Organoselenium Moieties Research Articles

Organosulfur and Organoselenium Functionalized Benzimidazo[1,2-a]quinolines: From Experimental and Theoretical Photophysics to All-Solution-Processed OLEDs.

In this study, we present the synthesis of benzimidazo[1,2-a] quinoline-based heterocycles bearing organosulfur and organoselenium moieties through transition-metal-free cascade reactions involving a sequential intermolecular aromatic nucleophilic substitution (SNAr). Both sulfur and selenium derivatives presented absorption maxima located around 355nm related to spin and symmetry allowing electronic 1π-π* transitions, and fluorescence emission at the violet-blue region (~440nm) with relatively large Stokes shift. The fluorescence quantum yields were slightly influenced by the chalcogen, with the sulfur derivatives presenting higher values than the selenium analogs. In this sense, the quantum yields for selenium derivatives can probably be affected by the intersystem crossing or even the photoinduced electron transfer process (PET). The compounds were successfully applied in all-solution-processed organic light-emitting diodes (OLEDs), where poly(9-vinylcarbazole) was employed as a dispersive matrix generating single-layer device cells. The obtained electroluminescence spectra are a sum of benzimidazo[1,2-a]quinolines and PVK singlet and/or triplet emissive states, according to their respective energy band gaps. The best diode rendered a luminance of 25.4cd⋅m-2 with CIE (0.17, 0.14) and current efficiency of 20.2 mcd⋅A-1, a fivefold improvement in comparison to the PVK device that was explained by a 50-fold increase of charge-carriers electrical mobility.

Relationships between Molecular Characteristics of Novel Organic Selenium Compounds and the Formation of Sulfur Compounds in Selenium Biofortified Kale Sprouts.

Due to problems with selenium deficiency in humans, the search for new organic molecules containing this element in plant biofortification process is highly required. Selenium organic esters evaluated in this study (E-NS-4, E-NS-17, E-NS-71, EDA-11, and EDA-117) are based mostly on benzoselenoate scaffolds, with some additional halogen atoms and various functional groups in the aliphatic side chain of different length, while one compound contains a phenylpiperazine moiety (WA-4b). In our previous study, the biofortification of kale sprouts with organoselenium compounds (at the concentrations of 15 mg/L in the culture fluid) strongly enhanced the synthesis of glucosinolates and isothiocyanates. Thus, the study aimed to discover the relationships between molecular characteristics of the organoselenium compounds used and the amount of sulfur phytochemicals in kale sprouts. The statistical partial least square model with eigenvalues equaled 3.98 and 1.03 for the first and second latent components, respectively, which explained 83.5% of variance in the predictive parameters, and 78.6% of response parameter variance was applied to reveal the existence of the correlation structure between molecular descriptors of selenium compounds as predictive parameters and biochemical features of studied sprouts as response parameters (correlation coefficients for parameters in PLS model in the range-0.521 ÷ 1.000). This study supported the conclusion that future biofortifiers composed of organic compounds should simultaneously contain nitryl groups, which may facilitate the production of plant-based sulfur compounds, as well as organoselenium moieties, which may influence the production of low molecular weight selenium metabolites. In the case of the new chemical compounds, environmental aspects should also be evaluated.

Selenium-functionalized cyclic ethers derived from natural terpenic alcohols – biological in vitro profile

Terpenic alcohols linalool, nerolidol and α-terpineol were subjected to the PhSe-induced cyclization, where corresponding cyclic ethers were obtained. The heterocyclic product derived from α-terpineol is a derivate of the natural product eucalyptol, while linalool cyclization produces precursors of the natural product karahanaenone. All three cyclic ether products have an organoselenium moiety in the side chain, which can represent a significant source of bioactivities. Biological evaluation of obtained products, in vitro cytotoxicity and redox status parameters, was performed on two model systems: HCT-116 – immortalized colon cancer cell line, and MRC-5 – healthy fibroblasts isolated from lung pleura. The results indicate a strong prooxidative character of all compounds on colon cancer HCT-116 and healthy MRC-5 cells in the highest applied concentrations. Selectivity towards cancer cells was not observed, except when nerolidol-derived product was used for longer exposure time. A biological evaluation was conducted to establish the quantitative relationship between enhanced radical species formation and cell viability.

A Review on the Role of Transition Metals in Selenylation Reactions.

