Preparation of 2,5-Anhydrohexitols (Part I). Silicon-Directed Stereocontrolled Cyclization
摘要:
Stereoselective chain-extension of carbohydrate aldehydes with the hydroxymethylating reagent (dimethylphenylsilyl)methylmagnesium chloride (1) followed by acid-mediated cyclization gives access to 2,5-anhydro-hexitols. The stereoselectivity of the ring closure depends on the nature of the acid, i.e., treatment with excess BF3. Et2O or catalytic H2SO4 leads to tetrahydrofurans with 2,3-cis or 2,3-trans configuration, respectively. Concomitant elimination is effectively suppressed in case of cyclisation of the more sterically hindered isopropyl substituted silanes.
Chiral diphosphorus compounds and their transition metal complexes
申请人:Meseguer Benjamin
公开号:US20050080047A1
公开(公告)日:2005-04-14
The present invention relates to chiral diphosphorus compounds and their transition metal complexes, to a process for preparing chiral diphosphorus compounds and their transition metal complexes and also to their use in asymmetric syntheses.
Chirale Diphosphorverbindungen und deren Übergangsmetallkomplex
申请人:Bayer Chemicals AG
公开号:EP1400527A1
公开(公告)日:2004-03-24
Die vorliegende Erfindung betrifft chirale Diphosphorverbindungen und deren Übergangsmetallkomplexe, ein Verfahren zur Herstellung chiraler Diphosphorverbindungen und deren Übergangsmetallkomplexe sowie deren Verwendung in asymmetrischen Synthesen.
Chiral monophosphorus compounds and their transition metal complexes
申请人:——
公开号:US20040127430A1
公开(公告)日:2004-07-01
The present invention relates to chiral monophosphorus compounds and their transition metal complexes, to a process for preparing chiral monophosphorus compounds and their transition metal complexes and also to their use in asymmetric syntheses.
A tandem, proline-catalyzed alpha-chlorination/aldol reaction is described that involves a dynamic kinetic resolution of alpha-chloroaldehyde intermediates. The resulting syn-chlorohydrins are produced with good to excellent diastereoselectivity in high enantiopurity and provide new opportunities for the synthesis of carbohydrates.
Chirale Diphosphorverbindungen und deren Übergangsmetallkomplexe