Potassium permanganate, cyclic acetal

Potassium permanganate in acetic anhydride converts acyclic and larger cyclic rings into a-diketones. Thus cyclododecene is converted into the a-diketone (360) in 48% yield, with (361) and (362) as easily removable byproducts. ... 

They have also carried out the oxidation of selinene by means of ozone and potassium permanganate and have thus been able to establish that the regenerated selinene is not absolutely identical with the natural selinene. They are the first to record the existence of a hemi-cyclic-sesquiterpene this compound is termed pseudo-()3)-selinene. By passing a current of ozone into a solution of natural selinene (pseudo-( 8)-selinene). in acetic acid, there is obtained a diketone, CjjHogOj, which is purified by treatment with permanganate in acetone solution. Its properties are as. follows —... 

Although potassium permanganate does not oxidize acetals in aqueous media, with a phase-transfer catalyst under non-aqueous conditions, cyclic acetals are converted into hydroxyalkyl carboxylates [36]. 

To 5.69 g of this acetal in 410 ml of t-butanol and 11 ml of water was added a mixture of 5.80 g of potassium carbonate, 22,8 g of sodium periodate, and 270 mg of potassium permanganate in 1230 ml of water. The reaction mixture was stirred at 20-25°C for 20 hours and concentrated in vacuo to remove t-butanol. Ethylene glycole (0.5 ml) was added and reaction mixture extracted with 1 1 ether-benzene to remove neutral material. The aqueous layer acidified with solid sodium dihydrogen phosphate and extracted 4 times with 1 1 ethyl acetate-benzene. The organic layer was dried over sodium sulfate and evaporated to dryness in vacuo affording (+/-)-3-acetyl-2a-(2-carboxyethyl)-5-oxo-ip-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal as a mixture of the 3a and 3p isomers. 

Quinoxaline-2-carboxaldehyde has been converted into the 2-carboxylic acid by oxidation with potassium permanganate in acetone and reduced to the 2-hydroxymethyl compound by treatment with formalin and potassium hydroxide. It also undergoes other typical reactions of aromatic aldehydes such as benzoin formation on reaction with potassium cyanide - and condensation reactions with malonic acid and its diethyl ester and Schiff base formation. Acid-catalyzed reaction of quinoxaline-2-carboxaldehyde with ethylene glycol gives the cyclic acetal the diethylacetal has been prepared by reaction of 2-dibromomethylquinoxaline with sodium ethoxide. " An indirect preparation of the oxime 11 is achieved by treatment of 2-nitromethyl-quinoxaline (10) with diazomethane followed by thermolysis of the resulting nitronic ester. 

The Chemistry of Ringc.—The modification of ring c has centred on making available relays that are suitable for elaboration into more complex diterpenoids, the diterpenoid alkaloids, and triterpenoids. The unsaturated ketone (53) has proved to be a valuable relay for synthesis. It had been prepared previously from neoabietic acid, which is difficult to obtain pure. It has now been obtained from the levopimaric acid-formaldehyde adduct (50). Oxidation of the adduct with potassium permanganate not only formed the glycol but in an unusual step converted the cyclic ether into the (5-lactone (51). Dehydration, ozonolysis of the newly formed double bond, and then treatment of the keto-acetate (52) with chromous chloride afforded the a -unsaturated ketone (53). The last step involved hydrogenolysis, / -elimination. and decarboxylation. 

The reaction of dodecamethylcyclohexasilane with potassium permanganate, chromic oxide, and potassium dichromate in acetic acid gives a series of homologous cyclic siloxanes (20). Nitrobenzene and hydrogen peroxide (30%) in either formic acid or tcrt-butyl alcohol were found to be less effective oxidizing agents. 

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