Molecular recognition by artificial chiral catalysts utilizing a metal chelate. A remarkable difference in reactivity between geometrical isomers of silyl enolates in asymmetric aldol reactions using chiral tin(II) catalysts
作者:Shū Kobayashi、Mineko Horibe、Iwao Hachiya
DOI:10.1016/0040-4039(95)00505-7
日期:1995.5
remarkable difference in reactivity between (E)- and (Z)-enolates in the asymmetricaldolreactions of silyl enolates with aldehydes using chiral tin(II) Lewis acids was found. This difference can be interpreted to mean that the chiral catalyst coordinated by aldehydes via a metal chelate recognizes the geometry of the silyl enolates.
Highly selective enolization method for heteroatom substituted esters; its application to the ireland ester enolate claisen rearrangement
作者:Kouji Hattori、Hisashi Yamamoto
DOI:10.1016/s0040-4020(01)81109-1
日期:1994.3
A method for the stereoselective synthesis of silylketeneacetals from α-siloxy esters, β-hydroxy esters, and α-aminoesters is described. Internal quench with excess trimethylsilyl chloride of the lithium enolate at −100 °C, which is generated using a hindered base, LTMP, leads to the selective formation of E-silyl keteneacetal. In contrast, the deprotonation at −100 °C using LHMDS in THF-HMPA (4:1)
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.