A novelbifunctional organocatalyst library combining both aminocatalysis and phosphonicacid activation was used for the first time as an efficient tool for the stereoselectiveMichaeladdition of aldehydes with several aromatic nitroalkenes with good selectivities up to 95:5 dr and 93:7 er. Due to their high water solubility, the catalysts were easilyrecyclable and could be reused over several cycles
Construction of Fused Pyrrolidines and β-Lactones by Carbene-Catalyzed C−N, C−C, and C−O Bond Formations
作者:Xingxing Wu、Lin Hao、Yuexia Zhang、Maiti Rakesh、Rambabu N. Reddi、Song Yang、Bao-An Song、Yonggui Robin Chi
DOI:10.1002/anie.201700045
日期:2017.4.3
A carbene‐catalyzed intermolecular C−N bond formation, which initiates a highly selective cascade reaction for the synthesis of pyrrolidine fused β‐lactones, is disclosed. The nitrogen‐containing bicyclic β‐lactone products are obtained with good yields and excellent stereoselectivities. Synthetic transformations of the reaction products into useful functional molecules, such as amino catalysts, can
active chiral moieties along the network. The hybrid material was studied by means of different characterization techniques (TGA, NMR and IR spectroscopy, chemical and elemental analyses, TEM, and textural measurements), verifying the stability and integrity of the asymmetric active sites in the solid. The hybrid material, HybPyr, is an excellent asymmetric heterogeneous and recyclable catalyst for enantioselective
基于硅质骨架 HybPyr 中包含的吡咯烷单元,合成了一种新型手性介孔杂化材料,并由特定的双甲硅烷基化前体整合到有机-无机结构中。在软合成条件下且在没有复杂的结构导向剂的情况下,氟化物溶胶-凝胶方法可以产生介孔结构,活性手性部分沿网络均匀分布。通过不同的表征技术(TGA、NMR 和 IR 光谱、化学和元素分析、TEM 和结构测量)对杂化材料进行了研究,验证了固体中不对称活性位点的稳定性和完整性。杂化材料 HybPyr 是一种优异的不对称多相且可回收的催化剂,用于线性醛与 β-硝基苯乙烯衍生物的对映选择性迈克尔加成反应,并对反应产物具有高度立体控制。
Enamine Catalysis in Flow with an Immobilized Peptidic Catalyst
作者:Yukihiro Arakawa、Helma Wennemers
DOI:10.1002/cssc.201200740
日期:2013.2
Pep talk: An immobilizedpeptidiccatalyst achieves more than 600 turnovers in a continuous‐flow system, allowing the production of chiral γ‐nitroaldehydes with excellent stereoselectivities on a scale of >450 mmol (>100 g). Such a high efficiency opens the way for more practical applications of enaminecatalysis.
A new series of hybrid dipeptide‐like organocatalysts based on pyranoid ϵ‐ or ζ‐amino acids and proline have been prepared for the asymmetric Michael addition of aldehydes to β‐nitrostyrenes. The reaction proceeds under mild conditions to afford a wide range of γ‐nitroaldehydes with up to 98% yield and up to 96% ee. These dipeptides are bifunctional organocatalysts, with a proline at the N‐terminus