Organoselenium chemistry has emerged as a distinctive area of research with tremendous utility in the synthesis of biologically and pharmaceutically active molecules. Significant synthetic approaches have been made for the construction of C-Se bonds, which are useful in other organic transformations. This review focuses on the versatility of transition metal-mediated selenylation reactions, providing insights into various synthetic pathways and mechanistic details. Furthermore, this review aims to offer a broad perspective for designing efficient and novel catalysts to incorporate organoselenium moiety into the inert C-H bonds.

Oxyselenocyclization of 2‐Allylphenols for the Synthesis of 2,3‐Dihydrobenzofuran Selenides

AbstractThe reaction between Oxone® and various di(hetero)aryl or alkyl diselenides enables the formation of an electrophilic selenium species in situ capable to induce the oxyselenocyclization of 2‐allylphenols. This versatile and safe protocol was explored to combine two privileged scaffolds into the structure of products: the 2,3‐dihydrobenzofuran core and an organoselenium moiety. Fifteen 2‐[(organoselanyl)methyl]‐2,3‐dihydrobenzofurans were produced, broadening considerably the number of known examples of this hybrid compound. Moreover, preparation of sulfur and tellurium 2,3‐dihydrobenzofurans derivatives was also successfully demonstrated.

Light-Mediated Seleno-Functionalization of Organic Molecules: Recent Advances.

Organoselenium compounds constitute an important class of substances with applications in the biological, medicinal and material sciences as well as in modern organic synthesis, attracting considerable attention from the scientific community. Therefore, the construction of the C-Se bond via facile, efficient and sustainable strategies to access complex scaffolds from simple substrates are an appealing and hot topic. Visible light can be regarded as an alternative source of energy and is associated with environmentally-friendly processes. Recently, the use of visible-light mediated seleno-functionalization has emerged as an ideal and powerful route to obtain high-value selenylated products, with diminished cost and waste. This approach, involving photo-excited substrates/catalyst and single-electron transfer (SET) between substrates in the presence of visible light has been successfully used in the versatile and direct insertion of organoselenium moieties in activated and unactivated C(sp3 )-H, C(sp2 )-H, C(sp)-H bonds as well as C-heteroatom bonds. In most cases, ease of operation and accessibility of the light source (LEDs or commercial CFL bulbs) makes this approach more attractive and sustainable than the traditional strategies.

Iron‐Mediated Cyclization of 1,3‐Diynyl Propargyl Aryl Ethers with Dibutyl Diselenide: Synthesis of Selenophene‐Fused Chromenes

AbstractThe synthesis of selenophene‐fused chromene derivatives starting from 1,3‐diynyl propargyl aryl ethers is reported herein. The method is based on carbon‐carbon, carbon‐selenium, selenium‐carbon and carbon‐selenium bonds formation in a one‐pot protocol, using iron(III) chloride and dibutyl diselenide as promoters. The same reaction conditions were applied to propargyl anilines leading to the formation of 1‐(butylselanyl)‐selenophene quinolines. The results showed that the dilution and temperature of substrate addition had a crucial influence in the products obtained. When the substrates were added at room temperature, in the absence of a solvent, a mixture of products was obtained, whereas the slowly addition (15 min) of starting materials, as a dichloromethane solution, at 0 °C led to the product formation in good yields. The mechanistic study indicates that the cooperative action between iron(III) chloride and dibutyl diselenide was essential to promote the cyclization, whereas separately none of them was effective in promoting the cyclization. We proved the synthetic utility of heterocycles obtained in the Suzuki cross coupling reaction, giving the corresponding cross‐coupled products in good yields. In addition, the organoselenium moiety was removed from the structures of products by using n‐butyllithium.magnified image

Safety profile of AZT derivatives: Organoselenium moieties confer different cytotoxic responses in fresh human erythrocytes during in vitro exposures

