Supported and Unsupported Chiral Squaramides as Organocatalysts for Stereoselective Michael Additions: Synthesis of Enantiopure Chromenes and Spirochromanes
作者:José M. Andrés、Jorge Losada、Alicia Maestro、Patricia Rodríguez-Ferrer、Rafael Pedrosa
DOI:10.1021/acs.joc.7b01177
日期:2017.8.18
Novel supported chiral bifunctional squaramides have been easily prepared starting from diamines derivedfrom natural amino acids and commercially available aminoalkyl polystyrene resins. These squaramides behave as excellent stereoselective recoverable organocatalysts in different Michael additions, in neat conditions at room temperature. The reaction on 2-(2-nitrovinyl) phenol as electrophile lead
Enantioselective organocatalytic Michael reactions using chiral (<i>R</i>,<i>R</i>)-1,2-diphenylethylenediamine-derived thioureas
作者:Jae Ho Shim、Min Ji Lee、Min Ho Lee、Byeong-Seon Kim、Deok-Chan Ha
DOI:10.1039/d0ra03550e
日期:——
Although the Michael addition is a very well-known and widely applied reaction, cost-effective, metal-free, and readily prepared organic catalysts remain rare. A chiral, bifunctional, (R,R)-1,2-diphenylethylenediamine-derived thiourea organic catalyst was developed and applied to asymmetric Michael additions of nitroalkenes under neutral conditions. Generally, fluorine-substituted thiourea catalysts
尽管迈克尔加成反应是一种众所周知且应用广泛的反应,但具有成本效益、不含金属且易于制备的有机催化剂仍然很少见。开发了一种手性、双功能、( R , R )-1,2-二苯基乙二胺衍生的硫脲有机催化剂,并将其应用于中性条件下硝基烯烃的不对称迈克尔加成。通常,氟取代的硫脲催化剂在中性条件下表现出高化学产率和对映选择性。温和的反应对许多官能团具有耐受性,并提供了良好的产率,以及迈克尔加合物的高非对映和对映选择性。通过合成生物活性化合物 ( R )-Phenibut 证明了转化的效用。
Catalytic Asymmetric 1,4-Additions of β-Keto Esters to Nitroalkenes Promoted by a Bifunctional Homobimetallic Co2-Schiff Base Complex
Catalyticasymmetric1,4-addition of β-ketoesters to nitroalkenes is described. 2.5 mol % of a homobimetallic Lewis acid/Brønsted base bifunctional Co2-Schiff basecomplex smoothly promoted the reaction in excellent yield (up to 99%), diastereoselectivity, and enantioselectivity (up to >30:1 dr and 98% ee). Catalyst loading was successfully reduced to 0.1 mol %. Mechanistic studies suggested that
描述了 β-酮酯与硝基烯烃的催化不对称 1,4-加成反应。2.5 mol% 的均双金属路易斯酸/Brønsted 碱双功能 Co2-Schiff 碱配合物以优异的产率(高达 99%)、非对映选择性和对映选择性(高达 >30:1 dr 和 98% ee)顺利促进反应。催化剂负载成功地降低到 0.1 mol%。机理研究表明,两个 Co 金属中心的分子内协同功能对于高催化活性和立体选择性很重要。