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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 ...
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. The second step is a [2,3] sigmatropic reaction.
Oxidation of paraldehyde (acetaldehyde trimer) with SeO 2 gives glyoxal [9] and the oxidation of cyclohexanone gives 1,2-cyclohexanedione. [10] 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.
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.
Selenium forms two oxides: selenium dioxide (SeO 2) and selenium trioxide (SeO 3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen: [5] + It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase. It dissolves in water to form selenous acid, H 2 SeO 3.
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.
Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. Common production from the residue then begins by oxidation with sodium carbonate to produce selenium dioxide, which is mixed with water and acidified to form selenous acid (oxidation step).
Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids. [1] A variety of oxidants can be used.