Novel defluorinative alkylation of trifluoroacetaldehyde N,O-acetal derivatives and its application to multi-component reaction
作者:Hikaru Yanai、Takeo Taguchi
DOI:10.1039/b817599c
日期:——
The reaction of trifluoroacetaldehyde N,O-acetal derivatives with 2 molar equivalents of alkyllithium reagents proceeded viaβ-elimination of fluoride followed by alkyl transfer from excess alkyllithium to the generated keteneN,O-acetal intermediate at the β-carbon of fluorine groups.
A rapid and convergent synthesis of α,α-difluoro-β-hydroxyketones through regiospecific defluorinative alkylation reaction
作者:Hikaru Yanai、Tatsunori Ichikawa、Takeo Taguchi
DOI:10.1016/j.tetlet.2010.03.018
日期:2010.5
Both the defluorinative alkylation reaction of trifluoroacetaldehyde N,O-acetals using alkyllithiums and the following C-C bond formation with carbonyls as electrophiles were accelerated by a suitable diamine additive such as (-)-sparteine to give alpha,alpha-difluoro-beta-hydroxyketone N,O-acetal products in an excellent yield. We also found that N-benzyl-N,O-acetal group of the resultant products can be removed under palladium-catalyzed hydrogenolysis conditions giving rise to the corresponding alpha,alpha-difluoro-beta-hydroxyketones. The present two-step procedure is a useful and novel synthetic approach for functionalized alpha,alpha-difluoroketones. (C) 2010 Published by Elsevier Ltd.
Trihaloacetaldehyde N,O-acetals: useful building blocks for dihalomethylene compounds
作者:Hikaru Yanai、Takeo Taguchi
DOI:10.1016/j.tet.2010.04.061
日期:2010.6
The reaction of trifluoroacetaldehyde N,O-acetals with more than 2 equiv of alkyllithiums at −78 °C resulted in regiospecific defluorinative alkylation with unusual regioselectivity to give α,α-difluoroketone N,O-acetals in excellent yield. In contrast, under similar conditions, trichloroacetaldehyde N,O-acetals gave simple mono-dechlorinated product without the alkyl transfer reaction from alkyllithiums