51896-37-8Relevant 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.
t-BuOK promoted stereoselective isomerization of allyl aryl ethers
Shi, Mingqi,Wang, Liang,Chen, Qun,He, Mingyang,Shen, Minggui,Zhang, Zhi-hui
supporting information, (2020/08/06)
The t-BuOK promoted stereoselective isomerization of allyl aryl ethers has been developed. The reactions proceeded well in methyl tert-butyl ether (MTBE), providing the corresponding products in good to excellent yields (83–96percent). Most of the substra
Ruthenium(IV)-catalyzed isomerization of the C=C bond of O-allylic substrates: A theoretical and experimental study
Varela-Ulvarez, Adrian,Sordo, Jose A.,Piedra, Estefania,Nebra, Noel,Cadierno, Victorio,Gimeno, Jose
experimental part, p. 10583 - 10599 (2011/11/06)
A general mechanism to rationalize RuIV-catalyzed isomerization of the C=C bond in O-allylic substrates is proposed. Calculations supporting the proposed mechanism were performed at the MPWB1K/6-311+G(d,p)+SDD level of theory. All experimental observations in different solvents (water and THF) and under different pH conditions (neutral and basic) can be interpreted in terms of the new mechanism. Theoretical analysis of the transformation from precatalyst to catalyst led to structural identification of the active species in different media. The experimentally observed induction period is related to the magnitudes of the energy barriers computed for that process. The theoretical energy profile for the catalytic cycle requires application of relatively high temperatures, as is experimentally observed. Participation of a water molecule in the reaction coordinate is mechanistically essential when the reaction is carried out in aqueous medium.
Palladium charcoal-catalyzed deprotection of O-allylphenols
Ishizaki, Miyuki,Yamada, Makoto,Watanabe, Shin-Ichi,Hoshino, Osamu,Nishitani, Kiyoshi,Hayashida, Maiko,Tanaka, Atsuko,Hara, Hiroshi
, p. 7973 - 7981 (2007/10/03)
Allyl aryl ethers can be easily cleaved by the use of 10% Pd/C under mild and basic conditions. The present reaction would involve a SET process rather than a π-allyl-palladium complex. The scope and limitation of this new deprotective methodology is also described.
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.
A two step, non-stereospecific cation radical Diels-Alder reaction
Bauld, Nathan L.,Yang, Jingkui
, p. 8519 - 8522 (2007/10/03)
The cation radical Diels-Alder cycloadditions of cis- and trans-1-propenyl aryl ethers to 1,3-cyclopentadiene, catalyzed by tris(4-bromophenyl)aminium hexachloroantimonate in dichloromethane solution, are found to be non-stereospecific, in contrast to the stereospecificity observed in other cation radical Diels-Alder reactions previously studied. These and supporting experiments indicate that, in this particular system, the reaction occurs by a two step mechanism.
Convenient criterion for the distinction between electrophilic and electron transfer reactions of electron-rich alkenes
Bauld, Nathan L.,Aplin, J. Todd,Yueh, Wang,Endo, Stephanie,Loving, Angie
, p. 15 - 24 (2007/10/03)
Both experimental and theoretical studies confirm that the formation of aryl vinyl ether and aryl vinyl sulfide cation radicals from the corresponding neutral substrates correlates with the Brown σ+ parameters as opposed to Hammett σ values. Peak oxidation potentials for both classes of substrates correlate preferentially with σ+, as do gas-phase ionization energies calculated by both semi-empirical and ab initio methods. In contrast, the protonation energies of the same substrates, which relate to carbocation formation, correlate preferentially with σ values, as do rates of protonation and other electrophilic additions. These observations permit a sharp distinction between electrophilic and electron transfer reactions of these two common classes of electron-rich substrates. Using this criterion, the cycloadditions of tetracyanoethylene to these substrates are found to proceed via an electrophilic mechanism, rather than by a previously proposed electron transfer mechanism.