IntroductionThe incorporation of selenium in the structure of nucleosides is a promising strategy to develop novel therapeutic molecules. ObjectiveTo assess the toxic effects of three AZT derivatives containing organoselenium moieties on human erythrocytes. MethodologyFreshly human erythrocytes were acutely treated with AZT and selenium derivatives SZ1 (chlorophenylseleno), SZ2 (phenylseleno) and SZ3 (methylphenylseleno) at concentrations ranging from 10 to 500 μM. Afterwards, parameters related to membrane damage, redox dyshomeostasis and eryptosis were determined in the cells. ResultsThe effects of AZT and derivatives toward erythrocytes differed considerably. Overall, the SZ3 exhibited similar effect profiles to the prototypal AZT, without causing cytotoxicity. Contrary, the derivative SZ1 induced hemolysis and increased the membrane fragility of cells. Reactive species generation, lipid peroxidation and thiol depletion were also substantially increased in cells after exposure to SZ1. δ-ALA-D and Na+/K+-ATPase activities were inhibited by derivatives SZ1 and SZ2. Additionally, both derivatives caused eryptosis, promoting cell shrinkage and translocation of phosphatidylserine at the membrane surface. The size and granularity of erythrocytes were not modified by any compound. ConclusionThe insertion of either chlorophenylseleno or, in a certain way, phenylseleno moietes in the structure of AZT molecule was harmful to erythrocytes and this effect seems to involve a pro-oxidant activity. This was not true for the derivative encompassing methylphenylseleno portion, making it a promising candidate for pharmacological studies.

Straightforward synthesis and antioxidant studies of chalcogenoaziridines

Herein we reported the synthesis of chalcogenoaziridines through the introduction of the organoselenium moiety in the aziridine framework through the nucleophilic substitution of the OTs leaving group. In addition, the antioxidant activity, as reflected by free radical scavenging, was also evaluated. The new seleno aziridine 6a showed more effective antioxidant compared to other compounds. These findings also suggest that seleno aziridine 6a is a promising antioxidant and that its activity is not influenced by the presence of the substituents attached into the aromatic ring.

Synthesis of selenium-linked neoglycoconjugates and pseudodisaccharides

The introduction of organoselenium moieties within the structure of carbohydrates has received attention recently. Herein, we report on the synthesis of selenium-containing neoglycoconjugates and pseudodisaccharides by the reaction of nucleophilic selenium species, generated from sugar diselenides, with chiral N-Boc aziridines and sugar tosylates. The reaction proceeds with moderate to good yields for various substrates. The introduction of organoselenium moieties within the framework of various sugars, with increased levels of complexity, thus allowing the synthesis of disaccharide and glycoconjugate mimetics.

S-Nitrosothiol Detection via Amperometric Nitric Oxide Sensor with Surface Modified Hydrogel Layer Containing Immobilized Organoselenium Catalyst

A novel electrochemical device for the direct detection of S-nitrosothiol species (RSNO) is proposed by modifying an amperometric nitric oxide (NO) gas sensor with thin hydrogel layer containing an immobilized organoselenium catalyst. The diselenide, 3,3'-dipropionicdiselenide, is covalently coupled to primary amine groups in polyethylenimine (PEI), which is further cross-linked to form a hydrogel layer on a dialysis membrane support. Such a polymer film containing the organoselenium moiety is capable of decomposing S-nitrosothiols to generate NO(g) at the distal tip of the NO sensor. Under optimized conditions, various RSNOs (e.g., nitrosocysteine (CysNO), nitrosoglutathione (GSNO), etc.) are reversibly detected at </=0.1 microM levels, with sensor lifetimes of at least 10 days. The presence of reducing agents (e.g., glutathione) added to the test solution enhances the amperometric dynamic range output to approximately 25 microM levels of RSNO species. Sensitivities observed for different small molecule RSNO species are nearly equivalent, in sharp contrast to the behavior observed previously for a similar RSNO sensing configuration based on an immobilized Cu(I/II) catalytic layer. It is further shown that the new RSNO sensors can be used to assess the "NO-generating" ability of fresh blood samples by effectively detecting the total level of reactive low molecular-weight RSNO species present in such samples.

Conjugated Additions of Selenium Containing Enolates to Enones — Enantioselective Synthesis of δ‐Oxo‐α‐Seleno Esters and Their Facile Transformations.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Conjugated Additions of Selenium Containing Enolates to Enones – Enantioselective Synthesis of δ‐Oxo‐α‐Seleno Esters and Their Facile Transformations

AbstractTitanium enolates derived from methyl phenylselenoacetate and other acetates bearing a selenium containing chiral auxiliary have been employed to bring about 1,4‐addition reactions to enones. These reactions generate δ‐oxo‐α‐seleno esters in good yields and with excellent regio‐ and diastereoselectivities. The results obtained clearly indicate that the Lewis acids, employed to activate the starting enones towards addition, greatly influence reactivity as well as the stereochemical outcomes of these reactions. TiCl4 complexation resulted in particularly efficient promotion of the 1,4‐addition. Simple manipulations of the organoselenium moiety allowed some enantiomerically pure δ‐oxo‐α‐camphorseleno esters to be transformed into the corresponding δ‐oxo‐α‐hydroxy or δ‐oxo‐α‐allyl esters or into trisubstituted tetrahydrofurans. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Enantioselective Recognition of Aliphatic Amino Acids by β‐Cyclodextrin Derivatives Bearing Aromatic Organoselenium Moieties on the Primary or Secondary Side

