Chiral Squaramide Derivatives are Excellent Hydrogen Bond Donor Catalysts
作者:Jeremiah P. Malerich、Koji Hagihara、Viresh H. Rawal
DOI:10.1021/ja805693p
日期:2008.11.5
dominant platform for hydrogen bond promoted asymmetric catalysts. A large number of reactions, reported in scores of publications, have been successfully promoted by chiral thioureas. The present paper reports the use of squaramides as a highly effective new scaffold for the development of chiral hydrogen bond donor catalysts. Squaramide catalysts are very simple to prepare. The (-)-cinchonine modified
Scope and Mechanism of Enantioselective Michael Additions of 1,3-Dicarbonyl Compounds to Nitroalkenes Catalyzed by Nickel(II)−Diamine Complexes
作者:David A. Evans、Shizue Mito、Daniel Seidel
DOI:10.1021/ja0735913
日期:2007.9.1
Readily prepared Ni(II)-bis[(R,R)-N,N'-dibenzylcyclohexane-1,2-diamine]Br(2) was shown to catalyze the Michaeladdition of 1,3-dicarbonyl compounds to nitroalkenes at room temperature in good yields with high enantioselectivities. The two diamineligands in this system each play a distinct role: one serves as a chiralligand to provide stereoinduction in the addition step while the other functions
容易制备的 Ni(II)-双[(R,R)-N,N'-二苄基环己烷-1,2-二胺]Br(2) 在室温下可催化 1,3-二羰基化合物与硝基烯烃的迈克尔加成反应温度高,产率高,对映选择性高。该系统中的两个二胺配体各自发挥不同的作用:一个作为手性配体在加成步骤中提供立体诱导,而另一个作为底物烯醇化的基础。还研究了催化剂内的配体改性,以促进脂肪族硝基烯烃、1,3-二酮和 β-酮酸的反应。Ni(II)-双[(R,R)-N,N'-di-p-bromo-benzylcyclohex-1,2-diamine]Br(2) 在这些情况下被发现是一种有效的催化剂。此外,单二胺络合物,Ni(II)-[(R,R)-N,N'-二苄基环己烷-1,2-二胺]Br(2),在水存在下催化加成反应。所提出的立体化学诱导模型显示与 X 射线结构分析一致。
Ni(II)−Bis[(<i>R</i>,<i>R</i>)-<i>N</i>,<i>N</i>‘-dibenzylcyclohexane-1,2-diamine]Br<sub>2</sub> Catalyzed Enantioselective Michael Additions of 1,3-Dicarbonyl Compounds to Conjugated Nitroalkenes
作者:David A. Evans、Daniel Seidel
DOI:10.1021/ja052935r
日期:2005.7.1
A highlyenantioselectiveMichaeladdition of 1,3-dicarbonyl compounds to nitroalkenes has been developed that employs a newly developed Ni(II)-(bis)diamine based catalyst. The reaction scope includes substituted and unsubstituted malonates, beta-ketoesters, and nitroalkenes bearing aromatic and aliphatic residues. Ease of synthesis of this complex is noteworthy.
Toward Efficient Asymmetric Carbon-Carbon Bond Formation: Continuous Flow with Chiral Heterogeneous Catalysts
作者:Tetsu Tsubogo、Yasuhiro Yamashita、Shū Kobayashi
DOI:10.1002/chem.201202896
日期:2012.10.22
A chiral Ca catalyst based on CaCl2 with a chiral ligand was developed and applied to the asymmetric 1,4‐addition of 1,3‐dicarbonyl compounds to nitroalkenes as a model system. To address product inhibition issues, the Ca catalyst was applied to continuous flow with a chiral heterogeneous catalyst. The continuous flow system using a newly synthesized, polymer‐supported Pybox was successfully employed
A strategy for designing chiralBrønsted base organocatalysts through noncovalent modification of a chiral dibasic molecule with an achiral phosphoric acid diester is introduced for the first time. Such a molecular modification concept utilizing acid-base interactions may facilitate the on-demand design of asymmetric organocatalysts, as preliminarily demonstrated in this work.