Self-Supported Chiral Titanium Cluster (SCTC) as a Robust Catalyst for the Asymmetric Cyanation of Imines under Batch and Continuous Flow at Room Temperature
作者:Abdul M. Seayad、Balamurugan Ramalingam、Christina L. L. Chai、Chuanzhao Li、Marc V. Garland、Kazuhiko Yoshinaga
DOI:10.1002/chem.201200528
日期:2012.4.27
A robust heterogeneous self‐supported chiral titanium cluster (SCTC) catalyst and its application in the enantioselective imine‐cyanation/Streckerreaction is described under batch and continuous processes. One of the major hurdles in the asymmetric Streckerreaction is the lack of availability of efficient and reusable heterogeneous catalysts that work at room temperature. We exploited the readily
通过分批和连续过程介绍了一种稳健的异质自支撑手性钛簇(SCTC)催化剂及其在对映选择性亚胺氰化/ Strecker反应中的应用。不对称Strecker反应的主要障碍之一是缺乏在室温下工作的有效且可重复使用的非均相催化剂的可用性。我们利用预成型的手性钛醇盐配合物的可控水解,利用烷氧基钛的易水解性质来合成自支撑手性钛簇(SCTC)催化剂。分离出的SCTC催化剂非常稳定,对映选择性高达98%(ee),在室温下2小时内可将各种亚胺完全转化为亚胺。该非均相催化剂可循环使用10次以上,而活性或选择性没有任何损失。催化剂的坚固性,高性能和可回收性使其能够在填充床反应器中使用,以在连续流动下进行氰化。对于二苯甲基亚胺,在优化的流动条件下,在室温下,可以实现高达97%ee的定量转化和45 mg h -1的通量。此外,使用相应的醛和胺代替预先形成的亚胺,在连续流动下进行了三组分Strecker反应。获得了良好
Highly Enantioselective Titanium-Catalyzed Cyanation of Imines at Room Temperature
作者:Abdul Majeed Seayad、Balamurugan Ramalingam、Kazuhiko Yoshinaga、Takushi Nagata、Christina L. L. Chai
DOI:10.1021/ol902540h
日期:2010.1.15
A highly active and enantioselective titanium-catalyzed cyanation of imines at roomtemperature is described. The catalyst used is a partially hydrolyzed titanium alkoxide (PHTA) precatalyst together with a readily available N-salicyl-β-aminoalcohol ligand. Up to 98% ee was obtained with quantitative yields in 15 min of reaction time using 5 mol % of the catalyst. Various N-protecting groups such as