Peroxy acids, reduction

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

The data in Tables 19 and 20 show that both peroxysulphuric and peroxyacetic acid give the induced reduction of hydrogen peroxide by thiocyanate. The induced reduction depends strongly on the pH of the solution and on the concentration of thiocyanate. At pH > 3 both peroxy acids reacts more slowly... 

On the basis of these results it can be stated that the fast oxidation of thiocyanate by peroxy acids gives rise to the induced reduction of hydrogen peroxide. In order to elucidate the mechanism of this interesting reaction let us have a look at reactions of thiocyanate with peroxy compounds of different types. 

In solutions of pH > 3, when the rate of reduction of peroxy acid is much lower, the induced disappearance of hydrogen peroxide will be considerably reduced. 

The ring-A/B moiety (286) of the naturally occurring C2g steroidal lactone withaferin A has been incorporated into cholestane as outlined in Scheme 14.156 Hydride reduction of the epoxide (280) gave the diol (281) which reacted stereo-specifically with peroxy-acid to yield the a-epoxide (282), and this was in turn converted into the epoxy-enone (283). The yield of (283) based upon the epoxy-dienone (261) is 70%. Ring-opening of the oxide (283) afforded the 5a-alcohol (284) which was dehydrated to the A2,5-diene (285). The A5-bond was then epox-idized stereoselectively and quantitatively to the 5/3-oxide (286). Ring A of this 5/3 -oxide was shown to be in the boat conformation. 

Alkenes are converted to epoxides by oxidation with peroxy acids, and thereby they are protected with regard to certain chemical transformations. Alkaline hydrogen peroxide selectively attacks enone double bonds in the presence of other alkenes. The epoxides can be transformed back to alkenes by reduction-dehydration sequences or using triphenylphosphine, chromous salts, zinc, or sodium iodide and acetic acid. A more advantageous and fairly general method consists, however, of the treatment of epoxides with dimethyl diazomalonate in the presence of catalytic amounts of binuclear rhodium(II) car-boxylate salts. This deoxygenation proceeds under neutral conditions and without isomerization or cy-clopropanation of the liberated alkene (Scheme 97). Furthermore, epoxides can be converted to alkenes with the aid of various metal carbonyl complexes. Thus, they may be nucleophilically opened with... 

A three-stage synthesis of allylic alcohols has been devised (Scheme 32)," which consists of (i) alkylation of a sulfone-stabilized allylic carbanion (ii) peroxy acid oxidation of the allylic sulfone to give a 2,3-epoxy sulfone and (iii) reductive elimination of the 2,3-epoxy sulfone to give the allylic alcohol. The overall strategy is similar to that of the Evans-Mislow allylic alcohol synthesis based on the 2,3-sig-matropic rearrangement of allylic sulfoxides. However, there are regiochemical advantages to the sul-... 

Oxidation of an aldehyde group to a carboxyl group has often been used for identification of the compounds. As far as can be judged from the results, such oxidations, using chromium trioxide/acetic acid, bromine-water, - peroxy acids, - or chlorite, have not been accompanied by any important side-reactions. Hypoiodite titration, using the iodine in sodium bicarbonate-sodium carbonate procedure, has sometimes been used, giving almost stoichiometric aldehyde determinations. - - Reduction by the Meerwein-Ponndorf reaction, with borohydride - - ... 

Incubation of DPPC/LA idipalmitoylphosphatidylcholine/linoleic acid) LUV with AAPH increased the accumulation of LOOH (linoleic peroxy acid) formed from LA peroxidation. When the tested biphenols were added, a reduction in the amount of LOOH formed was observed and thus oleuropein proved more effective than hydroxy-tyrosol [62]. 

The stereochemistry of epoxidation of homoallylic alcohols has been established by reduction of the products with AIH4. The structure of resulting diols (334) and (335) demonstrates that the original peroxy-acid attack had occurred from the same side of the double bond as the OH group further peroxy-acid oxidation of (334) occurred from the opposite side owing to... 

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