Prilezhaev reaction

The Prilezhaev reaction is stereospecific, and a syn addition of the oxygen to the double bond is observed in all cases. This observation supports the assumption that the epoxidation of alkenes by peroxyacids is a concerted process. The reaction takes place at the terminal oxygen atom of the peroxyacid, and the n HOMO of the olefin approaches the o LUMO of the 0-0 bond at an angle of 180° (butterfly transition structure). 

A diastereoselective epoxidation of a tetrasubstituted double bond was accomplished with mCPBA in the total synthesis of (-)-21-isopentenylpaxilline by A.B. Smith et al. The tetracyclic lactone substrate containing the tetrasubstituted double bond was exposed to mCPBA in toluene at room temperature. The reaction mixture also contained sodium bicarbonate to neutralize the by-product m-chloro benzoic acid. The epoxidation exclusively took place from the less hindered a-face of the molecule. At a later stage, this epoxide was converted to the y-hydroxy enone moiety present in the natural product. 

During the first total synthesis of briarellin diterpenes, briarellins E and F, L.E. Overman and co-workers utilized the large reactivity difference between a triple and a double bond in peroxyacid oxidations to selectively epoxidize a trisubstituted double bond in the presence of a terminal alkyne. The epoxidation with mCPBA was carried out in DCM in the presence of a base to afford the a-epoxide in a 9 1 diastereomeric ratio. 

The hydroxyl group-directed epoxidation was utilized by M. Isobe et al. in their total synthesis of 11-deoxytetrodotoxin. ° The six-membered cyclic allylic alcohol was treated with mCPBA in the presence of a phosphate buffer to afford an almost quantitative yield of the desired (3-epoxide. 

The final step in J. Mulzer s total syntheses of epothilones B and D was the oxidation of the C12-C13 double bond of epothilone D via a highly diastereoselective Priiezhaev reaction to obtain epothilone B. The same mCPBA oxidation endgame was chosen by R. E. Taylor et al. in the total synthesis of these two natural products.  

The pinacol rearrangement reaction is of limited synthetic importance although it can be a useful alternative to the standard methods for synthesis of aldehydes and ketones. Especially in the synthesis of ketones with special substitution pattern—e.g. a spiro ketone like 5—the pinacol rearrangement demonstrates its synthetic potential  

The required vicinal diols are in general accessible by standard methods. Pinacol itself can be obtained by dimerization of acetone. For the rearrangement reaction concentrated or dilute sulfuric acid is often used as catalyst. 

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. 

The hydroxy oxygen of a peracid has a higher electrophilicity as compared to a carboxylic acid. A peracid 2 can react with an alkene 1 by transfer of that particular oxygen atom to yield an oxirane (an epoxide) 3 and a carboxylic acid 4. The reaction is likely to proceed via a transition state as shown in 5 (butterfly mechanism), where the electrophilic oxygen adds to the carbon-carbon n-hond and the proton simultaneously migrates to the carbonyl oxygen of the acid  

The mechanism formulated above is in agreement with the experimental findings, that stereospecifically a 5y -addition takes place the stereochemical relation between substituents in the alkene 1 is retained in the oxirane 3. 

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Peracids react heterolytically with olefins with the formation of epoxides by the Prilezhaev reaction. So, the co-oxidation of aldehydes with olefins has technological importance. Peracids react with ketones with formation of lactones. These reactions will be discussed in Section 8.2. The oxidation of aldehydes are discussed in monographs [4-8]. 

E. N. Prilezhaeva, Prilezhaev Reaction, Electrophilic Oxidation, Nauka, Moscow, U.S.S.R., 1974. 

Prilezhaev reaction Oxidation of alkenes to epoxides using peroxycarboxylic acids. 362... 

Related reactions Davis oxaziridine oxidation, Prilezhaev reaction, Sharpless asymmetric epoxidation, Shi asymmetric epoxidation ... 

Prilezhaev reaction The formation of an epoxide from the reaction of perbenzoic acid on an alkene. 

Chiral peroxy acids, such as monoperoxycamphoric acid, have been used in a classical Prilezhaev reaction for the preparation of chiral epoxides [1], however, the enantiomeric excess (e.e.) of the epoxides formed was below 10%,... 

We began our work with isoprene alcohol (see Scheme 11). While the Prilezhaev reaction with monoperoxyphthalic acid provided the appropriate dimethyl glycidol in good yield, we failed in our attempts to prepare the corresponding chiral epoxide by Sharpless epoxidation. Obviously, the reaction does not work in the case of this tertiary allylic alcohol. When the solution is allowed to warm up to room temperature a slow epoxidation takes place, however, the isolated dimethyl glycidol does not show any optical activity. Very recently the asymmetric epoxidation of a tertiary allylic alcohol in reasonable optical and chemical yield has been described [21]. 

The Prilezhaev reaction is the formation of epoxides by the reaction of alkenes with peracids. 

Nikolai Aleksandrovich Prilezhaev (1872-1944) was a Russian chemist. A biographical reference was published in 1973 in Zhurnal Ohschei Khimii.5 The reaction was first published in 1910. The Prilezhaev reaction has wide utility and has been reviewed.4,7... 

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