Modularly Evolved 2-AminoDMAP/Squaramides as Highly Active Bifunctional Organocatalysts in Michael Addition
作者:Murat Işık、M. Yagiz Unver、Cihangir Tanyeli
DOI:10.1021/jo5022597
日期:2015.1.16
We report a new family of chiral bifunctional acid/base type organocatalysts, 2-aminoDMAP/Squaramides, which are proved to be highly active (1 mol % cat. loading) promoters in conjugate addition of dibenzoylmethane to various trans-β-nitroalkenes. Steric demand of the catalysts was clearly seen by a set-by-set modulation of the squaramide unit through electronic and steric factors. The synergistic
Microwave-Assisted Synthesis of Guanidine Organocatalysts Bearing a Tetrahydroisoquinoline Framework and Their Evaluation in Michael Addition Reactions
作者:Tricia Naicker、Per I. Arvidsson、Hendrik G. Kruger、Glenn E. M. Maguire、Thavendran Govender
DOI:10.1002/ejoc.201200303
日期:2012.6
simple and practical syntheses of chiral guanidineorganocatalysts and their evaluation in the asymmetric Michaeladditionreaction of malonates and beta-keto esters with nitro-olefins is reported. These organocatalysts are the first of their kind based on a tetrahydroisoquinolineframework. In addition, a microwave-assisted procedure for introducing the guanidine unit onto amino amide derivatives is reported
thiourea-modified l-Leu-based peptide (3,5-diCF3Ph)NHC(=S)-(l-Leu-l-Leu-Ac5c)2-OMe} with five-membered ring α,α-disubstituted α-amino acids (Ac5c) catalyzed a highly enantioselective 1,4-addition reaction between β-nitrostyrene and dimethyl malonate. The enantioselective reaction required only 0.5 mol % chiral peptide-catalyst in the presence of iPr2EtN (2.5 equiv.), and gave a 1,4-adduct with 93 % ee of
N-末端硫脲修饰的基于l -Leu 的肽 (3,5-diCF 3 Ph)NHC(=S)-( l -Leu- l -Leu-Ac 5 c) 2 -OMe} 具有五元环α,α-二取代的α-氨基酸(Ac 5 c)催化了β-硝基苯乙烯和丙二酸二甲酯之间的高度对映选择性1,4-加成反应。在i Pr 2 EtN(2.5 当量)存在下,对映选择性反应仅需要 0.5 mol% 的手性肽催化剂,并得到 1,4-加合物,93% ee,产率为 85%。作为迈克尔受体,各种β-硝基苯乙烯衍生物,如甲基、对氟、对溴和对可以应用苯基上的-甲氧基取代基、2-呋喃基、2-噻吩基和萘基β-硝基乙烯。此外,各种丙二酸烷基酯和环状β-酮酯可用作迈克尔供体。很明显,肽链的长度、右手螺旋结构、酰胺 N-Hs 和 N 端硫脲部分在不对称诱导中起着至关重要的作用。
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。
Redox-configurable ambidextrous catalysis: structural and mechanistic insight
作者:Shahab Mortezaei、Noelle R. Catarineu、Xueyou Duan、Chunhua Hu、James W. Canary
DOI:10.1039/c5sc02144h
日期:——
A helically chiral copper complex is used as a switchable asymmetric catalyst capable of delivering either enantiomer of a Michael addition reaction.