major reaction product of BHA was isolated and identified as O-phenylcarbamyl benzohydroxamate. On the basis of these data and oxygen-18 isotope-labeling studies, we proposed that suicidal nucleophilic attack coupled with an unexpected double Lossen rearrangement reaction was responsible for this remarkable acceleration of the detoxication reaction. This is the first report of an unusually mild and facile Lossen-type rearrangement, which could take place under normal physiological conditions in two consecutive steps. Our findings may have broad biological and environmental implications for future research on hydroxamic acids and polyhalogenated quinoid carcinogens, which are two important classes of compounds of major biomedical and environmental interest.

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Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbsupporting

confidence: 59%

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 92%

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

Section: Major Reaction Product Of Bha Was Identified As O-phenylcarbmentioning

confidence: 99%

See 3 more Smart Citations

Detoxifying carcinogenic polyhalogenated quinones by hydroxamic acids via an unusual double Lossen rearrangement mechanism

Zhu

Mao

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Lipase and esterase-catalyzed acylation of hetero-substituted nitrogen nucleophiles in water and organic solvents

Hacking

Akkus

Rantwijk

et al. 2000

Biotechnol. Bioeng.

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Deprotonation of Amides and Polyfunctional Imides Probed by Heteronuclear NMR and Quantum Chemical Calculations

Bagno¹,

Comuzzi²

1999

Eur. J. Org. Chem.

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The site of deprotonation of several types of amide acids (carboxylic amides and imides, sulfonamides, cyanamide, N‐hydroxyurea) has been investigated by quantum chemical calculations and heteronuclear NMR measurements. Relative energies of tautomeric ions deriving from protonation at the various sites were determined both in the gas phase and in water (by the IPCM continuum solvation method). NMR properties (nuclear shielding and electric field gradient) of the involved heteronuclei were calculated and compared with experimental 14N, 17O and 33S chemical shifts and relaxation rates. It is shown that the combination of theoretical and experimental tools allows a reliable prediction of spectral parameters and ultimately of the deprotonation site of polyfunctional acids.

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The Chemistry of Hydroxamic Acids and N‐Hydroxyimides

Cited by 306 publications

References 122 publications

Detoxifying carcinogenic polyhalogenated quinones by hydroxamic acids via an unusual double Lossen rearrangement mechanism

Detoxifying carcinogenic polyhalogenated quinones by hydroxamic acids via an unusual double Lossen rearrangement mechanism

Lipase and esterase-catalyzed acylation of hetero-substituted nitrogen nucleophiles in water and organic solvents

Deprotonation of Amides and Polyfunctional Imides Probed by Heteronuclear NMR and Quantum Chemical Calculations

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