Fine Modification of Salen Ligands - Effects on the Salen-Ti-Catalyzed Asymmetric Cyanosilylation of Aldehydes
作者:Chengwei Lv、Qigan Cheng、Daqian Xu、Shoufeng Wang、Chungu Xia、Wei Sun
DOI:10.1002/ejoc.201100319
日期:2011.7
bifunctional N-oxide salen―Ti IV complexes and a pyrrolidine salen―Ti IV complex in combination with achiral N-oxide were developed and applied to the asymmetricaddition of trimethylsilyl cyanide to aldehydes. Notably, both enantiomers of trimethylsilyl ethers of cyanohydrins could be easily prepared by modifying the catalysts employed in this reaction, which are based on the same chiral diamine collar
开发了新的双功能 N-氧化物 salen-Ti IV 配合物和吡咯烷 salen-Ti IV 配合物与非手性 N-氧化物的结合,并将其应用于三甲基氰基氰化物与醛的不对称加成。值得注意的是,氰醇的三甲基甲硅烷基醚的两种对映异构体都可以通过修改该反应中使用的催化剂来轻松制备,这些催化剂基于相同的手性二胺环,源自 L-酒石酸。通过使用相对低的催化剂负载量和仅 1.05 当量的三甲基氰基氰化物 (TMSCN),通常以中等至良好的对映体过量和优异的产率获得产物。
A practical Ti-salen catalyst based on dimeric salen ligand for asymmetric addition of trimethylsilyl cyanide to aldehydes
作者:Chengwei Lv、Daqian Xu、Shoufeng Wang、Cheng-Xia Miao、Chungu Xia、Wei Sun
DOI:10.1016/j.catcom.2011.04.022
日期:2011.7
from L-tartaric acid was synthesized through linking two salen units with 1,6-dibromohexane. The corresponding Ti complex was proved to be an efficient catalyst for asymmetric addition of trimethylsilyl cyanide to aldehydes, providing the corresponding optically active trimethylsilyl ether of cyanohydrins with moderate to good enantiomeric excesses and excellent yields under relatively low catalyst
Dismantling the salen framework: design of new asymmetric silylcyanation catalysts
作者:Jérémy Ternel、Pascal Roussel、Francine Agbossou-Niedercorn、Régis M. Gauvin
DOI:10.1039/c2cy20818k
日期:——
A series of novel chiral phenoxyimine Al(III) complexes catalyzes asymmetric addition of SiMe3CN to a broad range of aldehydes with high yields and good to excellent enantioselectivities in the presence of a Lewis base.
Enantioselective Silylcyanation of Aldehydes and Ketones by a Titanium Catalyst Prepared from a Partially Hydrolyzed Titanium Alkoxide and a Schiff Base Ligand
作者:Kazuhiko Yoshinaga、Takushi Nagata
DOI:10.1002/adsc.200900207
日期:2009.7
base ligand, the enantioselective silylcyanation of aldehydes and ketones proceeded in a short reaction time at room temperature to afford the corresponding optically active cyanohydrinderivatives in excellent chemical yield with high enantiomeric excess (86–97% ee). The results indicate that partially hydrolyzed titanium alkoxides are a promising titanium source for the preparation of efficient catalysts
Enantioselective cyanation of aldehydes catalyzed by bifunctional salen–aluminum complex
作者:Chengwei Lv、Cheng-Xia Miao、Daqian Xu、Shoufeng Wang、Chungu Xia、Wei Sun
DOI:10.1016/j.catcom.2012.06.025
日期:2012.10
Chiral N-oxide salen ligands and their corresponding Al complexes were synthesized. Notably, the catalytic activity and asymmetric induction ability of the bifunctional N-oxide salen-Al for asymmetric cyanosilylation were compared with that of bi-component catalyst system including chiral pyrrolidine salen-Al complex and Ph3PO. Interestingly, introducing N-oxide group in salen unit could enhance the activity and enantioselectivity of bifunctional catalyst without further adding Ph3PO as co-catalyst and inverse configurations were generated from the two systems. In addition, excellent yields and high ee values could be obtained under milder conditions in bifunctional catalyst system compared with that of bi-component catalyst system. (C) 2012 Elsevier B.V. All rights reserved.