Claudio Santi

Green chemistry with selenium reagents: development of efficient catalytic reactions.

Selenium goes green! Recent advances in organoselenium chemistry clearly demonstrate that selenium-based catalysts can be used conveniently in a series of functional group transformations. Organoselenium compounds are promising “green catalysts” as they can transfer oxygen from environmentally friendly oxidants such as H2O2.

“The green side of the moon: ecofriendly aspects of organoselenium chemistry”

Organoselenium chemistry has proven to be a powerful tool for organic synthesis over several decades. Nevertheless, the use of selenating reagents has often been limited by a generally bad reputation surrounding selenium toxicity and its potential impact on the environment. In this review we would like to stress some aspects that will encourage the reader to discover an unexpected “green side” to this element and the chemistry connected with its organic derivatives.

Preparation of a new chiral non-racemic sulfur-containing diselenide and applications in asymmetric synthesis.

The synthesis of the new chiral non-racemic sulfur-containing diselenide, di-2-methoxy-6-[(1S)-1-(methylthio)ethyl]phenyl diselenide, is described. When treated with ammonium persulfate this diselenide is transformed into the corresponding selenenyl sulfate, which acts as a strong electrophilic reagent and adds to alkenes, in the presence of methanol or water, to afford the products of selenomethoxylation or selenohydroxylation, respectively, with excellent diastereoselectivities. Starting from alkenes containing internal nucleophiles, asymmetric cyclofunctionalization reactions also resulted in good chemical yields, complete regioselectivities, and high diastereoselectivities. This sulfur-containing diselenide can also be used in catalytic amounts to promote one-pot selenenylation-deselenenylation processes, from which several types of products can be obtained in high yield and with good enantiomeric excess.

New nitrogen containing chiral diselenides: synthesis and asymmetric addition reactions to olefins

Abstract A simple synthesis of two new nitrogen containing diselenides, 7 and 8 , is described. These compounds were employed as starting materials to effect the asymmetric methoxyselenenylation, the hydroxyselenenylation as well as the cyclofunctionalization of olefins. Starting from 7 all these addition processes occurred with good facial selectivity. Poor results were however obtained with 8 . One-pot selenenylation–elimination sequences using catalytic amounts of the diselenide 7 have also been investigated.

Selenium Containing Compounds from Poison to Drug Candidates: A Review on the GPx-like Activity

Abstract : Oxidative stress results from the formation of reactive oxygen species (ROS) such as peroxides that cause dam-age to cell membranes and react with various biomolecules in mammalian cells. The selenoenzyme glutathione peroxidase (GPx) destroys peroxides by catalyzing their reduction to alcohols or water with the stoichiometric reductant glutathione. The effects of oxidative stress have been implicated in a variety of degenerative processes and disease states and for these reasons, there is considerable interest in the discovery of small molecule compounds that could reproduce a GPx-like ac-tivity. A review on the most recent acquisition in this area is here reported. Keywords: Selenium, selenoprots, glutathione, ROS, ebselen. INTRODUCTION For a long time selenium has been considered a poison. The first observation about the toxicity of this element dates back to 1285 when Marco Polo lost his horses crossing the Shanxi Province of Western China; this event was explained only after the discovery of selenium in 1817 by the Swedish chemist Jons Jacob Berzelius and it was ascribed to the high concentration of this element in forages growing in the re-gion that caused selenosis in livestock. Later, several studies confirmed the occurring of important disorders in animals [1, 2] and humans [3] due to selenium bioaccumulation and thereby a role in the genesis of cancer was postulated [4]. In the second half of the 20

Synthesis of non-racemic nitrogen-containing diselenides as efficient precursor catalysts in the diethylzinc addition to benzaldehyde

Abstract Short synthetic procedures for the preparation of new chiral, non-racemic nitrogen-containing diselenides are described. Only 1 mol% of these diselenides can very efficiently catalyze the diethylzinc addition to benzaldehydes affording the secondary alcohols in high enantiomeric purities (up to 97% ee ).

Efficient asymmetric selenomethoxylation and selenohydroxylation of alkenes with a new sulfur containing chiral diselenide

The synthesis of a new chiral non-racemic sulfur containing diselenide is described. The electrophilic selenium reagent, produced from this diselenide by treatment with bromine and silver triflate, has been used to effect the selenomethoxylation and the selenohydroxylation of alkenes. These addition reactions occurred with good chemical yield and with high diastereoselectivities.

Catalytic chalcogenylation under greener conditions: a solvent-free sulfur- and seleno-functionalization of olefins via I2/DMSO oxidant system.

Herein, we report a solvent- and metal-free methodology for the alkoxy-chalcogenylation of styrenes, using molecular iodine as a catalyst, DMSO as a stoichiometric oxidant, and different nucleophiles under microwave irradiation. This eco-friendly approach afforded the desired products in good to excellent yields in only 10 min. In addition, using the same protocol, we carried out the cyclization reaction of relevant molecules, such as lapachol derivatives.

A sulfur-containing diselenide as an efficient chiral reagent in asymmetric selenocyclization reactions

Abstract Treatment of the di-2-[(1 S )-1-(methylthio)ethyl]phenyl diselenide with bromine and silver triflate afforded the corresponding selenyl triflate which was used in situ as a strongly electrophilic selenium reagent to effect the asymmetric synthesis of oxygen- or nitrogen-containing heterocycles. Cyclic ethers, lactones, lactams or N -protected pyrrolidines have been prepared in good yield with complete regioselectivity and high diastereoselectivity.

On water preparation of phenylselenoesters

PhSeZn-halides react under “on water” mild conditions with acid chlorides to provide a high yield route to a variety of aromatic and aliphatic phenylselenoesters.