Selenium compounds catalysts

Thiols add to alkenes under photochemical conditions to form thioethers, and the reaction can be done intramolecularly to give cyclic thioethers. Thiols also add to alkynes and with a palladium catalyst, vinyl sulfides can be formed. " Selenium compounds (RSeH) add in a similar manner. ... 

Nishibayashi Y, Uemura S (2000) Selenium Compounds as Ligands and Catalysts. 208 235-255... 

Urea complex with hydrogen peroxide (UHP) seems to be a very useful and convenient oxidation system in nonaqueous medium. The UHP reaction proceeds in methanol and is catalyzed by Mo (VI), W (VI) salts, or SeC>2 (83). Catalytic oxidation in a water-free medium can be carried out with alkylhydroxyperoxides, the catalysts being titanium alkoxides (84) or selenium compounds (85). The reaction appears to proceed quickly and with good selectivity. 

More examples are found for varied oxidation processes mainly for various epoxidations carried out by metal catalysts bearing F-modified ligands, such as porphyrins,139 Ru perfluoroacetylacetonate salt,140 or salen complexes,141 142 or using the 3 selenium compound as catalyst.143 The potential for enantioselective transformations offering an easy way to recover precious chiral reagents and catalysts was demonstrated in enantioselective epoxidation using fluorous chiral salen... 

In the Kjeldahl method, pulverized coal is boiled coal with concentrated sulfuric acid containing potassium sulfate and a suitable catalyst to reduce the time for digestion. The catalyst is usually a mercury salt, selenium itself, or a selenium compound, or a mixture of the two. Selenium is regarded as being particularly advantageous. 

ArCHO — ArOH. Aromatic aldehydes undergo Baeyer-Villiger reaction when treated with H202 (30%) in the presence of several selenium compounds as catalysts, of which areneseleninic acids are most effective. The resulting aryl formates are readily hydrolyzed to phenols. 

Chloriuatton of alkenes, Allylic chlorination is usually conducted by a free-radical reaction with NCS. Chlorination can be effected with catalysis by C6H5SeCl, in which case the main product is usually the rearranged allylic chloride. However, the formation of rearranged allylic chloride is sensitive to the structure of the alkenes and also to the particular selenium compound used as catalyst. See also N-phenylselenosuccinimide, this volume. 

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