Enantioface-differentiating protonation with chiral γ-hydroxyselenoxides
摘要:
Enantioface-differentiating protonation of achiral metal enolates of alpha-alkylcarbonyl compounds 7 has been developed using chiral gamma-hydroxyselenoxides 1 as a proton source. Reaction of zinc bromide enolates of 2-benzyl- and 2-n-propylcyclohexanones with (S-se)-1e gave (S)-2-benzylcyclohexanone 7a and (R)-2-n-propylcyclohexanone 7e in high enantiomeric excess, respectively. Intramolecular hydrogen bonding of the selenoxide 1, chelation effects between 1 and metal enolate, and 2-exo-hydroxy-10-bornyl-framework could contribute to this asymmetric induction. (C) 1997 Elsevier Science. Ltd.
The First Example of Enantioselective Protonation of Prochiral Enolates with Chiral<i>γ</i>-Hydroxyselenoxides
作者:Tamiko Takahashi、Naoki Nakao、Toru Koizumi
DOI:10.1246/cl.1996.207
日期:1996.3
Enantioselectiveprotonation of a simple enolate has been developed using an optically pure γ-hydroxyselenoxide 1 as a chiralprotonsource. Reaction of zinc bromide enolate 7b with (SSe)-selenoxide (SSe)-1c gave (S)-2-benzylcyclohexanone (S)-8 with high enantioselectivity. Intramolecular hydrogen bonding between hydroxy group and seleninyl-oxygen of 1 would contribute to this asymmetric induction