A novel Mannich-type reaction: Lanthanide triflate-catalyzed reactions of N-(α-aminoalkyl)benzotriazoles with silyl enolates
作者:Shū Kobayashi、Haruro Ishitani、Susumu Komiyama、Daniela C. Oniciu、Alan R. Katritzky
DOI:10.1016/0040-4039(96)00671-5
日期:1996.5
In the presence of a catalytic amount of a lanthanide triflate, N-(α-aminnoalkyl)benzotriazoles reacted with silylenolates to give the corresponding β-amino ketone or ester derivatives in high yields with high diastereoselectivities.
The first observation of the stereospecificity in the benzyne-olefin [2 + 2] cycloaddition is described. The key points reside in (1) the efficient method for generating benzyne species by the halogen-lithium exchange reaction of ortho-halo aryl triflates, and (2) the choice of ketene silyl acetal as the partner olefin.
De Novo Synthesis of Uronic Acid Building Blocks for Assembly of Heparin Oligosaccharides
作者:Alexander Adibekian、Pascal Bindschädler、Mattie S. M. Timmer、Christian Noti、Nina Schützenmeister、Peter H. Seeberger
DOI:10.1002/chem.200700141
日期:2007.5.25
An efficient de novo synthesis of uronic acid buildingblocks is described. The synthetic strategy relies on the stereoselective elongation of thioacetal protected dialdehydes 12 a and 17. The dialdehydes are prepared from D-xylose, a cheap and commercially available source. A highly stereoselective MgBr(2)OEt(2)-mediated Mukaiyama aldol addition to C4-aldehyde 12 a is performed to obtain D-glucuronic
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.