Peracid, reaction with alkenes

The first step in this preparation, the epoxidation of 1,4,5,8-tetra-hydronaphthalene, exemplifies the well-known selectivity exerted by peracids in their reaction with alkenes possessing double bonds that differ in the degree of alkyl substitution.12 As regards the method of aromatization employed in the conversion of ll-oxatricyclo[4.4.1.01-6]-undeca-3,8-diene to l,6-oxido[10]annulene, the two-step bromination-dehydrobromination sequence is given preference to the one-step DDQ-dehydrogenation, which was advantageously applied in the synthesis of l,6-metliano[10]annulene,2,9 since it affords the product in higher yield and purity. 

The Prilezhaev reaction is a rarely used name for the epoxidation of an alkene 1 by reaction with a peracid 2 to yield an oxirane 3. The epoxidation of alkenes has been further developed into an enantioselective method, that is named after Sharpless. 

Direct Oxidation with Stoichiometric Oxidants. Discovered by Prilezhaev in 1909,211 the typical epoxidation reaction of alkenes is their oxidation with organic peracids. Of the large number of different peroxycarboxylic acids used in... 

We now turn to the stereochemistry governed by a ring system, and we shall look at both nucleophilic and electrophilic attack, since usually they have similar stereochemical preferences rather than contrasting preferences. In addition to several reactions that are straightforwardly electrophilic attack, we shall see several which can be described as electrophilic in nature, like the reactions of alkenes with osmium tetroxide, with peracids, with some 1,3-dipoles, and with boranes, and of dienes with dienophiles in Diels-Alder reactions. Some of these reactions are pericyclic, the pericyclic nature of which we shall meet in Chapter 6. For now, it is only their diastereoselectivity that will concern us. 

Diboiyl compounds yield alkenes on reaction with chromic acid (equation 45), a reaction also noted in a peracid oxidation and oxidation with pyridinium chlorochromate. ... 

The introduction of oxygen atoms into unsaturated organic molecules via dihydroxylation reactions leads to 1,2-diols. 1,2-Diols can be synthesized by the reaction of alkenes either with peracids via corresponding epoxides and subsequent hydrolysis or with OSO4, KMn04, RUO4 and Cr(VI) compounds. 

Oxiranes may also be prepared by the cooxidation of aldehydes and olefins. There are two assumptions as regards the mechanism the oxidation occurs via either an acylperoxy radical or a peracid. The peracid oxidation is stereospecific. Experiments carried out with a view to assessing the radical versus nonradical mechanism indicate that the extent of the radical epoxidation depends on the structure of the olefin and the olefin/aldehyde ratio. Cooxidation in the presence of oxygen was achieved by irradiating the aldehyde and carrying out the reaction with the alkene after a suitable quantity of peracid had been obtained. Enantioselective epoxidation has been described in the reaction of (1-phenyl-alkylidene)malonitriles 63 catalyzed by optically active tertiary amines. ... 

Prilezhaev (Prileschajew) reaction. Formation of epoxides by the reaction of alkenes with peracids. 

The reaction of alkenes with peroxycarboxylic acids (or peracids) leads to the formation of epoxides in a concerted addition reaction. The peroxycarboxylic acid donates an oxygen atom to the double bond in a syn- addition reaction. 

Hydrogen peroxide and organic hydroperoxides are relatively poor oxidants in the absence of radical initiators or other specific reagents. No reaction occurs with alkenes unless a reagent capable of producing electrophilic intermediates, such as a peracid or metal peroxo complex, is used. 

---