Selenium Heterocycles Research Articles

Selenium‐Based Nonfused Electron Acceptors for Efficient Organic Photovoltaic Cells

Selenium heterocycles are widely used in constructing organic semiconductors due to their advantages in narrowing the bandgap and enhancing the intermolecular packing. Herein, the application of Se substitution in designing nonfused electron acceptors (nfEAs) is studied. From a thiophene analog (A4T‐16), three nfEAs with two (ASe‐1 and ASe‐2) or four (ASe‐3) selenophene units are synthesized. The results suggest that the incorporation of Se atoms will downshift the lowest unoccupied molecular orbit level, upshift the highest occupied molecular orbit level, and exhibit redshifted absorption spectra due to the enhanced quinoidal character. The crystallographic data indicate that Se‐containing molecules exhibit more planar conjugate skeleton and thus lead to the improvement of carrier mobility. When blended with a polymer donor PBDB‐TF, ASe‐1‐, ASe‐2‐, and ASe‐3‐based organic photovoltaic (OPV) cells obtain power conversion efficiencies of 12.7%, 11.0%, and 10.4%, respectively. This work provides a comprehensive study of the application of Se substitution in designing low bandgap nfEAs for efficient OPV cells.

Synthesis and Characterization of Some New Heterocyclic Selenium Derivatives of 3,5-Naphtho–1-Seleoncyclohexane

A new series of heterocyclic derivatives from 3,5–naphtho-1- selenocyclohexane have been prepared (C12 H10 SeX; X=CL Br, I) and C12H10 SeRX; R=CH3; X=I)
 The new compounds were characterized by elemental analysis, IR, H1NMR and molar conductance. Conductivity measurements of these compounds in DMSO solution indicated that they behave as week electrolytes 

A near-infrared acceptor incorporating selenium heterocycles for efficient semi-transparent photovoltaics and sensitive photodetectors

Near infrared (NIR) acceptors are the key components for the construction of efficient organic photovoltaics (OPVs) and organic photodetectors (OPDs). Herein, a near-infrared acceptor named 6TSe-OFIC incorporating selenium heterocycles has been designed, which shows an absorption onset around 1000 nm with a low optical bandgap of 1.29 eV. OPV device based on PCE10: 6TSe-OFIC demonstrates a power conversion efficiency (PCE) of 13.18% with a high and broad EQE response. The semi-transparent OPV device based on PCE10: 6TSe-OFIC shows a PCE of 10.06% with AVT 20%. With the same active layer, the OPD devices achieve the responsivities of 0.54 A W −1 at ∼850 nm. The results highlight the opportunities to careful design of the NIR molecules for efficient OPVs and OPDs. • A NIR acceptor 6TSe-OFIC incorporating Se in the molecular backbone has designed. • The semi-transparent device of PCE10:6TSe-OFIC achieves a PCE of 10.06% with an AVT over 20% and an outstanding CRI of 91. • The self-powered OPD device of PCE10:6TSe-OFIC demonstrates the responsivities of 0.54 A W −1 at ∼850 nm and a D* of over 10 12 jones from 400 to 960 nm. • The design idea can be a useful guideline for developing high efficiency semi-transparent OPV and sensitive OPD.

Triple-Click Chemistry of Selenium Dihalides: Catalytic Regioselective and Highly Efficient Synthesis of Bis-1,2,3-Triazole Derivatives of 9-Selenabicyclo[3.3.1]nonane

The catalytic regioselective and highly efficient synthesis of bis-1,2,3-triazole derivatives of 9-selenabicyclo[3.3.1]nonane was developed. The 1,3-dipolar cycloaddition reaction of 2,6-diazido-9-selenabicyclo[3.3.1]nonane with a variety of terminal acetylenes catalyzed by a copper acetate/sodium ascorbate system proceeded in a regioselective fashion, affording 2,6-bis(4-organyl-1,2,3-triazole)-9-selenabicyclo[3.3.1]nonanes in high yields (93–98%). The reaction of 2,6-diazido-9-selenabicyclo[3.3.1]nonane with dimethyl and diethyl acetylenedicarboxylates was carried out as thermal 1,3-dipolar Huisgen cycloaddition giving the corresponding 4,5-disubstituted 1,2,3-triazole derivatives of 9-selenabicyclo[3.3.1]nonane in high yields. The obtained products are potentially bioactive compounds and first representatives of selenium heterocycles combined with two 1,2,3-triazole moieties. 2.6-Diazido-9-selenabicyclo[3.3.1]nonane was obtained in quantitative yield via the reaction of sodium azide with 2,6-dibromo-9-selenabicyclo[3.3.1]nonane at room temperature. The latter compound was synthesized by stereoselective transannular addition of selenium dibromide to cis, cis-1,5-cyclooctadiene.

