1.2- Dioxane, manganese

The mixture is distilled until most of the ether has been removed and then refluxed for 8 hr. Ethyl acetate is added to decompose the excess reagent and concentrated aqueous sodium sulfate is then added until the precipitate begins to adhere to the sides of the flask. Finally ca. 100 g of solid sodium sulfate is added, the salts are removed by filtration and washed well with dioxane. Evaporation of the solvent gives a solid residue which is dissolved in 60 ml of chloroform and shaken with 3.5 g of manganese dioxide for 16 hr. Subsequently another 3.5 g of manganese dioxide is added and shaking continued for a further 16 hr. The solid is removed by filtration and washed well with hot chloroform. Evaporation of solvent and crystallization of the residue from acetone-hexane affords 0.51 g (72%) of 17a-hydroxy-17jff-ethylandrost-4-en-3-one mp 145-148°. 

Atkinson, G. Kor, S. K. (1965). The kinetics of ion association in manganese sulphate solutions. I. Results in water, dioxane-water mixtures, and methanol-water mixtures at 25 °C. Journal of Physical Chemistry, 69, 128-33. 

Manganese(lII) carboxylate complexes of nuelearity>5 are limited and are summarized in Table 10. The first hexanuclear complex, [Mn602(02CCMe3)i4] (109), was prepared from Mn(N03)3 and excess pivalic acid in dioxane. This neutral eomplex has an [Mn6(//4-0)2(/U3-02CCMe3)4-(/t-02CCMe3)6] core with both bridging and monodentate pivalates. All manganese centers have a distorted octahedral environment. 

Dihydroquinazolines 10 are readily oxidized to the corresponding quinazolines 9 with potassium hexacyanoferrate(III) in alkaline aqueous solution.Occasionally, a mixture of water and benzeneor water and dioxane is used as solvent. Oxidation can sometimes be carried out with manganese(IV) oxidein chloroform or benzene solution. Potassium permanganate is very seldom used for the oxidation of 3,4-dihydroquinazolines since oxidation of substituents can also take place [e.g., oxidation of 5,6-dimethoxy-4-methyl-3,4-dihy-droquinazolin-2(l//)-one with potassium permanganate in acetone for 96 hours at room temperature affords 5,6-dimethoxy-2-oxo-l,2-dihydroquinazoline-4-carboxylic acid in 50% yield and 5,6-dimethoxy-4-methylquinazolin-2(l//)-one in 5% yield]. 

A stirred solution of l-benzyl-5-hydroxymethylimidazole (0.79 g, 4.2 mmol) and activated manganese dioxide (3.6 g, 41 mmol) in dioxan (25 ml) is refluxed... 

Oxidation of oxygen functions. DDQ is useful for the selective oxidation of allylic " and benzylic alcohols. The reagent has the advantage of not showing the variability encountered with active manganese dioxide. It dehydrogenates 2-hydroxymethylene-3 ketosteroids in about 50% yield. The steroid is treated in dioxane solution at room temperature with 1.1 -1.5 equivalents of DDQ for 1 -5 min.. 

Abstract Synthesis of endoperoxides and hydroperoxides using tris(2,4-pentanedionato) manganese(IIl) or manganese(III) acetate is described. The reaction of various alkenes with tris(2,4-pentanedionato)manganese(lll) at ambient temperature in air gives 4-acetyl-l,2-dioxan-3-ols. The manganeseflll) acetate-catalyzed aerobic oxidation of various al-... 

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