Results 91 to 100 of about 31,425 (239)

Characterizations of matrix valued asymmetric truncated Hankel operators [PDF]

arXiv, 2023
In this paper we introduce the class of matrix valued asymmetric truncated Hankel operators. By using characterizations of matrix valued asymmetric truncated Toeplitz operators, we characterize matrix valued asymmetric truncated Hankel operators in the case when two involved inner matrices are J-symmetric.
arxiv  

Asymmetric Organocatalytic Synthesis of Sulfone‐Containing (Dihydro)pyrans via Formal (4+2)‐Cycloadditions of Allenylsulfones or Propargylsulfones and Michael Acceptors

ChemCatChem, Accepted Article.
The activation of electron poor allenes with Lewis base catalysts allows for unique transformations and chiral isochalcogenoureas were recently introduced as powerful catalysts for allenoate‐based (4+2)‐cycloadditions. We herein now report the use of these catalysts for the activation and control of allenylsulfones and propargylsulfones for asymmetric (
Mario Hofer, Markus Himmelsbach, Uwe Monkowius, Mario Waser   +3 more
wiley   +1 more source

Autoinductive Effects in Zinc‐Catalyzed Alkylations of Benzaldehyde Mediated by Simple Chiral β‐Amino Alcohol Ligands

ChemistryEurope, EarlyView.
The first report on zinc‐catalyzed enantioselective alkylation of aldehydes mediated by a chiral auxiliary is revisited, and the studies show much more complex behavior than previously thought. Studies show an enantiodivergence of the reaction as a function of its progress, due to an autoinduction phenomenon.
Joseph El Khoury, Thibault Thierry, Yannick Geiger, Stéphane Bellemin‐Laponnaz   +3 more
wiley   +1 more source

Supramolecular Gels as Active Tools for Reaction Engineering

Angewandte Chemie, Volume 137, Issue 24, June 10, 2025.
The unique combination of environments within gels, self‐assembled from low‐molecular‐weight gelators, offers the ability to control reactivity in new ways, achieving unique reaction outcomes, leading to the emerging concept of supramolecular gels as nanoreactors. Smart chemical engineering methods enable the use of such gels to fabricate materials and
David K. Smith
wiley   +2 more sources

ORGANOCATÁLISE ENANTIOSSELETIVA: EVOLUÇÃO E ASPECTOS RECENTES

Química Nova
In the last two decades, enantioselective organocatalysis has established itself as one of the three pillars of asymmetric catalysis. The rapid growth in the area is due to the rationalization of organocatalysis based on the generic modes of catalyst ...
Fernanda G. Finelli, Bruno M. da S. Santos, Lívia C. R. M. da Frota   +2 more
doaj   +1 more source

Asymmetric organocascades involving the formation of two C-heteroatom bonds from two distinct heteroatoms [PDF]

, 2012
International audienceIn the vast and expanding world of enantioselective organocascades, the ones in which two C-heteroatom bonds are created from two distinct heteroatoms are rare.
Bonne, Damien, Constantieux, Thierry, Coquerel, Yoann, Rodriguez, Jean   +3 more
core   +2 more sources

Reactivity of δ‐Functionalized para‐Quinone Methides in Nucleophilic Addition Reactions

Chemistry – A European Journal, Accepted Article.
The electrophilic reactivities of para‐quinone methides (pQMs) with functional groups at the exocyclic polarized carbon‐carbon double bond were determined by photometrical monitoring the kinetics of their reactions with carbanions in DMSO at 20°C. The experimental second‐order rate constants k2 were evaluated by the Mayr‐Patz equation, that is, the ...
Christoph Gross, Andreas Eitzinger, Peter Mayer, Armin R. Ofial   +3 more
wiley   +1 more source

Total Asymmetric Synthesis of Monosaccharides and Analogues

CHIMIA, 2011
Since the discovery of the 'formose reaction' by Butlerow,[1] total synthesis of carbohydrates has undergone rapid development. The most important methods for the asymmetric synthesis of monosaccharides and analogues of biological importance are
Inmaculada Robina, Ana T. Carmona, Antonio J. Moreno-Vargas, Elena Moreno-Clavijo   +3 more
doaj   +1 more source

Phenol‐Rich Carbon Dots as Metal‐Free Nano‐Photocatalysts for [3 + 2] Cycloaddition Reactions

ChemSusChem, EarlyView.
Phenol‐rich carbon dots can be effectively used, in combination with a proper base and the Schreiner thiourea (A), as nano‐photocatalysts to drive synthetically relevant [3 + 2] cycloaddition reactions between cyclopropyl ketones 1 and unsaturated hydrocarbons 2. Carbon dots (CDs) are unique carbon‐based nanoparticles with potential applications in the
Martina Mamone, Giuseppe Gentile, Maurizio Prato, Giacomo Filippini   +3 more
wiley   +1 more source

Strong and Confined Acids Enable a Catalytic Asymmetric Nazarov Cyclization of Simple Divinyl Ketones [PDF]

, 2019
We report a catalytic asymmetric Nazarov cyclization of simple, acylic, alkyl-substituted divinyl ketones using our recently disclosed strong and confined imidodiphosphorimidate Brønsted acids.
De, C., Farès, C., Kennemur, J., List, B., Ouyang, J.   +4 more
core   +2 more sources