Peroxy acids alcohols

Ameisen-. formic, -aldehyd, n. formaldehyde. -amylMther, -amylester, m. amyl formate, -ather, m. formic ether (ethyl formate), geist, m. (Pharm.) spirit of ants (a mixture of formic acid, alcohol and water), -naphta, n. = Ameisenather. -persaure, /. peroxy-formic acid, performic acid, ameisensauer, a. of or combined with formic acid, formate of. — ameisensaures Salz, formate. 

Allylic alcohols can be converted to epoxy-alcohols with tert-butylhydroperoxide on molecular sieves, or with peroxy acids. Epoxidation of allylic alcohols can also be done with high enantioselectivity. In the Sharpless asymmetric epoxidation,allylic alcohols are converted to optically active epoxides in better than 90% ee, by treatment with r-BuOOH, titanium tetraisopropoxide and optically active diethyl tartrate. The Ti(OCHMe2)4 and diethyl tartrate can be present in catalytic amounts (15-lOmol %) if molecular sieves are present. Polymer-supported catalysts have also been reported. Since both (-t-) and ( —) diethyl tartrate are readily available, and the reaction is stereospecific, either enantiomer of the product can be prepared. The method has been successful for a wide range of primary allylic alcohols, where the double bond is mono-, di-, tri-, and tetrasubstituted. This procedure, in which an optically active catalyst is used to induce asymmetry, has proved to be one of the most important methods of asymmetric synthesis, and has been used to prepare a large number of optically active natural products and other compounds. The mechanism of the Sharpless epoxidation is believed to involve attack on the substrate by a compound formed from the titanium alkoxide and the diethyl tartrate to produce a complex that also contains the substrate and the r-BuOOH. ... 

In the field of enzyme catalysis, heme-proteins such as cytochrome P450, for example, exhibit both types of 0-0 bond cleavages in organic hydroperoxides and peroxy acids (178). Heterolytic cleavage of HOOH/ROOH yields H20 or the corresponding alcohol, ROH and a ferryl-oxo intermediate (Scheme 4). Homolytic 0-0 bond cleavage results in the formation of a hydroxyl (HO ) or an alkoxyl (RO ) radical and an iron-bound hydroxyl radical. 

Based on these calculations, one can conclude that TSs for epoxidation of alkenes and allylic alcohols with peroxy acids, dioxiranes, and Re-peroxo complexes share a spiro geometry in which the plane of the attacking peroxo... 

Triethyl- and triphenylphosphine have been used for deoxygenation not only of hydroperoxides to alcohols but also of dialkyl peroxides to ethers, of diacyl peroxides to acid anhydrides, of peroxy acids and their esters to acids or esters, respectively, and of endoperoxides to oxides [290] in good to excellent yields. The deoxygenation of ascaridole to l-methyl-4-isopropyl-l,4-oxido-2-cyclohexene [290] was later challenged the product is claimed to be p-cymene instead [668]). 

Oxidation of 167 with peroxy acids in the presence of alcohols led71 to trfm.s-2-alkoxytetrahydropyran-.3-ol (173) in 65-80% yield. 

Furfuryl alcohol is oxidized directly to 2,3-dideoxy-DL-pent-2-eno-pyranosid-4-nlose (325, R = H) by treatment with m-chloroperoxy-benzoie acid.236 A variety of substituted furfuryl alcohols have thus been converted into over 60 enediulose derivatives (345) in connection with studies of their antimicrobial activity.211 It was later found that pyridinium chlorochromate may be applied in this reaction, instead of a peroxy acid.237... 

The epoxidation of allylic alcohols can be carried out with peroxy acids in aqueous medium. In the case of polyolefinic alcohols, regioselectivity results from control of the pH of the reaction the proton of the allylic hydroxy group plays a fundamental role when the oxidation is carried out at a high pH296. 

The products of bromination in water are called bromohydrins. They can be treated with base, which deprotonates the alcohol. A rapid intramolecular Sjyj2 reaction follows bromide is expelled as a leaving group and an epoxide is formed. This can be a useful alternative synthesis of epoxides avoiding peroxy-acids. 

With one exception—when the substituent is a hydroxyl group. When an allylic alcohol is epoxidized, the peroxy-acid attacks the face of the alkene syn to the hydroxyl group, even when that face is more crowded. For cyclohexenol the ratio of syn epoxide to anti epoxide is 24 1 with m-CPBA and it rises to 50 1 with CF3CO3H. 

The reason is shown in the transition state the OH group can hydrogen bond, through the H of the alcohol, to the peroxy-acid,... 

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. 

Simple alcohols can be obtained from the decomposition of peroxy acids in cyclohexane or benzene at reflux. This chain reaction, which is efficient for adamantane-l-carboxylic acid (equation 40), is unfortunately usually complicated by side reactions involving hydrogen abstraction from the substrate or sol-... 

Moderate selectivity has been observed in the epoxidation of the homoallylic alcohol (64 equation 25). In the nonsteroidal conformation of (64), the axial hydroxy is suitably oriented for forming a hydrogen bond with the peroxy acid in the transition state. That the epoxidation of (64 R = OH) is indeed hydroxy-directed is supported by the observation that the epoxidation of the acetate (64 R = OAc) furnishes exclusively the a-epoxide (66 R = OAc). 

---