Synthesis of enantiomerically enriched β-hydroxy selenides by catalytic asymmetric ring opening of meso-epoxides with (phenylseleno)silanes

The Chemistry of Selenosilanes: A Topic Overview

Selenium-containing molecules represent a valuable class of compounds with a variety of applications in chemical and biological fields. Selenated reagents are used as intermediates to introduce functional groups (e.g., double bonds) onto different substrates or in the synthesis of various selenated derivatives. Among the variety of selenium-containing reagents, silyl selenides are frequently used to transfer a selenated moiety due to the smooth functionalization of the Se-Si bond, which allows for the generation of selenium nucleophilic species under mild conditions. While the use of the analogous sulfur nucleophiles, namely silyl sulfides, has been widely explored, a relatively limited number of reports on selenosilanes have been provided. This contribution will focus on the application of selenosilanes as nucleophiles in a variety of organic transformations, as well as under radical and redox conditions. The use of silyl selenides to prepare metal complexes and as selenium precursors of materials for atomic layer deposition will also be discussed.

Selenium-Epoxy ‘Click’ Reaction and Se-Alkylation—Efficient Access to Organo-Selenium and Selenonium Compounds

This work establishes the ‘click’ nature of the base-catalyzed oxirane ring opening reaction by the selenolate nucleophile. The ‘click’-generated ß-hydroxy selenide can be alkylated to afford cationic selenium species. Hemolytic studies suggest that selenonium cations do not lyse red blood cells even at high concentrations. Overall, these results indicate the future applicability of the developed organo-selenium chemistry in the preparation of a new class of cationic materials based on the seleno-ether motif.

Asymmetric Ring-Opening of Epoxides Catalyzed by Metal–Salen Complexes

The asymmetric ring-opening of epoxides is an important reaction in organic synthesis, since it allows for the enantioselective installation of two vicinal functional groups with specific stereochemistry within one step from a highly available starting material. An effective class of catalysts for the asymmetric ring-opening of epoxides is metal–salen complexes. This review summarizes the development of metal–salen catalyzed enantioselective desymmetrization of meso-epoxides and kinetic resolution of epoxides with various nucleophiles, including the design and application of both homogeneous- and heterogeneous epoxide-opening catalysts as well as multi-metallic covalent and supramolecular catalytic systems.

Ring opening reactions of heterocycles with selenium and tellurium nucleophiles

An overview of the preparation and synthetic potentialities of functionalized organoselenium and organotellurium compounds is presented.

Electrophilic Cyclization Involving Carbon-Selenium/Carbon-Halide Bond Formation: Synthesis of 3-Substituted Selenophenes

The butylselanyl propargyl alcohols reacted with iodine to afford 3-iodoselenophenes. The change of nucleophile position from propargyl to homopropargyl was crucial for the aromatization and formation of selenophene rings. The experiments revealed that bromine and N-bromosuccinimide were not able to cyclize the butylselanyl propargyl alcohols; however, when the bromine source was copper(II) bromide the corresponding 3-bromoselenophenes were obtained in good yields. In addition, the reaction of butylselanyl propargyl alcohols with diorganyl diselenides catalyzed by copper(I) iodide gave the 3-(organoselanyl)selenophenes. The reaction took place with aromatic rings substituted by either electron-donating or -withdrawing groups in the alkynes and propargyl positions. The steric effects of substituents were dominant in determining the yields, whereas electronic effects had only a minor influence. Furthermore, by monitoring the reaction by ¹H NMR, we were able to identify the key intermediate, which supported the elaboration of a proposed reaction mechanism. The 3-iodoselenophenes prepared allowed the synthesis of multifunctional selenophenes via application in metal-catalyzed coupling reactions, such as Sonogashira, Ullmann and Suzuki type reactions.

Iodine-mediated regioselective 5-endo-dig electrophilic cyclization reaction of selenoenynes: synthesis of selenophene derivatives

Selenoenynes underwent electrophilic cyclization reactions with iodine in the presence of an appropriate nucleophile to give 3-iodo-selenophenes and 3-organoselenyl-selenophenes.

Mesoporous MgO·Al2O3 nanopowder-supported meso–macroporous nickel catalysts: a new path to high-performance biogas reforming for syngas

Mesoporous nanocrystalline MgO·Al₂O₃ powders with different MgO/Al2O3 molar ratios synthesized by a new and simple sol–gel route using C₃H₆O as a gelation agent exhibited high potential as support for nickel catalysts in biogas reforming.