Organoselenium Reagents Research Articles

Recent Advances in Organoselenium Catalysis.

Organoselenium chemistry has developed as an important tool in the field of synthetic and medicinal chemistry. Various organoselenium reagents have been developed and used successfully to achieve different organic transformations such as selenocyclizations, oxyselenenylations, selenoxide eliminations, etc. Additionally, organoselenium reagents' potential is not limited to their use as stoichiometric reagents, but they have been successfully used as organocatalysts in a number of synthetic transformations. Various organic and inorganic oxidants have been identified as terminal oxidants to regenerate the active catalytic species. In this review article, the recent progress of organoselenium reagents in catalysis is being highlighted along with their asymmetric variants.

Selenium-Based Fluorescence Probes for the Detection of Bioactive Molecules.

Chemistry of organoselenium reagents have now become an important tool of synthetic organic and medicinal chemistry. These reagents activate the olefinic double bonds and used to archive the number of organic transformations under mild reaction conditions. A number of organoselenium compounds have been identified as potent oxidants. Recently, various organoselenium species have been employed as chemical sensors for detecting toxic metals. Moreover, a number of selenium-based fluorescent probes have been developed for detecting harmful peroxides and ROS. In this review article, the synthesis of selenium-based fluorescent probes will be covered including their application in the detection of toxic metals and harmful peroxides including ROS.

Organoselenium-catalyzed enantioselective syn-dichlorination of unbiased alkenes

The enantioselective dichlorination of alkenes is a continuing challenge in organic synthesis owing to the limitations of selective and independent antarafacial delivery of both electrophilic chlorenium and nucleophilic chloride to an olefin. Development of a general method for the enantioselective dichlorination of isolated alkenes would allow access to a wide variety of polyhalogenated natural products. Accordingly, the enantioselective suprafacial dichlorination of alkenes catalyzed by electrophilic organoselenium reagents has been developed to address these limitations. The evaluation of twenty-three diselenides as precatalysts for enantioselective dichlorination is described, with a maximum e.r. of 76:24 Additionally, mechanistic studies suggest an unexpected Dynamic Kinetic Asymmetric Transformation (DyKAT) process may be operative.

Electrochemical Aminoselenation and Oxyselenation of Styrenes with Hydrogen Evolution.

The use of additive-free conditions is an ideal approach to prepare organoselenium reagents from readily available unsaturated substrates. Thus, we report the electro-induced aminoselenation and oxyselenation of styrenes without any acids or oxidants as additives. This transformation is compatible with various functional groups, which leads to vicinal difunctionalized organoselenium compounds. Our strategy improves the potential of this protocol for use in the pharmaceutical industry. Based upon the preliminary mechanism studies, we propose two possible pathways.

Selenium and Tellurium Electrophiles in Organic Synthesis

Abstract This chapter highlights the utility of electrophilic achiral and chiral organoselenium reagents in organic synthesis. A range of reactions from alkene functionalizations, the functionalization of aliphatic and aromatic C–H bonds using stoichiometric and catalytic approaches as well as rearrangement reactions are described. In addition, the utility of organotellurium reagents in organic synthesis is covered in this chapter.

Electrophilic Selenocyclofunctionalization in the Synthesis of Biologically Relevant Molecules

The cyclofunctionalization reactions promoted by electrophilic selenium species are undoubtedly very powerful methodologies in organic chemistry for the construction of different oxygen- and nitrogen-containing heterocycles. If alkene is bearing suitably oriented internal nucleophile, such as OH, COOH, NHR, a variety of heterocyclic compounds, such as ethers, lactones, pyrolidines, piperidines can be synthesized by the usage of this extremely useful synthetic protocol. In the last decade great progress had been done in the field of selenium promoted ring closure reactions by the means of selectivity, efficiency in asymmetric synthesis and simplicity of the procedure. Vast variety of heterocyclic products that can be prepared by this method, combined with its other advantages, has inspired its utilization in some total synthesis of naturally occurring compounds which have nitrogen or oxygen heterocycles as scaffolds in their structures. Our review is focused on broad possibilities of electrophilic selenocyclofunctionalization protocol as decisive and important stage in the total synthesis of biologically important molecules. Keywords: Organoselenium reagents, cyclization, total synthesis, bioactive compounds, oxygen heterocycles, nitrogen heterocycles.

