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The Riley oxidation is a selenium dioxide-mediated oxidation of methylene groups adjacent to carbonyls. It was first reported by Harry Lister Riley and co-workers in 1932. [ 1 ] In the decade that ensued, selenium -mediated oxidation rapidly expanded in use, and in 1939, Andre Guillemonat and co-workers disclosed the selenium dioxide-mediated ...
The selenium starting material is reduced to selenium, and precipitates as a red amorphous solid which can easily be filtered off. [10] This type of reaction is called a Riley oxidation. It is also renowned as a reagent for allylic oxidation, [11] a reaction that entails the following conversion Allylic oxidation. This can be described more ...
Specifically, SeO 2 will convert an allylic methylene group into the corresponding alcohol. A number of other reagents bring about this reaction. Scheme 1. Selenium dioxide oxidation. In terms of reaction mechanism, SeO 2 and the allylic substrate react via pericyclic process beginning with an ene reaction that activates the C−H bond.
Selenium disulfide has been used in shampoo as an antidandruff agent, an inhibitor in polymer chemistry, a glass dye, and a reducing agent in fireworks. [6] Selenium trioxide may be synthesized by dehydrating selenic acid, H 2 SeO 4, which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide: [8]
The conversion of valencene to nootkatone is an example of allylic oxidation. In the synthesis of some fine chemicals, selenium dioxide is used to convert alkenes to allylic alcohols: [15] R 2 C=CR'-CHR" 2 + [O] → R 2 C=CR'-C(OH)R" 2. where R, R', R" may be alkyl or aryl substituents.
Allyl alcohols in general are prepared by allylic oxidation of allyl compounds, using selenium dioxide or organic peroxides. Other methods include carbon-carbon bond-forming reactions such as the Prins reaction, the Morita-Baylis-Hillman reaction, or a variant of the Ramberg-Bäcklund reaction. Hydrogenation of enones is another route.
The Kharasch–Sosnovsky reaction is a method that involves using a copper or cobalt salt as a catalyst to oxidize olefins at the allylic position, subsequently condensing a peroxy ester (e.g. tert-Butyl peroxybenzoate) or a peroxide resulting in the formation of allylic benzoates or alcohols via radical oxidation. [1]
Selenium oxide may refer to either of the following compounds: Selenium dioxide, SeO 2; Selenium trioxide, SeO 3; Diselenium pentoxide, Se 2 O 5