Dialkyl amides of L-valine, L-isoleucine, and L-tert-leucine (2) are excellent chiral auxiliaries for the construction of quaternary stereocenters at ambient temperature. Enaminoesters 3, prepared from these auxiliaries 2 and Michael donors 1, undergo a copper-catalyzed asymmetricMichaelreaction with methyl vinyl ketone (MVK, 4) to afford products 5 in 70-90% yield and 90-99% ee (enantiomeric excess)
LSB can efficiently promotecatalyticasymmetricMichaelreactions in CH2Cl2, inducing high enantiomeric excesses on the Micheal donor side. The multifunctional character of LSB appears to give rise to high stereoselectivity, offering the most efficient asymmetricreaction of its type.
The stereoselective α-alkylation of chiral β-hydroxy esters and some applications thereof
作者:G. Fráter、U. Müller、W. Günther
DOI:10.1016/s0040-4020(01)82413-3
日期:1984.1
The stereoselectivity of the α-alkylation of chiral β-hydroxyester is discussed. The configuration of the alkylated product was proved chemically (Scheme 2). A one pot aldol-alkylation reaction was developed leading stereoselectively to racemic (s*,s*)-α-alkyl-β-hydroxy ester (Scheme 3,4). Baker's yeast reduction of 2-alkyl-3-keto ester led to valuable chiral (2RS,3S)-intermediates, which were converted
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