ChemInform Abstract: Lewis Acid Catalyzed Preparation of Some Carbamates and Sulfonylureas. Application to the Determination of Enantiomeric Purity of Chiral Alcohols.

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

Download Full-text

Benzyl ethers of methyl α-D-glucopyranoside

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19801959 ◽

1980 ◽

Vol 45 (7) ◽

pp. 1959-1963 ◽

Cited By ~ 1

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.

Download Full-text

Determination of the degree of adsorption and the heat of adsorption for 1-butylamine and ammonia on NaHY zeolites

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19842739 ◽

1984 ◽

Vol 49 (12) ◽

pp. 2739-2743 ◽

Cited By ~ 5

Author(s):

Miloslav Křivánek ◽

Pavel Jírů

Keyword(s):

Lewis Acid ◽

Adsorption Isotherms ◽

Heat Of Adsorption ◽

Brønsted And Lewis Acid

The degree and heat of adsorption of 1-butylamine and ammonia were measured on samples of NaHY zeolites activated at 400-600°C. The adsorption isotherms and calorimetric curves were compared for the two bases, and the amount of Bronsted and Lewis acid centres was determined from the calorimetric curves.

Download Full-text