AbstractSpectrophotometric titrations have been performed in order to determine the stability constants of inclusion complexation of some aliphatic amino acids with four structurally related organoselenium‐modified β‐cyclodextrins: mono(6‐phenylseleno‐6‐deoxy)‐β‐cyclodextrin (1a), mono[6‐(p‐methoxyphenylseleno)‐6‐deoxy]‐β‐cyclodextrin (1b), mono(2‐phenylseleno‐2‐deoxy)‐β‐cyclodextrin (2a), and mono[2‐(p‐methoxyphenylseleno)‐2‐deoxy]‐β‐cyclodextrin (2b). Conformation analysis by circular dichroism and 2D NMR spectroscopic studies revealed that the aryl‐substituted β‐cyclodextrins gave self‐inclusion intramolecular complexes in aqueous solution, while the extent of penetration depended both on the positions and on the structures of substituents. Quantitative investigation on the binding ability of the hosts with amino acids showed that they were able to recognize the size and the shape of guests, affording supramolecular complexes with quite small stability constants ranging from 24 to 355 M−1. The molecular recognition abilities are discussed from the viewpoints of induced‐fitting mechanisms, geometric complementary, and cooperative binding processes. Furthermore, these β‐cyclodextrin derivatives displayed considerable enantioselectivity towards L/D‐amino acid isomers, giving the highest L‐enantioselectivity (up to 8.4) for inclusion complexation between leucine and 2a. The binding modes of L/D‐leucine with 1b were elucidated from NOESY studies and the chiral recognition phenomena were interpreted accordingly. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

ChemInform Abstract: REACTIONS OF ENOLATES WITH VINYL SELENOXIDES AND VINYL SELENONES. ONE‐STEP SYNTHESIS OF CYCLOPROPYLCARBONYL COMPOUNDS

AbstractDie aus Carbonylverbindungen (I) gebildeten Enolatanionen reagieren mit entsprechenden Vinylselenoxiden (II) (durch einen prim. konjugierten Additions‐ und nachfolgenden Substitutionsprozeß; Diskussion des Mechanismus) unter Bildung der Titelverbindungen (IV) [analoge Darstellung von (V)‐(VII)].

Reactions of Enolates with Vinyl Selenoxides and Vinyl Selenones. One-step Synthesis of Cyclopropylcarbonyl Compounds

Abstract In the reactions with enolate anions, organoselenium moieties of aryl vinyl selenoxides and selenones have exhibited two important roles, e.g., activation of C=C bonds for conjugate addition reaction and behaviors as excellent leaving groups. Owing to such characteristic features, ketone enolates react with p-chlorophenyl vinyl selenoxide to afford the corresponding cyclopropyl ketones through an initial conjugate addition followed by substitution processes. On the other hand, use of vinyl selenones usually gives much better results with anionic species of active methylene compounds. Vinyl selenones bearing hydroxyl, ketone, and ester groups can also be employed equally well for this type of transformation.

Chemical characterization of the selenoprotein component of clostridial glycine reductase: identification of selenocysteine as the organoselenium moiety.

A small, heat-stable selenoprotein, one of the components of the glycine reductase complex, was labeled with 75Se by growth of Clostridium sticklandii in the presence of Na2 75SeO3. The selenium-containing moiety, which is essential for the biological activity of the protein, was shown to be a selenocysteine residue. It was isolated as its Se-carboxymethyl, Se-carboxyethyl, and Se-aminoethyl derivatives from digests of the pure 75Se-labeled protein that had been reduced and treated with the various alkylating agents prior to hydrolysis. In each instance the 75Se-labeled moiety obtained from an alkylated protein sample and the corresponding alkyl derivative of authentic selenocysteine were indistinguishable. Several studies of the native selenoprotein detected a chromophore (UVmax 238nm) that appeared upon reduction of the protein with KBH4 and rapidly disappeared upon exposure to oxygen. This oxygen-labile chromophore is thought to be the ionized -SeH group of the selenocysteine residue.