We describe a column based flow system in which a cinchona alkaloid based reagent/catalyst solid-phase promotes the asymmetric a-chlorination of acid chlorides to afford highly optically active alpha-chloroesters in high enantiomeric excess and in good yields. (c) 2005 Published by Elsevier Ltd.
Generation of Ketenes from Acid Chlorides Using NaH/Crown Ether Shuttle-Deprotonation for Use in Asymmetric Catalysis
作者:Andrew E. Taggi、Harald Wack、Ahmed M. Hafez、Stefan France、Thomas Lectka
DOI:10.1021/ol0172525
日期:2002.2.1
[GRAPHICS]We describe methodology for the in situ generation of reactive monosubstituted ketenes from acid chlorides through a shuttle deprotonation process using NaH as an inexpensive stoichiometric base and a crown ether cocatalyst. We have successfully applied this new procedure to the catalytic, asymmetric synthesis of beta-lactams and alpha-haloesters.