Using fluoroform for constructing aromatic and heterocyclic trifluoromethylselenyl compounds

Fluoroform is used to prepare CuCF3 according to literature procedures. This nucleophilic trifluoromethyl moiety was reacted with aromatic and heterocyclic selenium cyanide derivatives to form the corresponding trifluoromethylselenium compounds. Selenium cyanides were made with 1,3-dicyanotriselenide prepared in situ from malononitrile and selenium dioxide. The electrophilicity of the reagent (δ+SeCN) was enough to attack aniline derivatives at the para position, but with other aromatics it was advantageous to use the corresponding boronic acid as the moiety was easily displaced by the selenium cyanate moiety.

Serendipitous Formation of Various Selenium Heterocycles Hidden in the Classical Synthesis of Selenophene.

Synthesis of complex di(selenophen-3-yl)diselenides and 3-methylene-3H-1,2-diselenoles directly from 1-bromobutadiynes is described. The transformation is performed under conditions used before for the synthesis of simple selenophenes from butadiynes. The reaction is operationally straightforward, and complex products were obtained in high yields. Structures of the final products were unambiguously confirmed by the means of 77Se NMR and single-crystal X-ray diffraction.

Diorganyl diselenides: a powerful tool for the construction of selenium containing scaffolds.

Organoselenium compounds find versatile applications in organic synthesis, materials synthesis, and ligand chemistry. Organoselenium heterocycles are widely studied agents with diverse applications in various biological processes. This review highlights the recent progress in the synthesis of selenium heterocycles using diorganyl diselenides with keen attention on green synthetic approaches, scopes, C-H selanylation, the mechanisms of different reactions and insights into the formation of metal complexes. The C-H selanylation using diorganyl diselenides with different catalysts, bases, transition metals, iodine salts, NIS, hypervalent iodine, and other reagents is summarised. Finally, the diverse binding modes of bis(2/4-pyridyl)diselenide with different metal complexes are also summarised.

Novel Five- and Six-Membered Rings of Phosphorus-Selenium Heterocycles from Selenation of Amido-Schiff Bases.

Woollins’ reagent, [2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide], serving as a selenating-reductive cycloaddition reagent, reacts with nonconjugated amido-Schiff bases to give the corresponding six-membered 1,3,4-selenadiazoles via a ring-expansion accompanied by an additional selenation/cyclization to the imine bond and C=O group; meanwhile, under the same reaction conditions, the selenation of conjugated amido-Schiff bases leads to a series of fused heterocycles with two five-membered rings. Eight single-crystal X-ray structures confirming the formation of these five- and six-membered heterocycles are discussed.

A novel methodology for the synthesis of condensed selenium heterocycles based on the annulation and annulation–methoxylation reactions of selenium dihalides

A novel methodology for accelerating the annulation was developed based on the reactions of selenium dihalides in the presence of alcohols.

Synthetic Aspects and First-time Assessment of 2-amino-1,3-selenazoles Against Mycobacterium tuberculosis

Background: 2-aminoselenazoles became an important core in medicinal chemistry after the discovery of Ebselen and Ethaselen. Therefore, many researchers have reported the synthesis of small selenazole intermediates via Hantzsch cyclization using a wide array of methodologies andcatalysts. Methods: In this work, we investigated the formation of 2-aminoselenazoles on various organic solvents and in water, under catalyst-free conditions. Moreover, these molecules and their 2-aminothiazoles analogues were assessed in vitro for their antitubercular activity against Mycobacterium tuberculosis and the results compared. Results: Instant reactions were observed when using polar aprotic solvents and all selenazoles were synthesized in water using sonochemistry. Furthermore, two selenazoles and one thiazole displayed activity in the μM range and the selenium heterocycles seems to be more potent than their sulphur analogues. Conclusion: This is the first study of selenazoles against M. tuberculosis. It is noteworthy that 2-amino-1,3-selenazoles are interesting synthetic intermediates that could be incorporated into novel prototypes against tuberculosis.

