Potassium permanganate, cyclic acetal oxidation

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]. 

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 —... 

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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