Mechanism and Stereochemistry of the Hydrolysis of 4-Arylamino-1,2,3,4- tetrahydroquinaldines

1974 ◽  
Vol 52 (6) ◽  
pp. 884-887 ◽  
Author(s):  
T. P. Forrest ◽  
G. A. Dauphinee ◽  
W. F. Miles
Keyword(s):  
Nitrogen Atom ◽  
Equilibrium Mixture ◽  
Hydroxyl Group ◽  
Amino Group ◽  
Heterocyclic Nitrogen ◽  
Carbonium Ion ◽  
Kinetically Controlled ◽  
Leaving Group ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Rates of acid-catalyzed hydrolysis of the benzylic amino group in stereoisomers of 4-arylamino-1,2,3,4-tetrahydroquinaldines have been determined by n.m.r. spectroscopy. Those isomers which have a pseudo-axial leaving group react more rapidly than those with a pseudo-equatorial leaving group, forming in each case the isomer with a pseudo-axial hydroxyl group as the kinetically controlled product. This product is converted in time to an equilibrium mixture of the two stereoisomeric alcohols. The reaction is inhibited by excess acid and appears to proceed through an intermediate carbonium ion which is stabilized by the heterocyclic nitrogen atom.

The proton affinities and deprotonation enthalpies of β-D-fructopyranose and α-L-sorbopyranose

1991 ◽  
Vol 69 (12) ◽  
pp. 1917-1928 ◽  
Author(s):  
Robert J. Woods ◽  
Walter A. Szarek ◽  
Vedene H. Smith Jr.
Keyword(s):  
Hydrogen Bonding ◽  
Oxygen Atom ◽  
Intramolecular Hydrogen Bonding ◽  
Hydroxyl Group ◽  
Proton Affinities ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Acids And Bases ◽  
Intramolecular Hydrogen ◽  
Hydrolysis Of

The proton affinities (PAs) and deprotonation enthalpies (DPEs) were calculated for the pyranoid forms of two naturally occurring sugars, D-fructose and L-sorbose. In both molecules the PAs of the primary hydroxyl group (HO-1), the anomeric hydroxyl group (HO-2), and the ring-oxygen atom (O-6) were calculated, as were the DPEs of HO-1 and HO-2. The stabilities of the conjugate acids and bases of these sugars are enhanced by the presence of intramolecular hydrogen bonding, a feature that is significant in explaining the differences in sweetness and the rates of mutarotation of the title compounds, as well as the differences in the rates of acid-catalyzed hydrolysis of ketopyranosides. Key words: proton affinity, deprotonation enthalpy, ab initio calculations, AM1, hexuloses.

Cis- and trans-2,4-dimethoxytetrahydropyran. Models for the study of the anomeric effect

1968 ◽  
Vol 46 (9) ◽  
pp. 1543-1548 ◽  
Author(s):  
F. Sweet ◽  
R. K. Brown
Keyword(s):  
Good Yield ◽  
Methoxy Group ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Kcal Mole ◽  
Mild Acid Hydrolysis ◽  
Acid Catalyzed ◽  
Cis And Trans ◽  
Hydrolysis Of ◽  
Mild Acid

Acid-catalyzed methanolysis of 2-methoxy-5,6-dihydro-2H-pyran gave, in good yield, a 4.0:1.0 mixture of trans- and cis-2,4-dimethoxytetrahydropyran. Mild acid hydrolysis of 2-methoxy-5,6-dihydro-2H-pyran followed by acid-catalyzed reaction with methanol gave a cis-trans mixture of 4-hydroxy-2-methoxytetrahydropyran in very poor yield.From the equilibrium mixture of trans- and cis-2,4-dimethoxytetrahydropyran (4.0:1.0), the magnitude of the anomeric effect of the 2-methoxy group was calculated to be 1.4 kcal/mole.

Alkylation by secondary alcohols. I. The reaction of xanthydrol with some N1-monosubstituted sulfanilamides and related compounds

1967 ◽  
Vol 45 (13) ◽  
pp. 1411-1424 ◽  
Author(s):  
R. E. Moskalyk ◽  
L. G. Chatten
Keyword(s):  
Nitrogen Atom ◽  
Tautomeric Form ◽  
Heterocyclic Ring ◽  
The Other ◽  
Secondary Alcohols ◽  
Amino Group ◽  
Aromatic Character ◽  
Carbonium Ion ◽  
Other Hand ◽  
Related Compounds

Sulfanilamides were found to undergo alkylation with xanthydrol, yielding either mono- or di-xanthenyl derivatives. The site of substitution, common to all sulfanilamides having a free p-amino group, was shown to be the N4-position in the sulfanilamide molecule. Three additional unique reactive sites were observed. Sulfanilamides carrying a thiazole, thiadiazole, or pyridazine substituent in the N1-position were also alkylated on the annular nitrogen atom of the heterocyclic ring, the reaction having occurred from the imido tautomeric form. Sulfisoxazole (IK), on the other hand, reacted from the amido form to give the N1,N4-dixanthenyl derivative. Sulfadimethoxine (Ih) was substituted at carbon, as well as at nitrogen, to yield N4-xanthenyl-N1-(2,6-dimethoxy-5-(9-xanthenyl)-4-pyrimidyl)sulfanilamide.Sulfanilamides possessing pKa values of about 5.5 were found to be sufficiently acidic to catalyze their own reaction with xanthydrol, and no external catalyst was necessary. The exceptional ease of formation of the xanthylium ion was postulated to be associated with the resulting stability of this carbonium ion by virtue of its acquired aromatic character.

