Oxidation permanganate-mediated

An alternative to the direct anodic oxidation of organic contaminants are the methods of indirect oxidation with the aid of oxidizers formed electrochemically in situ. These oxidizers (or mediators) can be obtained in both anodic and cathodic processes. Anodic agents are the salts of hypochloric acid (hypochlorites), the permanganates, the persulfates, and even ozone. 

The corresponding syzz-isomer was, on the other hand, prepared from the potassium permanganate-mediated oxidation of trifluorocrotonate 10, derived from -hydroxy-butyrate. In this procedure, the diol ester with syn relative configuration was the only product detected. After acetylation, syn-11 was employed as a substrate for the enzymatic resolution affording both (2S,3S)-11... 

An asymmetric permanganate-promoted oxidative cyclization of 1,5-dienes using a chiral phase-transfer catalyst was recorded <2001AGE4496>, and a diastereoselective permanganate-mediated oxidative cyclization with an Oppolzer sultam has been employed in the total synthesis of m-solamin <20020L3715>. In a metal-oxo-mediated approach to the synthesis of 21,22-di- /)7-membrarollin based on the use of a camphor-derived Oppolzer sultam as... 

Ruthenium- or permanganate-mediated oxidations of internal aikynes are highly dependent on solvent conditions and generally afford the corresponding a-diketones." ... 

The corresponding syn-isomer was, on the other hand, prepared from the potassium permanganate-mediated oxidation of trifluorocrotonate 12, derived from... 

In the presence of tw 5-2-tritylcyclohexanol (TTC) as a highly effective chiral controller, the permanganate-mediated oxidative cyclization of a series of 2-methylenehept-5-eneoates bearing different chiral auxiliaries led to the formation of the 2,5-disubstitutedTHF diols in which the tra 5-THF systems were obtained with high diastereoselectivity (14OL5104). 

The resolution of the hot debate on the mechanism of metal-oxo mediated oxidations is one of the success stories of DFT calculations. An early publication by Sharpless on chromylchloride oxidations of alkenes10 started a long ongoing discussion11-25 on the mechanism of metal-oxo mediated oxidations. Sharpless proposed an interaction between the chromium metal and the alkene and generalized his proposal to include all metal-oxo compounds, especially osmium tetroxide and permanganate. Especially the mechanism of the reaction of osmium tetroxide with alkenes was the subject of an intense debate within the community of experimental organic chemists (Scheme 2). 

In general, the radicals dimerize rapidly unless inhibited by pyranyl ring substitution 2-(4-nitrophenyl)benzopyranyl is reported not to dimerize, however.The kinetics of the formation of a series of 36 by reduction of the precursor flavylium ions by Cr(II) have been investigated a Hammett plot of the second-order rate constants versus has p = 1.03. Most work has been concerned with the polarography of the parent cations there appear to be no ESR results for benzopyranyl radicals. The mediation of benzopyranyl radicals in the oxidation of 2-phenyl-2//-benzopyrans by potassium permanganate has been suggested.(See Section II,B,5,b for radicals from anthocyanidins.)... 

The phase-transfer-assisted permanganate oxidation of alkynes and alkenes has been reviewed. Terminal and internal alkynes are oxidized to 1,2-dicarbonyl compounds by the combined action of diphenyl disulphide, ammonium peroxidisulphate and water or by sodium periodate in the presence of ruthenium dioxide (equation 34). Other reagents for the conversion of acetylenes into 1,2-dicarbonyl compounds are hydrogen peroxide in the presence of (2,6-dicarboxylatopyridine)iron(II), the complex oxo(A, A -ethylenebissalicylideneiminato)chromium(V) trifluoromethanesulphonate (216)and ruthenium tetroxide as a mediator in electrooxidation. l-Acetoxyalkan-2-ones 217 are obtained by the oxidation of terminal acetylenes with sodium perborate and mercury(II) acetate in acetic acid ". Terminal alkynes give a-ketoaldehydes 218 on treatment with dilute hydrogen peroxide, combined with mercury(II) acetate and sodium molybdate or sodium tungstate under phase-transfer conditions. ... 

Other Reactions.—As in the case of quaternary ion PTC, several different types of reaction are catalysed by complexing agents such as crown ethers, in both the liquid-liquid and solid-liquid mode of operation. Among these are metal boro-hydride reductions of ketones, " permanganate oxidation of alkenes in non-polar solvents (hence purple benzene ) and cyanide-mediated benzoin condensations (Equation 13). ... 

Permanganate was the first reagent that was demonstrated to have the ability to carry out the oxidative cyclization of 1,5-dienes [47]. Brown and coworkers have continued the development of this area by discovering a diastereoselective KMn04-mediated 1,5-diene cyclization that leads to 2,5-cis-tetrahydrofuran derivatives. They have used a camphorsultam chiral auxiliary to ccaitrol the facial selectivity and have found that polyunsaturated substrates can be chemoselectively manipulated. As an... 

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