Efficient Intramolecular Hydroalkoxylation of Unactivated Alkenols Mediated by Recyclable Lanthanide Triflate Ionic Liquids: Scope and Mechanism
作者:Alma Dzudza、Tobin J. Marks
DOI:10.1002/chem.200902269
日期:2010.3.15
catalytic pathway that involves kinetically significant intramolecular proton transfer. The present activation parameters—enthalpy (ΔH≠)=18.2 (9) kcal mol−1, entropy (ΔS≠)=−17.0 (1.4) eu, and energy (Ea)=18.2 (8) kcal mol−1—suggest a highly organized transition state. Proton scavenging and coordinative probing results suggest that the lanthanide triflates are not simply precursors of free triflic acid. Based
[Ln(OTf)3 ]类型的镧系三氟甲磺酸盐配合物(Ln = La,Sm,Nd,Yb,Lu)可作为有效的可循环催化剂,用于伯/仲和脂族/芳族化合物的快速分子内加氢烷氧基化(HO)/环化咪唑基室温离子液体(RTIL)中的羟基烯烃,生成相应的呋喃,吡喃,螺双环呋喃,螺双环呋喃/吡喃,苯并呋喃和异色满衍生物。产物直接从催化溶液中分离出来,转化表现出马尔可夫尼科夫区域选择性,周转频率高达47 h -1在120°C下。初级烯醇环化的环大小速率依赖性为5> 6,与空间控制的过渡态一致。末端烯醇的加氢烷氧基化/环化速率比内部烯醇的加氢烷氧基化/环化速率稍快,这表明在环状过渡态中适度的空间需求。芳基官能化羟基烯烃的环化速率比线性烯醇的环化速率更快,而五元和五元/六元螺双环骨架也被区域选择性封闭。在主要的空间受限的烯醇的环化过程中,从La 3+(1.160Å)到Lu 3+,对金属离子半径的周转频率依赖性降低了约80倍(0
Efficient Intramolecular Hydroalkoxylation/Cyclization of Unactivated Alkenols Mediated by Lanthanide Triflate Ionic Liquids
作者:Alma Dzudza、Tobin J. Marks
DOI:10.1021/ol8029559
日期:2009.4.2
Lanthanide triflates, Ln(OTf)3, serve as efficient catalysts for the intramolecular hydroalkoxylation (HO)/cyclization of primary/secondary and aliphatic/aromatic hydroxyalkenes in room temperature ionic liquids (RTILs). Cyclizations are effective in the formation of five- and six-membered oxygen heterocycles with Markovnikov-type selectivity. Reaction rates exhibit first-order dependence on [Ln3+]
The SO3H-tethered imidazolium and triazolium salts, nonvolatile and recyclable Brønstedacidicionicliquids, efficiently mediate intramolecular hydroalkoxylations of alkenyl alcohols. They have been successfully employed in the synthesis of (±)-centrolobine.
SO 3 H系咪唑鎓盐和三唑鎓盐,不挥发且可回收的布朗斯台德酸性离子液体,可有效介导链烯醇的分子内加氢烷氧基化反应。它们已成功地用于合成(±)-中心洛宾。
Niobium-Catalyzed Intramolecular Addition of O–H and N–H Bonds to Alkenes: A Tool for Hydrofunctionalization
A convenient, versatile, and easy to handle intramolecular hydrofunctionalization of alkenes (C–O and C–N bonds formation) is reported using a novel niobium-based catalytic system. This atom economic and eco-friendly methodology provides an additional synthetic tool for the straightforward formation of valuable building blocks enabling molecular complexity. Various pyran, furan, pyrrolidine, piperidine
Intramolecular Additions of Alcohols and Carboxylic Acids to Inert Olefins Catalyzed by Silver(I) Triflate
作者:Cai-Guang Yang、Nicholas W. Reich、Zhangjie Shi、Chuan He
DOI:10.1021/ol051065f
日期:2005.10.1
[reactions: see text] Intramolecular additions of hydroxyl or carboxyl groups to inert olefins catalyzed by simple silver(I) triflate are described. Good to excellent yields can be obtained for a range of substrates under relatively mild conditions. This reaction represents one of the simplest methods to construct cyclic ethers or lactones.