Alcohols methyltrioxorhenium

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. 

Methyltrioxorhenium-based oxidants, i.e. MT0/H202, MT0/H202/substituted pyri-dines and MTO/UHP , are active in the epoxidation of many double-bond typologies, including allylic alcohols. Regiochemical and stereochemical probes have been... 

Oxidation of alcohols may be achieved also using the methyltrioxorhenium/H202 catalytic system Primary benzylic and secondary aliphatic alcohols afforded the... 

Pyridine, methyltrioxorhenium hgands, 460-1 Pyridine-2,6-dicarboxylate (dipic), transition metal peroxides, 1060, 1061 Pyridinium dichromate, alcohol oxidation, 787-8... 

Allylic alcohols can also be epoxidized with methyltrioxorhenium (MTO). However, in contrast to the early transition metal catalysts, metal-alcoholate binding does not appear to be operative, but rather straightforward hydrogen bonding, as demonstrated by the epoxidation of geraniol (20)... 

Hi. Epoxidation of allylic alcohols with special synthetic utility or academic interest. In 1999, Adam and coworkers reported on the methyltrioxorhenium (MTO) catalyzed... 

Re has recently come to the forefront in liquid phase oxidation catalysis, mainly as a result of the discovery of the catalytic properties of the alkyl compound CH3Re03 [methyltrioxorhenium (MTO)]. MTO forms mono-and diperoxo adducts with H2O2 these species are capable of transferring an oxygen atom to almost any nucleophile, including olefins, allylic alcohols, sulfur compounds, amides, and halide ions (9). Moreover, MTO catalysis can be accelerated by coordination of N ligands such as pyridine (379-381). An additional effect of such bases is that they buffer the strong Lewis acidity of MTO in aqueous solutions and therefore protect epoxides, for example. 

In methyltrioxorhenium-catalysed reactions, residual pyridine, pyrazole or imidazole may deactivate the active catalyst and the ionic liquid should be purified accordingly.118 191 The nature of the ionic liquid may decide the success or failure of a given reaction and, for example, Ru-catalysed alcohol oxidations appear to be very sensitive to the type and quality of ionic liquid used. 

Adam, W., Mitchell, C. M., Saha-Moeller, C. R. Regio- and Diastereoselective Catalytic Epoxidation of Acyclic Ailylic Alcohols with Methyltrioxorhenium A Mechanistic Comparison with Metal (Peroxy and Peroxo Complexes) and Nonmetal (Peracids and Dioxirane) Oxidants. J. Org. Chem. 1999, 64, 3699-3707. 

C. di Valentin, R. Gandolfi, P. Gisdakis, N. Rosch, Allylic alcohol epoxidation by methyltrioxorhenium A density functional study on the mechanism and the role of hydrogen bonding, J. Am. Chem. Soc. 123 (2001) 2365. 

Oxidation of secondary alcohols with catalyzed by methyltrioxorhenium (MTO) as homogeneous catalyst and supported MTO (polyvinylpyridine/MTO and polystyrene/MTO) as heterogeneous catalysts was investigated by Crucianelli et al. [3]. 

Jain SL, Sharma VB, Sain B (2006) Methyltrioxorhenium and sodium bromide-catalyzed oxidation of alcohols to carbonyl compounds with using l-butyl-3-methylimidazolium tetrafluo-roborate ionic liquid as a novel recyclable green solvent. Bull Chem Soc Jpn 79 1601-1603... 

A recent improvement to this type of reaction often selects for the formation of tetroxanes over the trimeric hexaoxonane analogs. The use of fluorinated alcohols such as trifluoroethanol (TEE) or, often better, HFIP, as solvent and methyltrioxorhenium (MTO) as catalyst, as well as a substrate concentration of 1 M, are considered important for success (Equation (26) Table 3) <2003TL6309, 2006T1479, 2006BMC7790>. 

Adam, W., A. Corma, A. Martinez, C.M. Mitchell, T.I. Reddy, M. Renz, and A.K. Smerz, Diastereoselective Epoxidation of Allyhc Alcohols with Hydrogen Peroxide Catalyzed by Ttitanium-Containing Zeohtes or Methyltrioxorhenium Versus Stoichiometric Oxidation with Dimethyldioxirane Clues on the Active Species in the Zeolite Lattice, J. Mol Catal A Chem. 117 357-366 (1997). 

Methyltrioxorhenium (MTO) also catalyzes the oxidation of alcohols with H2O2 via a peroxometal pathway [137,138]. Primary benzyhc and secondary aliphatic alcohols afforded the corresponding aldehydes and ketones, respectively, albeit using two equivalents of H2O2. In the presence of bromide ion the rate was increased by a factor 1000 [137]. In this case the active oxidant could be hypobromite (HOBr), formed by MTO-catalyzed oxidation of bromide ion by H2O2. 

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