Just mix to get six: Sixcontiguousstereocenters, including one quaternary stereocenter, and three CC bonds are created by a new copper‐catalyzed tandem reaction (see scheme). Rigid chiral diamine ligands enabled this asymmetric tandem reaction to proceed with excellent stereoselectivity (complete diastereoselectivity and high enantioselectivity) and high yield under mild reaction conditions.
Diastereo- and enantioselective conjugate addition of α-keto esters to nitroalkenes: Complete switch in the enantioselectivity by tuning the metal center or rigidity of the ligand
作者:Xiangning Chen、Han Zhou、Hanmin Huang
DOI:10.1016/s1872-2067(14)60199-6
日期:2015.1
been developed to control the dual enantioselectivity of the conjugate addition of α-keto esters to nitroalkenes. The use of the chiral diamine (1 S ,1’ S )-1,1′-biisoindoline as a chiral ligand with either (Cu(OAc) 2 ·H 2 O or Ni(OAc) 2 ·4H 2 O as the catalyst provide facile access to the respective enantiomers resulting from the conjugate addition reaction with high levels of enantioselectivity (94%
摘要 已经开发了一系列有效的催化系统来控制 α-酮酯与硝基烯烃共轭加成的双重对映选择性。使用手性二胺 (1 S ,1' S )-1,1'-双异二氢吲哚作为手性配体,以 (Cu(OAc) 2 ·H 2 O 或 Ni(OAc) 2 ·4H 2 O 为催化剂)以高水平的对映选择性(94% ee vs 93% ee)轻松获得由共轭加成反应产生的各个对映异构体。此外,使用 Cu(OAc) 2 ·H 2 O 作为金属中心允许对映选择性通过调节手性二胺配体的刚性(94% ee vs 94% ee)来切换共轭加成反应。
Diastereo- and Enantioselective Conjugate Addition of α-Ketoesters to Nitroalkenes Catalyzed by a Chiral Ni(OAc)<sub>2</sub> Complex under Mild Conditions
A highly efficient, catalytic, diastereo- and enantioselectiveconjugateaddition of alpha-ketoesters to nitroalkenes has been devised. The reaction was applicable to various substrates. Notably, the combination of endogenous and exogenous bases was effective, allowing a small amount of the catalyst (0.1-1 mol % Ni) to promote the reaction efficiently. The synthetic utility of this reaction was demonstrated
As a part of our research project on hard anion-late transition metal complexes as mild acid-base catalysts, we describe herein that Cu-II hydroxo complexes having chiral N-substituted-diaminocyclohexanes are mild and selective catalysts, which are applicable to the catalytic asymmetric conjugate addition of alpha-keto esters to nitroolefins. The reaction proceeded diastereoselectively without the detectable formation of self-aldol products, affording the corresponding coupling products with anti-stereochemistry in an enantioselective manner. (C) 2010 Elsevier Ltd. All rights reserved.
Experimental and Computational Investigation of Facial Selectivity Switching in Nickel–Diamine–Acetate-Catalyzed Michael Reactions
Chiral Ni complexes have revolutionized both asymmetric acid–base and redox catalysis. However, the coordination isomerism of Ni complexes and their open-shell property still often hinder the elucidation of the origin of their observed stereoselectivity. Here, we report our experimental and computational investigations to clarify the mechanism of β-nitrostyrene facial selectivity switching in Ni(I