Diastereo- and Enantioselective Synthesis of α,α′-Disubstituted,<i>C</i>
<sub>2</sub>-Symmetric Ketones Using the SAMP-/RAMP-Hydrazone Method
作者:Dieter Enders、Winfried Gatzweiler、Udo Jegelka
DOI:10.1055/s-1991-28405
日期:——
Starting from simple, symmetric ketones such as, 3-pentanone,1, 3-diphenyl-2-propanone and 2,2-dimethyl-1,3-dioxan-.5-one, α,α′-bisalkylation of the corresponding SAMP-hydrazones (S)-2 and (S)-8 [(S)-1-(alkylideneamino)-2-(methoxymethyl)pyrrolidines and (S)-1-(2,2-dimethyl-1,3-dioxan-5-ylideneamino)-2-(methoxymethyl)pyrrolidines, respectively], followed by oxidative cleavage with ozone affords chiral, C2-symmetric ketones 5 and (S,S)-11 of high diastereo- and enantiomeric purity (de, ee > 98%).
Asymmetric Synthesis of Pseudo C2-Symmetric 2-Methyl Substituted 1,3-Diols
作者:Dieter Enders、Matthias Voith
DOI:10.1055/s-2002-19337
日期:——
enantioselective synthesis of pseudo C 2 -symmetric, 2-methyl substituted, acetonide protected (4) and free 1,3-diols 5 employing the SAMP-hydrazone mothodology with virtually complete asymmetric induction (de > 96%, ee ≥ 98-99%) is reported. The efficient protocol involves the asymmetric α,α'-bis-alkylation of hydrazone 1, the epimerization-free Wittig olefination of the resulting ketones 2 and subsequent hydrogenation