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