22661-19-4Relevant academic research and scientific papers
Dynamics in Catalytic Asymmetric Diastereoconvergent (3 + 2) Cycloadditions with Isomerizable Nitrones and α-Keto Ester Enolates
Adachi, Masaya,Akakabe, Mai,Ezawa, Tetsuya,Hashizume, Daisuke,Koshino, Hiroyuki,Sodeoka, Mikiko,Sohtome, Yoshihiro
, p. 9094 - 9104 (2021)
Reaction design in asymmetric catalysis has traditionally been predicated on a structurally robust scaffold in both substrates and catalysts, to reduce the number of possible diastereomeric transition states. Herein, we present the stereochemical dynamics in the Ni(II)-catalyzed diastereoconvergent (3 + 2) cycloadditions of isomerizable nitrile-conjugated nitrones with α-keto ester enolates. Even in the presence of multiple equilibrating species, the catalytic protocol displays a wide substrate scope to access a range of CN-containing building blocks bearing adjacent stereocenters with high enantio- and diastereoselectivities. Our computational investigations suggest that the enantioselectivity is governed in the deprotonation process to form (Z)-Ni-enolates, while the unique syn addition is mainly controlled by weak noncovalent bonding interactions between the nitrone and ligand.
Solvent-free synthesis of nitrones in a ball-mill
Colacino, Evelina,Nun, Pierrick,Colacino, Francesco Maria,Martinez, Jean,Lamaty, Frédéric
, p. 5569 - 5576 (2008/09/21)
Various C-aryl and C-alkyl-nitrones were synthesized within 0.5-2 h via condensation of an equimolar amount of aldehydes and N-substituted-hydroxylamines under solvent-free conditions in?a ball-mill apparatus. Reactions can be performed without the need of excluding air and moisture and yields the expected products with no need for further purification. The study has been complemented by Differential Scanning Calorimetry (DSC) and solid-state 13C MAS nuclear magnetic resonance experiments. We have also studied the temperature profile during the reaction. A comparative study with the corresponding solvent-free microwave activated reaction showed the superiority of the ball-milling method; 31 examples are described, including the synthesis of the anti-aging agent C-phenyl-N-tert-butyl nitrone (PBN) and one of its analogues C-2-pyridyl-N-tert-butylnitrone (2-PyBN).
