Amino acid-derived hydroxamic acids as chiral ligands in the vanadium catalysed epoxidation
作者:Andrei V. Malkov、Zaïnaba Bourhani、Pavel Kočovský
DOI:10.1039/b505324b
日期:——
New sulfonamide-derived hydroxamicacids have been developed as chiralligands for the V-catalysed asymmetricepoxidation, showing high reactivity at subzero temperatures and moderate to good enantioselectivity. The strong accelerating effect exhibited by the ligands of this type can be attributed to the sulfonamide functionality. A range of cinnamyl type allylicalcohols were epoxidised with up to
Enantioselective iminium-catalyzed epoxidation of hindered trisubstituted allylic alcohols
作者:Roman Novikov、Jérôme Lacour
DOI:10.1016/j.tetasy.2010.06.002
日期:2010.6
The reactivity of diastereomeric biaryl iminium cations made of a (Ra)-5,5',6,6',7,7',8,8'-octahydrobinaphthyl core and exocyclic appendages derived from (S)- or (R)-3,3-dimethylbutyl-2-amine was investigated with hindered trisubstituted allylic alcohols a class of alkenes which had not been previously studied in detail in epoxidation reactions with cyclic iminium catalysts (ee up to 98%). Surprisingly, generally strong matched/mismatched effects are observed not only in terms of reactivity but also on the enantioselectivity of the reaction (Ace up to 16%). Also, for the most hindered substrates, two sets of reaction conditions were tested in a preliminary study and little advantage was found in running reactions in MeCN/water instead of CH(2)Cl(2)/water/18-C-6. In any case, the presence of the hydroxyl group did not reveal any anchimeric effect. (C) 2010 Elsevier Ltd. All rights reserved.
A CATALYTICAL ASYMMETRIC EPOXIDATION
申请人:UNIVERSITY OF CHICAGO
公开号:EP1706205B1
公开(公告)日:2008-10-29
Catalytic asymmetric epoxidation
申请人:Yamamoto Hisashi
公开号:US20070203347A1
公开(公告)日:2007-08-30
The present invention relates to the synthesis of chiral epoxides via a catalytic asymmetric oxidation of olefins. Additionally, the methodology provides a method of asymmetrically oxidizing sulfides and phosphines. This asymmetric oxidation employs a catalyst system composed of a metal and a chiral bishydroxamic acid ligand, which, in the presence of a stoichiometric oxidation reagent, serves to asymmetrically oxidize a variety of substrates.