179938-94-4Relevant articles and documents
Specific Z-Selectivity in the Oxidative Isomerization of Allyl Ethers to Generate Geometrically Defined Z-Enol Ethers Using a Cobalt(II)(salen) Complex Catalyst
Huang, Guanxin,Ke, Miaolin,Tao, Yuan,Chen, Fener
, p. 5321 - 5329 (2020/05/19)
Enol ether structural motifs exist in many highly oxygenated biologically active natural products and pharmaceuticals. The 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. This methodology also demonstrates the effectiveness in controlling the Z-selective isomerization reaction of diallyl ethers at room temperature. This catalytic system provides an alternative pathway to extend the traditional reductive isomerization of allyl ethers.
Lewis acid promoted double bond migration in O-allyl to Z-products by Ru-H complexes
Wang, Haibin,Liu, Shaodong,Sun, Tingting,Lv, Zhanao,Zhan, Zhen,Yin, Guochuan,Chen, Zhuqi
, p. 10 - 17 (2019/03/11)
In catalytic double bond migration reaction, E-configuration olefins were normally generated as the dominant product because E-configuration was thermodynamically favored. However, Z-configuration products are sometimes desired in pharmaceutical chemistry owing to the structure-activity relationship. In this paper, we have demonstrated a new strategy that Lewis acid promoted an widely employed and convenient ruthenium(II) complex for the catalytic isomerization 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 Acid catalysts was suitable for various substituted O-allylethers and other types of substrates. Through mechanism study including kinetic study, ligand inhibition effect and molecular spectroscopy, the dissociation of PPh3 ligand by the addition of Lewis acid, and the formation a five-membered Ru complex from anchimeric assistance were both recognized as essential steps to improve the reactivity and to control the stereoselectivity of catalytic double bond migration reaction through metal hydride addition-elimination mechanism. This new strategy may provide a new opportunity to produce thermodynamic-unfavored product in heterocyclic compounds for pharmaceutical chemistry.
Thermodynamic, spectroscopic, and density functional theory studies of allyl aryl and prop-1-enyl aryl ethers. Part 1. Thermodynamic data of isomerization
Taskinen, Esko
, p. 1824 - 1834 (2007/10/03)
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.
