Organoselenium Compounds as Catalysts in Nature and Laboratory

The importance of selenium as essential trace element is today generally recognized. The major biological form of this element is represented by the selenocysteine, incorporated into certain protein having redox motifs. Selenoenzymes are known to catalyze in nature the reduction of peroxides (gluthathione peroxidase) as well the selective deiodination of iodothyronine (iodothyronine deiodinase) and the reduction of dithiol-disulfides (thioredoxin reductase). A variety of organoselenium compounds have been proven to be useful for organic synthesis over several decades. Organoselenium species can be introduced as either nucleophiles or electrophiles to other organic molecules, producing useful intermediates for organic synthesis. Optically active organoselenium derivatives and their application to highly selective asymmetric synthesis are also of current interest. Probably the most interesting aspect, which emerged in recent years, concerns the possibility of effecting some functional group conversions using catalytic amounts of the electrophilic selenium reagent or using selenium containing compounds as chiral ligands in metal catalyzed reactions. The developments of all these catalytic processes probably represent the most important results which have been reported recently in this field. Their conceptual and synthetic relevance considerably increases the importance of organoselenium chemistry and are here reviewed.