Organic Peroxyacids

Perhaps the most common method for the epoxidation of simple alkenes is their reaction with peroxyacids, which has occasionally been referred to as the Prilezhaev (Prileschajew) reaction. O This reaction does not require transition metal catalysis and the yield of epoxide is often high. Peroxyacids such as 156 are prepared by reaction of carboxylic acids with hydrogen peroxide. An equilibrium is established during the reaction that favors the peroxyacid, although several alternative methods are available.279 in general, strong 

Neighboring group effects are important in reactions of peroxyacids, as they were with reactions of hydroperoxides. Reexamination of the epoxidation of 171 using MCPBA rather than TBHP reveals that the peroxyacid gave a 95 5 mixture of 172 and 173. Using MCPBA rather than TBHP led to a slight increase in diastereoselectivity for the reaction, although this depends on the substitution pattern of the alkene. Sharpless 

More highly substituted alkenes are electron rich and react faster with peroxyacids than do less substituted alkenes. In general, the relative rate of epoxidation increases with the nucleophilic character of the alkene l (CH2=CH2 has a relative rate of 1, RCH=CH2 = 24, RCH CHR = 500, R2C=CH2 = 500, R2C=CHR = 6500, 

A buffer is often added to epoxidation reactions involving peroxyacids. The byproduct of the reaction is a carboxylic acid, as mentioned several times above. If trifluoroperoxyacetic acid (CF3CO3H) is used as the 

Conjugation diminishes the reactivity of an alkene in epoxidation reactions. Conjugated esters, for example, are less reactive than simple alkenes due to the electron-withdrawing effect of the carbonyl. Isolated (unconjugated) alkenes are usually epoxidized before conjugated alkenes, as seen in the reaction of 204 to give 205, in Hiyama s synthesis of 3-sinesal.309 

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There are two broad classes of organic peroxyacids peroxycarboxyUc acids, R[C(0)00H], where R is an alkyl, aralkyl, cycloalkyl, aryl, or heterocycHc group and n = 1 or 2, and organoperoxysulfonic acids, RSO2—OOH. PeroxycarboxyUc acids are commonly named by adding the prefix peroxy to the parent acid as in peroxypropionic acid. The prefix per- is accepted only for the weU-estabHshed products, ie, performic, peracetic, and perbenzoic acids. 

Inorganic acids with a peroxide function are given the IUPAC name above, which distinguishes them from the organic peroxyacids. Collectively they are a group of very powerful oxidants, individual compounds being ... 

There are two broad classes uf organic peroxyacids peroxycarboxylic acids, R[C(0)00H] , where R is an alkyl, aralkyl, cycloalkyl, aryl,... 

TABLE 9. PROPERTIES OE SOME ORGANIC PEROXYACIDS Peroxyacid Structure Mp. °C... 

CAUTION All preparations and reactions with hydrogen peroxide and organic peroxyacids must be conducted behind a safety screen, because these reactions sometimes proceed with violence. 

Inorganic and organic peroxyacids can be used as a source of hydroxy cations HO+ for the oxidation of aromatic rings. 

The Baeyer-Villiger oxidation of aromatic ketones by peroxyacids is a widely applicable method for the synthesis of phenols . This oxidation can be carried out by organic peroxyacids such as peroxyacetic , trifluoroperoxyacetic , 4-nitro-and 3,5-dinitroperoxybenzoic acids . However, m-chloroperoxybenzoic acid is most frequently used. Hydrogen peroxide is sometimes used, but it works only in the presence of strong acids . 

EP 0 564 250 (1993) J. L. Coope et al., Unilever PLC Amido or imido organic peroxyacid Structured hquid with add or neutral pH, containing a pH jump system... 

The reaction in eq. 8.17 is suitable only for ethylene oxide. Other epoxides are usually prepared by the reaction of an alkene with an organic peroxyacid (often called simply a peracid). 

Nitrogen and Oxygen-containing Heterocycles.—A study of the oxidation of (/ )-(—)-diphenylmethylene-a-methylbenzylamine (291) with organic peroxyacids has... 

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