Base-Catalyzed Isomerization of 2-Isoxazolines Enables a Two-Step Enantioselective Synthesis of β-Hydroxynitriles from Enals
摘要:
The asymmetric synthesis of beta-hydroxynitriles remains a challenge in organic synthesis. Herein we report a convenient synthesis of beta-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 beta-hydroxynitriles from alpha,beta-unsaturated aldehydes in high enantiomeric purity.
Enantioselective Synthesis of 2-Isoxazolines by a One-Flask Conjugate Addition/Oxime-Transfer Process
作者:Antti Pohjakallio、Petri M. Pihko
DOI:10.1002/chem.200802684
日期:2009.4.14
Enantioselective isoxazoline synthesis: A combination of 1) a catalytic enantioselectiveconjugateaddition of oximes to α,β‐unsaturated aldehydes and 2) an acid‐catalyzed intramolecular oxime‐transfer reaction lead to the first asymmetric synthesis of 3‐unsubstituted 2‐isoxazolines (see scheme).