Methyltrioxorhenium solubility

The oxidation of alkenes and allylic alcohols with the urea-EL202 adduct (UELP) as oxidant and methyltrioxorhenium (MTO) dissolved in [EMIM][BF4] as catalyst was described by Abu-Omar et al. [61]. Both MTO and UHP dissolved completely in the ionic liquid. Conversions were found to depend on the reactivity of the olefin and the solubility of the olefinic substrate in the reactive layer. In general, the reaction rates of the epoxidation reaction were found to be comparable to those obtained in classical solvents. 

The low solubility of oxygen in most ionic liquids limits its application in oxidation catalysis in these liquids. However, oxidation by H2O2 or organoperoxide is not subject to this limitation when the ionic liquids are properly chosen. An example of catalytic oxidation is the methyltrioxorhenium (MTO)-catalyzed epox-idation of alkenes with the urea-H202 adduct in [EMIMJBF4 (228). High conversions and yields were obtained. 

A -sulfinylacetamide 297 in greater than 90% yield when a catalytic amount of methyltrioxorhenium is employed. Futhermore, the hetero-Diels-Alder adduct is highly soluble in both chlorinated and ethereal solvents. A detailed investigation of the retro-Diels-Alder reaction of 298 by thermogravimetric analysis revealed an onset temperature of 120 °C and complete conversion of bicycle 298 to pentacene 296 at 160 °C, which are temperatures compatible with the polymer supports typically used in electronics applications. The electronic properties of these newly prepared OTFTs are similar to those prepared by traditional methods. Later improvements to this chemistry included the use of A -sulfinyl-/< r/-butylcarbamate 299 as the dienophile <2004JA12740>. The retro-Diels-Alder reaction of substrate 300 proceeds at much lower temperatures (130 °C, 5 min with FlTcatalyst 150 °C, Ih with no catalyst). 

Even by 1989, the importance of rhenium compounds in oxidation catalysis was still minimal [1], This picture has changed dramatically since organorhenium(VII) oxides, especially the water-soluble methyltrioxorhenium (MTO, 1), have proven to be excellent catalyst precursors for a surprisingly broad variety of processes, most notably for a variety of oxidation reactions [2, 3]. This article summarizes the behavior of MTO and its peroxo derivatives in the presence of water and under catalytic condition in aqueous systems, particular attention being given to the most recent findings. 

Miscellaneous Reactions of Phosphines.- The basicities of a series of bidentate phosphines have been determined by a study of their enthalpies of protonation with trifluoromethanesulphonic acid in 1,2-dichloroethane. Ring-opening of sultones via nucleophilic attack by nitrogen occurs on treatment with tri-(2-pyridyl)phosphine, with the formation of the water-soluble phosphine systems (91). A novel aldehyde-olefination procedure is afforded by the reactions of aldehydes, diazomethanes, and tertiary phosphines in the presence of a catalytic amount of the powerful Lewis acid methyltrioxorhenium. Attempts to prepare carboxyphenylphosphines by the ring metallation of triphenylphosphine followed by... 

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