0000000000147661
AUTHOR
Antti Pohjakallio
showing 6 related works from this author
ChemInform Abstract: Enantioselective Synthesis of 2-Isoxazolines by a One-Flask Conjugate Addition/Oxime-Transfer Process.
2009
Enantioselective isoxazoline synthesis: A combination of 1) a catalytic enantioselective conjugate addition of oximes to alpha,beta-unsaturated aldehydes and 2) an acid-catalyzed intramolecular oxime-transfer reaction lead to the first asymmetric synthesis of 3-unsubstituted 2-isoxazolines (see scheme).
Synthesis of 2-isoxazolines: enantioselective and racemic methods based on conjugate additions of oximes.
2010
The formation of 3-unsubstituted 2-isoxazolines by means of condensation reactions between α,β-unsaturated aldehydes and oximes proceeds readily in the presence of catalytic amounts of anilinium salts. Mechanistically, the process involves a fast conjugate addition of the oxime and a slower intramolecular oxime-transfer reaction. The rate of oxime transfer was found to correlate with the acidity of the catalyst. This finding enabled us to discover an enantioselective process in which the fragile conjugate-addition product generated in the first stage is rapidly cyclized into the stable isoxazoline under acidic conditions, with conservation of enantiomeric excess. In summary, herein we descr…
Base-catalyzed isomerization of 2-isoxazolines enables a two-step enantioselective synthesis of β-hydroxynitriles from enals.
2010
The asymmetric synthesis of β-hydroxynitriles remains a challenge in organic synthesis. Herein we report a convenient synthesis of β-hydroxynitriles from enantiomerically enriched 3-unsubstituted 2-isoxazolines via a base-catalyzed ring-opening reaction that takes place without loss of enantiopurity. In combination with organocatalytic enantioselective synthesis of 3-unsubstituted 2-isoxazolines, the ring-opening enables a short 2-step synthesis of β-hydroxynitriles from α,β-unsaturated aldehydes in high enantiomeric purity.
Enantioselective Synthesis of 2-Isoxazolines by a One-Flask Conjugate Addition/Oxime-Transfer Process
2009
Enantioselective isoxazoline synthesis: A combination of 1) a catalytic enantioselective conjugate addition of oximes to alpha,beta-unsaturated aldehydes and 2) an acid-catalyzed intramolecular oxime-transfer reaction lead to the first asymmetric synthesis of 3-unsubstituted 2-isoxazolines (see scheme).
ChemInform Abstract: Base-Catalyzed Isomerization of 2-Isoxazolines Enables a Two-Step Enantioselective Synthesis of β-Hydroxynitriles from Enals.
2011
Treatment of chiral isoxazoles with catalytic amounts of DBU results in efficient formation of optically active β-hydroxynitriles.
ChemInform Abstract: Synthesis of 2-Isoxazolines: Enantioselective and Racemic Methods Based on Conjugate Additions of Oximes.
2011
Acidic anilinium salts catalyze the direct formation of racemic 2-isoxazolines from enals and oximes by means of consecutive oxime conjugate-addition and intramolecular oxime-transfer reaction.