Unique electrochemical behavior of heterocyclic selenium–sulfur cathode materials in ether-based electrolytes for rechargeable lithium batteries

Mixed chalcogenide systems represent a new class of promising cathode materials for high performance rechargeable lithium batteries. Among them, heterocyclic selenium–sulfur (SexSy) cathodes, coupling the good conductivity of Se and high capacity of S, have attracted great attention in recent years. However, further research is still needed to better understand the lithiation/delithiation process of SexSy cathodes in ether-based electrolytes. Herein, SexSy-based composites with covalent Se–S bonds were prepared by infiltrating various proportions of S and Se powders into the mesoporous carbon microsphere (MCM) host at 500°C in vacuum. As cathodes for rechargeable lithium batteries, SexSy/MCM composites exhibit unique electrochemical behavior rather than a simple hybrid of Li–S and Li–Se batteries in ether-based electrolytes. The Se–S bonds in SexSy/MCM could anchor S during cycling, and effectively reduce the formation of long-chain polysulfides. As a result, the SexSy/MCM cathodes demonstrate superior overall electrochemical performance than Se/MCM or S/MCM. Moreover, Se/S ratio could also affect the electrochemical behavior of SexSy/MCM composites. The optimal Se2S5/MCM cathode delivers the best performance with a high reversible capacity of 796.4mAhg−1 at 0.5C over 100 cycles, and good rate capability of 688.8mAhg−1 at 5C. Especially, a superior coulombic efficiency of ~100% is achieved without addition of LiNO3. This work could help us to better understand the inherent synergistic mechanism behind SexSy cathodes for high performance rechargeable lithium batteries in ether-based electrolytes.

Old Selenium Heterocycles Revisited: Synthesis, Spectroscopic, and Structural Characterization ofN‐Acyl‐1,3‐selenazol‐2(3H)‐imines and 5‐Acyl‐1,3‐selenazol‐2‐amines from Acylselenourea Derivatives

A series of five‐membered selenium heterocycles was prepared from the reaction of various selenoureas and phenacyl bromides. In the case of 1‐acyl‐3‐arylselenoureasN‐acyl‐1,3‐selenazol‐2(3H)‐imines are formed, whereas the analogous reaction with 3,3‐disubstituted 1‐acylselenoureas affords 5‐acyl‐1,3‐selenazol‐2‐amines. The compounds were characterized by NMR spectroscopy and mass spectrometry. In addition, the proposed structures were unambiguously confirmed by X‐ray diffraction studies.

Full four‐component relativistic calculations of the one‐bond 77Se–13C spin‐spin coupling constants in the series of selenium heterocycles and their parent open‐chain selenides

Four-component relativistic calculations of (77)Se-(13)C spin-spin coupling constants have been performed in the series of selenium heterocycles and their parent open-chain selenides. It has been found that relativistic effects play an essential role in the selenium-carbon coupling mechanism and could result in a contribution of as much as 15-25% of the total values of the one-bond selenium-carbon spin-spin coupling constants. In the overall contribution of the relativistic effects to the total values of (1)J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin-orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second-order polarization propagator approach (CC2) with the four-component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of (1)J(Se,C). Solvent effects in the values of (1)J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2-78.4) are next to negligible decreasing negative (1)J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of (77)Se-(13)C spin-spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1-0.2-Hz loss of accuracy.

Recent Advances in the Synthesis of Iodoheterocycles via Iodocyclization of Functionalized Alkynes

Iodocyclization reactions are acquiring an increasing importance in organic synthesis, in view of the possibility to obtain iodine- containing heterocycles starting from readily available acyclic substrates under mild reaction conditions. Various aspects of these iodocyclization reactions have been recently reviewed, including the application of iodocyclization processes to the synthesis of natural products, heterocyclic derivatives, and carbocyclic derivatives, as well as the construction of heterocyclic libraries. The present mini-review is intended to highlight some very recent (from 2010 to the beginning of 2013) and particularly interesting examples of the synthesis of heterocyclic derivatives by the iodoheterocyclization of functionalized alkynes. The iodoheterocyclization of acetylenic substrates bearing a suitably placed nucleophilic group is a powerful method for the direct synthesis of unsaturated iodinecontaining heterocycles. The products obtained can be further elaborated through various cross-coupling reactions (such as Heck, Suzuki- Miyaura, and Sonogashira reactions), making the process of particular synthetic interest. Moreover, the iodocyclization reaction is carried out under very mild reaction conditions (generally room temperature), using a simple source of electrophilic iodine, such as I2, ICl, or NIS (N-iodo-succinimide), usually in the presence of a base to help buffer the acid produced by deprotonation of the nucleophilic functional group present in the substrate. The mini-review is divided into three parts: Synthesis of iodine-containing oxygen heterocycles; Synthesis of iodine-containing nitrogen heterocycles; and Synthesis of iodine-containing sulfur and selenium heterocycles. The examples shown in the mini-review demonstrate that the iodoheterocyclization of functionalized alkynes is a wide-scope synthetic methodology, which can also be useful for the synthesis of biologically active molecules and complex natural products.

