Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts
作者:Simon H. Eitel、Sascha Jautze、Wolfgang Frey、René Peters
DOI:10.1039/c3sc50419k
日期:——
The direct asymmetric conjugate addition of α-cyanoacetates to enones generating densely functionalized α-amino acid precursors with adjacent quaternary and tertiary stereocenters is described comparing mono- and bis-palladacycle catalysts. This edge article features the complementary value of mono- and bimetallic catalysis in a case study using related catalyst systems. Different major diastereomers
which the cooperativity of two Pd centers has already been demonstrated. To get more insight into the role of the Pd/Pd distance in such metallocene bismetallacycles, in the present study a corresponding ruthenocene based Pd2-complex has been prepared by the first direct diastereoselective biscyclopalladation of a chiral ruthenocene ligand. In addition, the first highly diastereoselective direct monocyclopalladation
Catalytic enantioselective fluorination of α-cyano acetates catalyzed by chiral palladium complexes
作者:Hye Ran Kim、Dae Young Kim
DOI:10.1016/j.tetlet.2005.02.164
日期:2005.4
The catalytic enantioselective electrophilic fluorination promoted chiral palladium complexes is described. Treatment of α-cyano acetates with N-fluorobenzenesulfonimide as the fluorine source under mild reaction conditions afforded the corresponding α-cyano α-fluoro acetates in high yields with excellent enantiomeric excesses (85–99% ee).
Enantioselective and Z/E-Selective Conjugate Addition of α-Substituted Cyanoacetates to Acetylenic Esters Catalyzed by Bifunctional Ruthenium and Iridium Complexes
作者:Yasuharu Hasegawa、Ilya D. Gridnev、Takao Ikariya
DOI:10.1002/anie.201003585
日期:2010.10.25
Metal‐based catalysts: The title reaction provided the chiral adducts in high yields, excellent enantiomeric excess, and high Z/E selectivity. A combined NMR/DFT study revealed a key intermediate for the stereoselective reaction and a possible reaction mechanism (see the optimized transition‐state structure).
金属基催化剂:标题反应可提供高收率,优异的对映体过量和高Z / E 选择性的手性加合物。NMR / DFT组合研究揭示了立体选择反应的关键中间体和可能的反应机理(请参见优化的过渡态结构)。
Enantio‐ and Diastereoselective Synthesis of Chiral Tetrasubstituted α‐Amino Allenoates Bearing a Vicinal All‐Carbon Quaternary Stereocenter with Dual‐Copper‐Catalysis
The asymmetric γ-additions of 1-alkynyl ketimines under dual-copper-catalysis have been developed, affording chiral tetrasubstituted α-amino allenoates with a vicinal all-carbon quaternary stereocenter in high yields (up to 99 % yield) with excellent stereoselectivities (up to 99 % ee, up to >20 : 1 dr). Mechanistic experiments and DFT calculations demonstrated that the asymmetric γ-addition reactions