Thermodynamic, spectroscopic, and density functional theory studies of allyl aryl and prop-1-enyl aryl ethers. Part 1. Thermodynamic data of isomerization
作者:Esko Taskinen
DOI:10.1039/b101837j
日期:——
A chemical equilibration study of the relative thermodynamic stabilities of seventy isomeric allyl aryl ethers (a) and (Z)-prop-1-enyl aryl ethers (b) in DMSO solution has been carried out. From the variation of the equilibrium constant with temperature the Gibbs energies, enthalpies, and entropies of isomerization at 298.15 K have been evaluated. Because of their low enthalpies, the (Z)-prop-1-enyl aryl ethers are strongly favored at equilibrium, the Gibbs energies of the a→b isomerization ranging from −12 to −23 kJ mol−1. The entropy contribution is negligible in most reactions, but occasionally small positive values less than +10 J K−1 mol−1 of the entropy of isomerization are found. The equilibration studies were also extended to involve two pairs of related isomeric ethers with a Me substituent on C(2) of the olefinic bond. The Me substituent was
found to increase the relative thermodynamic stability of the allylic ethers by ca. 3.4 kJ mol−1.
Ruthenium(IV)‐Catalyzed Isomerization of the CC Bond of<i>O</i>‐Allylic Substrates: A Theoretical and Experimental Study
作者:Adrián Varela‐Álvarez、José A. Sordo、Estefanía Piedra、Noel Nebra、Victorio Cadierno、José Gimeno
DOI:10.1002/chem.201101131
日期:2011.9.12
carried out in aqueous medium. The new mechanistic proposal helped to develop a new experimental procedure for isomerization of allylethers to 1‐propenylethers under neutral aqueous conditions. This process is an unique example of efficient and selective catalytic isomerization of allylethers in aqueous medium.
and convenient ruthenium(II) complex for the catalyticisomerization of O-allylethers, leading to thermodynamic-unfavored Z-product under mild conditions. The model substrate of allyl phenyl ether can be simply scaled up to 20 mmol to produce Z-product with TON of 2453 and TOF of 13,430 h−1 at 40–60 °C. The system of Ru(II)/Lewis Acidcatalysts was suitable for various substituted O-allylethers and other
在催化双键迁移反应中,通常以E-构型烯烃为主要产物,因为E-构型在热力学上是有利的。然而,由于结构-活性关系,有时在药物化学中需要Z-构型产物。在本文中,我们证明了一种新的策略,即路易斯酸促进了广泛使用且方便的钌(II)络合物用于O-烯丙基醚的催化异构化,导致在温和条件下产生热力学不利的Z产物。烯丙基苯基醚的模型底物可以简单地按比例放大至20 mmol以生产TON为2453,TOF为13,430 h -1的Z产物在40–60°C下。Ru(II)/路易斯酸催化剂体系适用于各种取代的O-烯丙基醚和其他类型的底物。通过包括动力学研究,配体抑制作用和分子光谱在内的机理研究,通过添加路易斯酸使PPh 3配体解离,以及由嵌合助剂形成五元Ru络合物均被认为是提高反应性和稳定性的必要步骤。通过金属氢化物加成消除机理控制催化双键迁移反应的立体选择性。这一新策略可能为生产用于药物化学的杂环化合物中热力学不利的产品提供新的机会。
Photochemical Radical Cation Cycloadditions of Aryl Vinyl Ethers
TiO2 photochemical [2+2] and [4+2] cycloadditions using arylvinylethers as radical cation precursors. The construction of various four- and six-membered rings is made possible by these radical cation cycloadditions. The diene is found to be more radicalophilic than the alkene and effectively traps the radical cation of the arylvinylethers.
在此,我们报道了使用芳基乙烯基醚作为自由基阳离子前体的 TiO 2光化学 [2+2] 和 [4+2] 环加成反应。通过这些自由基阳离子环加成,可以构建各种四元环和六元环。发现二烯比烯烃更亲自由基并且有效地捕获芳基乙烯基醚的自由基阳离子。
Specific <i>Z</i>-Selectivity in the Oxidative Isomerization of Allyl Ethers to Generate Geometrically Defined <i>Z</i>-Enol Ethers Using a Cobalt(II)(salen) Complex Catalyst
作者:Guanxin Huang、Miaolin Ke、Yuan Tao、Fener Chen
DOI:10.1021/acs.joc.0c00004
日期:2020.4.17
synthesis of the geometrically less stable Z-enol ethers is challenging. An efficient Z-selective oxidative isomerization process of allyl ethers catalyzed by a cobalt(II) (salen) complex using N-fluoro-2,4,6-trimethylpyridinium trifluoromethanesulfonate (Me3NFPY•OTf) as an oxidant has been developed. Thermodynamically less stable Z-enol ethers were prepared in excellent yields with high geometric control.