Oxidation of Epoxides Oxiranes

The oxidative cleavage of epoxides with hydrogen peroxide gives vicinal hydroxy hydroperoxides [178]. With dimethyl sulfoxide in the presence of trifluoromethanesulfonic acid and diisopropylethylamine, epoxides are converted into a-hydroxy ketones [1014], and with periodic acid, dicarbonyl compounds are formed [761] (equations 343 and 344). 

Aldehydes are transformed into carboxylic acids by hydrogen peroxide and its derivatives. In the presence of selenium dioxide as a catalyst, acrolein is oxidized to acrylic acid in 90% yield on treatment with a 12% solution of hydrogen peroxide in tert-amyl alcohol at 40 C for 3 h [725]. Methacrolein is converted into methacrylic acid by 90% hydrogen peroxide in the presence of selenium dioxide at 60 °C [725] or by peroxysulfuric acid 200 (equation 346). 

Potassium peroxymonosulfate (2KHS05 KHS04 K2S04) oxidizes benzaldehyde in chloroform and dilute sulfuric acid to benzoic acid at room temperature within 2 days in a 70% yield [205]. 

The reagent of choice for the conversion of aldehydes into carboxylic acids is silver oxide, which is often prepared in situ from silver nitrate in alkaline medium [3(55]. Enanthol heated with silver oxide affords enanthoic acid [77]. 3-Cyclohexene-l-carboxaldehyde (1,2,3,6-tetrahydrobenzalde-hyde) gives a 62.5% yield of the carboxylic acid on treatment with silver nitrate and ethanolic potassium hydroxide at room temperature [3(55] (equation 347). 

Other examples of oxidations using silver oxide in alkaline media are variations of the preceding reaction [206, 362, 366, 367] (equation 348). 

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