Electrophilic Selenium/Tellurium Reagents: Reactivity and their Contribution to Green Chemistry

Abstract

Selenium moieties are conveniently introduced into an organic molecule using electrophilic selenenylating reagents and the process is generally highly chemo‐, regio and stereoselective requiring mild experimental conditions. In addition, organoselenium derivatives can be directly converted into a number of different functional groups and the organoselenium moiety can be employed for further stereoselective manipulation of the molecule. Several applications are described for the inter‐ and intramolecular carbon–oxygen, carbon–nitrogen and carbon–carbon bond formation as well as for the α‐functionalization of carbonyl derivatives and the nucleophilic aromatic substitution reactions. More recently, the development of simple and efficient procedures for the preparation of chiral selenium reagents allowed their successful application in electrophilic asymmetric synthesis. Nowadays, probably the most recent aspect of this kind of chemistry is correlated with some new reactions that can be effected using organoselenium compounds as catalysts in renewable or alternative non‐toxic media (water, glycerol, ionic liquids) bringing this kind of research in line with the concept of ‘Green and Sustainable Chemistry’. During the last half century, the application of tellurium reagents has undergone a notable improvement, overcoming the reluctance of several researchers mainly due to the characteristic persistent smell of many tellurium derivatives. In this chapter some general aspects of the chemistry promoted by electrophilic selenium and tellurium compounds are described exploiting also the differences between these two reagents.

Iron(III) Chloride and Diorganyl Diselenide‐Promoted Nucleophilic Closures of 1‐Benzyl‐2‐alkynylbenzenes in the Preparation of 9‐(Organoselanyl)‐5H‐benzo[7]annulenes

“…T his last product probably arises from the electrophilic addition of phenylselenyl chloride to the carbon-carbon triple bond. [22] When at rimethylsilyl group was introduced at the carbon-carbon triple bondo ft he 1-benzyl-2-alkynylbenzene 1z,t he 2-chlorovinyl selenide 7 product was still formed anda ny amount of cyclized product was obtained [Scheme 4, Eq. (4)].…”

Enantioselective Selenocyclization via Dynamic Kinetic Resolution of Seleniranium Ions by Hydrogen-Bond Donor Catalysts

“…Selenofunctionalization of alkenes proceeds via reaction of a π system with an electrophilic selenium source to generate a seleniranium ion, followed by nucleophilic ring opening. 3 The resulting selenide product can be elaborated in a variety of synthetically useful transformations including oxidative elimination and radical substitution reactions. However, the development of catalytic, enantioselective variants of the selenofunctionalization reaction remains a challenge that is largely unmet.…”

Ultrasound‐Promoted Radical Synthesis of 5‐Methylselanyl‐4,5‐dihydroisoxazoles

“…[5] Another important class of compounds are the organoselenium ones, which are used both as intermediate in organic synthesis and in drug discovery. [6] There are several methods to introduce selenium into organic molecules, which include the use of nucleophilic, [7] electrophilic [8] and radical Se-centered reagents. [9] Among the methodologies described to prepare isoxazole derivatives, the 1,3-dipolar cycloaddition of alkenes and oximes (Scheme 1a) [10] or oxime chlorides (Scheme 1b) are the most atom-efficient.…”

“…Another important class of compounds are the organoselenium ones, which are used both as intermediate in organic synthesis and in drug discovery . There are several methods to introduce selenium into organic molecules, which include the use of nucleophilic, electrophilic and radical Se‐centered reagents …”