Stereo- and Regioselective Synthesis of Cyclic Ethers by Means of Organoselenium- Mediated Cyclization of Unsaturated Alcohols

In the past several decades, significant progress has been made in the exploration of cyclofunctionalization reactions promoted by electrophilic organoselenium reagents. Numerous natural and biologically active products have been prepared by using this synthetic route. Increased research interest in this topic brings several relevant reviews, which cover wide scope of selenium-induced heterocyclizations. The reaction of electrophile selenium- induced cyclization of alkenes bearing suitable oriented hydroxyl group (termed selenoetherification) present useful tool for the preparation of different cyclic ethers units, which are the key structural units of many natural products. The coverage of this review will be limited to the examples of stereoselective and regioselective synthesis of five- and six-membered cyclic ethers by means of selenium-induced cyclization of unsaturated alcohols. The influence of some Lewis acids and bases, as additives, on regioselection of selenoetherification reaction will be also discussed. Keywords: Unsaturated alcohols, organoselenium reagents, cyclic ethers, cyclization, asymmetric synthesis, regioselective synthesis.

Developments in Synthetic Application of Selenium(IV) Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen-Transfer Agents.

A variety of selenium compounds were proven to be useful reagents and catalysts for organic synthesis over the past several decades. The most interesting aspect, which emerged in recent years, concerns application of hydroperoxide/selenium(IV) oxide and hydroperoxide/organoselenium catalyst systems, as “green reagents” for the oxidation of different organic functional groups. The topic of oxidations catalyzed by organoselenium derivatives has rapidly expanded in the last fifteen years This paper is devoted to the synthetic applications of the oxidation reactions mediated by selenium compounds such as selenium(IV) oxide, areneseleninic acids, their anhydrides, selenides, diselenides, benzisoselenazol-3(2H)-ones and other less often used other organoselenium compounds. All these compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2-dihydroxylation, and α-oxyfunctionalization of alkenes, as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl or active methylene groups into formyl groups, oxidation of carbonyl compounds into carboxylic acids and/or lactones, sulfides into sulfoxides, and secondary amines into nitrones and regeneration of parent carbonyl compounds from their azomethine derivatives. Other reactions such as dehydrogenation and aromatization, active carbon-carbon bond cleavage, oxidative amidation, bromolactonization and oxidation of bromide for subsequent reactions with alkenes are also successfully mediated by selenium (IV) oxide or organoselenium compounds. The oxidation mechanisms of ionic or free radical character depending on the substrate and oxidant are discussed. Coverage of the literature up to early 2015 is provided. Links have been made to reviews that summarize earlier literature and to the methods of preparation of organoselenium reagents and catalysts.

ChemInform Abstract: Stereoselective Reactions of Organoselenium Reagents Including Catalysis

AbstractReview: 254 refs.

Aryl(trimethylsilyl)selenides as Reagents for the Synthesis of Mono- and Diselenoesters

Silylated organoselenium reagents react under mild conditions with acid chlorides to provide a high yield route to aromatic selenoesters. The synthesis, structures, and spectroscopic properties of the selenoesters C6H5SeC(O)R (R = CH2CH3, 1; p-CH3C6H4, 2; p-C6Me4Br, 3; p-C6Me4C(O)SeC6H5, 4) and RC(O)SeFcSeC(O)R (Fc = Fe(C5H4)2; R = CH2CH3, 5; p-CH3C6H4, 6; p-BrC6Me4, 7) and RC(O)Se(C6H4)nSeC(O)R (n = 1, R = CH2CH3, 8a; n = 2, R = CH2CH3, 8b; n = 1, R = p-CH3C6H4, 9a; n = 2, R = p-CH3C6H4, 9b; n = 1, R = p-C6Me4Br, 10a; n = 2, R = p-C6Me4Br, 10b) and C6H5SeC(O)CH2CH2C(O)SeC6H511 are discussed. Although 11 can be prepared in high yield from the reaction of C6H5SeSiMe3 and ClC(O)CH2CH2C(O)Cl in tetrahydrofuran solvent, similar reactions in the absence of solvent led to the competitive formation of both 11 and (C6H5Se)3CCH2CH2C(O)OSiMe312. The new selenoesters have been characterized by multinuclear NMR (1H, 13C, 77Se), IR, and UV–vis spectroscopies, electrospray mass spectrometry, and, for complexes 2, 4, 7,...

