A practical and versatile access to dihydrosalen (Salalen) ligands:: Highly enantioselective titanium in situ catalysts for asymmetric epoxidation with aqueous hydrogen peroxide

被引：50

作者：

Berkessel, Albrecht ^{[1
]}

Brandenburg, Marc ^{[1
]}

Leitterstorf, Eva ^{[1
]}

Frey, Julia ^{[1
]}

Lex, Johann ^{[1
]}

Schaefer, Mathias ^{[1
]}

机构：

[1] Univ Cologne, Inst Organ Chem, D-50939 Cologne, Germany

来源：

ADVANCED SYNTHESIS & CATALYSIS | 2007年 / 349卷 / 14-15期

关键词：

asymmetric catalysis; epoxidation; in situ catalysts; salalen ligands; titanium;

D O I：

10.1002/adsc.200700221

中图分类号：

O69 [应用化学];

学科分类号：

081704 ;

摘要：

A modular synthesis for chiral and non-symmetrical salalen ligands (i.e., mono-reduced salens), carrying an imine and an amine functionality has been developed. The ligands can be assembled in situ by Schiff base formation of an N-(2-hydroxybenzyl)diamine with a salicylic aldehyde, thus allowing rapid and easy variation/optimization of the ligand structure. Aiming at optimal activity and enantioselectivity in the titanium-catalyzed asymmetric epoxidation of non-functionalized olefins, a positional scanning of the two ligand halves was carried out. High epoxide yields were achieved, and up to 98 % ee. The composition of the titanium complex catalysts was determined by high resolution mass spectrometry and X-ray crystallography for one selected example.

引用

页码：2385 / 2391

页数：7

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