Asymmetric radical reaction in the coordination sphere. 2. Asymmetric addition of alkane- and arenesulfonyl chlorides to olefins catalyzed by a ruthenium(II)-phosphine complex with chiral ligands
Highly stereoselective Friedel–Crafts alkylations of unactivated benzenes by episulfonium ion cyclizations
作者:Bruce P Branchaud、Heather S Blanchette
DOI:10.1016/s0040-4039(01)02173-6
日期:2002.1
Intermolecular additions of highly enantiomerically enriched episulfonium ions onto activated benzene rings are known to accomplish chiral Friedel–Craftsalkylations. Unactivated benzenes are either unreactive or can give low stereoselectivities. Intramolecular cyclizations should be faster than intermolecular additions; thus, cyclization reactions should be able to avoid undesired episulfonium ion
Convenient preparation of ytterbium(III) chalcogenolate complexes by insertion of ytterbium into chalcogen-chalcogen bonds. Application in the ring-opening of epoxides
Convenient conditions are reported for the preparation of ytterbium(III) chalcogenolate complexes by insertion of ytterbium metal into the chalcogen–chalcogen bond of disulfides, diselenides, and ditellurides. The resulting complexes have been found to transfer arylsulfanyl, -selenanyl, and -telluranyl groups to epoxides in a facile ring-opening reaction. The ytterbium(III) chalcogenolate complexes
Stereoselective β-Mannosylation by Neighboring-Group Participation
作者:Hidde Elferink、Rens A. Mensink、Paul B. White、Thomas J. Boltje
DOI:10.1002/anie.201604358
日期:2016.9.5
The stereoselective synthesis of glycosidic bonds is the main challenge of oligosaccharide synthesis. Neighboring‐group participation (NGP) of C2 acyl substituents can be used to provide 1,2‐trans‐glycosides. Recently, the application of NGP has been extended to the preparation of 1,2‐cis‐glycosides with the advent of C2 chiral auxiliaries. However, this methodology has been strictly limited to the
糖苷键的立体选择性合成是寡糖合成的主要挑战。C2酰基取代基的邻近基团参与(NGP)可用于提供1,2-反式-糖苷。最近,随着C2手性助剂的出现,NGP的应用已扩展到1,2-顺式糖苷的制备。但是,这种方法严格限于合成1,2-顺式葡萄糖型糖。本文报道了新型甘露糖基供体的设计和合成,该供体通过NGP硫醚助剂提供1,2-顺式-甘露糖苷。设计中的关键要素是使用1 C 4锁定甘露糖醛酸内酯,以使C2助剂具有NGP。除了C2参与外,还确定了C4苄基的一种新的远程参与模式,并提供了1,2-顺式甘露糖苷。
A Raney nickel — sodium hypophosphite combination system for reductive desulfurization without racemization of optically active secondary alcohol
Sulfides and sulfoxides bearing an optically active secondary alcohol were desulfurized with a Raneynickel (W-2)-sodium hypophosphite combination system to give optically active alcohols in high yields without racemization. However, the combination system was not effective with sulfides which comprise an alkylthio group and the corresponding sulfoxides. This system exhibited the reductive desulfurization
Carbonyl compounds having asymmetric carbon center at β position and phenylthio group on γ carbon were produced by the reaction of optically active 2-hydroxyalkyl phenyl sulfides with enolsilylethers in the presence of Lewis acid through “chiral episulfonium ions”.