Chlorotrimethylsilane promoted asymmetric Michael reaction of chiral enamines of α-alkyl β-keto esters
作者:Kiyoshi Tomioka、Wonjun Seo、Kaori Ando、Kenji Koga
DOI:10.1016/s0040-4039(00)96933-8
日期:——
By the promotion of chlorotrimethylsilane, asymmetricMichaelreaction of the chiral enamines (2) of α-alkyl β-keto esters (1) with methyl vinyl ketone and ethyl acrylate proceeded to afford, after hydrolysis, either enantiomer of the corresponding adducts (4) in a good enantioselectivity.
Stereoselective reactions. XXIV. Chlorotrimethylsilane promoted asymmetric Michael reaction of chiral lithioenamines derived from α-alkyl β-keto esters
作者:Kaori Ando、Wonjun Seo、Kiyoshi Tomioka、Kenji Koga
DOI:10.1016/s0040-4020(01)89317-0
日期:1994.1
Chlorotrimethylsilane promoted asymmetric Michael reaction of the chiral lithioenamines derived from α-alkyl β-keto esters and (S)-valine tert-butyl ester is described. Complementary asymmetric syntheses producing either enantiomers from the same starting material have been realized by changing the solvent system. That is, the lithioenamines react with methyl vinyl ketone or ethyl acrylate in THF in
Stereoselective reactions. XXI. Asymmetric alkylation of α-alkyl β-keto esters to α,α-dialkyl β-keto esters having either (R)- or (S)-chiral quaternary center depending on the solvent system
作者:Kaori Ando、Yataka Takemasa、Kiyoshi Tomioka、Kenji Koga
DOI:10.1016/s0040-4020(01)80346-x
日期:——
Asymmetric alkylation reaction of chiral enamines prepared from alpha-alkyl beta-keto esters and (S)-valine tert-butyl ester leading to either enantiomer is described. Lithiated chiral enamines can be alkylated with alkyl halides in a toluene solvent in the presence of HMPA to give, after hydrolysis, alpha,alpha-dialkyl beta-keto esters in 70-99%ee. The reactions in the presence of THF, dioxolane, or trimethylamine. instead of HMPA, afford the corresponding antipodes with enantiomeric purities of 44-92%ee. The present method provides a procedure for the synthesis of both enantiomers of alpha,alpha-dialkyl beta-keto esters in high enantiomeric purities starting from the same chiral enamines.
Asymmetric Michael reaction of α-alkyl β-keto esters via chiral enamines
作者:Kiyoshi Tomioka、Kaori Ando、Kōsuke Yasuda、Kenji Koga
DOI:10.1016/s0040-4039(00)84081-2
日期:1986.1
Ando, Kaori; Yasuda, Kousuke; Tomioka, Kiyoshi, Journal of the Chemical Society. Perkin transactions I, 1994, # 3, p. 277 - 282