Practical Synthesis of β-Ketothioesters by Acid-Catalyzed Hydrolysis of Ketene N,S -Acetals with Amino as the Leaving Group

2019 ◽  
Vol 2019 (22) ◽  
pp. 3704-3710 ◽  
Author(s):  
Qi Xu ◽  
Baihui Zheng ◽  
Ling Pan ◽  
Qun Liu ◽  
Yifei Li
Keyword(s):  
Leaving Group ◽  
Practical Synthesis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Studies Relating to Aziridine Antitumor Antibiotics. Part I. Asymmetric Syntheses. Part II. Chiral Aziridines and their Conversion to α-Aminoacids

1973 ◽  
Vol 51 (6) ◽  
pp. 856-869 ◽  
Author(s):  
J. W. Lown ◽  
T. Itoh ◽  
N. Ono
Keyword(s):  
Acid Hydrolysis ◽  
Sodium Iodide ◽  
Equilibrium Mixture ◽  
Antitumor Antibiotics ◽  
Optical Yield ◽  
Asymmetric Syntheses ◽  
Independent Synthesis ◽  
Acid Catalyzed ◽  
Cis And Trans ◽  
Hydrolysis Of

Separable diastereomeric cis-l-menthyl 2-phenyl-3-aziridinecarboxylates (4 and 5) were prepared by the Gabriel reaction. N-Acylation with p-nitrobenzoyl chloride or p-anisoyl chloride of 4 and 5 gives 7 and 8, and 23 and 24, respectively. Sodium iodide-catalyzed rearrangement of the N-acylated aziridines is regiospecific with exclusive attack at C-2 and from 8 is obtained the chiral 2-oxazolines cis-9 and trans-10 in a ratio of 30:70 together with the unsaturated amide 11. The structure of the latter was proven by independent synthesis. The intermediate l-menthyl N-p-nitrobenzoyl-3-iodophenyl-alaninate (18) was isolated at lower temperatures and shown to form the equilibrium mixture of 9 and 10 with triethylamine owing to partial racemization by a Finkelstein identity reaction. Use of an N-p-anisoyl substituent in the aziridine improves the yield of chiral 2-oxazolines by preventing the formation of 11, and allows the separation of pure cis- and trans-oxazolines for characterization. The aziridines bearing N-p-anisoyl substituents display a greater sensitivity to attack by weaker nucleophiles than the p-N-nitrobenzoyl analogs.Acid hydrolysis of 9 and 10 gives D-allo-β-phenylserine in an optical yield of about 17% from which 5 and 8 are tentatively assigned the 2R,3R configuration. Similar acid hydrolysis of the 2-p-anisyl-2-oxazoline (26b) allowed the isolation of the intermediate l-menthyl O-anisoyl-allo-β-phenylserinate (30a), hydrolysis of which gave D-allo-β-phenylserine in about 18% optical yield. The isolation of allo-β-phenylserine only from cis- and trans-2-oxazolines is attributed to acid-catalyzed inversion at the benzylic center to the conformationally more stable allo form.

Allylic Amination via Acid Catalyzed Leaving Group Activation

2016 ◽  
Vol 3 (2) ◽  
pp. 145-159
Author(s):  
Marija Skvorcova ◽  
Aigars Jirgensons
Keyword(s):  
Allylic Amination ◽  
Leaving Group ◽  
Acid Catalyzed

The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

1985 ◽  
Vol 50 (4) ◽  
pp. 845-853 ◽  
Author(s):  
Miloslav Šorm ◽  
Miloslav Procházka ◽  
Jaroslav Kálal
Keyword(s):  
Catalyst Concentration ◽  
Low Molecular Weight ◽  
Imidazolium Chloride ◽  
First Order ◽  
Nitrobenzoic Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Ethanol In Water ◽  
Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

Benzyl ethers of methyl α-D-glucopyranoside

1980 ◽  
Vol 45 (7) ◽  
pp. 1959-1963 ◽  
Author(s):  
Dušan Joniak ◽  
Božena Košíková ◽  
Ludmila Kosáková
Keyword(s):  
Kinetic Study ◽  
Spectrophotometric Determination ◽  
Reductive Cleavage ◽  
Ether Bond ◽  
Benzyl Ethers ◽  
Acid Catalyzed ◽  
Model Substances ◽  
Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

ChemInform Abstract: ACID-CATALYZED HYDROLYSIS OF 3-ALKOXY-4′-SUBSTITUTED CROTONOPHENONES

1979 ◽  
Vol 10 (42) ◽  
Author(s):  
S. D. BRYNES ◽  
L. R. FEDOR
Keyword(s):  
Acid Catalyzed ◽  
Hydrolysis Of
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