New C 2 -symmetric chiral disulfide ligands derived from ( R )-cysteine
作者:Antonio L Braga、Helmoz R Appelt、Paulo H Schneider、Oscar E.D Rodrigues、Claudio C Silveira、Ludger A Wessjohann
DOI:10.1016/s0040-4020(01)00199-5
日期:2001.4
Several sulfur-containing optically active C2-symmetrical ligands have been synthesized from (R)-cysteine and applied successfully as chiral catalysts in the asymmetric addition of diethylzinc to aldehydes. The resulting secondary alcohols could be obtained in good yields and excellent enantiomeric excess.
Design of a Chiral Ionic Liquid System for the Enantioselective Addition of Diethylzinc to Aldehydes
作者:Mariana Ferrari Bach、Cassiana Herzer Griebeler、Caroline Gross Jacoby、Paulo Henrique Schneider
DOI:10.1002/ejoc.201701426
日期:2017.12.15
immobilisation in ionic solvents to provide a chiral supramolecular structure. These new catalytic systems were used in the enantioselective addition of alkylzinc to aldehydes and proved to be very efficient, capable of providing chiral secondary alcohols in excellent enantiomeric excesses and yields. This system also enabled the recycling of the ionic media and the ionic ligand, taking into account green chemistry
A new functionalized, chiral disulfide derived from l-cysteine: (R,R)-bis[(3-benzyloxazolan-4-yl)-methane] disulfide as a catalyst in the diethylzinc addition to aldehydes
作者:Antonio L Braga、Helmoz R Appelt、Paulo H Schneider、Claudio C Silveira、Ludger A Wessjohann
DOI:10.1016/s0957-4166(99)00145-7
日期:1999.5
A new, easily accessible, chiral disulfide 3 was prepared from L-cysteine in a short synthetic sequence (Scheme 1) and applied successfully as a highly efficient catalyst for the enantioselective addition of diethyl zinc to aromatic and aliphatic aldehydes to afford the product alcohols in up to more than 99% ee. In contrast to the more common amino alcohols used in similar reactions, catalyst 3 does not have a protic hydrogen in the form of a free hydroxy group. (C) 1999 Elsevier Science Ltd. All rights reserved.