Synthesis and Reactions of 1,3,4-Selenadiazines

Various 1,3,4-selenadiazines were prepared by cyclization of selenosemicarbazides with phenacyl bromides. The compounds generally exist in their 6H-tautomeric form and contain an exocyclic imino group in the solid state. 1,3,4-4H-Selenadiazines, available from 1,2-dimethylated selenosemicarbazides, cannot be isolated because they rapidly undergo a deselenation reaction under the conditions of their formation. Deselenation can be induced for 1,3,4-6H-selenadiazines under forcing conditions by reflux of a solution in glacial acetic acid. On the other hand, a ring contraction is observed when concentrated HCl or HBr is used. INTRODUCTION Selenium represents an essential element for higher organisms and selenium containing enzymes, such as Glutathioneperoxidase and 5’-Deiodase type 1, play an important role in the organism. Selenium containing molecules, such as the antitumor and antiviral C-glycosyl selenazole selenazofurin, are of considerable pharmacological importance because selenium deficiency can result in a number of diseases. However, selenium heterocycles are mostly less stable as compared to their sulfur analogues. In HETEROCYCLES, Vol. 88, No. 2, 2014 1397

ChemInform Abstract: Organo Phosphorus—Selenium Heterocycles Derived from Haloalkanols and Alkenes.

AbstractFive‐ or six‐membered heterocycles are synthesized by treatment of bromoalkanones or alkenes with Woollin′s reagent (I).

Organo Phosphorus–Selenium Heterocycles Derived from Haloalkanols and Alkenes

Treating Woollins’ reagent with an equimolar amount of sodium 2-bromoalkanolates (which were prepared in situ from the reaction of bromoalkanol and NaH) in THF gave five- or six-membered PSeOC n (n = 2 or 3) phosphorus–selenium heterocycles 3 and 4 in good yields. Woollins’ reagent reacting with one equivalent of conjugated 1,3-dienes led to the formation of different end products: with 1,4-diphenylbuta-1,3-diene giving a five-membered 2,3,5-triphenyl-4-styryl-1,2,5-selenadiphospholane 2,5-diselenide; however, with 2,3-dibenzyl-1,3-butadiene affording 4,5-dibenzyl-2-phenyl-3,6-dihydro- 2H -1,2-selenaphosphinine 2-selenide as a major isolable product. Refluxing Woollins’ reagent with one equivalent of unconjugated 2,5-dimethyl-1,5-hexyldiene in toluene produced P–Se heterocyclic compound 3-methyl-3-(3-methylbut-3-en-1-yl)-2,5-diphenyl-1,2,5-selenadiphospholane 2,5-diselenide with the same five-membered C 2 P(Se)SeP(Se) motif as 2,3,5-triphenyl-4-styryl-1,2,5-selenadiphospholane 2,5-diselenide. Furthermore, heating a toluene solution of Woollins’ reagent with an equimolar amount of N -allylaniline gave rise of a five-membered C 2 NP(Se)Se heterocycle 5-methyl-2,3-diphenyl-1,3,2-selenazaphospholidine 2-selenide; carrying out a reaction of cinnamonitrile with an equivalent of Woollins’ reagent under identical conditions did not give any air-stable product, however, 3-phenylprop-2-eneselenoamide was isolated in 95% yield after treatment with water. Three demonstrative X-ray structures are reported.

ChemInform Abstract: Small Organophosphorus—Selenium Heterocycles from the Selenation of Conjugated Ketones and Enals.

Abstractα,β‐Unsaturated ketones and aldehydes react with Woollins′ reagent (II) to give novel five‐membered heterocycles as diasteromeric and isomeric mixtures.

ChemInform Abstract: Tellurium‐Containing Heterocycles. Part 31. A Facile and Practical Solvent‐Free One‐Pot Synthesis of (Z)‐4‐Methylene‐3‐selenaquinoline Derivatives from o‐Ethynylanilines and Isoselenocyanates.

AbstractAniline substrates bearing the free ‐NH2 group react best under solvent‐ and catalyst‐free conditions to yield the desired selenium heterocycles.

Formation of new organoselenium heterocycles and ring reduction of 10-membered heterocycles into seven-membered heterocycles

Abstract Reacting 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [{PhP(Se)(μ-Se)}2], Woollins’ reagent, with an equivalent of aromatic diol in refluxing toluene afforded 10-membered phosphorus–selenium heterocycles 1 and 2 with an O–P(Se)–Se–Se–P(Se)–O linkage. Two equivalents of aromatic diol and Woollins’ reagent in refluxing toluene gave seven-membered phosphorus–selenium heterocycles 3 and 4 with an O–P(Se)–O linkage together with 10-membered phosphorus–selenium heterocycles 1 and 2. It was also found that the diphosphorus species O–P(Se)–Se–Se–P(Se)–O rings 1 and 2 could be readily ring contracted into the monophosphorus rings 3 and 4 in almost quantitative yields via further reaction with another equivalent of corresponding aromatic diol. One representative X-ray structure is reported.