Potassium permanganate diols

PerfluoroaUcenes are converted to vicinal diols when no fluonne atom is present at the double bond Configurational isomers of perfluoroalkenes [29] (equations 20 and 21) are oxidized stereospecifically Perfluorbicyclo[4 3 0]non-1(6) ene gives the corresponding 1,6 diol m a 24% yield upon oxidation with potassium permanganate at 18 °C for 1 h [29]... 

Potassium permanganate or osmium tetroxide oxidize alkenes to furnish 1,2-diols (glycols). 

Primary and secondary alcohols are oxidized slowly at low temperatures by benzyltriethylammonium permanganate in dichloromethane primary alcohols produce methylene esters (60-70%), resulting from reaction of the initially formed carboxylate anion with the solvent, with minor amounts of the chloromethyl esters and the carboxylic acids. Secondary alcohols are oxidized (75-95%) to ketones [34] the yields compare favourably with those obtained using potassium permanganate on a solid support. 1,5-Diols are oxidized by potassium permanganate under phase-transfer catalytic conditions to yield 8,8-disubstituted-8-valerolactones [35] (Scheme 10.1). 

The oxidation of alkenes with potassium permanganate in the presence of chiral menthylammonium salts has been reported to produce chiral 1,2-diols with low optical purity. It is possible that the products are contaminated with the catalysts or their decomposition products, as no asymmetric induction was observed with (+)-l-phenylethylammonium salts [30]. 

Substance 18 was treated with hydrocyanic acid to produce the 20-cyanhydrin derivative, which in turn was dehydrated to the A -20-cyanopregnadiene 19. Oxidation with potassium permanganate in piperidine gave 3-ethylenedioxy-A -pregnene-17a, 21-diol-l 1,20-dione... 

Pentenal was employed30 for an effective synthesis of the 2,3-di-deoxy-DL-pentose (50a). The aldehyde was converted into the dimethyl acetal 48 this was ci.s-hydroxylated with potassium permanganate to give diol 49. Mild, acid hydrolysis of 49 afforded the methyl... 

The corresponding syzz-isomer was, on the other hand, prepared from the potassium permanganate-mediated oxidation of trifluorocrotonate 10, derived from -hydroxy-butyrate. In this procedure, the diol ester with syn relative configuration was the only product detected. After acetylation, syn-11 was employed as a substrate for the enzymatic resolution affording both (2S,3S)-11... 

The reaction may be followed by thin-layer chromatography. The ratio of the Rf values for cyclohexene and c/s-diol 2 is 2 1 (commercial silica gel plates, ethyl acetate). The plates are best visualized by first spraying with 1 % aqueous potassium permanganate, then with methanolic sulfuric acid, followed by charring with heat. The checkers found that, if the procedure is followed exactly, monitoring the reaction by thin-layer chromatography is unnecessary. 

Potassium permanganate is a classical reagent for such Wagner-type dihydroxylations. Initially formed vicinal diols 50 immediately eliminate hydrogen fluoride to give x-diketones 51.90... 

An epoxide is formed from alkene and peroxymethanoic acid (H202 -l- HC02H) but is cleaved by the HC02H present to a frans-diol. Alternatively, osmium tetroxide may be used in fe/t-butyl alcohol and leads to the c/ s-diol. Potassium permanganate in neutral can be useful for preparation of c/ s-glycols. (See Section 11-70.)... 

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). 

Exercise 16-37 An elegant modification of the two-step procedure to prepare ketones from alkenes by hydroxylation and oxidative cleavage of the diol formed uses a small amount of potassium permanganate (or osmium tetroxide, 0s04) as the catalyst and sodium periodate as the oxidizing agent ... 

An unusual regiocontrolled oxidation (epoxidation and dihydroxylation) of l-halo-1,3-dienes (equation 13) has been accomplished by use of potassium permanganate-MgSCU, after initial treatment with 2,2-dimethoxypropane78. The preferred epoxy diol is formed with the epoxide being adjacent to the chloro substituent. Further elaboration of these molecules yields highly sought after inositols with controlled stereochemistry. 

The two tests employed for the detection of unsaturation are decolourisation of a dilute solution of bromine in dichloromethane, and reaction with dilute aqueous potassium permanganate. It is essential to apply both tests since some symmetrically substituted alkenes (e.g. stilbene, C6H5,CH=CH-C6H5) react only slowly under the conditions of the bromine test. With dilute potassium permanganate solution the double bond is readily attacked, probably through the intermediate formation of a ds-diol. 

Oxidative cycHzation of5,6-dihydroxyalkenes. Oxidation of unsaturated diols la and lb with either Collins reagent or pyridinium chlorochromate results in the corresponding ci.v-tetrahydrofuranediols (2) as the major product.1 The selective stereochemistry is very similar to that observed in the oxidative cycHzation of 1,5-hcxadienes with potassium permanganate (9, 388-389) to civ-2,5-disubsli luted tetrahydrofuranes. 

The same reaction can also be carried out using cold alkaline potassium permanganate (KMn04) followed by treatment with aqueous base (Following fig.). It is important to keep the reaction cold since potassium permanganate can cleave the diol by further oxidation (Fig. E). 

The term glycol generally means a 1,2-diol, or vicinal diol, with its two hydroxyl groups on adjacent carbon atoms. Glycols are usually synthesized by the hydroxylation of alkenes, using peroxyacids, osmium tetroxide, or potassium permanganate (Section 8-14). 

A mixture of potassium permanganate and copper sulfate will oxidize sim de 1,4- and l,S-dioxidize selectively primary-secondary diols (21 equation 24) and (22 equation 2S) to the corresponding lactones. ... 

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