Alkenes permanganate oxidation

The intermediate formed in the oxidation of alkenes by permanganate ion is considered a cycHc manganate(V) ester (92). Investigations have suggested that manganate(V) intermediates play a significant role in virtually all permanganate oxidation reactions. It is therefore the further reactions of the... 

When compound (443), which contains alkene and alkyne moieties, was reacted with benzonitrile oxide, both an isoxazoline (444) and isoxazole (445) were produced, with the former predominating. Oxidation of (444) with permanganate produced 3-phenyl-2-isoxazoline-5-carboxylic acid (446) (67ZOR82i). The reaction of 1-trimethylsilylbut-l-yne-3-ene produced only a compound which reacted at the alkenic unit. Oxidation of the adduct also produced (446) (68ZOB1820). These reactions are shown in Scheme 102. 

Ketols are also observed as products of permanganate oxidation of alkenes. The ketols are believed to be formed as a result of oxidation of the cyclic intermediate.35... 

Further variations on the epoxyketone intermediate theme have been reported. In the first (Scheme 9A) [78], limonene oxide was prepared by Sharpless asymmetric epoxidation of commercial (S)-(-)- perillyl alcohol 65 followed by conversion of the alcohol 66 to the crystalline mesylate, recrystallization to remove stereoisomeric impurities, and reduction with LiAlH4 to give (-)-limonene oxide 59. This was converted to the key epoxyketone 60 by phase transfer catalyzed permanganate oxidation. Control of the trisubstituted alkene stereochemistry was achieved by reaction of the ketone with the anion from (4-methyl-3-pentenyl)diphenylphosphine oxide, yielding the isolable erythro adduct 67, and the trisubstituted E-alkene 52a from spontaneous elimination by the threo adduct. Treatment of the erythro adduct with NaH in DMF resulted... 

The Phase-Transfer-Assisted Permanganate Oxidation of Alkenes and Alkynes... 

Solvent Effects. Information on the effect of solvent polarity of the phase transfer assisted permanganate oxidation of alkenes has been obtained by studying the oxidation of methyl cinnamate by tetrabutylammonium permanganate in tv/o different solvents, acetone and methylene chloride (37). 

Less rigorous reaction conditions are required to cleave the double bond to form ketones and carboxylic acids. Phase-transfer-assisted permanganate oxidations in the presence of quaternary ammonium salts,439 652-654 crown ethers,439,655 or polyethers566 usually ensure high yields. Terminal alkenes are transformed to carboxylic acids with one carbon atom less than the starting compound.653,654... 

Diols are prepared from alkenes by oxidation with reagents such as osmium tetroxide, potassium permanganate, or hydrogen peroxide (Section 11-7C). However, ethylene glycol is made on a commercial scale from oxacy-clopropane, which in turn is made by air oxidation of ethene at high temperatures over a silver oxide catalyst (Section 11-7D). 

Alkenes are oxidized to acids by heating them with solutions of potassium permanganate (KMn04) or potassium dichromate (K2Cr207). 

Alkenes undergo a number of other reactions, such as hydroboration, permanganate oxidation, and ozonolysis. 

Table 1. Fluorinated telechelic diols obtained from the permanganic oxidation of fluorinated alkenes...

In addition to its synthetic value, the permanganate oxidation of alkenes provides a simple chemical test for the presence of an alkene. When an alkene is added to a clear, deep purple aqueous solution of potassium permanganate, the solution loses its purple color and becomes the murky, opaque brown color of Mn02. (Although there are other functional groups that decolorize permanganate, few do it as quickly as alkenes.)... 

The oxidation of alkenes by permanganate is one of the frequently used examples in freshman chemistry. It is also well known as the Baeyer test for unsaturation. There are many reagents that add two hydroxyl groups to a double bond,44 but osmium tetroxide and permanganate are the most prominent ones. The mechanism of the permanganate oxidation is believed to be similar to the oxidation of alkenes by 0s0445 46... 

Recent evidence on the mechanism of permanganate oxidation of alkenes has been summarized the initial step probably involves a [3 2] cycloaddition between permanganate ion and the alkene to give a cyclic manganese(V) ester (2 see Section 3.3.1). 

S-8-S carbon skeleton of Aisicoccins and ophiobolins (equation 10). Trisubstituted alkenes yield keto acids (equation 11). A related reaction, known as the Lemieux-von Rudloff (periodate-permanganate) oxidation, is also used to oxidize alkenes to acids or ketones (equation 12). If aldehydes are required... 

With careful choice of reagent and reaction conditions, alkenes containing other functionalities can be selectively hydroxylated without complicating side reactions. For example, the oxidation may be carried out in the presence of ester, ether, sulfide, carboxylic acid, acetal, carbonyl, halo, alcohol and aryl groups. Regioselective hydroxylation is also possible in dienes in which one center is electron poor, and some selectivity is also found between isolated double bonds. For example, syn hydroxylation of diene (5) with a catalytic amount of osmium tetroxide and N-methylmorpholine N-oxide as the secondary oxidant gives diol (6) in 46% yield, and phase transfer catalyzed permanganate oxidation of diene (7) affords diol (8) in 83% yield. 

Permanganate oxidation of alkenes. Substituent and solvent effects. Difficulties with MP2 calculations ... 

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