Stereo-Modulating Catalysis by Europium(III) Complexes in Aldol Reactions of Chiral .ALPHA.-Alkoxy Aldehydes with Ketene Silyl Acetals.
作者:Masahiro Terada、Jin-Hua Gu、Dibakar C. Deka、Koichi Mikami、Takeshi Nakai
DOI:10.1246/cl.1992.29
日期:——
The Eu(fod)3- or Eu(dppm)3-catalyzed aldol reactions of the four chiral α-alkoxy aldehydes having different protecting groups with (E)- or (Z)-ketene silyl acetals are shown to provide the high levels of diastereocontrol, the sense depending on the nature of the protecting group. The catalytic stereo-modulation is explained in terms of the mode of aldehyde/catalyst complexation (chelation vs. nonchelation)
Highly selective generation and application of (E)- and (Z)-silyl ketene acetals from .alpha.-hydroxy esters
作者:Kouji Hattori、Hisashi Yamamoto
DOI:10.1021/jo00072a005
日期:1993.9
A method for the stereoselective synthesis of silyl ketene acetals from a-hydroxy esters is described. Internal quench with excess TMSCI of the lithium enolate at -100-degrees-C, which is generated using a hindered base, LTMP, leads to the selective formation of (E)-silyl ketene acetal. In contrast, the deprotonation at -100-degrees-C using LHMDS in THF-HMPA (4:1), followed by treatment with tert-butyldimethylsilyl chloride affords the (Z)-silyl ketene acetal selectively. The method can be applied to the stereoselective reaction of the Ireland ester enolate Claisen rearrangement and aldol synthesis.
Hattori Kouji, Yamamoto Hisashi, Tetrahedron, 50 (1994) N 10, S 3099-3112
作者:Hattori Kouji, Yamamoto Hisashi
DOI:——
日期:——
NARASAKA, KOICHI;ICHIKAWA, YUH-ICHIRO;KUBOTA, HIDEKI, CHEM. LETT.,(1987) N 11, 2139-2142