Kinetics of the intramolecular displacement of alcohols from o-hydroxyaminobenzoates

Cox, Brian G.; Grieve, Duncan McL. A.; Porter, A. E. A.

doi:10.1039/p29750001512

Cited by 6 publications

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“…The rates of cleavage of the amides of A-methylamine, , -dimethylamine, aniline, and A-methylaniline were measured in aqueous hydrochloric or perchloric acid solutions, with acid concentrations varying between 2 X 10-3 and 5.5 M. Amide concentrations were ca. 10-4 M. In all cases, the observed rate law was as shown in eq 1 -d[S]/dt -*e [S] (1)…”

Section: Resultsmentioning

confidence: 70%

“…However, it is possible to set an upper limit to the rate (in the absence of added acid) of any reversible or preequilibrium cyclization of MA-dimethyl-o-hydroxylaminobenzamide to give a tetra- This may be attributed to restricted rotation about the C-N bond of the amide910 and, as reversible cyclization of the amide (III ^IV), would provide a mechanism for rotation about the C-N bond; the absence of even any observable broadening of the two TV-methyl singlets of III puts a limit of ca. 1 sec-1 for this exchange process (this being estimat-ed11 from the chemical shift difference of the two methyl signals). In view of the fact that rate constants for the overall cleavage reaction in aqueous acid solution as high as 0.7 sec-1 were observed (Table I), it seems unlikely that this reaction involves an uncatalyzed preequilibrium cyclization to a tetrahedral intermediate as has been suggested for the corresponding reactions of maleamic acids (Scheme II).8 NMR studies on , -dimethylmaleamic acids might provide additional evidence relevant to the mechanism of their hydrolyses.…”

Section: Discussionmentioning

confidence: 99%

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The general acid catalyzed displacement of amines from o-hydroxylaminobenzamides in aqueous and nonaqueous solvents

Cox¹,

Porter²

1976

J. Am. Chem. Soc.

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The general acid catalyzed displacement of amines from o-hydroxylaminobenzamides, with formation of 2, l-benzoxisoxazolin-3-one, occurs readily in water and a wide variety of nonaqueous solvents. This, together with the fact that the o-hydroxylaminobenzamides can be obtained simply and quantitatively from the corresponding o-nitrobenzamides by reduction, suggests that amines may be conveniently masked as their o-nitrobenzoyl derivatives. This has been confirmed for some simple amines in preliminary synthetic studies. Kinetic measurements in both aqueous and nonaqueous solvents show that the o-hydroxylamino group strongly promotes the liberation of the amines. In aqueous perchloric acid solutions, for example. the cleavage of o-hydroxylamino-N,N-dimethylbenzamide occurs some 105-106 times more rapidly than the hydrolysis of the unsubstituted N,N-dimethylbenzamide. The mechanism of the reaction is discussed and, in particular, it is suggested that the relatively rapid reaction in solvents such as carbon tetrachloride and benzene can only be accounted for by a one encounter mechanism.The liberation of alcohols from esters of o-hydroxylaminobenzoic acid, with formation of 2,1-benzisoxazolin-3-one (I), has been shown by kinetic' and synthetic studies2 to be I rapid and quantitative in basic solution. The corresponding reaction in acid solution, although considerably slower than in alkaline solution, also shows evidence for direct participation of the hydroxylamino group.' The hydroxylaminobenzoates can be readily prepared from the corresponding o-nitrobenzoates by reduction, and this has led to the proposal* of o-nitrobenzoate as a protecting group for phenols and alcohols.An attempt2 to mask amines as their o-nitrobenzoyl derivatives (Scheme I) was, however, less successful. Thus it was reported that the cyclohexylamide of o-hydroxylaminobenzoic acid (produced by reduction of the o-nitroamide) did not readily liberate cyclohexylamine with base. In an earlier study,3 Cohen and Gray reported rapid cleavage of o-hydroxylamino-N.N-dimethylbenzamide in aqueous alkali, although the yield of the amine was not reported (51% of benzisoxazolinone was recovered). Preliminary work in this laboratory also suggests that, in base solution, the reactions of the amides are not as simple as those of the esters.'q2 However, we have found that the reactions proceed quite rapidly and without complications in acid solutions in both aqueous and nonaqueous solvents.In the present paper, we report a detailed study of the kinetics of the acid catalyzed liberation of amines from the corresponding o-hydroxylaminobenzamides and some preliminary results of a synthetic study on the usefulness of this reaction sequence (Scheme I) for the protection of amines. Experimental SectionMaterials. The nitroamides were prepared according to the procedure of Barton, Coates, and Sammes.2 Reduction of Nitrobenzamides. The nitroamide (3 g) in tetrahydrofuran (THF) (30 ml) was added to a solution of ammonium acetate (8 g) in water (30 ml) and the resultant mix...

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Section: Resultsmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

The general acid catalyzed displacement of amines from o-hydroxylaminobenzamides in aqueous and nonaqueous solvents

Cox¹,

Porter²

1976

J. Am. Chem. Soc.

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“…This nonlinearity is a characteristic of reactions that feature multistep mechanisms. 63,64 Monitoring the same reactions of 2 and 3 with GSH over a shorter time scale of less than 0.2 s revealed a well-defined reaction event, which we postulate is the bioconjugation process featuring coordination of the Cys sulfur ligand to the metal center (Figure 3B). The observation of two resolvable reaction events within the stopped-flow data provides unprecedented insight into the mechanism of bioconjugation by an organometallic Cys arylation reagent.…”

Section: ■ Results and Discussionmentioning

confidence: 81%

“…Monitoring the absorbances of these reactions over the course of 120 and 2 s, respectively, revealed a nonlinear relationship between the observed rate constants and GSH concentration (Figure A). This nonlinearity is a characteristic of reactions that feature multistep mechanisms. , Monitoring the same reactions of 2 and 3 with GSH over a shorter time scale of less than 0.2 s revealed a well-defined reaction event, which we postulate is the bioconjugation process featuring coordination of the Cys sulfur ligand to the metal center (Figure B).…”

Section: Resultsmentioning

confidence: 84%

Ultrafast Au(III)-Mediated Arylation of Cysteine

Doud,

Tilden,

Treacy

et al. 2024

J. Am. Chem. Soc.

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Through mechanistic work and rational design, we have developed the fastest organometallic abiotic Cys bioconjugation. As a result, the developed organometallic Au(III) bioconjugation reagents enable selective labeling of Cys moieties down to picomolar concentrations and allow for the rapid construction of complex heterostructures from peptides, proteins, and oligonucleotides. This work showcases how organometallic chemistry can be interfaced with biomolecules and lead to a range of reactivities that are largely unmatched by classical organic chemistry tools.

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ChemInform Abstract: KINETICS OF THE INTRAMOLECULAR DISPLACEMENT OF ALCOHOLS FROM O‐(HYDROXYAMINO)BENZOATES

Cox¹,

Grieve²,

Porter³

1976

Chemischer Informationsdienst

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Kinetics of the intramolecular displacement of alcohols from o-hydroxyaminobenzoates

Cited by 6 publications

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The general acid catalyzed displacement of amines from o-hydroxylaminobenzamides in aqueous and nonaqueous solvents

The general acid catalyzed displacement of amines from o-hydroxylaminobenzamides in aqueous and nonaqueous solvents

Ultrafast Au(III)-Mediated Arylation of Cysteine

ChemInform Abstract: KINETICS OF THE INTRAMOLECULAR DISPLACEMENT OF ALCOHOLS FROM O‐(HYDROXYAMINO)BENZOATES

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