Methyltrioxorhenium preparation

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). 

Hydrogen peroxide in the presence of catalytic amounts of methyltrioxorhenium(VII), ReMeOs, is a convenient and efficient method for the a-hydroxylation of ketones. Particularly interesting is the HiOi/cetylpyridinium peroxotungstophosphate system which, under phase transfer conditions, provides a facile method for preparing aldehydes with one carbon atom less than the parent precursors. The ratio of the products changes with the experimental conditions. 

Methyltrioxorhenium (MTO) supported on silica functionalized with polyether tethers (prepared by a sol-gel procedure) was shown to catalyze epoxidations with 30% H2O2 in the absence of solvent [69]. The silica-attached polyether phase is assumed to act as a solvent for the MTO (see Figure 3). The hydropho-... 

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... 

AU of these compounds can be prepared from methyltrioxorhenium(Vll), abbreviated as MTO. Reduction to rhenium(V) is accomphshed in these procedures with thiols, phosphanes, and sulfanes. ° Suitable stabdizing ligands must be present to intercept the MeRe02 intermediate, which is quite reactive even perchlorate ions are reduced by it. With neither a stabilizing hgand nor an oxidant, a black precipitate is formed from the polymerization of methyldioxo-rhenium(V). ... 

Chemicals and solvents are purchased from commercial sources and used as received. The rhenium products are stable toward O2 and moisture, and so the synthetic procedures can be carried out in air. Methylrhenium trioxide is prepared by a literature route. Abbreviations used MTO = methyltrioxorhenium(VII) H2EDT = 2-ethanedithiol H(HQ) = 8-hydroxyquinoline. 

Methyltrioxorhenium, CHsReOs, prepared from Re20y and (CH3)4Sn, anchored to a Si02-Al203 support is a moderately active catalyst without any additive [49], Model calculations showed that the active carbene species is formed via hydrogen atom transfer to a Re-O-Si bridging oxygen atom on the support, leading to a methylidene hydroxo derivative [50] ... 

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