Selenium and Tellurium Complexes in Organic Synthesis

The chemistry of organoselenium compounds is currently recognized as an important field of research both in synthetic and medicinal chemistry. Organoselenium compounds are currently investigated for their potential biological activities but also as powerful reagents and/or intermediates in innovative chemical transformations, characterized by chemo-, regio- and stereoselectivity. After a brief overview of some recent developments in the field or electrophilic selenium reagents that are the most studied and applied reaction in organic synthesis, this chapter focuses on the preparation and reactivity of metal selenolates, unique organometallic selenium reagents that can be efficiently applied in organic synthesis. Among the different metals applied in selenolate chemistry, zinc is the most interesting. Zinc selenolates can be prepared in situ using a recyclable biphasic system or can be obtained as bench stable nucleophilic reagents. Among this latter class PhSeZnX reagents (X = halide, named as Santi's reagents) are nowadays commercially available and are characterized by a broad applicability and an unprecedented reactivity, often accelerated when used in water suspension. Several applications are highlighted and compared. Both in electrophilic and nucleophilic reactions of the analogous tellurium derivatives were more rarely investigated. These limited examples are reported and discussed with the selenium congeners.