Selenium at higher oxidation state

Until recently, selenium derivatives at a higher oxidation state had found rather limited use in organic synthesis. The last ten years, however, have shown that these species are valuable reagents and intermediates which allo w clean and high-yielding transformations of a variety of functional groups even in very complex structures in a chemo- regio- and stereoselective man ner, under rather mild reaction conditions. A comprehensive review of the s ynthetic utility of these compounds is presented here with particular empha sis on the stereochemical aspects of their use as reagents.