“Green” Synthesis of Cadmium Selenide Nanocrystals: The Scope of 1,2,3-Selendiazoles in the Synthesis of Magic-Size Nanocrystals and Quantum Dots

A range of cadmium selenide nano-particles (the quantum dots (QDs), the magic-size nano-crystals (MSNCs) or the mixture of two) have been synthesized by the use of organoselenium reagents viz. 1,2,3-selenadiazole and metal salts in an appropriate choice of long chain fatty acids e.g., oleic acid with or without a solvent. These different types of nanocrystals can be easily obtained simply by variation in reaction temperature. The employed approach does not use any hazardous reagents and is typically non-aqueous and can be considered "green." The temperature at which the reaction is carried out along with the ratio of reactants and surfactant affect the nature of products and have led to understanding of some parameters affecting the formation of either "thermodynamic" or "kinetically" stabilized products. We have obtained sub-nanosized particles (magic-sized nanocrystals), zero-dimensional quantum dots and self-assembled structures by these methods. The materials have been studied by UV-Visible spectroscopy (UV-Vis), Photoluminescence spectroscopy (PL), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersion X-ray analysis (EDAX), and Transmission electron microscopy (TEM).

ChemInform Abstract: Efficient One-Pot Conversion of Carbonyl Compounds to Their α,β-Unsaturated Derivatives Using a Recoverable, Minimally Fluorous Organoselenium Reagent.

ChemInform Abstract: Efficient One-Pot Conversion of Carbonyl Compounds to Their α,β-Unsaturated Derivatives Using a Recoverable, Minimally Fluorous Organoselenium Reagent.

Organo-Selenium Induced Radical Ring-Opening Intramolecular Cyclization or Electrophilic Cyclization of 2- (Arylmethylene)cyclopropylaldehyde: A Tunable Synthesis of 1-Naphthaldehydes or 3-Oxabicyclo[3.1.0]hexan-2-ols

1-Naphthaldehydes and 3-oxabicyclo[3.1.0]hexan-2-ols can be prepared, respectively, by the intramolecular alkylation and cyclization of (E)-2-(arylmethylene)cyclopropylaldehyde 1 mediated by different organo-selenium reagents. The properties of selenium reagents may play an important role in the reactions. A rationale for these transformations is proposed.

Selenium promoted synthesis of enantiopure pyrrolidines starting from chiral aminoalcohols

Starting from commercially available enantiomerically pure aminoalcohols and using simple conversions promoted by organoselenium reagents, several enantiomerically pure substituted pyrrolidines were prepared. After double protections (R)- or (S)-2-phenylglycinols were converted into the β-amino selenides by displacing the tosyl group with phenyl selenolate anions. The phenylseleno group was then substituted by an allyl group by treatment with allyltributyltin and AIBN. The reaction of these allylic derivatives with electrophilic phenylselenium reagents afforded selenium containing pyrrolidines as the result of a 5-exo-trig cyclization. The pyrrolidine derivatives thus obtained were reductively deselenylated with triphenyltin hydride and AIBN. Moreover, the selenides were converted into the selenones, which easily gave substitution with different nucleophiles. Enantiopure 2,5-pyrrolidines containing azido, methylthio, cyano and iodo groups were thus obtained.

Solid-Phase Synthesis of β-Keto Sulfones

A novel method for the preparation of β-keto-sulfones through the use of organoselenium reagents in the solid phase by polystyrene-supported benzeneselenosulfonate or tolueneseleno­sulfonate with acetylenes has been developed.

Synthesis of Optically Pure 1,4‐Dioxanes from Alkenes Promoted by Organoselenium Reagents

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Enantioselective Synthesis of Heterocyclic Compounds Mediated by Organoselenium Reagents

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Enantioselective synthesis of heterocyclic compounds mediated by organoselenium reagents

The syntheses of several types of enantiopure or enantiomerically enriched heterocyclic compounds by electrophilic additions, nucleophilic substitutions and radical additions ring closure reactions, promoted by chiral non racemic as well as by achiral organoselenium reagents, are presented and discussed.

Asymmetric Syntheses Promoted by Organoselenium Reagents

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric Syntheses Promoted by Organoselenium Reagents

Using chiral nonracemic electrophilic-organoselenium-reagents-asymmetric alkoxy-, hydroxy-, azido- and amido-selenenylation of alkenes were effected with high diastereoselectivity. These reagents have also been employed in catalytic amounts to promote one-pot selenenylation-deselenenylation processes. The asymmetric cyclization of properly substituted alkenes diastereoselectively afforded lactons, tetrahydrofurans oxazolines, thiazolines, pyrrolidines, isoxazolidines, 1,2-oxazines, and cyclic nitrones. Enantiopure dioxane, morpholine, tetrahydrofuran, oxazolidin-2-one and aziridine derivatives were prepared from alkenes, PhSeX, and optically active nucleophiles or substrates.