Substituent and Isotope Effects on the Hydrolysis Rates of 2‐Aryl‐2‐diazocarboxylic Esters

Bui‐Nguyen, Mai‐Huong; Dahn, H.; McGarrity, John F.

doi:10.1002/hlca.19800630108

Cited by 14 publications

(4 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[10]. Least-squares fitting produced zero-buffer-concentration intercepts (k int ) which, [10] k obs = k int + k cat [buffer] together with the observed first-order rate constants determined in perchloric acid and sodium hydroxide solutions, were used to construct the rate profile shown in Fig. 4.…”

Section: -Hydroxybenzofuran-2-one (Dilute Solutions)mentioning

confidence: 99%

“…Observed firstorder rate constants determined in each solution series increased linearly with increasing buffer concentration, and the data were, therefore, analyzed using the buffer dilution expression shown in eq. [10]. Least-squares fitting produced zero-buffer-concentration intercepts (k int ) which, [10] k obs = k int + k cat [buffer] together with the observed first-order rate constants determined in perchloric acid and sodium hydroxide solutions, were used to construct the rate profile shown in Fig.…”

Section: -Hydroxybenzofuran-2-one (Dilute Solutions)mentioning

confidence: 99%

See 1 more Smart Citation

Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)

Chiang¹,

Kresge²,

Meng³

2002

Can. J. Chem.

View full text Add to dashboard Cite

Rates of acid-catalyzed hydrolysis of 3-diazobenzofuran-2-one, measured in concentrated aqueous perchloric acid and hydrochloric acid solutions, were found to correlate well with the Cox-Yates X o excess acidity function, giving k H + = 1.66 × 10 -4 M -1 s -1 , m ‡ = 0.86 and k H + /k D + = 2.04. The normal direction (k H /k D > 1) of this isotope effect indicates that hydrolysis occurs by rate-determining protonation of the substrate on its diazo-carbon atom. It was found previously that the next higher homolog of the present substrate, 4-diazoisochroman-3-one, also undergoes hydrolysis by this reaction mechanism but with a rate constant 15 times greater than that for the present substrate; this difference in reactivity can be understood in terms of the various resonance forms that contribute to the structures of these substrates. The product of the present hydrolysis reaction is 3-hydroxybenzofuran-2-one, which itself quickly undergoes subsequent acid-catalyzed hydrolysis to 2-hydroxymandelic acid. The acidity dependence of this subsequent hydrolysis is much shallower than that of the diazo compound precursor, and rates of reaction correlate as well with [H + ] as with X o . This is due in part to incursion of a nonproductive protonation on the hydroxy group of 3-hydroxybenzofuran-2-one that impedes hydrolysis and produces saturation of acid catalysis. Rates of hydrolysis of the hydroxy compound were also measured in dilute HClO 4 and NaOH solutions as well as in CH 3 CO 2 H, H PO 2 4 − , ( ) CH OH CNH 2 3 3 + , and NH 4 + buffers, and the rate profile constructed from these data showed the presence of uncatalyzed and hydroxide ion-catalyzed reactions. This hydroxide-ion catalysis became saturated at [NaOH] ≅ 0.05 M, implying occurrence of yet another nonproductive substrate ionization.Résumé : On a observé que les vitesses de réactions d'hydrolyse acidocatalysées de la 3-diazobenzofuran-2-one en solutions aqueuses des acides perchlorique et chlorhydrique donnent une bonne corrélation avec la fonction d'acidité en excès de Cox-Yates, X o , qui conduit à k H + = 1,66 × 10 -4 M -1 s -1 , m ‡ = 0,86 et k H + /k D + = 2,04. La direction normale (k H /k D > 1) de cet effet isotopique indique que l'hydrolyse se produit par une étape de protonation du substrat cinéti-quement déterminante sur l'atome de carbone du diazo. On avait observé antérieurement que l'homologue directement supérieur au substrat étudié, la 4-diazoisochroman-4-one, subit aussi une hydrolyse par ce mécanisme réactionnel, mais que la constante de vitesse de sa réaction est 15 fois supérieure à celle observée avec le substrat étudié ici; cette diffé-rence de réactivité peut s'expliquer en termes de diverses formes de résonance qui contribuent aux structures de ces substrats. Le produit d'hydrolyse du produit considéré ici est la 3-hydroxybenzofuran-2-one qui subit rapidement une hydrolyse acidocatalysée subséquente conduisant à l'acide 2-hydroxymandélique. La dépendance de cette hydrolyse subséquente sur l'acidité est beaucoup plus faible que celle s...

