Other Reactions Halogenation and Oxidation of a-H

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117). Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, P-unsaturated carbonyl compounds in aqueous acetic acid. Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid. Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

Protonic acid and Lewis acids can activate carbonyls to facilitate the addition of nucleophile attacks in aqueous media. The Prins reaction, reaction with alkyne, and Friedel-Crafts-type reactions have been discussed in related chapters in detail. 

Rico-Lattes, I., Schmitzer, A., Perez, E., Lattes, A., Chirality 2001, 13, 24. 

Meziane, S., Lanteri, P., Longeray, R., Amaud, C., Compt Rend. TAcad. Sci. Serie He Chim. 1998, i, 91. 

For a recent review on the reaction of a-hydroxy hydroperoxide, see Ganeshpure, P. A., Adam, W., Synthesis 1996, 179. 

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