Oxygenated and reduced selenium and tellurium compounds, particularly thoese of practical importance have been extensively investigated especially during the last few decades. Selenium(IV) oxide, selenoxides, selenones, seleninic and peroxyseleninic acids, selenenamides and seleninamides are involved in oxyfunctionalization of unsaturated hydrocarbons, their derivatives, alkylarenes, sulfides and amines, carbon‐oxygen and carbon‐carbon bond cleavage, ring closure and ring transformations,
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‐elimination, sigmatropic [2,3]‐rearrangement and other, chemo‐ regio‐ and stereocontrolled reactions. The chemistry of oxygenated tellurium compounds has been less extensively explored than their selenium counterparts;, nevertheless some of them have been successfully used for oxyfunctionalization of different groups of organic compounds while telluroxide elimination has gained more attention in the last years becoming a well‐established method for the synthesis of olefins. Hydrogen selenide and telluride, alkali selenides and tellurides, selenoles and telluroles are the most common reduced derivative of these elements. Their properties are expressed in many reactions such as reduction and deoxygenation of different groups of organic compounds alkenes, alkynes, ethers, carbonyl compounds, esters, lactones, oxiranes, nitrogen, sulfur and halogen compounds, as well as dealkylation of tertiary amines. The method for preparation of the different oxygenated and reduced selenium and tellurium compounds are described, their reactions are reviewed, their usefulness in synthesis is indicated and more representative mechanisms are discussed.
