Phase-transfer reagents permanganate

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. 

The phase-transfer-assisted permanganate oxidation of alkynes and alkenes has been reviewed. Terminal and internal alkynes are oxidized to 1,2-dicarbonyl compounds by the combined action of diphenyl disulphide, ammonium peroxidisulphate and water or by sodium periodate in the presence of ruthenium dioxide (equation 34). Other reagents for the conversion of acetylenes into 1,2-dicarbonyl compounds are hydrogen peroxide in the presence of (2,6-dicarboxylatopyridine)iron(II), the complex oxo(A, A -ethylenebissalicylideneiminato)chromium(V) trifluoromethanesulphonate (216)and ruthenium tetroxide as a mediator in electrooxidation. l-Acetoxyalkan-2-ones 217 are obtained by the oxidation of terminal acetylenes with sodium perborate and mercury(II) acetate in acetic acid ". Terminal alkynes give a-ketoaldehydes 218 on treatment with dilute hydrogen peroxide, combined with mercury(II) acetate and sodium molybdate or sodium tungstate under phase-transfer conditions. ... 

Crown ethers have found a niche in the organic chemistry laboratory as phase transfer reagents. Thus, although potassium permangante (KMn04) is insoluble in benzene (CeHe), the addition of a trace of dibenzo[18]-crown-6 produces a purple solution ( purple benzene ) and permits transfer of the permanganate ion (Mn04 ) into a medium, for example, for oxidation, in which it would otherwise be insoluble. 

The macrocyclic polyethers were prepared by Pedersen a decade ago and shown to complex a variety of cationic substrates [39]. Among these substrates are alkali metal cations, alkaline earth cations and ammonium ions [40]. It has been shown that hindered esters could be saponified by KOH in toluene solution in the presence of dicyclo-hexyl-18-crown-6 [41] or cryptate [42]. Potassium hydroxide is both solubilized in toluene and activated by the crown ether [43]. Sam and Simmons, however, first clearly demonstrated the potential of crowns as phase transfer reagents by solubilizing potassium permanganate in benzene solution (see Eq. 1.15) and using the solubilized reagent in a variety of oxidation processes [44]. 

Transition metal oxidants such as permanganate, ruthenium tetroxide and diromium(VI) oxide are convenient and efficient reagents for routine cleavage reactions. The use of phase transfer catalysts (quaternary ammonium and phosphonium ions, primarily) has made it possible to solubilize transition metal oxides such as permanganate and chromatt in nonaqueous solvents, and to therdry increase the scope of these reactions substantially. ... 

The residue is treated with 0.6 ml. of dioxane, 0.2 ml. of 0.1 N potassium permanganate, and 0.25 ml. of 0.01 N periodic acid and is allowed to stand at room temperature for 15 minutes. If the permanganate color disappears, additional 0.1 ml. portions of this reagent are added. The reaction mixture is transferred quantitatively to a small separatory funnel with about 10 ml. of water and 30 ml. of benzene and the mixture is thoroughly shaken. After discarding the aqueous layer, the benzene phase is washed once with 10 ml. of freshly prepared sodium dithionite solution and then with three 10 ml. portions of water. After removal of the solvent under reduced pressure at a temperature below 60 °C. the residue is ready for polarography. 

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