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
A very simple one-step, environmentally friendly procedure for the synthesis of α-aminonitriles from aldehydes and ketones, using trimethylsilyl cyanide in the absence of solvent, is reported. The active catalyst of this three-component (Strecker) reaction was the amine employed in the transformation. In general, aldehydes react more rapidly than ketones and give almost quantitative yields of the corresponding α-aminonitriles in less than fifteen minutes. However, only cyclic ketones afford the corresponding α-aminonitriles in excellent chemical yields under these conditions.
TITANIUM COMPOUNDS AND PROCESS FOR CYANATION OF IMINES
申请人:Seayad Abdul Majeed
公开号:US20110319629A1
公开(公告)日:2011-12-29
The present invention relates to titanium catalysts for synthesis reactions produced by bringing a reaction mixture comprising a titanium alkoxide and a ligand in contact with water, wherein the ligand is represented by the general formula (e): wherein R
1
, R
2
, R
3
, and R
4
are independently a hydrogen atom, an alkyl group, or the like, and (A) represents a group with two or more carbon atoms. The titanium catalysts may be isolated in solid form and may be stored. The invention further relates to a process for cyanation of imines, wherein the process comprises reacting an imine with a cyanating agent in the presence of the titanium catalyst.
Aldehydes vs Aldimines. Unprecedented Aldimine-Selective Nucleophilic Additions in the Coexistence of Aldehydes Using a Lanthanide Salt as a Lewis Acid Catalyst
作者:Shū Kobayashi、Satoshi Nagayama
DOI:10.1021/ja971153y
日期:1997.10.1
It is well-recognized that aldimines are less reactive than aldehydes toward nucleophilic additions. In this paper, an unprecedented change in the reactivity is described: preferential reactions of aldimines over aldehydes in nucleophilic additions using a lanthanide salt as a Lewis acidcatalyst. In the presence of a catalytic amount of ytterbium triflate (Yb(OTf)3), only aldimines reacted with silyl
Described herein are compounds of formula (I), related compositions, and their use, for example in the formation of α-amino acids or a precursor thereof such as an α-aminonitrile.
stereodivergent synthesis of styrylglycine nitriles has also been accomplished by using racemic and enantioenriched 2‐methylbenzhydrylamine. Thus, accompanied with a small rearrangement of the common substrate from achiral toward chiral, the present reactions induce an enhancement of chirality, and expands the concept of stereoselective synthesis to increase the opportunity to access highly enantioenriched compounds