show abstract

Section: -Hydroxybenzofuran-2-one (Dilute Solutions)mentioning

confidence: 99%

Section: -Hydroxybenzofuran-2-one (Dilute Solutions)mentioning

confidence: 99%

Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)

Chiang¹,

Kresge²,

Meng³

2002

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Crystallographic data for the structures have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication CCDC-999525 ( 6a ) and CCDC-998320 ( 12d ). Compounds 1a , 1b , 1c , 1d , 1e , 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i and 2j were prepared by the reported procedures.…”

Section: Methodsmentioning

confidence: 99%

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds

et al. 2014

View full text Add to dashboard Cite

Transformations of 2-azabuta-1,3-dienes, formed in Rh2(OAc)4-catalyzed reactions of diazo carbonyl compounds with 2H-azirines, dramatically depend on the nature of substituents. 4,4-Diphenyl-2-azabuta-1,3-dienes with two electron-acceptor substituents at C(1) undergo thermal 1,5-cyclization to give indoles in good yields. The increase in electron-withdrawing ability of C(1)-substituents facilitates the reaction that proceeds via pseudopericyclic 1,5-electrocyclization of 2-azabutadiene into 7aH-indolium ylide followed by prototropic shift. 3,4-Diphenyl-2-azabuta-1,3-dienes, resulting from reaction of 2,3-diphenyl-2H-azirine and diazo compounds, do not produce indoles via 1,5-cyclization due to the trans-configuration of the 4-Ph-group and the nitrogen, but undergo 1,4-cyclization to 2,3-dihydroazetes. 1,6-Cyclization into 2H-1,4-oxazines with participation of the oxygen of ester or amide group at C(1) of corresponding 2-azabuta-1,3-dienes does not take place due to kinetic and thermodynamic reasons. Instead of this, 1,6-electrocyclization with participation of phenyl substituent at C(4) of the 2-azabuta-1,3-dienes, providing isoquinoline derivatives, can occur at elevated temperatures. The DFT-calculations (mPWB1K/6-31+G(d,p)) confirm the dependence of 2-azabuta-1,3-diene transformation type on the nature of substituents.

show abstract

“…[14,15] This complexation enables the amplification of the acidity of the organic acid, which in the presence of a Brønsted basic diazo compound, undergoes a proton transfer through species D. The proton transfer, converting D to C, may be rate determining in this process because it has been shown that a-aryldiazoacetate hydrolysis occurs through a general acid-catalyzed A-S E 2 mechanism, although additional studies are required to provide tangible evidence in this case. [16,17] The catalytic cycle would conclude with the diazonium species in C reacting with the urea-stabilized anion (X À ) to generate the observed insertion products (4 or 6). The weak interaction of 4 or 6 with difluoroboronate urea 1 a would then free the urea to re-enter the catalytic cycle.…”

mentioning

confidence: 99%

Urea‐Induced Acid Amplification: A New Approach for Metal‐Free Insertion Chemistry

Couch

Auvil

Mattson

2014

Chemistry A European J

View full text Add to dashboard Cite

The enhanced catalytic activity of difluoroboronate ureas proved to be essential as an acidity amplifier to promote metal-free O-H and S-H insertion reactions of α-aryldiazoacetates in high yield. This methodology was found to be generally applicable to a broad substrate scope and presents a conceptually new approach for organocatalytic diazo insertion reactions. Mechanistic investigations suggest that the reaction pathway involves a urea-induced protonation of the α-aryldiazoester.

show abstract

Substituent and Isotope Effects on the Hydrolysis Rates of 2‐Aryl‐2‐diazocarboxylic Esters

Cited by 14 publications

References 36 publications

Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)

Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds

Urea‐Induced Acid Amplification: A New Approach for Metal‐Free Insertion Chemistry

Contact Info

Product

Resources

About